FBG pressure sensor in pressure distribution monitoring of ship

High-performance interrogator with bilateral input MMI-based AWG

Compact fiber Bragg grating (FBG) interrogator is a widely investigated topic in the field of fiber optic sensing. Here we report a dense spectral arrayed waveguide grating (AWG) chip designed for FBG interrogation. By integrating a multimode interference (MMI) coupler with the AWG, bilateral input phase-differential optical signals were achieved at the input port of the AWG. This chip effectively doubles the output channel count without altering the device footprint, while concurrently reducing the channel spacing without modifying the bandwidth and spectral slope of the output spectrum. We further optimized the method for selecting interrogation channels. The results demonstrate that the dynamic range of the interrogation reaches 13.5 nm with an absolute wavelength resolution of 4 pm and an absolute accuracy better than 20 pm.

A Double FBGs Temperature Self-Compensating Displacement Sensor and Its Application in Subway Monitoring

In order to ensure the effective vibration-reduction and vibration-isolation of the steel spring floating plate rail and meet the safe operation requirements of the subway, a Fiber Bragg Grating (FBG) displacement sensor for the deformation monitoring of the subway floating plate is proposed. The sensor adopts double FBGs to realize temperature self-compensation. The elastic ring is used as the elastic conversion structure after the fiber grating is pre-stretched; the two ends are pasted and fixed in the groove in the diameter direction of the ring, which avoids the waveform distortion caused by the full pasting of the fiber grating. The combination of linear bearing and displacement probe rods can increase stability and reduce friction loss so that the sensor has the advantages of high sensitivity and accurate measurement results. The test results and error analysis show that in the range of 0~20 mm, the sensitivity of the sensor is 164.2 pm/mm, the accuracy reaches 0.09% F.S, and the repeatability error and hysteresis error are only 1.86% and 0.99%, respectively. The thermal displacement coupling experiment proves that the sensor has good temperature self-compensation performance. It provides a new technical scheme for the effective monitoring and condition assessment of the built-in steel spring floating plate rail.

PLC-Based Arrayed Waveguide Grating Design for Fiber Bragg Grating Interrogation System

A fiber Bragg grating (FBG) interrogator is a scientific instrument that converts the wavelength change of FBG sensors into readable electrical signals. To achieve miniaturization and integration of FBG interrogator, we designed and fabricated a 36-channel array waveguide grating (AWG) on silica-based planar lightwave circuits (PLC) as a key device in a built FBG interrogation system. It is used to achieve continuous demodulation in C-band, while maintaining high resolution. This AWG has a 1.6 nm channel spacing, 3-dB bandwidth of 1.76 nm, non-adjacent channel crosstalk of -29.76 dB, and insertion loss of 3.46 dB. The dynamic range of the FBG interrogation system we built was tested to be 1522.4-1578.4 nm, with an interrogation resolution of 1 pm and accuracy of less than 1 pm in the dynamic range of 1523.16-1523.2 nm. The test results show that the FBG interrogation technology, based on AWG, can realize FBG wavelengths accurately demodulated, which has high application value in aerospace, deep sea exploration, and environmental monitoring, as well as other fields.