Implementation of a distributed temperature sensor utilising a chirped Moiré fibre Bragg grating

A distributed temperature sensor is presented which uses a chirped Moiré fibre Bragg grating to give a thermal resolution of 0.2 °C with a spatial resolution of 164 μm. The wavelength sensitivity of the device is 0.01 ± 4 × 10−4 nm/°C. Such a sensor has biomedical and industrial applications where accurate measurement of location and intensity of temperature is essential. The sensor may be used as a one- or two-dimensional temperature monitor, depending on the configuration.

Implementation of a distributed temperature sensor utilising a chirped Moiré fibre Bragg grating

A distributed temperature sensor is presented which uses a chirped Moiré fibre Bragg grating to give a thermal resolution of 0.2°C with a spatial resolution of 164 μm. The wavelength sensitivity of the device is 0.01 ± 4 × 10-4 nm/°C. Such a sensor has biomedical and industrial applications where accurate measurement of location and intensity of temperature is essential. The sensor may be used as a one- or two-dimensional temperature monitor, depending on the configuration. © 2004 Elsevier B.V. All rights reserved.

Quadratic behavior of fiber Bragg grating temperature coefficients

We describe the characterization of the temperature and strain responses of fiber Bragg grating sensors by use of an interferometric interrogation technique to provide an absolute measurement of the grating wavelength. The fiber Bragg grating temperature response was found to be nonlinear over the temperature range -70°C to 80°C. The nonlinearity was observed to be a quadratic function of temperature, arising from the linear dependence on temperature of the thermo-optic coefficient of silica glass over this range, and is in good agreement with a theoretical model.

Tunable and multiple-wavelengths/temporal output from gain-switched diode laser and a four Bragg-grating fiber

The spectral narrowing and selective tuning of picosecond pulse outputs from gain-switched diode laser and a four Bragg-grating fiber, were investigated. The fiber used under investigation was designed to provide spectral narrowing and multiple wavelength/temporal output. The maximum transmission out of each of the four output fibers was ∼7.5 mW, for a current of 180 mA. The results show that an output of any combination of multiple wavelengths is only produced at modulation frequencies which satisfy resonant conditions for all cavity arms simultaneously.

Experimental demonstration of an optical differentiator based on a fiber Bragg grating in transmission

We report the first experimental demonstration of single transmissive fiber Bragg grating implementation of a first-order optical differentiation. The device has been designed and fabricated, and the experimental results show a good performance over an operational bandwidth of ∼2 nm. © 2013 Optical Society of America.

Virtual delay line interferometer by a transmissive phase-modulated fiber Bragg grating

A novel approach based on transmissive phase-modulated fiber Bragg grating (FBG) to implement a virtual delay line interferometer (DLI) is proposed, designed, numerically simulated and fabricated. The resulting devices provide the functionality of a Mach-Zehnder interferometer (MZI), or equivalently a Michelson-Morley interferometer (MMI).

Fiber Bragg grating Fabry-Perot structures under loading and their applications in switchable multi-wavelength lasers

Characteristics of fiber Bragg grating based Fabry-Perot (FBG-FP) structures under transversal loading are investigated. A novel switchable multi-wavelength fiber laser employing loaded FBG-FP is also demonstrated. © 2012 OSA.

Simple design of nonuniform fiber Bragg grating with sharp reflection

In this paper we consider the possibility of using intermediate solutions, in which ideal apodisation profile for a dispersion-free, sharp-reflection profile fibre Bragg grating approximated in different degrees. The ideal apodisation profile for a flat dispersion, 50 GHz bandwidth grating was obtained using the layer-peeling algorithm. To verify the modelled results a version of the 5-section grating has been manufactured with excellent agreement between the model and the experimental results. The performance penalty due to multiple reflections from the FBGs in different situations was studied. The results showed that in the approximated gratings some post-compensation must be included to account for the local deviations from zero dispersion. © 2003 IEEE.

Sensing applications of arrayed waveguide grating devices

Progress in optical fibre sensor research has often been achieved by taking advantage of components developed for use in telecommunications, where the greater existing market is able to support the rapid commercialisation of novel devices. In the last few years there has been considerable interest in the telecommunications community in deploying arrayed waveguide gratings (AWGs) produced in a range of technologies in a variety of roles. We feel it is therefore surprising that there have been very few reports of research into using AWGs for sensing. In this paper we consider some possible roles for these devices in interrogation systems for interferometric and fibre Bragg grating (FBG) sensors.

Suppression of cladding-mode coupling loss in Bragg grating using standard single-mode fiber

We present a technique for suppressing cladding-mode coupling loss in fiber Bragg grating fabrication. Suppression of cladding-modes down to 0.2 dB in a Bragg grating of 18dB reflectivity has been achieved in hydrogen-loaded standard single-mode fiber.

Rectangular pulse generation based on pulse reshaping using a superstructured fiber Bragg grating

In this paper, we present a technique for the shaping of short pulses based on the use of superstructured fiber Bragg gratings (SSFBGs), We apply this technique to demonstrate the generation of 20-ps rectangular pulses by phase and amplitude profiling of 2.5-ps soliton pulses. Numerical calculations validate our experimental findings.

Highly sensitive liquid level monitoring system utilizing polymer fiber Bragg gratings

A novel and highly sensitive liquid level sensor based on a polymer optical fiber Bragg grating (POFBG) is experimentally demonstrated. Two different configurations are studied and both configurations show the potential to interrogate liquid level by measuring the strain induced in a POFBG embedded in a silicone rubber diaphragm, which deforms due to hydrostatic pressure variations. The sensor exhibits a highly linear response over the sensing range and a good repeatability. For comparison, a similar sensor using a FBG inscribed in silica fiber is fabricated, which displays a sensitivity that is a factor of 5 smaller than the POFBG. The temperature sensitivity is studied and a novel multi-sensor arrangement proposed which has the potential to provide level readings independent of temperature and the liquid density.

Chromatic dispersion effect in a microwave photonic filter using superstructured fiber Bragg grating and dispersive fiber

In this paper a microwave photonic filter using superstructured fiber Bragg grating and dispersive fiber is investigated. A theoretical model to describe the transfer function of the filter taking into consideration the spectral width of light source is established. Experiments are carried out to verify the theoretical analysis. Both theoretical and experimental results indicate that due to chromatic dispersion the source spectral width introduces an additional power penalty to the microwave photonic response of the filter. © 2005 Optical Society of America.

Time-dependent variation of fiber Bragg grating reflectivity in PMMA-based polymer optical fibers

In this paper we investigate the effects of viscoelasticity on both the strength and resonance wavelength of two fibre Bragg gratings (FBGs) inscribed in microstructured polymer optical fibre (mPOF) made of undoped PMMA. Both FBGs were inscribed under a strain of 1% in order to increase the material photosensitivity. After the inscription the strain was released and the FBGs spectra were monitored. We initially observed a decrease of the reflection down to zero after which it began to increase. After that, strain tests were carried out to confirm the results and finally the gratings were monitored for a further 120 days, with a stable reflection response being observed beyond 50 days.