Application on Demodulation of FBG Sensing Signals using Phase Detection Algorithm of Intake and Exhaust

Fiber Fabry-Perot tunable filter (FFP-TF) based fiber Bragg grating (FBG) demodulation has been widely applied in many areas, in which F-P etalon is commonly used as wavelength reference. The traditional demodulation algorithm requires the whole spectrum data of each cycle to calculate the sensing signal wavelength, seriously affecting the real-time performance. The spectrum of the fiber-optic F-P etalon is a uniform comb spectrum with a typical marker, similar to the engine crankshaft signal. When an engine runs at high speed, the intake and exhaust phase needs to be demodulated as soon as possible. In this paper, a low delay FBG sensing demodulation algorithm is proposed, drawing on the experience of the intake and exhaust phase demodulation algorithm. When the scanning speed is 1k Hz, the delay can be reduced more than ten times (e.g., from 0.1ms to 0.01ms).