Fiber Optic Technology - Science topic

Dear community members,

I need to study the fluorescence of certain analytes in an aqueous solution. Currently, I am investigating fluorescence in a physiological solution. To conduct this study, I am using an Avantes spectrophotometer.

My goal is to obtain calibration curves for specific analytes in water at different concentrations.

The experimental setup consists of a peristaltic pump drawing the aqueous solution from a beaker containing the analyte. The solution flows through a plastic tubing. A small section of the plastic tubing consists of a circular plastic cuvette housed inside a light-shielded box. Inside this box, there are two LEDs and the entrance of the optical fiber that captures the light from the LEDs and the fluorescence of the solution excited by the LED light. Once crossed the box containing the LEDs, the liquid through the plastic tube returns to the beaker where the solution is recirculated for the experiment.

As mentioned, there is an optical fiber that captures the light from the LEDs and the fluorescence of the analytes dissolved in the water. The captured light travels through the fiber and goes into the box where the conversion of the light signal to an electrical signal takes place, along with all subsequent electronic processing. The spectrophotometer is connected via Ethernet to a Raspberry Pi, and I see the software interface on the screen to manage the spectrophotometer parameters. We have two LEDs: LED 1 emits light at 445 nm, and LED 2 emits light at 340 nm. One analyte absorbs at 445 nm and emits fluorescence between 500 and 600 nm, with a peak at 523 nm. Another analyte absorbs at 340 nm and emits fluorescence between 400 nm and 600 nm with a peak at 461 nm.

Now that I have explained the operation, let me describe the optical problem I am encountering.

In short, I observe a problem of "drift" in the light intensity detected by the light-to-electric signal converter. Let me explain it better. The LEDs (unless proven otherwise) always absorb the same amount of current (the voltage across the resistor is always the same over time, and they operate in the linear region), so they always emit the same light intensity. I observe that depending on how I bend the optical fiber and how it is touched and moved, the optical fiber affects the detected light signal, accentuating or attenuating a constant increase in detected light. If the optical fiber remains bent with very pronounced curves, I observe the drift phenomenon, i.e., a weak but constant linear increase over time in the light intensity of the LEDs or the fluorescence of the analytes, as shown in the plot attached. Let me explain it better. If the fluorescence peak of an analyte at 523 nm is, for example, 250 counts at a certain concentration, if no additional concentration of the analyte is added, and the circulating solution is always the same, then the fluorescence of the analyte at that constant concentration should remain constant. Instead, I observe a linear, weak but persistent increase in the fluorescence of the analytes at all emission wavelengths. So, if at time t, I observe fluorescence at 523 nm equal to 250 counts, after, for example, t + Dt, now the entire spectrum has grown, and, for example, the peak is at 1000 counts. Obviously, this "drift" in light intensity is not due to the LEDs because I believe their light intensity remains constant over time since the current they receive remains the same. At most, the LED intensity should decrease over time. It is not due to the auto-fluorescence of the analyte from ambient light because this phenomenon is observed even when the room is completely dark. There are no chemical reactions or degradation of the analytes (I would observe a decrease in fluorescence, not an increase because the degradation products of these substances do not absorb at 445 or 340 nm). Also, this positive drift phenomenon is observed even with plain water or air. It is not due to problems with the light-to-electric signal conversion electronics or due to bugs present in the source code.

I attribute it to the optical fiber, which, if it is straight, this problem is attenuated, but if it is very bent, this effect of increasing the detected light manifests. Attached, you will also find photo and plot files showing the abnormal trend over time of the fluorescence of the analytes or the light captured by the LEDs. I do not believe this anomalous trend depends on the light source.

I'm using a FT600EMT - 0.39 NA, Ø600 µm Core Multimode Optical Fiber

In your opinion, what could this uncommon phenomenon in the optical fiber be due to? And how could it be resolved?

I would appreciate any suggestions. Thank you for your patience and the time you've taken to read my question.

Best regards,

Lorenzo

By converting AC to DC then to light signals,then is it possible to transmit the light signals through optic fibre cables?  

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? 

Dear Colleagues,

I'm studying the optical limiting effect in organic material due to reverse saturation absorption. As we know, in reverse saturation absorption, the transmission coefficient decreases as the intensity increases, or the absorption coefficient increases as the intensity increases, resulting in power loss. So, when we increase the laser power to a threshold P0, there are two competing processes: the increase in input power and the power loss due to reverse saturation absorption. If these two processes are in equilibrium, the optical limit curve is horizontal (as in the attached pictures.) However, if the amount of lost power is greater than the increase in input power, the curve must go down at P0. Why in the paper on optical limiting don’t we  see such cases?

Thank you and hoping for your insightful response.      

I've recently heard about this new material called Quantum Stealth which is supposed to be a 'Invisibility cloak' . Apparently the material bends light waves around a target which allows complete invisibility. Is all this true?

Actually, the reason we can see objects is because light reflects from them or because light is modified in some way travelling through them. Water, for example, is transparent but we can see it because it both reflects some light and refracts light through it from objects immersed. If we want to hide an object then, ideally, what you do is take light from one side of the object and bend it around it.

Can we do this? Well, in theory, yes. One way is to have a series of cameras on one side of an object and light sources, like an HD TV on the other. You basically take a photograph of what lies behind one surface and project that onto the opposite surface. This is very hard to do for multiple surfaces because you need each of them to have lots of cameras and lots of light emitters and the sheer amount of data is astronomical.

What you might be able to do instead is develop materials that can guide light around the object. Instead of photographing and re-emitting light, you use the original light and just bounce it in a clever way to get it to emerge on the opposite side of the object. This is definitely possible, we can do it already with fibre optics, but the problem is complexity and cost.

Theoretically, I have attached a recent paper explain how it can be.

Actually, I found many websites speaking about it like;

Let us discuss this interesting issue.

Hi

Does someone know how we can calculate absorption coefficient in optical fiber at different wavelengths (such as 1117 nm).

What is the procedure to simulate fiber optic SPR in matlab?

SInce you use a multimode fiber, I am guess yoy are using a partially coherent light source (LED or Helogen).

I am particularly interested in what is the lioght source and how much power could you couple in the multimode fiber.

Henrique

I'm looking for publications related to the study of micro and macro bending losses in optical fibers as a function of their constructional parameters.

I am trying to couple NIR light from a high power LED to a multimode optical fiber. Ideally only a few (five) modes would be coupled but I am concerned about how it affects time coherence if compared to original time coherence (from LED). 

The LED is 850nm/30nm and 1W power. 

I am aware of power loss but I expect a few mW in the fiber output.

I need to couple the light emerging a VCSEL into a single mode fibre. I searched the internet, and I couldn't find any out-of-box commercial product to buy.

Are there any particular tool like a receptacle I could use to achieve a high coupling efficiency?

PS: I tried the traditional way, i.e., focusing the VCSEL beam into a single mode fibre using an objective lens. However, the setup sensitivity to vibrations and other impacts makes it impractical.

What is the best way of calculating or measuring the fraction of power from a seed leaser that is coupled into a semiconductor optical amplifier by a series of free space optics? Any help or references to relevant papers is much appreciated. Thanks.

why bending losses major losses in photonic crystal fiber????

If you  have a  B. Sc. student and if you like to do research in laser practices with fibers (laser application) it will be my pressure to work supervision together ?

regard

Raad

Hello,

We are looking for large core diameter graded-index silica MMF. Core diameter must be higher than standard 62.5 µm and cladding remaining at standard value of 125 µm. So far, we have found two providers : DrakaElite TM (100/125) and Leoni (85/125). The lengths we need is just a few meters.. Unfortunately Draka sells only 2.2 km minimum and is too expensive for our project. Furthermore they have a strict policy to not send samples.. Leoni they don't have it on stock..

So, is there anybody who use these fibers and could sell us a short piece ? Or maybe anyone knows alternative suppliers for that kind of fiber ?

Looking forward to your feedback.

Cheers,

Miguel

What are the expressions for the TM02 mode of an step index optical fiber for Z, r and ϕ components?

I merely fused two ports of the coupler together.

The coupling ratio is 99:1 and the port configuration is as below.

Besides, all the fibers are single mode fibers, no polarization-maintaining property. The whole optical system is placed into a vibration and thermo-isolator.

What can the reason be causing these non-periodic resonant dips?

Hi, I am using double-clad LMA-YDF fiber which has Cladding Absorption 4.80 dB/m near 976 nm. How I can predict the optimum fiber length of the amplifier while my seed signal is 100 mW and pump diode  is 9 W at 976 nm? Please suggest some reference.

At first glance, it seems unnecessary to clearly define the the strong mode coupling and weak mode coupling in few mode fiber? However,  the concepts of strong mode coupling in different publishing works seems have different meaning. In [], the author define the strong mode coupling by using the mode coupling coefficient. The larger of the mode coupling coefficient means the stronger of mode coupling. This definition is intuitionistic and has been widely used for analysis the linearly mode coupling for two mode situation. However, for 3mode or more number of modes, one of mode coupling coefficient is obviously not enough to define the strong mode coupling. In [], the authors define the strong mode coupling according to the length of the so-called correlation length. However, is the correlation length parameter enough for defining the strong mode coupling?

Greetings friends, I've been working on a prototype for our physics laboratory in my school in order that our undergraduate students understand the phenomena of resonant modes in a box. Before adding all the electronic stuff to achieve the goal I decided to make the experiment by myself. I'm using an osciloscope to make the observations and also calculate the modes list using the theoretical equation. the problem is that experimentally I cant see the most part of the modes (I have just identified at least 4 that correspond, and the first peak of high amplitude frequency doesn't even correspond to the first mode). Since this is a prototype I want to ask you If some of you are using some kind of techniques in order to see the bigger quantities of modes, Or an opinion about how should I do My prototype or maybe an test circuit, Any information will be useful. Thanks In advance.

My laser beam is TEM00 mode and has horizontal polarization, and the PM

fiber is panada configuration. I use a collimator with fixed focal length connected to the fiber, this system is also mounted on a rotation mount , so the fiber slow axis can be rotated to match the laser polarization. And a beam walk method with 2 mirrors is taken to get the largest coupling efficiecy. However, the output power often fluctuates. Is there any other methods to handle PM fiber? 

In PL measurement, we get PL intensity vs. wavelength. One generally present PL intensity data in Arbitrary unit. I need to convert that data Number of photons vs. wavelength.

I'm working on an experiment with a microstructured optical fiber (MOF) which was fabricated in our laboratory and has a very high NA. What is an appropriate way to couple light emitted from the output end of MOF into a normal single mode fiber (SMF) ?

< SMF >

NA : 0.13

Core diameter : 9.0 um

< MOF >

Core : Tellurite glass (n = 2.0 @ 1.55 um)

Cladding : Air

Core diameter : 5.0 um

I am trying to get decent power out of a fiber I am coupling to my laser (dynamic range: 100mW) but am having a hard time.  The fiber is 400um multimode, 0.39 NA and is connected to an SMA adapter threaded to a mount whose angle you can adjust.  The fiber post is mounted on a translational stage.  I do not have any convex lenses between the fiber and lens at the moment because my spot size is already very, very small.  But the power that comes out of my fiber when the laser is set to ~60mW is around 1uW... Any tips?

Hi everyone,

I am a student from Coventry University and i am conducting an experiment on tensile and flexural tests for fibre optic embedded in carbon composite material specifically in twill weave bi – directional woven fabric and biaxial  ±45° fibre orientation with different fibre optic coatings (polyimide and acrylate), i would like to seek opinion on few aspects:

Your opinion and advice is much appreciated! 

PMD in a fiber cable increases with time due to weather in the cable. As it increases, the cable becomes less usable until a time it crosses the PMD tolerance of the equipment installed to use the cable hence the cable deteriorates at some rate.  Is the Arrhenius model the best to apply while determining this? are there other models? 

I am doing long term measurements of fiber bragg gratings with an Anritsu MS9740A. The device is calibrated (optical alignment with DFB laser, wavelength calibration with internal light source). The room temperature is stable at 20±0.5°C. This room temperature fluctuation causes fluctuations/ drifts in the detected peak wavelength of ±30 pm. The peak is detected with a algorithm using a quadratic fit over the 300nm. and is highly accurate. Slides 1-4 show the results of a temperature controlled DFB laser (S3FC1550 from thorlabs) and a temperature controlled FBG.

I contacted Anritsu Australia with that issue and they say the equipment is not made for long term measurements and the fluctuation are in spec.

I then compared my MS9740A to another unit of the same model from another group. Both calibrated before measurements. Slide5 shows the results recorded over the last day. The loan OSA has a significantly smaller drift then my OSA. The drift of the loaner is about 10-15pm and similar to the temperature drift, whereas the drift of my OSA is 40 pm and inverse to the temperature drift.

So the questions I have are:

Have you experienced similar stability problems with Anritsu optical spectrum analysers or Anritsu equipment in general? Is that fluctuation normal and acceptable? Is the difference in drift/fluctuation (comparing two identical OSA) normal and acceptable?

The ultimate capacity of single-mode-fiber (SMF) has been shown to be limited by fiber nonlinearities. Space-Division-Multiplexing (SDM) is one of the promising approaches to further increase the capacity of fiber-based transmission system. Several techniques have been proposed on SDM in optical fibers. It would be very nice if someone shares some information about the potential applications of SDM in optical communication. Thanks in advance.

I'm looking for an optically decoupled joystick for an EEG study ... that is, fibre-optic, properly calibrated ... need not be MRI-compatible.

Most scientific joysticks are either electrically wired/tethered, or MRI-compatible (e.g. expensive).

Any suggestion is welcome...

Using spdc as the source of pairs of photons each photon is coupled to a fiber coupler 50/50 at 810 nm. Are the vibrations of the optical table important to improve visibility? What are other factors that may afect, besides temperature?

I have a single-mode optical fibre that allows the 488 nm line to go through it. I know that in the past, the same optical fibre has been used for using other lines.

I have now several blue lines and I need to use the optical fibre to couple it with the scan head of our microscope. If for instance, the optical fibre was able to transport the 488 and 457.9 lines, individually, what would happen if I try to couple both lines at the same time?

By the way, I am only interested in the 488 line but I would be very grateful if any expert on optical fibres could clarify me this doubt.

Many thanks for your help!

1nm bandwidth BPF has been employed in our sysytem. But hardly helps.

Hello Everyone,

  I want to understand the fiber optic cabling process. There are several cables employing optical fiber such as- armoured cables, unarmoured cables for duct appln., drop cable , multi-tube micro cable etc. Could you please suggest me a book which explains the cabling process ?

I am overlapping multiple focused beams (different wavelengths) at the focal plane of the fiber coupling lens. What would be the expected coupling efficiency in this case? Is the there a factor of 1/n in insertion loss, where n is the number of beams?

Yb doped fiber laser of 1kW

H1E1 mode has wavelength greater than cut off wavelength in single mode fiber . if wavelength is greater than  cut off wavelength then energy will be lost in wave guide fiber is also a cylindrical wave guide . please explain

im working about a project about media converter. we have any signal like serial (RS232,RS485) video analog, ethernet wireless, ... . these signals convert to fiber optic by media converter and sending. Receiver can get these signals in denotation. now i want to know in detail how this device denote these signals?

Thanks in advance

hello dear

I am working on Glass simulator ..i have some problems:

1-NIC player ..LSP player .. Queue player ..optical player.. Don’t work . so I can’t see result’s . also I could not get a graph by GMPLS Plotter

2-some examples in GLASS don’t work “like( diffserv_over_mpls_te), (fault_restoration_mpls_net)”

3-I want to write an algorithm but I couldn’t get the source of your algorithms “like best fit, shortestPathDistance, k_algorithm” , how can I get some help to write an algorithm..

Thank you all

In an OFDM-based optical network, how will spectrum overlapping between connections (which are served at their requested transmission rate) affect the Routing, Modulation Level, and Spectrum Allocation (RMLSA) problem?

Can we explain the light guiding principle inside a single mode fiber by ray theory approach like a multimode fiber and how?

Hi all,

I'm modelling the light distribution on tissue surface. My light source would be an LED which its light is collimated via a lens and collimated light is transferred into the tissue using a fiber optic. Now I need to know what is the intensity of light at the tip of the probe (i.e. light exiting the probe and entering the tissue).

Assuming that I know characteristics of the LED how can I obtain light intensity (probably per unit area) hitting the tissue?

Any ideas or suggested reading are greatly appreciated.

In distributed fiber optic sensors to generate a stimulated Brillouin scattering we insert a signal at the other end of the fiber. This signal is commonly continuous. I want to know the reason about being continuous and not pulsed. What about the common OTDR why it is pulsed in that systems?

It is needed for the optical fiber sensor.

As we know,the group velocity dispersion of a fiber mode can be obtained by derivating the propagation constant twice.But if the  the imaginary part of the propagation constant has influence on the dispersion? tahnk you very much.

The resonance wavelengths of both LPFG and FBG are determined by the phase matching condition, i.e.,

lamda_FBG=period*(n_corei+n_corej)

lamda_LPFG=period*(n_corei-n_cladj)

What leads to the quite different full widths at half maximum (FWHM) of their transmission spectra?

What difference zener diode and avalanche diode?

I want to know what's single mode fiber optic transceiver, differences between single mode and multi mode fiber? I want to get clear concepts about the two.

I want to know that what would be the fastest fiber optic network card for a pc ? and does those things offer the actual speed mentioned? any one who uses a fiber optic network card please help me. something similar to this.

I build a Er-Yb codoped fiber laser with two FBG as the cavity mirror and output coupler. The laser output should be continous-wave running in the time domain. But the output is running with random pulse. I want to know how to eliminate this self-pulsing and why there is self-pulsing?

On the basis of literature available on multi-core fiber systems, most of the researchers have fabricated couplers or other devices related to multi-core fiber system architecture. But I am unable to find the way to simulate multi-core fiber systems. Please provide some suggestions.

I noticed green glowing from Er-doped fiber after it has been pumped by 975 nm. This Er-doped fiber used as an active gain medium in ring fiber laser. I need a clear explanation for that.

I want to measure the output power of fiber laser. The output port of fiber coupler was connected to OSA (AQ6370C YOKOGAWA).  The attached file shows the output spectrum. While the power meter reading was about 3 mW. Which reading considered as the real one??

Dear all

I am working on FBG. I connected a simple system includes only FBG and circulator with OSA. Each time I measure the peak of the obtained signal, I obtaine different reading for the peak wavelength. the resolution of osa is 0.01nm. Can anyone explain why this is happens? and its explaination physically please.

Thank you for attention

Explain and give suitable explanation. 

I'm trying to simulate the pulse propagation in HC-PCF using the professor Govind Agrawal's NLSE solver software [attached]. I think this software can't fulfill all the HC-PCF parameters requirements. Thats why I'm not getting the desired output even i'm using the same parameter values from the papers (attached).

Can anyone please help me in this regard ?

For a given optical fiber profile, I can simulate effective index (n_eff) or a given mode as function of wavelength λ. Using numerical differentiation, I can then estimate group index (n_g) or group velocity (v_g). However, if I calculate n_g for the vector modes of a given group (for instance TE_0,1, TM_0,1, and HE_2,1), and if I do the same for the corresponding LP modes (e.g. LP_1,1), the value for n_g I obtain for the LP mode is not the the average of n_g of constituting vector modes. In some cases, I even can obtain a value for LP mode that is lower than each constituting vector modes. Is it normal?

In other words, if I launch a pulse of a LP_1,1 mode in a fiber, and that I measure the time of flight in a long enough fiber, should I see three distinct peaks for each of the constituting vector modes, or should I see only one peak, as if the LP pulse was only one mode? 

Does the simulated n_g value I get for LP modes means anything?

I need to know the minimum length of this fiber to get signal gain

I want to simulate the GI POF channel considering the major parameters such as the mode attenuation, modal and intermodal dispersion, and mode coupling. In addition, please advise the proper method, WKB or SSFM, that can be used to solve this equation ?.Thanks.

Attenuation is basically a signal loss which is happened due to bending of fiber cables and absorption. If it is possible then how? Help me with mathematical equations.

Does anyone know the reason for poor sensitivity and commercial unavailability of Resonant Fiber Optic Gyro (RFOG)?

I am simulating a hexagonal photonic crystal fiber in mode-solution and need to use anisotropic PML. but there is no such an option. can any one guide me?

I am attempting to obtain the fluorescence emission spectra from nanocrystals that I have prepared.  The spectrophotometric equipment utilizes a fiber optic cable (1 meter long) to collect the emitted light and bring it to the spectrophotometer.  This fiber optic cable is of the UV-VIS variety, however, there is a substantial increase in attenuation due to the fiber at wavelengths less than 400 nm (see attached graph from the manufacturer). 

My primary interest is in emissions in the 250-400 nm range.  Is there a way to correct the spectral data to account for the increased attenuation from the fiber at < 400 nm?    

I want to measure the azimuth angle of a elliptically polarized light. Could you give me some suggestions?

I need to simulate the refractive index of GeO2 doped silica as function of wavelength, to be able to predict optical fiber properties such as group index, chromatic dispersion, and dispersion slope. Currently, I'm aware of two different models: one using a linear interpolation of the Sellmeier equation (Fleming1984), and one using Claussius-Mossotti interpolation (Sunak1989). Is it the best currently available model, or is there any more recent advances in that field?

I have simulated a solid core photonic crystal fiber with a pitch of 'P'. Is it necessary to define a PML for it? then, how should set its parameters in Comsol?

I'm using a fiber optic bundle as a 2d displacement sensor to measure a small displacement. The bundle contains 40 000 micro fibers and those fibers are glued inside the bundle but not fused. That leads to a multiple dead zone between fibers. In order to improve the active surface of the bundle, we want to fuse the optical fibers at high temperature ( industrial process) but I want to know before performing this operation how can I estimate the impact of coupling between optical fibers when they are fused at high temperature , knowing that we use a borocylicate fibers with a 50 µm core diameter and a clading of 5µm only.  

How can I get a good fiber end facet? I'm now use a 3SAE LCC-II fiber cleaver to cleave photonic crystal fiber, however it does not work very well, every time I cleave the fiber, I aways see some little damage on the fiber end facet（Some mists and hackles）, which have already affected my experiment! So I want to know is there anyone who also use the same cleaver?And if you have a other good method to get a good fiber end facet such as grinding,you could also tell me how to do it, thank you very much!

If I pull the optical fiber from both ends, the fiber will get stretched. Its diameter is going to shrink, so how would it affect the refractive index of the core of optical fiber and birefringence?

So far I'm not able to find any text or article regarding this situation. If anyone could please guide me, I'd be really thankful.

In optical networks, generally TDM or WDM or Hybrid WDM-TDM is used for multiplexing

Hi all.

I need to couple a maximum light power from a big fiber in small. But i dont know how i can link them without loss more energy.