Zhuoxuan Li

Experimental research of temperature sensor based on twin-core fiber

A low-cost, compact, and lossless temperature sensor based on a twin-core fiber (TCF) is demonstrated and manufactured by splicing two single-mode fibers to the ends of a TCF. The extinction ratio of the comb transmission spectrum is bigger than 15 dB, and the temperature sensitivity of the coupling angle is -0.02 rad/(oC.m) at -30-90 oC and -0.032 rad/(oC.m) at 90-175 oC. Finite element method is used to calculate the supermodes of the TCF, and the result agrees well with the experiment.

Spectra analysis of nonuniform FBG-based acousto-optic modulator by using Fourier mode coupling theory

Fourier mode coupling theory was first employed in the spectral analysis of several nonuniform fiber Bragg grating (FBG)-based acousto-optic modulators (NU-FBG-AOMs) with the effects of Gaussian-apodization (GA), phase shift (PS), and linear chirp (LC). Because of the accuracy and simplicity of the algorithm applied in this model, the modulation performances of these modulators can be acquired effectively and efficiently. Based on the model, the reflected spectra of these modulators were simulated under various acoustic frequencies and acoustically induced strains. The simulation results of the GA-FBG-AOM and PS-FBG-AOM showed that the wavelength spacing between the primary reflection peak and the secondary reflection peak is proportional to the acoustic frequency, and the reflectivity of reflection peaks depends on the acoustically induced strains. But for the LC-FBG-AOM, the wavelength spacing between the neighboring reflection peaks increased linearly and inversely with the acoustic frequency, and the extinction ratio of each peak relates to the acoustically induced strain. These numerical analysis results, which were effectively used in the designs and fabrications of these NU-FBG-AOMs, can broaden the AOM-based application scope and shed light on the performance optimization of optical wavelength-division multiplex system.

CCD fiber Bragg grating sensor demodulation system based on FPGA

A CCD fiber Bragg grating sensor demodulation system based on FPGA is proposed. The system is divided into three units: spectral imaging unit, signal detection unit and signal acquisition and processing unit. The spectral imaging unit uses reflective imaging system, which has few aberration, small size, simple structure and low cost. In the signal detection unit, information of spectrum are accessed by CCD detector, the measurement of spectral line is converted into the measurement of the pixel position of spot, multi point can be simultaneously measured, so the systems reusability, stability and reliability are improved. In the signal acquisition and processing unit, drive circuit and signal acquisition and processing circuit are designed by programmable logic device FPGA, fully use of programmable and high real-time features, simplified system design, improved the systems real-time monitoring capabilities and demodulation speed.

Fabrication of twin-core fiber and its application in all-fiber comb filter

Twin core fibers(TCFs) with different parameters were fabricated and its low loss splicing techniques are studied. The fiber comb filters based on a TCF coupler with an uniform free spectral range and based on a TCF M-Z interferometer with flat passband have been discussed.

Precise method for modifying birefringence of stress-induced high-birefringence fiber

A precise method for modifying the birefringence of stress-induced high-birefringence (Hi-Bi) fiber is demonstrated by side polishing a Panda-type fiber with a maximum polished length of at least 14 cm. The polishing depth is controlled with an accuracy of 0.1 microm by piezoelectric ceramic microdisplacement. The accuracy of the birefringence is of the order of 10(-6). This method allows high-quality Hi-Bi fiber segments to be conveniently implemented with low loss at any desired birefringence between 3.17 x 10(-4) and 7.5 x 10(-5) in our experiment from one stress-induced Hi-Bi fiber and without changing the directions of the stress axes. The finite-element method is used to simulate the procedure, and the numerical results agree with the experiment.