Fiber acoustic sensor has been widely investigated due to its compact size, light weight, and immune to electro-magnetic interference. For the interrogation techniques, edge filtering and phase demodulation are commonly used. Traditional technologies usually require complicated working point control or extra modulators. In addition, the environmental perturbations may also have impact on the sensor head, leading to a cross-effect or signal distorsion.

Professor Ping Lu of the Wuhan National Laboratory for Optoelectronics (WNLO) proposed a novel spectrum interrogation method for fiber acoustic sensor. Due to the dynamic spectrum variation in synchronize with the acoustic signal, a ripple waveform will appear since the intensity of different wavelength is monitored at different time due to the scanning process. The frequency components of the acoustic signal can be analyzed from the ripple spectrum through the wavelength scanning speed. By taking the differential between the ripple waveform and its self-fitted curve, the time domain signal can be obtained. The differential process can eliminate the surrounding factors interference.

This work has been published in Opt. Express Vol.25, No.4, 4429-4437 (2017) in 16, February, titled " Spectrum interrogation of fiber acoustic sensor based on self-fitting and differential method ". This work was supported by the National Natural Science Foundation of China under Grant 61275083 and Grant 61290315.