-
[show abstract]
[hide abstract]
ABSTRACT: A novel method for dew detection based on photonic crystal fiber (PCF) interferometer that operates in reflection mode is presented in this paper. The fabrication of the sensor head is simple since it only involves cleaving and fusion splicing. The sensor shows good sensitivity to dew formation with a large wavelength peak shift of the interference pattern at the onset of dew formation. The device's response to ambient humidity and temperature are also studied and reported in this paper. From our experiment it is also concluded that by attaching a thermoelectric cooler with temperature feedback, the sensor head demonstrated can be used as a miniature dew point hygrometer.
Journal of Lightwave Technology 05/2012; · 2.78 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The measurement of interaction forces in minimally invasive surgical devices, sensorized with photonic crystal fiber (PCF) sensors, is presented in this paper. Two types of PCF sensors are used: a tapered PCF interferometer and a microhole-collapsed PCF interferometer for the detection of interaction forces generated in surgical devices without the influence of ambient temperature variation. The demonstration devices used for force characterization are a laparoscopic scissor and a standard surgical scissor blade. The force sensitivity of each sensorized blade is examined and compared with fiber Bragg grating (FBG)-sensorized blades. Results show that the PCF-sensorized surgical blades outperform the blades fitted with the FBG sensors during static load measurement.
IEEE transactions on bio-medical engineering 12/2011; 59(2):332-8. · 2.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This paper reports on unique and scalable sensorized medical scissor blades for application in minimally invasive robotic surgery. The blades exploit the strain sensing capabilities of a single fiber Bragg grating (FBG) sensor bonded to the blade surface. This smart sensing structure allows detection of friction and material fracture forces during cutting and subsequently enables accurate estimation of the blade kinetic friction coefficient and fracture toughness values of the material being cut. We present theory on the determination of strain variation along the blade length during combined direct and lateral loading of the blade element during operation. Demonstration of the sensorized instrument is realized on an application specific experimental test-bed employing a commercial interrogation system for signal demodulation. Friction and cutting forces measured using the FBG are validated against load cell force data from the test-bed. Characterization tests showed that the sensorized blade has an unfiltered force sensing resolution of 0.5 N over a 30 N load range. This work demonstrates that a single optical fiber placed onto cutting instrument blades can, in an unobtrusive manner, reliably measure friction forces and material fracture properties during surgical cutting.
Smart Materials and Structures 08/2011; 20(10):105004. · 2.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Reported is an experimental study of a novel fibre heterostructure that utilises multimode interference employing two multimode fibre sections to allow simultaneous measurement of both strain and temperature. By measuring two peak wavelengths, strain and temperature can be determined with a demonstrated sensitivity to strain of 0.35 pm/ in the strain range 0-1556 and a temperature sensitivity of 11.16 pm/°C in the temperature range 10-30°C.
Electronics Letters 07/2011; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have proposed the use of a single bent singlemode -multimode-singlemode (SMS) fiber structure to measure both displacement and temperature simultaneously and independently. Our experimental results show that this sensor has a sensitivity of 5.89 pm/μm for displacement and 11.6 pm/°C for temperature.
IEEE Photonics Technology Letters 02/2011; · 2.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A fiber Bragg grating (FBG)-based strain sensing system for minimally invasive telerobotic cutting applications is presented in this paper. Investigations assume that a scissor blade can be approximated as a uniformly tapered cantilever beam. A replica of the scissor blade is produced and strain characterization has been carried out using an FBG sensor system. Results are validated against measurements obtained using conventional electrical resistance strain gauges. The scissor blade experiences both direct and lateral forces during cutting, hence the system is characterized for a direct load range of 0-30 N and a lateral load range of 0-10 N. The results show a very good linear response for direct loading and some sensitivity to lateral loading. An actual sensorized scissor blade prototype is also characterized and results compared with that of the replica blade. The FBG interrogation system used was a macro-bend fiber filter-based ratiometric system. The use of FBGs together with macro-bend fiber-based interrogation system eliminates the influence of temperature on the sensing system and hence temperature independent strain information from the blade is obtained. The results obtained using the macro-bend fiber filter are compared with that of a commercial interrogation system and found to be in agreement. By implementing an all fiber sensing system based on fiber Bragg gratings and macrobend fiber filter interrogation system, remote operation of telerobotic cutting applications can be made more cost effective while providing a competitive accuracy and resolution solution.
IEEE Sensors Journal 01/2011; · 1.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A photonic crystal fibre interferometer that operates in reflection mode for humidity detection is presented for the first time, which has the advantage that it does not require the use of any hygroscopic material. The fabrication of the sensor head is therefore simple since it only involves cleaving and splicing. The all-silica nature of the device has potential for many applications.
Electronics Letters 10/2010; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A temperature sensor fabricated using a bent singlemode-multimode-singlemode (SMS) fibre structure is presented. Experimental results show, that compared to a sensor based on a straight SMS fibre structure, this temperature sensor has a much higher sensitivity of 31.97 pm/°C over a temperature range from 20 to 80°C, based on the measurement of the mean 3 dB wavelength shift, and offers a resolution of 0.1°C for a temperature range from 45 to 80°C when demodulated by a simple ratiometric interrogation technique.
Electronics Letters 09/2010; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A novel and simple fibre optic microphone (FOM) based on hetero-core fibre structure is presented. A multimode-singlemode fibre structure attached to an aluminium membrane is employed as an acoustic sensor. The sound vibrations are detected by measuring the change of intensity of the transmitted light coupled from a multimode fibre to a singlemode fibre because of the deformation of the splicing section in the multimode-singlemode fibre structure. Experiments are carried out to study the performance of the proposed hetero-core fibre microphone. The results show that the multimode-singlemode (MS) structure based FOM can detect sound signals within the frequency range 300 Hz-20 kHz and shows a good sensitivity especially when sound frequency is below 12 kHz.
Electronics Letters 07/2010; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A singlemode-multimode-singlemode (SMS) fibre structure for temperature measurement that utilises a simple intensity-based interrogation system is proposed. The temperature dependence of the SMS fibre structure utilised as a sensor is investigated numerically and experimentally. It is found that a strong temperature dependence for the SMS fibre structure exists at selected wavelengths. The temperature characteristic at such wavelengths is linear in nature and can be used for temperature measurements. The proposed temperature sensor offers a high resolution and accuracy, and also benefits from a simple configuration and low cost when compared to other fibre-optic temperature sensors.
Electronics Letters 11/2009; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The electronic tunability of ferroelectric liquid crystal filled photonic crystal fibres is demonstrated for the first time. The tunability is obtained in the wavelength range of 1500-1600-nm, with a free spectral range of-20-nm. The electronic tunability is achieved by applying an electric field onto the infiltrated photonic crystal fibre which facilitates the photonic bandgap tuning owing to the microsecond-order switching speeds of ferroelectric liquid crystals. The polarised transmission spectrum shows the behaviour of a tunable notch filter with a change in applied voltage. The results obtained could pave the way for the fabrication of fast tunable all-in-fibre devices in the telecom wavelength range.
Electronics Letters 07/2009; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The temperature dependence of polarization-dependent loss (PDL) for a macro bending standard single-mode fiber (SMF28) is investigated both theoretically and experimentally. The experimental results show an overall agreement with the proposed theoretical model over a temperature range from 0degC to 70degC. An SMF28-based edge filter is used as an example regarding temperature-dependent PDL performance. It is shown that the temperature variations have a significant influence on the polarization dependence of macro bending loss, and further impact on such a fiber bend loss edge filter used in a wavelength measurement application. It is also concluded that by using the proposed models, such a temperature-dependent birefringence can be beneficially predicted in bending fiber sensing applications.
IEEE Photonics Technology Letters 05/2009; · 2.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A low polarization-sensitive all-fiber wavelength measurement system using a twisted macro-bend fiber edge filter together with polarization-insensitive (PI) 3-dB coupler is presented. Eliminating the polarization-dependent loss (PDL) is essential when macro-bending single-mode fiber is utilized as an edge filter. A new bending configuration to eliminate the PDL of a fiber edge filter is proposed in this letter by twisting the fiber by 90deg between two bending sections with equal length. The PDL of this configuration retains a low value even while the bending length is increased to achieve a steeper response for the edge filter. This configuration together with a PI 3-dB coupler makes the system to have very low polarization sensitivity and as a result high wavelength accuracy can be achieved.
IEEE Photonics Technology Letters 10/2008; · 2.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The polarisation-dependent loss (PDL) of a ratiometric wavelength measurement system and its influence on system's accuracy are investigated theoretically and experimentally. The PDL of a ratiometric system and the corresponding power ratio fluctuation is modelled, from which the accuracy of the measured wavelength can be estimated. An all-fibre wavelength measurement system is built to allow comparison of modelled and actual results. The measured ratio variation lies within the estimated limits. The measured wavelength error reaches about 1.41 plusmn 0.09 nm at 1550 nm in the demonstrated example (with an edge filter of average slope 0.22 dB/nm), which indicates the significant influence of PDL on the accuracy of a ratiometric wavelength measurement system.
IET Optoelectronics 05/2008; · 1.03 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This paper presents an investigation on a single-mode-multimode-single-mode fiber structure. A one-way guided-mode propagation analysis for the circular symmetry waveguide is employed to model the light propagation and the approximated formulations are derived and evaluated concerning the accuracy. Phase conjunction of the multimode interference within the fiber structure is revealed. A simple way to predict and analyze the spectral response of the structure is presented through the space to wavelength mapping with the derived approximated formulations. The prediction of spectral response is verified numerically and experimentally.
Journal of Lightwave Technology 04/2008; 26(5):512-519. · 2.78 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An all-fibre temperature sensor is proposed based on a macro-bend singlemode fibre loop using a ratiometric power measurement scheme. The sensor has a linear characteristic with temperature at a fixed wavelength and bend radius. A direct linear relationship between the bend loss of the singlemode fibre and temperature is reported for the first time. By measuring the change in bend loss of the system a change in temperature can be measured assuming the system is calibrated. The proposed sensor has a higher temperature resolution than other conventional fibre-optic sensors and also benefits from simplicity.
Electronics Letters 02/2008; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An optimized all-fiber edge filter is developed, based on a one-turn macrobending bare fiber structure. The discrimination range is 16.32 dB over a wavelength range from 1500 to 1600 nm, which can be employed for wavelength measurement applications. It offers a simpler structure compared to the previously developed macrobending fiber loss edge filters, without an increase in the polarization-dependent loss.
IEEE Photonics Technology Letters 09/2007; · 2.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An integrated polarization beam splitter based on a directional coupler (DC) with an etched slot and filled-in liquid crystal covering layer, which utilizes the birefringence of liquid crystal materials, is proposed. A supermode solution for the DC involving birefringence materials and the corresponding full-vector anisotropic beam propagation method are employed as modeling tools. A numerical design of the proposed structure is presented. Beam propagation behavior along the whole structure involving curved input and output regions and central coupling region is simulated. Simulation result shows an extinction ratio of 25.3 and 41.9 dB for the TE and TM mode, respectively.
IEEE Journal of Selected Topics in Quantum Electronics 12/2006; · 3.78 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Temperature dependence of an edge filter based on singlemode–multimode–singlemode (SMS) fiber structure is investigated numerically and experimentally. The experimental results and numerical results are in good agreement within an operational temperature range from 10 °C to 40 °C. It is found that the thermo-optic coefficient (TOC) has a more significant effect on the temperature dependence of an SMS edge filter compared to the thermal expansion coefficient (TEC). In the ratiometric wavelength measurement using two SMS edge filters, a small temperature variation can induce the ratio variation and in turn the wavelength measurement error. It is found the SMS edge filter’s response to both wavelength and temperature is linear. It is proposed that self-monitoring of temperature can be carried out using an updated ratiometric scheme. Self-monitoring of the temperature reduces temperature induced wavelength error to ±0.7 pm at 1545 nm, regardless of the ambient temperature variation.
Optics Communications 283(7):1291-1295. · 1.49 Impact Factor
