Research On Interrogation Technology In Large Capacity Fiber Bragg Sensring System

Fiber Bragg gratings (FBGS) have been widely applied as the sensing elements, which have a low cost, light weight and high detection sensitivity. To improve the capability and detection precision of the Fiber Bragg sensing system, the novel interrogation technique and detection algorithm based on the tunable ring laser and multiplexing technology are proposed for the multi-channel Fiber Bragg grating sensing system, which can realize the real-time monitoring of 32 channels more than 1,000 FBG sensors. In the scheme, a tunable optical filter controlled by a scanning voltage is used to scan through the working range of FBG spectra and detect the peak wavelength of each FBG sensor in multi-channels. Here, we use the comb filter as multi-wavelength reference instead of the traditional reference grating array. Because the small comb filter isn’t sensitive to the temperature, the factors of temperature drift, nonlinear, and peristalsis can be greatly reduced, the measurement accuracy is greatly improved. Experimental results show that the power of laser source is improved greatly and has a narrow width. With the combination of the numerical simulation and experiment, it is demonstrated that the average precision of interrogation is improved over the working range of 1525-1585 nm. The system can realize the real-time monitoring of 32 channels more than 1,000 FBG sensors. In the experimental system, the reflection spectra of the FBG sensors in the multi-channel FBG system are recorded for 100 times within 1 minute. Moreover, a fast wavelength detection algorithm based on the half-power point is proposed. The present work shows that the algorithm described in this paper can reduce the signal noise ratio (SNR) at the input of the system which influences the precision of interrogation. Compared to other schemes, the interrogation method is greatly improved in the measurement precision, wavelength range, and working reliability. The resolution is 0.1pm and interrogation accuracy is 2pm, which means the strain measurement accuracy is 1μεand the temperature measurement accuracy is 0.1℃.The system of a wide scale and high precision can be well applied to practical engineering applications.