Zhengying Li

Delay Calibration Method for Wavelength-Swept Laser-Based FBG Demodulation System

A remote fiber optical sensors network which uses optical fiber to connect the fiber Bragg grating sensors network and demodulation system has been widely applied in the industrial monitoring field. Due to the long distance and hence large delay between the sensing grating and the swept laser, the wavelength of the returned light is different from that of the launching light. Such wavelength mismatch will cause demodulation error. In this letter, we propose a novel autocalibration method. By switching the swept laser between two different scanning rates, the delay-caused error can be estimated and hence compensated. Experimental results show that the wavelength demodulation error can be reduced from over 20 nm to 10 pm only. The method reported here is autoadaptive to different fiber lengths, which leads to much faster response time, and the nonlinearity during wavelength scanning is suppressed, which enables an accuracy as high as 10 pm.

Performance Optimization Design for a High-Speed Weak FBG Interrogation System Based on DFB Laser

A performance optimization design for a high-speed fiber Bragg grating (FBG) interrogation system based on a high-speed distributed feedback (DFB) swept laser is proposed. A time-division-multiplexing sensor network with identical weak FBGs is constituted to realize high-capacity sensing. In order to further improve the multiplexing capacity, a waveform repairing algorithm is designed to extend the dynamic demodulation range of FBG sensors. It is based on the fact that the spectrum of an FBG keeps stable over a long period of time. Compared with the pre-collected spectra, the distorted spectra waveform are identified and repaired. Experimental results show that all the identical weak FBGs are distinguished and demodulated at the speed of 100 kHz with a linearity of above 0.99, and the range of dynamic demodulation is extended by 40%.

Optical Gas Sensor Based on Gas Conjugated Interference Light Source

A high-speed gas-specific approach for gas detection is proposed and experimentally demonstrated. It is based on a conjugated interferometer which transforms the absorption spectrum of the sample gas to a conjugated emission spectrum. By combining such conjugated interferometer with broadband optical gain medium, a comb light source which emits light at gas absorption lines is produced. The absorption of the conjugated interference source is very weak for other types of gases whose absorption lines are typically different, but is relatively strong for the same type of gas used in the conjugated interferometer. A high sensitivity, high speed, and high specificity gas sensor is produced with the conjugated interference source.

Conjugate Interferometer-Based Optical Detection System for Multi-component Gas Sensing

An optical gas detection system for multi-component gas based on gas conjugate interferometer was proposed. The experimental results show that the system can simultaneously detect multi-component gases and has good sensing linearity.