SOI dispersive-medium-based interrogation system for quasi-distributed weak fiber Bragg gratings

In this paper, a quasi-distributed fiber optic sensing interrogation system based on Silicon-On-Insulator (SOI) dispersive medium is proposed. It is used for the demodulation of weak fiber Bragg gratings (WFBGs). In contrast to the conventional use of tunable lasers or spectrometers, the method proposed in this paper utilizes a SOI chip and relies on its wavelength sensitivity as a dispersive medium to detect WFBGs. Instead of charge coupled device (CCD) sensors, four-channel highspeed InGaAs photodetectors (PDs) are used as receivers to capture rapidly changing scattering pattern information. The implementation relies on a simple table lookup algorithm for processing the scattering data and querying the temperature change. The proposed demodulation system has been experimentally validated in 200 WFBGs with a reflectivity of 0.05%. The experimental results show that the system is able to measure the temperature change with an accuracy of 0.1℃ in the range of 120℃ with a demodulation speed of 24Hz. The system opens up a new way for distributed WFBG sensing with a simple design.