Papers by Keyword: Bragg Grating

Abstract: A novel demultiplexer based on surface plasmon polaritons with the Bragg structure has been proposed and numerically investigated. The finite difference time domain method with perfectly matched layer absorbing boundary condition is adopted to simulate and study their properties. By introducing Bragg grating structure in the couple area, high extinguish ratio can be achieved. The extinction ratio in 1550nm was 27.5db. Meanwhile, the photonic device can be made in the way of high level of integration, because SPPs has the ability of strongly localizing the signal mode in the area beyond the limit of diffraction. The longitudinal dimension of this demultiplexer was 650nm. The demultiplexer may become a good choice for the design of devices in highly integrated optical circuits.

Abstract: In this paper the possibility of using the novel polymeric photosensitive medium for the fabrication of integrated optics elements was demonstrated. The medium is based on PMMA doped by beta-diketonatoboron difluorides. Planar and strip waveguides with the attenuation losses less than 1.8 dB/cm were fabricated in the layer of the medium. The photoinduced recording of the diffraction grating with the spatial frequency up to 3000 mm^-1 and diffraction efficiency ~5% in such waveguides was demonstrated. The possibility to improve the diffraction efficiency of recorded gratings up to 51% by chemical treatment was demonstrated.

Abstract: The traditional wavelength filter only have one face of grating, the gratings length must be long enough to obtain good filtering result, so the filter device can not be made to a small size. We describe a procedure for rapidly and conveniently prototyping Bragg grating on the three side of the polymer ridge waveguide using holographic interferometry and micro-molding processes. In this experiment, the master of the periodic structure was created on an i-line submicrometer positive photoresist film by a holographic interference using a He-Cd (325nm) laser. A subsequent mold using polydimethylsiloxane (PDMS) polymer was cast against this master and used as a stamp to transfer the grating pattern onto a UV cure epoxy. The technique shows accurate control for the transferring of a gratings period and depth. It can obtain the filtering result with very short grating length which means that it can be made with a small filtering device.

Abstract: In this paper, we proposed a method to fabricate a D-shaped optical fiber of Bragg surface grating filter component by D-shaped fiber polishing along with photolithography、holographic interference lithography technologies and micro-molding process. The optical fiber was side-polished until it reaches the core of fiber. The master Bragg grating was first fabricated on the positive photoresister by using the holography interference lithography, then the patterned resist was used as a mother mold to transfer the pattern onto a hard polydimethylsiloxane (hPDMS)/ polydimethylsiloxane (PDMS) mold. The gratings pattern on hPDMS/PDMS was then transferred onto the UV polymer on the surface of a D-shaped fiber using a UV replication process. The transmission spectra of the resulting gratings were measured, with test results showing the transmission dip of -17dB , and 3-dB-transmission bandwidth of 9nm.

Abstract: A novel fiber Bragg grating vortex flowmeter was designed in this work, where the Bragg grating was enfolded in a cylinder eddy generator. Bragg grating subject to force and the corresponding strain were analyzed. Subsequently, the relationships between grating’s axial strain and flow were developed. In order to improve the flowmeter's resolution, the system was simplified by a mass-spring-damper model, which was used to analyze resonance and choose acrylic glass as cylinder's material. In terms of the resolution of FBG sensor demodulation device and factors of vortex's formation, the measuring range of flowmeter is 1200L/h~5000L/h. The resolution is less than 40L/h with flow exceeding 2000L/h. The damping ratio is not sensitive to the flow when it is less than 2000L/h.

Abstract: A kind of strain measurement system of electromagnetic railguns based on Bragg Grating technology was introduced in this paper. The Bragg grating strain measurement system of electromagnetic railguns was designed. The data processing and the calibration of the measurement system were discussed. The experiments of strain measurement in electromagnetic launch were accomplished. The results show that the Bragg grating strain measurement system can work reliably in strong electromagnetic interference, which satisfied the special demand of anti- electromagnetic interference for the strain measurement system.

Abstract: In this paper, we proposed a method to fabricate a D-shaped optical fiber of Bragg surface grating filter component by D-shaped fiber polishing along with photolithography、holographic interference lithography technologies and micro-molding process. The optical fiber was side-polished until it reaches the core of fiber. The master Bragg grating was first fabricated on the positive photoresister by using the holography interference lithography, then the patterned resist was used as a mother mold to transfer the pattern onto a hard polydimethylsiloxane (hPDMS)/ polydimethylsiloxane (PDMS) mold. The gratings pattern on hPDMS/PDMS was then transferred onto the UV polymer on the surface of a D-shaped fiber using a UV replication process. The transmission spectra of the resulting gratings were measured, with test results showing the transmission dip of -17dB , and 3-dB-transmission bandwidth of 9nm.

Abstract: An electrically controlled optical add-drop multiplexer (OADM) based on silicon on insulator is presented, which possesses 16 tunable add/drop wavelength channel of 100 GHz channel spacing. The OADM is integrated lateral p-i-n diodes with single-mode Mach-Zehnder interferometer filter, which transforms the change of refractive index induced by the plasma dispersion effect into a voltage controlled variation of add/drop wavelength. The 3dB bandwidth of add/drop wavelength is less than 0.8 nm when the etch depth, period, Bragg wavelength and length of Bragg grating are 500 nm, 223 nm, 1548.5 nm and 1000 mm, respectively. When the applied voltage is 1.059~1.2219V, the tunable add/drop wavelength of OADM is between 1547.7 and 1536.5nm. Also, the add/drop wavelength could be controlled precisely by changing the grating period, which can satisfy the requirement of other wavelength range.

Abstract: This paper describes a technique to fabricate instrumented composite cylinders made by the filament winding process and based on the insertion of Bragg grating sensors contained in an optical fiber, so that real time monitoring of the temperature and strain response can be made. The main advantage of this method is that, for the first time, the strain response of the wound layers as a function of time and temperature can be monitored during fabrication without alteration of the composite structure, since the sensor is a filament itself. The sensor data reveals the existence of several phenomena related to the manufacturing process and material response. The results show that during the curing stage of the fabrication of the composite cylinders there is a dimensional contraction without change in temperature which indicates that a material transformation occurs, and also that at the last stage there is a residual compressive strain which may affect the in-service behavior of the composite cylinder.

Abstract: The objective of this work was to study, understand and evaluate the effect of different geometric configurations of carbon plies, in the reflected wavelength spectrum of Bragg grating structure together with the effect of the recoating process of the sensor. The different possibilities depend upon the orientation and location of the optical fibre relative to the composite reinforcement orientation and the presence/absence of recoating. The material stacking sequence and the cure conditions were are also studied and the influence of the different possibilities was considered. The optical spectrum response obtained by the interaction of the optical fibre with the host material is shown.