A modified phase generated carrier (PGC) demodulation algorithm for interferometric sensor is presented in this letter. Compared with the differential-cross-multiplying measure (PGC-DCM algorithm), the effect of light intensity disturbance (LID) is eliminated. Additionally, the harmonic distortion of arctangent measure (PGC-arctan algorithm) is well suppressed. In the experiment, while the simulated LID frequency is settled to 50 Hz, the signal-to-noise of the improved PGC algorithm respectively receives an increase of 10.3 dB and 18.2 dB over PGC-DCM and PGC-Arctan algorithms. The system has a dynamic range of 45.9 dB at 600 Hz by employing the improved PGC demodulation algorithm.
The phase-shifted sensitivity of an interferometer can be enhanced by increasing the group index. In this paper, we experimentally demonstrate a slow light sensor by placing an active fiber Bragg grating (FBG) in one arm of the Michelson’s interferometer. A 25 KHz AC voltage was applied to a piezoelectric (PZT) set nearby the active FBG. Once the wavelength is varied to near the FBG band edge, the maximum phase-shifted amplitude appears, which is about 1.8 rad and is 4 times greater than that when wavelength is near the center of the reflection band. The active FBG is pumped by a 980 nm laser diode, which can help us to stabilize the system works in the slow light regime to obtain the maximum phase shift. It provides a very simple approach to increase the phase-shifted sensitivity, which is likely to have important applications for strain and acoustic sensors.