Science topic

# Optical Fibers - Science topic

Thin strands of transparent material, usually glass, that are used for transmitting light waves over long distances.
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We working on translucent concrete. Could anyone help us giving the vendor/supplier details for using in translucent concrete? Thanks in advance.
Regards,
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Hello,
I wanted to know if a lensed fiber can guide a light of wavelength (1550 nm) longer than the working wavelength of the fiber (780 nm).
Thanks.
each type of fiber has its own transmission window characteristics according to the material composition of the fibre;
See for example Fig. 6 of:
Even at the spectral sections, which are not labelled as window, you are able guide light, but you will experience a lot of losses here.
Attaching a lense will not change the fiber attenuation but you will be able to increase the light intensity at the input port of the fiber.
Best regards
G.M.
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I want to optimize the different parameters to limit the dispersion in the optical fiber, which objective function to use according to these parameters, and the initial dispersion in order to estimate the error, thank you in advance
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Almost all optical fiber manufacturers produce optical fiber bobbins length of maximum 50 to 100kms. If longer length bobbins are produced then it will be easy for both user and producer as it reduces cost.
suggest If any technical papers available on this
Fiber attenuation, which is also called signal loss or fiber loss, is the consequence of the intrinsic properties of an optical fiber (multimode and single mode fiber). Apart from the intrinsic fiber losses, there are some other types of losses in the optical fiber that contribute to the link loss, such as splicing, patch connections, bending, etc.
a)Absorption losses in optical fiber are the major cause of optical fiber losses during the transmission.
b)Dispersion losses are the results of the distortion of optical signal when traveling along the fiber.
c)Scattering losses in optical fiber are due to microscopic variations in the material density, compositional fluctuations, structural inhomogeneities and manufacturing defects.
You need to consider the cable type ( Single mode / Multimode) and the wavelength of transmission for the calculation of losses which is expressed in
dB/ Km also given in the EIA/TIA-568 standards for reference on fibre losses for different fibre types.
Please refer to FS.com website for more details.
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Hello
I asked about nonlinear phase shift φNL in optical fiber. How can estimation φNL? and how the power effected on it?
Hi, this is a straight-forward calculation. The nonlinear phase shift is given as,
ΔφNL(t) = ϒ* Leff* P(t)
Where, ϒ is the fiber nonlinear coefficient,
Leff= (1- e-α*L)/α, is the effective nonlinear length of the fiber, and
P(t) is the optical power.
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I am trying to modify optical fiber with gold nanoparticles for particle plasmon resonance applications.
I am using 2% 3-Mercaptopropyl)dimethoxysilane (MPDMS)/Toluene as silanization.
I tried different time of fiber immersion in MPDMS (2 to 20h) and gold nanoparticle solution(2-16h). But no gold particles(AuNPs) stick to the optical fiber.
Can anyone give me some suggestions how to do this?
You can also suggest some other easy ways to modify fiber with AuNPs.
There are several ways to coat the optical fibers. Our research group tried a block copolymer templating method. If you are interested, please refer to our work (DOI:
• 10.1021/acsami.0c15311).
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I am currently working on optical fiber. It would be great if I get some suggestion on books or tutorials to study in details of optical fiber starting from the basic theories.
"Optical Fiber Communications" By: JOHN M. SENIOR
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How can we draw a graph of transmission in terms of wavelength in optical fiber sensors? Is there a mathematical formula in this field?
According to my studies in these few days and review of articles, I came to this conclusion. Can we calculate the transmission in the structure of fiber sensors using the following two formulas?
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I want to proceed the experiment using optical fiber. However, there is a problem. In one of the processes, the temperature reaches almost 600 degrees(Celsius). I know that the glass transition temperature of the soda lime glass is around 600 degrees.
In addition, the commercial glass optical fiber is consisting of 3 parts, core(pure silica) cladding(doped silica),and buffer layer(polyimide). The company says that this fiber can endure even at 400 degrees because of the polyimide, which is heat-resisting polymer. But, I think that it can endure up to 600 degrees if there is no polymer. Is it true? I will use the fiber as just a substrate, so I don't need any other layer except the core.
After I etch the polymer, what is the limit temperature for the glass optical fiber?
the commercial glass optical fiber is comsist of core and cladding, core is doped with GeO2, cladding is pure solica. the pure silica can be used under 1600C but the dopant can't. If you want to monitor the temperature base on the optical fiber, I suggest you use FBG sensor. After writing FBG on the commercial optical fiber and then you can regenerate the FBG, then the FBG sensor can be used under 1000C. There is another option is to use the PCF which is made from pure silica.
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Using COMSOL I want to observe the self-image phenomena in singlemode-multimode-singlemode (SMS) fiber. But there is some problem that could be due to boundary condition. How to use boundary condition for this case?
Thank You
Nazirah Mohd Razali
1) Yes, I have set PML layer.
2) Yes, you got the problem. I will try.
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We are trying to visualize stress rods in polarization maintaining (PM) optical fiber and so far we have used UV light source (310 nm) to visualize stress rods in PM fiber. The resulting image is not having much appreciable contrast difference. Is there any other way of doing this ?
@Mickey Ken : Thanks for your answer. I want to view it when the fiber ( after coating is stripped ) is inside a capillary tube ( silica glass ). We are using UV camera and UV LED to view it. But the contrast is not very good at the moment.
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I've made good optogenetic fiber implants for lasers in the past using lower numerical aperture (NA) silica core fiber from Thorlabs.  Recently, we've been working with LEDs which require a higher NA fiber in the 0.6 - 0.7 range. The highest NA fiber that Thorlabs carries is 0.5. Prizmatics has the right silica core fiber with high NA, but they only have core diameters of 200um & 250um.
Does anyone know a good vendor for this kind of fiber ( bare fiber, silica core, ~0.65NA)?
I'm going to buck the trend here and suggest you do not use such high NA fibres, regardless of your light source. The problem is that any increase in NA makes the light coming out the end scatter more, decreasing your effective stimulation distance. With a higher NA fibre you need ridiculously high light output to maintain your effective stimulation depth.
For example, in a typical experiment with a 200um fibre and requiring an irradiance of 1mW/mm^2 to activate ChR2, if you wanted to have effective stimulation for 1 mm from the end of your fibre, you would need approximately 4.6 mW from a 0.22 NA fibre. But if you used a 0.65 NA fibre, you would need 27.4 mW. I ran these calculations based on the Aravanis model, and using my online optogenetics power calculator at: https://nicneuro.net/power-calculator/
My experience, using both Plexon and Prizmatix LED's, is that increasing the NA of your fibre only gives a small increase in light power. For example, I recently tested 0.22 NA and 0.50 NA fibres with a Plexbright blue LED and achieved 7.4 and 11.0 mW, respectively. In this case, increasing the NA produced a 50 % increase in light output, but due to the massive increase in light divergence gave an approximate 30 % DECREASE in effective stimulation distance in the mouse brain.
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Hello everyone,
I am looking for an optical fiber where the cladding is removed at one end (about 1cm long). I have read some papers that explain how to do it, usually with HF, but I would like to know if there are providers that offer this type of product. So far, I know Thorlabs doesn't offer it.
Hello,
You can check the following website. It is a french company
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Hello,
We are exploring the fabrication of an optical coupler ( fused biconic taper type ), where 1 fiber is having 80 microns cladding diameter with a LP11 cutoff around 850 nm. The other fiber is a standard 125 microns cladding diameter SMF ( LP11 cutoff around 1250 nm). It is understood that the first fiber will be lossy at 1550 nm. My question is if we want to taper both of these fibers to say 10:1, what would be the problem with 1 of them having a much lower cutoff wavelength ?
If the parameters of the original fiber are somewhat different, a null coupler may result, where light launched into one fiber will emerge only from the corresponding end, and coupling occurs only e.g. under the influence of a sound wave propagating in the taper region. That way, one obtain an unusual kind of acousto-optic modulator.
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Hello, i hope you are doing well, i want to know how the etching of the cladding of an optical fiber is done in a controlled way, does anyone have a method or know somewhere i can do that ?
Thank you very much for your answer, i have much clear idea on how to do it now !
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Dr E. M. Wright
Sol Photonics offers an easy to use program to simulate many different kinds of FBGs. Uniform, chirped, apodized, etc.
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I am using Quick View mode of the Ocean View software for Ocean FX spectrometer.
When I check the Dark Spectrum (taken when the fiber inlet is closed and the Spectrometer is covered with Black cloth and the Background Spectrum is when the Optical fiber is placed when no source is there, only ambient light is ON.
I would also like to know why there is a dip around 550 nm?
Hmmm …. That’s interesting. Its hard to see with such a small difference, but it looks to me like the extra counts are uniform across the whole spectrum. The whole sensor is counting higher. You could subtract to be sure. If so, that suggests to me that the extra counts aren‘t from light. Oh, it could be light leaking into the box from somewhere other than the entrance, but, frankly, that almost never happens. You could double check by doing it again with the room lights off. If it doesn’t change, it’s not light.
The only thing I can think of that would cause this is temperature. Could it be that when you cover it you are preventing the room circulation from reaching the sensor, and perhaps also trapping heat? The sensor does produce a small but non negligible amount of heat, and, even though the visible spectrometers don’t have fans, they do rely on conduction through the case and room convection to shed that heat.
The dark rate is a combination of read noise (what you get at zero integration time) and dark noise (the part that is proportional to integration time). It is impossible for me to tell how much of the ~ 3700 counts is dark noise, but I assume most of it. Dark noise is a strong function of temperature and it would only take a very small temperature increase to raise the dark noise 5 or 10 counts out of 3700.
By the way, you can be confident that the black cloth isn’t necessary. Spectrometer housings don’t leak light. If it doesn’t enter through the fiber connector it doesn’t enter. (Unless someone has taken it apart and put it back together poorly). Again, you can verify by comparing the counts with the room lights on and with them off.
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I would like to calculate the Mode Field Diameter of a step index fiber at different taper ratios. I understand that at a particular wavelength, the MFD will be decreasing as the fiber is tapered. It may increase if it's tapered more. I am looking to reproduce the figures ( attached ) given in US Patent 9946014. Is there any formula I may use ? Or it involves some complex calculations?
Using COMSOL or MATLAB or other simulation softwares it is easy to calculate the MFD. You need consider the change of wave-guiding difference as the tapering diameter decreasing: initially silica/(silica+Ge) and then air/silica. I believe you cannot use a simple formula to get the accurate result
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Most of the authors presented their work on Mach-Zehnder modulator in fiber optic communication. When I saw Mach-Zehnder Modulator on internet for buying it is showing it with fiber optic cable both sides of Mach-Zehnder Modulator(input and oupt side). My question is that can we use Mach-zehnder modulator for intensity modulation in wireless optical communication? Please help.
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I want to calculate the propagation constant difference for LP01 and LP02 modes for a tapered SMF-28 (in both core and cladding).
Is there a simple formula that I can use? My goal is to see if the taper profile is adiabatic or not.
I am using this paper for my study : T. A. Birks and Y. W. Li, "The shape of fiber tapers," in Journal of Lightwave Technology, vol. 10, no. 4, pp. 432-438, April 1992, doi: 10.1109/50.134196.
equation in attached figure
Well, one way would be to consider the transcendental modal equations for the LP modes and compute the propagation constants for LP01 and LP02 for different values of the core radius. Infact, as long as the fiber is an FMF, you could find the propagation constants of all the LP modes allowed by the structure. Then you could use the equation given above to check if the criteria is met or not.
The criterion will be slightly modified for structures with more than two modes. For eaxmple, if your structure has LP02 mode as well, then you must check the above criteria more for coupling between LP01 and LP11 modes rather than LP02 mode.
The modified criteron will contain the computation of the minimum of (\beta_a - \beta_b) for different pairs of \beta.
Let me also add that this critereon of only considering the Eigenvalues is not very efficient. The adiabaticity theorem is often extended the photonics context to consider both the eigenvalue (propagation constant) and the eigen function (the modal profile) for a better adiabaticity criteria. You could find many paper to this regard. Some of my PhD work also might be useful.
Thank you
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In my experiment I have a double cladding fiber spliced on to a reel of SMF-28. The double cladding fiber has total cladding diameter about 2 times more than that of the SMF-28. The source is a SLD, and there is a polarization scrambler after the source which feeds onto one end of the reel of SMF-28. The output power from the 1 km long reel is X mW. But when I splice a half meter length of the specialty fiber to the reel output and measure the power it is 0.9Y mW, where Y is the power output after the polarization scrambler (Y = 3.9X). I am not sure why the power reading suddenly increased.
Problem solved : The reel was getting pinched and deflected at the bare fiber adapter to the detector causing a huge drop in power.
Vincent Lecoeuche Thanks for your thoughts as well.
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My set up is as follows : Elliptically polarized light at input -> Faraday Rotator -> Linear Polarizer (LP) -> Photodiode
The LP is set such that the power output is minimum. I use a lock -in-amplifier to measure the power change due to the Faraday effect. I have a more or less accurate measurement of the magnetic field and the length of the fiber. The experimental Faraday rotation (Rotation Theta= Verdet constant*MagneticField*Length of fiber) , is more than the theoretical prediction, so I was wondering if I am observing the effect of elliptical polarization at the input to the system.
Yes, you can say both polarizations get rotated. Taking each component separately, they both would get rotated by the same amount, and superposition applies, so together they do the sum of what each of the pieces would do.
However, if it helps, that is not the only way to think of it. We like to think in terms of linear polarization. We like to think of arbitrary polarization as a superposition of two orthogonal linear polarizations. It’s easy to make the diagrams. It also makes sense for linear polarizers and linear retarders. However, that is not the only choice. You can just as easily express an arbitrary polarization as the superposition of left and right circular polarizations. In the basis of right and left circular polarization a Faraday rotator is in fact a phase retarder. if the two components have equal amplitude the result is linear polarization. The relative phase determines the orientation of the linear polarization, so retarding the phase rotates the linear polarization. If the two components have different amplitude, you get an ellipse where the major and minor axes are the sum and difference of the amplitudes. Again, if you retard the phase, the whole ellipse just rotates.
As to why your experiment is producing answers that don’t quite seem right, I think this measurement has several things that can confuse the result. Although I don’t see why you wouldn’t put a polarizer on the entrance, I doubt the entering ellipticity is really the problem. That should just reduce your modulation amplitude making the signal a little weaker, but it shouldn’t impact the phase. A much more likely culprit is linear birefringence in the fiber. Fibers can have significant residual birefringence from the manufacturing, but also bending through the fiber acts as a retardation. For example, sequential coils of fiber called fiber paddles are sold as polarization manipulators.
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As we know, when we get a type of fiber from a company, we can get a few dispersion parameter D at corresponding wavelengths( lambda).so we can also get the dispersion slope dD/d_lambda.
Then how can we get the value of 4th disperison beta_4 with the value of D and dispersion slope dD/d_lambda?
i am also comfuse about the beta valume, how can we calculate the beta2, beta 3...
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Many of the research papers I looked through have the laser or light source at one end of the fiber optic cable and a detector at the other end. But I wanted to know if there was any research on how we could transmit light through the cladding so that it propagates both ways to the two ends of the fiber optic cable?
One idea that I had was to polish off the cladding at the middle of the fiber cable so that the core is exposed. Then point the light source at the middle exposed core so that the rays pass to both ends. But I wanted to know if there was any other way to do this without altering the fiber?
Nirmal,
Apply a grating coupler on the clad layer of the fiber. Regards, Shigeo.
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I need to simulate a setup like in the attached image. The source of light is the end of an optical fiber. In order to avoid simulating the fiber, I though about using a lens with the same NA as the optical fiber.
Any ideas/suggestions are welcome!
If you are unsure of the exact fibre type, and not too concerned about accuracy, a reasonable assumption is that the fibre is single mode, and emits an ideal Gaussian beam.
I would expect one or more of the simulation packages you mention to support free space propagation of Gaussian beams, but there is a lot you can do with pencil, paper and a pocket calculator. https://en.wikipedia.org/wiki/Gaussian_beam
For SMF 28e+ fibre, the nominal mode field diameter is 9.2 µm at 1310 nm and 10.4 µm at 1550 nm. https://www.corning.com/content/dam/corning/media/worldwide/coc/documents/Fiber/PI-1463-AEN.pdf
So at 1550 nm, the radiant exitance at the fibre exit facet falls to 1/e2 of the peak value at a radius, w0 = 5.2 µm.
At distances much greater than the Rayleigh range (0.055 mm), the angle at which the radiant intensity falls to 1/e2 of the peak is θ0 = λ/(π w0) = 0.095 radian. Note that the numerical aperture of 0.14 specified in the Corning data sheet is measured at 1% intensity, corresponding to a wider divergence and a lower intensity.
At a distance of 14 mm from the fibre tip, the 1/e2 radius of the irradiance is 1.33 mm, so most of the light from the fibre will pass through a 3.5 mm aperture.
(The half-angle subtended by a 3.5 mm circular aperture at a distance of 14 mm corresponds to a numerical aperture of 0.125 - which is why I mentioned that value).
More generally, for a Gaussian beam of radius w, the fraction of the total power transmitted through a circular aperture of radius R is [1 - exp(-2 R2/ w2)].
Peak irradiance is 2 P0 / (π w2) where P0 is the total power.
Specifically, if your technician holds the fibre 14 mm from his eye, 97% of the 500 mW power will fall inside a 3.5 mm circle aligned with the centre of the beam, so 497 mW. Peak irradiance of 18 W/cm2 is significantly higher than the 4 W/cm2 threshold for thermal corneal damage.
Note that at 1550 nm, most of the power will be absorbed in the cornea, and will not reach the retina of a human eye.
At 1310 nm, transmission is higher, but there is significant absorption in the lens of the eye.
At 850 nm, 980 nm or 1060 nm, transmission to the retina will be much higher.
The effective focal length of the human eye is approximately 17 mm, so light from a fibre only 14 mm from the subject will not be focused onto the retina. The retinal damage threshold will be reached much sooner with the fibre at a greater distance from the eye, such that the radiation converges to a smaller retinal spot. Is this one of the factors you intend to address in your model?
If you have not seen it already, this paper may be of interest:
D. Sliney et. al, "Adjustment of guidelines for exposure of the eye to optical radiation from ocular instruments: statement from a task group of the International Commission on Non-Ionizing Radiation Protection (ICNIRP)", Applied Optics, vol. 44, np 11, 2005.
Also: https://en.wikipedia.org/wiki/Laser_safety has some useful links.
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I'm curious if anyone can share their measurement of the coupling loss as a function of the gap between two SMF FC/APC fibers at various wavelengths. If not, it would be great if you can refer me to a datasheet or a paper where this type of measurement was done.
Thanks!
you may ahve a look at equation 1a and 1b for a description of the gap and wavelength dependence of the coupling loss/ transmission in a butt joint SM-fiber connection:
But, sorry, no experimental data yet...
Best regards
G.M.t
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Hi,
Is there any company that sell Yb-doped fiber with core diameter larger than 90 micrometer?
Thanks.
(200-micron core Yb-doped fiber for high pulse energy applications)
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Hello,
I'm calculating the mode overlap between my Spot Size Converter (SSC) and an optical fiber (SMF-28, NA = 0.14) in Lumerical FDTD using the Mode Expansion Monitor and Linear DFT Monitor. At the same time, I'm comparing the result with the Mode Overlap Integral of SSC (fig is attached).
The difference value is too much (~20% of difference) and I would like to know if by using the Mode Expansion Monitor the mode overlap calculation is similar to the model attached. The model attached is found in many papers and to use it I simply export the E fields calculated by Lumerical (the SSC and optical fiber E field) and import them in matlab to calculate the Mode Overlap between the fields.
Does anyone know the difference and which would be more accurate?
Thank you.
Taynara Oliveira - regarding the Lumerical article, as far as I can tell, they are calculating a 2-D overlap integral over the waveguide cross-section.
I believe there are some errors in the web page, for example using S rather than dS in the first overlap integral. Their approach using both E and H fields looks similar to an integral over contributions to the Poynting vector which I had not seen before. Google found references to its use with waveguides which are birefringent or chiral, and these may give you more background.
Lumerical reference A. W. Snyder and J. D. Love, "Optical Waveguide Theory". London: Kluwer Academic Publishers (1983).
Snyder and Love describe both vector treatments and scalar wave approximations for waveguide propagation. Chapter 20 begins with the vector results, but mostly deals in the weakly guiding limit, where it is sufficient to consider only the electric field components. They consider various Gaussian approximations (as suggested by David A. Ackerman) in some detail.
As I pointed out in my first response, and as David also states, with radial symmetry, it is possible to reduce the 2D overlap to 1-dimensional integrals, but it is essential to include the appropriate radial weighting.
Not including a radial weighting factor is a likely reason for your 20% discrepancy.
Attatched is a comparison of 1D and 2D overlap integrals for a Gaussian mode field, and a "top hat" illumination field.
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I built a optical fiber probe (one emission surrounded by six for collection, no filters) and I wish to capture Raman spectra.
The lasers I have available to me are at 976nm but they do have a lot of power (>4W), however, I don't seem to be able to measure any Raman signal.
What might I be doing wrong?
For detection there are many factors: the geometry for retrieving the signal, the sensitivity of the detector, the resolution of the spectrometer, and how well you can filter out the Raman signal from the high level scattered laser signal. All this aspects need optimization, and any one of them may be giving you problems,
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The aim is to characterize a DAS instrument connected to a fiber optic cable.
what are the properties that I should look into ? white noise ? Dynamic range? SNR ?
I did some choc tests and I'm thinking on how should I calculate the SNR. Should I calculate a SNR for different frequency band ?
At any way statistically standard deviation can be used to refer for the root mean square value, of signal, then separate information signal from noisy signal by the means of signal processing to calculate SNR.
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If I reduce the dimensions of an optical fiber through a tapering process, I expect high losses of confinement. I am wondering:
1) If I recoat the fiber (after the tapering process) with a low-index external coating (lower refractive index with respect to the cladding refractive index), will I expect high internal reflections?
2) Otherwise, due to the extinction coefficient of the coating, could I consider the power losses absorbed by it?
What is the right behavior of external fiber coating?
many factors determine the amount of loss you are going to encounter.
coating refractive index is a very important parameter for guiding the wave in the core, but this index may lead to a weakly guided wave or guided wave.
losses depend on waveguide structure and class of materials used
I would recommend the following textbook to expand your knowledge
Optical Fiber Communications 4th by Gerd Keiser
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I tried methylene chloride and chloroform for several days, but they didn't work.
The information of optical ferrule and optical fiber:
You can try a scalpel to scrape the epoxy off the sides of the ferrule. This is effective, but you can accidentally break the fiber off during the scraping process. Improperly cleaved / scribed fibers can result in fiber break / crack defects.
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We are measuring vegetation (grassland canopy) reflectance with a handheld spectrometer, using the sun as the light source. When taking white reference measurement Is it important that the distance from the optical fiber to the white reference standard is the same as the distance from the optical fiber to the sample (grassland canopy)?
Eg. Our optical fiber has a 30 degrees field of view (FOV), which would mean a ground footprint of about 0.25 square meters when holding the optical fiber at about 1m above the grassland canopy. We can use a small diameter ( 50 mm) white reference standard held close to the optical fiber end (to cover the whole FOV) or we could get a large diameter white reference standard (wide enough to cover the 0.25 square meters FOV) that we hold at grassland canopy level- 1m below the optical fiber.
The total spectrum/wavelengths has the same intensity dependence with the distance of your fiber tip. So, in a real aplication, it is quite difficult to analyze the total intensity reflectance values, but you can analyze spectrum changes (intra-).
Try to use a wavelenght, that you are prety sure is not related with a characteristic of your plant analyzed, as reference, allowing you to check the intensity fluctuations (due to sun-light variation intensity or experimental changes, etc..) Now, use other spectral region related with the plant characteristic, divided by the intensity of the wavelength reference. Therefore, the spectral analysis is not more sentitive to sun-light fluctuations.
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I was searching for a bragg Grating simulation example in comsol, but I did not find any. The only one that I found was incomplete. Does anyone have a Bragg Grating simulation example in comsol? It can be the file or even a tutorial of the simulation.
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How would the spectrometer signal change if the target molecule was well dispersed in a solution and placed on the fiber optic SPR cable VS the target molecule concentrated at a specific region on the fiber optic cable?
The effect can be very strong. If the concentration change is e.g. aggregation, then not only shielding effect blocks light from reaching molecules inside an aggregate, but also spectra might be changed by interactions between the molecules in the aggregate. In some cases, addition of 0.1% of a solvent which prevents aggregation transforms a clear (for eyes) solution into a deeply colored one, even when no precipitation was seen in the original suspension.
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I am using a Blue-Wave spectrometer with an optic fiber that has a field of view (FOV) of 30 degrees to measure the reflectance of the crop canopy.
If I hold the fiber optic cable approximately at 1.25 m above the canopy for reflectance measurements, I have a ground footprint of 0.27 m in diameter.
What happens with the footprint diameter if I attach to the optic fiber a fore optic: a collimating lens (LENSQ-COL, StellarNet) that has FOV 3 degrees, an 5 mm diameter?
What field of view you will get depends on the core size of your fiber. 3 degrees is a capability of the lens, not an indication of what you will get. What they are saying is that the lens will focus well onto the focal plane at field angles of up to 3 degrees off axis, but you won't actually have anything to catch the light 3 degrees off axis at the focal plane. The full-angle field of view you will actually get is 2*arctan(fiber core diameter/(2*focal length))
The flip side which is probably equally important to you is that the reduced field of view comes with a larger collection area (and so sensitivity to signal). The aperture diameter is increased from the core size in the case of the bare fiber to 2*tan(arcsin(fiber NA))*focal length
This all assumes a multi-mode fiber which is almost certainly your case.
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Does intensity of light used in OFC, effect the data rate and bandwidth provided by the OFC? If yes, should we need increase the intensities of light that is currently being used? Also by increasing intensity of light, the power and energy density carried by the light increases and does that heat up surface of the OFC (core and cladding) and should we consider such factors in improving the technology or while working with OFCs?
Data rates are mostly affected by the noise level on the detector side. The ultimate limit is shot noise, which scales with the square root of the number of photons detected. Doubling the intensity should therefore enable about 40% higher data rates at best. If you are working near 1.5 microns, there is virtually no absorption in the core of the fiber, at least as far as heating is concerned. However, the cladding is typically coated with an absorptive material. If you are launching light into the fiber and you do not exactly match your mode, you will see a lot of absorption in this coating, and the fiber will start to burn. This will limit the power that you can launch into the fiber. I recall that I managed to launch more than a watt into a single-mode fiber, but this is probably far beyond practical levels as you would immediately destroy your receiver with such elevated power levels.
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I am carrying out research on MCF - MDM based optical transmission line performance analysis
There could be multiple ways. However, if the transverse and the longitudinal extent of the device is large, then its will be a computationally intensive problem while using FEM. This is especially the case for low contrast devices. However, here is a possibility which could be extended.
You could use COMSOL to compute the modes of the composite structure. Then by exciting a certain core and propagating the field, you are essentially propagating a superposition of those modes each acquiring a different phase during propagation. The propagated field could be analyzed to compute the coupling coefficients.
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The rays concentrated by convex lens is passed through 1m optical fiber. But only the ray enter into optical axis reaches fiber end, other rays are not? Can anyone suggest where i went wrong?
It looks as if you designed it in sequential mode. That means ray interaction with surfaces is only checked in the exact order you define the surfaces. If you want to simulate interactions where the order is not known beforehand you must design it in non-sequential mode. Then a model of a multimode waveguide will work, but not a singlemode waveguide, which is poorly described by rays.
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In our current era there is a big confusion about the usage of G.652 and G.655 optical fiber cable.
Theoretically G.655 is much better than G.652 but the operator feel that G.652 is giving almost same performance while the cost is quite less.
Anyone having direct experience please share your feedback, also I will soon be making a survey on it, so if anyone is interested in the survey then he can let me know.
Thanks.
Hi Abdul Aziz Khan: - Can you explain in more detail how my answer differs from the established view of DWDM performance? In particular:
• Have you any links with supporting technical details beyond a simple statement that G.655.D is superior?
A useful resource is the Handbook of Optical Fiber, Cables and Systems, published by the International Telecommunications Union in 2009. By now, this is a little dated and does not cover recent developments in QAM modulation formats and coherent systems. Having said this, the basic information remains valid.
In particular, you may find the following sections may of interest
• Chapter 7, Optical System Design
• Section 2.7 Penalty due to fibre non linearities
• Section 2.7.2 p 180, SRS
• Section 2.7.4 p 181, XPM
• Section 2.7.5 p 182, FWM
• Section 2.7.6 p 184, Maximum power threshold due to non-linear effects
My previous answer reflects my understanding of the state of the art around 2011. At that time I had been involved in developing commercial WDM transmission systems for 18 years. My responsibilities included analysis of non-linear propagation impairments and establishing robust and efficient link budgeting techniques. Since then I have not followed developments in detail, but I am not aware of any technical developments or changes to our understanding of the underlying physics which would change my conclusions.
Consider that Google is a search engine and advertising platform. The links it returns reflect accessibility and some measure of popularity. Judging technical merit is a more difficult task for an automated system.
Out of interest, I did search Google for differences between G652 and G655 fibres, and near the top of the hits found several blog sites of questionable reliability. Is this where you found your opinions?
Note that fosn.com, fs.com, medium.com, thefoa.com, mefiberoptic.com and mjadom.com, typically display very similar graphics, and most include a table indicating that G652 fibre is unsuitable for long haul DWDM or data rates. This suggests to me that they may be more closely linked than is apparent, rather than expressing independent opinions.
The graph common to several, showing positive and negative dispersion fibres is highly incongruous to anyone familiar with single mode fibre design. Although there was a short period in the mid-1990s where negative dispersion fibres were investigated for their insensitivity to modulation instability, these fibres had positive dispersion slope, not negative as shown in the graph.
Sylvie Liu on https://medium.com/@sylvieliu66/single-mode-fiber-type-g652-vs-g655-fiber-fbbcc6db67ee is more specific. She states "G655 is an enhanced single mode fiber with the characteristic of elimination of FWM and low dispersion value". It absolutely does NOT eliminate FWM. This is not a matter of opinion or debate. Low dispersion is well known to greatly increase the magnitude of four wave mixing,
I note that the post is dated 9 May 2018, but states that G.655 has A, B and C subcategories. She does not mention the G.655.D and G.655.E versions from the 2006 release of the standard, or that the A and B subcategories were dropped. Such lack of attention to detail does not inspire confidence, and she reveals little understanding of non-linear Kerr effect crosstalk in WDM systems.
A more focused Google search found a more recent publication. I have not downloaded the full paper, but the abstract indicates a much more realistic understanding of DWDM propagation. It reports a mixed line rate comparison of G.652, G.652D, G.653, G.654, G.655 and LEAF fibres, with G.652 showing best performance.
Bajpai, R., Sengar, S., Iyer, S. et al. Performance investigation of MLR optical WDM network based on ITU-T conforming fibers in the presence of SRS, XPM and FWM. Int. j. inf. tecnol. 11, 213–227 (2019). https://doi.org/10.1007/s41870-018-0212-2
The benefits of high chromatic dispersion in suppressing WDM non-linearity was understood from the earliest demonstrations of FWM in optical fibres.
K.O.Hill et. al, "CW three-wave mixing in single mode optical fibers", J. Appl Phys 49, p 5098, 1979. https://aip.scitation.org/doi/abs/10.1063/1.324456
The impact of low dispersion on FWM was explored in more detail in the paper by N. Shibata, R. Braun & R. Waarts, "Phase-mismatch dependence of efficiency of wave generation through four-wave mixing in a single-mode optical fiber" IEEE JQE vol 23, #7, pp1205-1210, (1987), https://ieeexplore.ieee.org/document/1073489/
As modulation rates increased from 2.5 to 10 Gb/s, cross phase modulation became the dominant WDM penalty for many systems. There is a rather more complex relationship between fibre dispersion, channel spacing, and dispersion compensation strategy for XPM impairments, discussed by Rongqing Hui, K.R. Demarest, & C.T. Allen, "Cross-phase modulation in multispan WDM optical fiber systems", JLT, 17, #6, pp 1018-1026, 1999.
In spite of their poorer DWDM performance, there can be valid reasons to deploy near-zero dispersion-shifted fibres to reduce the need and expense of dispersion compensation modules. Typically, this will be where cost of terminal equipment is more important than maximising capacity and the potential for future enhancements. However, stating that G652 fibre is unsuitable for 10 Gbit/s DWDM is demonstrably untrue.
The introduction of electronic dispersion compensation eliminated much of any potential cost benefit for reduced dispersion fibre in high capacity long-haul transmission, avoiding the need for fibre dispersion compensation modules. For example: Doug McGhan, Charles Laperle, Alexander Savchenko, Chuandong Li, Gary Mak, and Maurice O’Sullivan, "5120-km RZ-DPSK Transmission Over G.652 Fiber at 10 Gb/s Without Optical Dispersion Compensation", IEEE Photonics Technology Letters, Vol. 18, No. 2, January 15, 2006
Coherent detection and digital signal processing at the receiver gave further improvements in performance, even on legacy fibre with relatively poor polarisation mode dispersion.
C.Laperle, "WDM performance and PMD tolerance of a coherent 40-Gbit/s dual-polarization QPSK transceiver" JLT Feb 2008.
Note that the papers above used G652 fibre. This is not only because G652 fibre is very widely deployed, but also because it delivers significantly better WDM performance for this type of system.
Here is more recent work using ULA fibre with an even higher chromatic dispersion than G652 to improve the WDM performance
I have no plans at present to publish a more detailed justification. As I hope I have shown, there is a huge volume of work published in peer-reviewed journals supporting much of what I stated. Have you identified an audience who are unable to access such information, or do they simply need to know what questions to ask?
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What is the reason of the received optical signal to be slimmed down in multi-mode fiber?
I have 4 km multi-mode fiber
Dear Egalon,
I have attached a picture of transmitting and receiving optical signal in MMF optical fiber.
There is no spectral shift
Best regards
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Dear colleagues,
We have observed large fluctuations in laser power in our setup and traced them down to fluctuations in laser beam polarisation. Attached is a schematic of the relevant part of our setup. We have experienced large fluctuations in laser intensity at the sample (after the microscope objective). Attached is a plot of laser power measured at the sample plane. We have checked the laser itself and its output power is stable. We have checked also the laser power at the exit of the optical fibre collimator (before the polarising beamsplitter) at different time points (when the power after the objective was around its maximum and when its was around its minimum) and it remains stable as well. From that we concluded that it is the plane of the polarisation that is changing in time. We have then checked the laser alone and this time placed a polariser between the laser and the power-meter. The power is still stable, showing that the polarisation of the laser output is stable in time. So there's nothing wrong with the laser itself.
Do you have any idea what could be the source of those fluctuations? I know that reflection of laser beam back to the cavity can destabilise the laser, but can this make the plane of polariation rotate? And can it happen on such a slow timescale? Thanks for your answers.
Good question
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Hello dear researchers.
I want to solve a cylindrical waveguide, lick an ordinary standard optical fiber. I am familiar enough with the 2D-axis-symmetric model, but as I knew from the equations and output results (if I'm right) 2D-axis-symmetric models just solve the symmetric model in relation to the r=0 axis, and a simple revolve node, in the dataset, revolves the whole answer around the r=0 axis, and if the coordinate is not defined earlier, you may achieve only a revolved data where the data is multiplied by 2*pi.
Now, if I define a new coordinate system, particularly I mean it for electromagnetic waves, is it possible to introduce the 2D-axis-symmetric model to solve such vector-based problems properly???
I think that
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Hi. I am new to chromatic dispersion related work and have read how it affects the shape of optical pulses. I want to ask how does it work for analog continous wave laser signal? why all books only mention laser pulses and pulse broadening of digital signals. what about using analog CW laser and modulating analog IF signals on it. How will CD affect it through pulse broadening . . . secondly, books mention that CD is a linear process. Is it because the pulse broadening factor equation has only L (not L square?) because the GVD equation contains lambda square (square of wavelength or frequency). how is it a linear process then? thanks a lot
May be
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Please recommend the optimal optical component and its parameters.
Thanks a lot
to couple a image to a fiber is focusing the image on the surface of the fiber end by convergent lens is placed after the image and before the fiber
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Hi everybody!
I am working on my diploma thesis regarding eye endoscope. I would like to know more about the speckles in the multimode fiber. I would like to reduce speckles in MM fiber using vibration. I do not know why the vibration reduce the speckles and what happens with modes that are in the optical fiber.
Regards
Barbora Spurná
Jörn Bonse provides a very clear explanation of speckle motion in MM fiber resulting from fiber flexion. The next question is how to move the fiber to reduce the speckles adequately to meet you needs. Presumably, your aim is to create a smooth illumination field for your endoscope. So, how to vibrate the fiber, in terms of direction of motion, amplitude, frequency, etc? Some of these questions can be answered through experiment -- you will be time averaging (integrating) the moving speckle field over the frame time or exposure of your camera. Therefore, the vibration period must be less than 1/10 of the exposure and preferably much shorter to enable speckle patterns to average out. The amplitude of the vibration only needs to be enough to 'shake' the speckle pattern by a few characteristic speckle dimensions or so. Once you have a mechanism to vibrate the fiber, you can ensure that the amplitude of vibration is large enough. Finally, you need to create a diverse set of speckle patterns during an exposure time. Some schemes use two vibrators in orthogonal directions at different frequencies (that are not low integer multiples). It is probably best to build up your system with vibration frequency set first, then experiment to ensure that the speckle pattern averages out enough for your purposes. Add complexity if it is needed. Finally, there are other ways to smooth speckle patterns that use spinning diffusers in the light path. However, in your endoscope, your idea of vibration seems practical. Here is an interesting reference: https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-28-9-13662&id=431120.
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I would like to make an Fabry-Perot cavity without welding or adhesvie.
The simplest way is to use a fiber fusion splicer. By playing with the parameters of splicing such as charging time, strength as well as the distance between the two fibers, you can get the structure as you want.
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Hi everybody!
I am working on my diploma thesis regarding eye endoscope. I would like to know more about the origin of speckles in the multimode fiber. I suppose that the speckles depend on fiber modes but I do not know why should high-order modes move with higher speed than low-order modes. And how does this fact influence the speckles.
Regards
Barbora Spurná
speckle patters arise whenever lights from a variety of directions hit a scree, When the number of different directions is large (≈>50) the one sees the "normal" speckle pattern (BTW each fo the black spec is actually a phase singularly, or optical vortex). A multimode fibre typical supports >1000 fibre modes so their addition/interference is what creates the speckle.
within a ray optical picture, the rays associated with different fibre modes zig-zag down the fibre at different angles from each other 8every mode having ≈ its own zig zag). the higher order modes zig zag more tightly. remember that the wavevector has x, y, and z components (kx^2+ky^2 +kz^2 = k0^2). if the ray has non zero kx and ky then kz must be reduced below k0. the more tight the zig zag the more kz is reduced. phase velocity in z-direction is omega/kz, smaller kz gives larger Vphase.
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I'm looking for a company that provides square core optical fiber at a relatively low cost. Core size I need is ideally 1000 um x 1000 um (or as close as possible). So far optoskand has it but its \$475 per meter so anything less expensive than that would be decent. It doesn't need to be connectorized either just the fiber.
Fibercore
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BER analyzer parameters meaning.
The reliability of data transmission characterizes the probability of getting a distortion for the transmitted data bit. This indicator is often referred to as the Bit Error Rate (BER). The BER value for communication channels without additional means of error protection is 10-4 — 10-6, in optical fiber — 10-9. A ber value of 10-4 indicates that on average, one bit is distorted out of 10,000 bits. The q-factor of the receiving system Q is determined from the expression:
Q = GA/TC,
or, in logarithmic form:
Q[dB] = GA[dB] - 10lgTC[x].
It is the q-factor of the receiving system that determines the signal-to-noise ratio (C/N) at the output of the low-noise Converter (LNC or LNB). It is important to note that the final C/N value does not depend on the LNC gain.
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Hello,
For a special research project, we are looking for high temperature resistant optical fiber. A PPT document is attached in this mail to explain our application more precisely. Ideally, we are looking for an optical fiber that can withstand up to 1000-degree celsius.
Other specifications: - Approximate Length of optical fiber- 2m - Working temperature- 700°c- 1000°c - Approximate wavelength range - 200nm-1200nm - Mode type - Single-mode
Is it able to find these high temperature resistant optical fiber??
(Any specific companies offering these high-temperature optical fibers??)
Best regards, Vayalthota Gopikishore
I can give a link to the work where such high-temperature optical fibers were studied "high-temperature optical FIBERS WITH a COPPER coating" Approximate characteristics of the Type of optical fibers: Single-mode (G. 652), multimode.(G. 651), “quartz-quartz”
Type of coating: copper, aluminum and alloys based on Them
Operating temperature: 500 °C (aluminum coating),
800 °C (copper-based coating)
Length: up to 5 km (continuous)
Optical losses: minimal (depends on the design of the light guide and operating conditions) 1-4 dB/km (at 20 °C) at λ=1310, 1550 nm
2-4 dB/km (at 700 °C) at λ=1310, 1550 nm
Strength: 8-10 GPa
Diameter of the light guide: 125-1000 microns.
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I have a divergent beam coming from a sample in the NIR region. I need to converge the light into a fiber and take the spectrum. A rough sketch of the set up is attached here. Could some please suggest on how to select the specifications of the lenses and the optical fiber so that the emitted radiation is effectively coupled into fiber.
essentially, you have to match the collection angle of the your collecting lens to the NA numerical aperture of the optical fiber as well as the image size should be matched to the core diameter of the optical fiber.
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I am planning to concentrate the sunlight using the Fresnel lens onto the fiber optic cable for my indoor experiments. But I am thinking that I will face the following problems:
1. The aperture of the fiber optical cable is very small. Can it hold and transmit all concentrating light rays as optical cables have a particular angle of acceptance?
2. The magnitude of concentrated light is approximately 1000 x 1000 W/m2. Can the cable sustain the high temperature produced by the concentrated beam and transfer the sunlight from one place to the another?
3. What are the losses occurred in transporting the light along-with their magnitudes?
4. What is the maximum distance traveled by the concentrated light beam through the optical cable?
5. Where can I purchase the concentrated fiber optic cable from and how much does it cost (approximately)?
I will be thankful to you if you answer any of the aforementioned questions.
Lets make simple estimation: Angular diameter of sun is about 10 mrad. Maximum diameter of custom fiber bundle (available at the market) is ~2 cm. So maximum focal length of ideal concentrator is 2: 0.01 = 200 cm. Supposing maximum available NA (full acceptance angle) = 0.5, we obtain maximum diameter of concentrator 100 cm. So, available sun light power from one module "concentrator + fiber bundle" at the input is ~ 800 W. To get 1000x1000 W you need to use ~1250 modules (in the best case).
May be better to concentrate the light by spherical mirror instead Fresnel lens ?
Dont worry about losses in fiber, main losses you will get before the input.
Standard fiber bundles have a length <2 m. But I suppose there are military systems with much longer bundles, the technology allowes to make longer bundles. Look for the supplier by yourselves. Standard bundles will not satisfy you.
At the fiber input the maximum power density is ~ 250 W/cm2. It is not very high. Also you can reject UV and IR before input and obtain much less than 200 W/cm2.
So, in total your idea seems real, but not good. To my opinion, free space transportation of sun light is more resonable.
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During the process of inscription of FBG on the silica/glass optical fiber few centimeters of the fiber had to be stripped. Bare fiber is too fragile for mechanical measurements, so I thought about recoating it. Unfortunately - I don't have an access to a recoater.
Is there any chemical solution I can use for DIY recoating purpose?
In our last experiment, we used PMMA as a coating for the FBG sensor. However, the low thickness of the PMMA layer did not affect the principle of operation of our sensor:
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I am in the process of acquiring equipment for a second in vivo electrophsyiology rig, and I can't seem to find who produced the cannula holder that we use on our other rig. We want to be able to position multiple optic fibers simultaneously while recording, and the tapered and elongated construction of the cannula holder that we have now is ideal.
Does any one know who produced the cannula holder in the images attached?
Yes, after a long search I was able to find the product.
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As we all know, if an optical fiber is designed with the right material and properly bent, light can be transmitted along the fiber with very little attenuation.
Figure 1 shows the interaction of radiation F with a conical structure. The cone is a hollow mass with an internal reflector layer or a homogeneous mass of transparent material. Due to the non-ideal incident angle of radiation F (as shown in figure 1), radiation F will be easily reflected back or transferred out of the cone.
In the case of the above cone is a system of multiple optical fibers (figure 2). Optical fibers are arranged as a multi-branch tree: Start by an optical fiber at the bottom, then it is gradually branched at the upper rows and the top row will have the most fibers. Optical fibers have one narrow end below and the other larger end above. The optical fibers are separated by a vacuum layer so that total internal reflection can occur optimally. It can be noticed that radiation F will be easily transmitted along the fiber inside the cone.
We find that with the same incident angle and interaction position, radiation F in the two figures will have two different directions. It can be seen that a system of multiple optical fibers will have a much larger acceptance angle.
The key is to find the right material for the fiber and bend the fibers properly (without bending too strongly) so that radiation F is not refracted out of the fiber during transmission.
Extending from radiation F, can we use the above multiple optical fibers system to optimize solar energy harvesting (similar to Winston cones or Fresnel lenses but with higher efficiency)?
Dear Viet Nguyen ,
nice idea.
You should have a look at the planes perpendicular to the fibers. I assume you think on circular fibers . So the net area when picking up the light in the case of fibers is much smaller than the real area which is exposed to light. So you will pick up only about 2/3 of the light. At the planes where you will transfer the light from one fiber system to the next you will have additional areal losses.
Have you taken all these losses into account?
From that point of view, I think, any lense( e.g. a Fresnel lense) will have a better efficiency than your system.
Please check the areal coupling losses.
Good luck
By the way: In your drawing you have presented one of the very few rays which successfully end up at your output port. There are a lot of rays which will not end up there, even for perpendicular incidence at your entrance port.
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Hi,
I am trying to find out Young's modulus of an optical fiber. I am not sure which two points should I use to calculate young's modulus? Should I calculate it from initial point? or any two points from linear region is okay? I have two linear region and I am confused which part should I take into consideration?
Could anyone help me?
Slope of the initial linear portion should be used to be absolutely sure that you are truly in the elastic region. Perhaps you need more data points at low stress/strain regions
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How to design a rectangular step-index optical fiber using Comsol Multiphysics Software
Dear Rajib Biswas Sir, the 2nd and 3rd links are not open. Can you please resend it.
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I have a task to simulate optical beam profile from skewed optical fiber tip.
Can Zemax simulate it ?
Fiber SMF28. Skew angle 8 degree. Wavelength 1500 nm.
You can design a code by matlab to analyze the optical beam profile or used a CCD.
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In many optical fiber papers, authors report the refractive index difference (Δ n) instead of the absolute refractive indice. As a material scientist, sometimes I need the absolute values of the core and cladding materials to do some calculations. This troubles me a lot, some papers have the exact material I'm intrested in, bu they only provide the RI differences (Δ n), not the absolute values. Is there a way to get the absolute values from the known Δ n?
Your question Dear Xiaojing Xia, is akin to asking what the end values are if one knows the birefringence of a given unknown mineral particle. If that is correct then I completely agree with those who say you can not pin down the RI of core and/or cladding. On the other hand, if an optical microscope is available you could grind some up and examine it to discover the RI of both materials ... if it makes sense to snip off a sample of a given fiber.
3. Video: https://tinyurl.com/uajcnxx (open in a video player)
4. 20200512 1325 Final E% COORDINATES & MORE .pdf, https://tinyurl.com/y9lrmnec
and maybe also by paying a visit to some of the other Supplemental Materials in folder https://tinyurl.com/to8tsbt .
I hope that this helps and that you will, in turn, share with me any thoughts you may have about how I could improve any aspect of my work.
With all best wishes for your own continuing successes! :-)
Sincerely, -Steve- gambist@gmail.com
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need to make something right at right moment
you can use the bidirectional fiber in Optisystem tool which include the SBS effect. Have a look at this article
Simulation and experimental validation of gain saturation in raman fiber amplifier
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A fiber Bragg grating consists of a periodic modulation of the refractive index in the core of a single-mode optical fiber. These types of uniform fiber gratings, where the phase fronts are perpendicular to the fiber’s longitudinal axis with grating planes having constant period
So, as I understand you right, you are asking the following question:
What is the effect of changing the length of a uniform fiber Bragg grating (https://en.wikipedia.org/wiki/Fiber_Bragg_grating)?
So, I try to answer this question:
When light is send through the fiber with fiber Bragg grating (FBG), it reflects a specific wavelength, which is determined by the refractive index and the grating period. So in the spectrum of the reflected light you will observe a peak.
Changing the FBG length will change the reflected peak of the FBG. The Full-Width-Half-Maximum (FWHM) for example, is influenced by the FBG length.
Moreover, the FBG length also influences the reflectivity.
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I am going to conduct experiment on sunlight collection. First the sunlight is collected using Fresnel lens. Then the concentrated light is transported via silica optical fiber. Since the concentrated sunlight is so bright its very difficult to look through naked eye. Can anyone suggest a good protective eye wear to do this experiment? Somewhere i read welding glass is enough. Is it so?
Welding glasses sound appropriate. Maybe it would be helpful to use a high dynamic range camera with log response and monitor or video goggles. This would bridge the stark contrast between the brightly illuminated center and the surrounding.
Just some example from the web:
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Can anybody suggest a resource which includes the modeling of pulse propagation in optical fiber using split step fourier method and model the nonlinear optics theories in the book nonlinear fiber optics by G.P.Agrawal? If there is a basic course ,a lecture series or a book in computation optics, please do recommend it.
Hi. You should take a look at these books:
- Computational Fourier Optics a MATLAB tutorial (2010)
- Computational Photonics An Introduction with MATLAB by: Marek S. Wartak (2013)
- Fundamentals of Electromagnetics with Matlab, By: Karl E. Lonngren, Sava V. Savov (2005)
- Guided Wave Photonics _ Fundamentals and Applications with MATLAB (2012)
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Details:
The input beam is launched to the fiber. It is scattered inside the fiber and not reaching to the other end of the fiber. The problem could be due to the boundary condition. How to use boundary condition at the input and output face of the fiber ?
Thank you very much @Seyed Hadi Badri for your solution. I was also busy in solving this. I would like to share that the error was due to defining the cylindrical waveguide. COMSOL takes propagation direction in x-axis while I was defining it in z-axis. Now, it is working.
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I'm interested in directing as much light as possible from the LED into the SMA-terminated optical fibre. What sort of adaptor or bushing would I need to be able to connect the LED to the fibre? I am using Osram SFH 4725S for the NIR LED and a lab-grade patch cord from Ocean Optics.
Unfortunately, the "etendue" of LED's prevents efficient coupling into fibers. A large portion of the light generated is contained in very high angle rays that simply cannot be coupled into the fiber. Optics wont help this case as conservation of irradiance says that as the apparent source size is reduced (demag) the NA is increased. Making the source spot small to match the fiber mode size increase the source NA and ends up not being guided in the fiber. Laser diodes have a much smaller NA in both axis and fiber designs have been tailored (or maybe both) to work with each other.
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I want to insert a metal probe into the body. This probe is a metal enclosure that contain of an optical fiber. The light comes out of the fiber end and through the hole in the end of the tube. I want to paste the optical fiber to the metal enclosure with a transparent biocompatible adhesive. What is the best adhesive for this work? This adhesive should to be resistant to disinfectants agents.
Gordon Yiu
Thanks a lot
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I need to reflect exited beam from optical fiber to 90 degree in a narrow path as shown in attached figure. The path is circular with 2 mm diameter and 10 mm length. I need to reflect beam in just one direction! For example Z direction!
How can I do it?
You can cut the fiber end at 45°.. If the fiber is in air, you should probably have a total reflection on the end face fiber (it is the case for standard optical fibers). If not, you can coat this cut end face with some metallic coating depending on the wavelength you intend to work. That will minimize your space at the maximum, and will have your 90° reflection quite easily.
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I need to coupling a 250mW laser diode source light into a 1.5 mm multi mode optical fiber. I have done it with a double convex lens. But, I have a lot of dissipation! How I can coupling laser diode light into the optical fiber without dissipation? I need to receive 250mW output power from the end of the fiber!
Mohammadreza Maleki: by "without dissipation" I assume you mean with minimal coupling losses.
Manuel Gómez' answer is appropriate if you have a well-collimated beam from your laser diode source. Note that he suggested using a microscope objective lens, not an entire compound microscope instrument.
Having said that, if the core diameter of your fibre is 1.5 mm, and the numerical aperture reasonably large (say 0.2 or greater), I see little need for tilt adjustment on the fibre mount. For industrial applications, a singlet lens is probably good enough. An aspheric lens, or a plano-convex lens with the planar side towards the fibre, and the convex side facing the collimated beam, will have lower aberrations than a bi-convex lens.
On the other hand, if you are attempting to couple light directly from the exit facet of a laser diode into the fibre, you need to consider the size of the active area and the far-field radiation pattern.
What is the numerical aperture of your fibre? Does it have a graded refractive index profile or (more likely) a step refractive index profile?
For efficiency reasons, the active volume of a diode laser is usually a thin stripe, with a far-field radiation pattern which is highly divergent out of the plane of the stripe. https://www.newport.com/t/laser-diode-technology
It is not uncommon for the divergence angle (half-width at 1/e2 intensity) to exceed 30°, with significant power at angles as high as 50 degrees.
If this is the case, a high numerical aperture lens is essential. A decent quality aspherical lens may be more cost-effective than a microscope objective, and could offer comparable efficiency. Precision machined and polished aspheres offer near diffraction-limited performance, but a moulded lens is probably good-enough to couple to your a 1.5 mm core diameter fibre.
In the case of a broad stripe laser such as that described in the paper by Lee, Mawst, & Botez linked above, the laser cannot be treated as a point source, and there will be some increase in aberrations at the outer edges of the active area of the laser facet. This will be more pronounced for shorter focal length lenses, but I doubt this will have a significant impact with focal lengths of 8 mm or larger. Shorter focal lengths could be acceptable, but I am guessing here as I don't have direct experience.
You appear to be aiming for 100% efficiency which will not be possible. 99% will be very difficult to achieve, with perhaps 85%-95% more likely. At normal incidence you lose 4% of light from each uncoated air-glass interface, so anti-reflection coatings with good performance at the laser wavelength are essential. Are you able to AR coat the fibre entrance and exit facets to avoid Fresnel losses here?
You can improve the collection of high angle light by combining a high NA aspheric with a longer focal length best form, plano-convex or achromat secondary lens. Mount with each lens' with most strongly curved surface facing the other lens. With a 100 μm stripe laser, I suggest a secondary lens directing light to the fibre with a focal length 5x to 10x larger than that of the asphere collecting light from the laser.
Magnification = focal length of secondary / focal length of primary asphere
Choose magnification > Aspheric lens NA / Fibre NA
Choose magnification < Fibre core diameter / laser stripe width
A ray tracing package such as Zemax will allow more precise optimisation if the highest possible efficiency is essential.
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