The invention relates to HiBi-FLM (High
Birefringence Fiber Loop Mirror) temperature sensor based on PCF-LPG (
Photonic Crystal Fiber-Long Period
Grating) differential
demodulation. Two ports at one side of a 3dB coupler are respectively and optically connected with a
broadband light source and one end of a PCF-LPG. The two ports at the other side of the 3dB coupler are respectively and optically connected with one end of a panda polarization maintaining
fiber and one end of a
polarization controller. The other end of the panda polarization maintaining
fiber is optically connected with the other end of the
polarization controller. The other end of the PCF-LPG is optically connected with the input end of a
spectrometer. The two output ends of the
spectrometer are respectively and optically connected with one ends of two optical filters, wherein the two optical filters are the same in bandwidth and different in central
wavelength. The central
wavelength of one
optical filter is within the negative
linear region of a PCF-LPG transmission spectrum and is smaller than the
wavelength of a HiBi-FLM
resonance peak. The central wavelength of the other
optical filter is within the positive
linear region of the PCF-LPG transmission spectrum and is greater than the wavelength of the HiBi-FLM
resonance peak. The other ends of the two optical filters are optically connected with a photoelectric converter and a
signal processing unit. The 3dB coupler, the
polarization controller and the panda polarization maintaining
fiber form a HiBi-FLM which is a sensing element. The PCF-LPG, the
spectrometer, the optical filters, the photoelectric converter and the
signal processing unit form a demodulator of the HiBi-FLM sensor. The invention effectively eliminates the jittering of the
light source and the interference caused by various unstable factors of the
sensing system, and greatly improves the
system accuracy.