HiBi-FLM (High Birefringence Fiber Loop Mirror) temperature sensor and device based on PCF-LPG (Photonic Crystal Fiber-Long Period Grating) differential demodulation

Abstract

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.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, and relates to a high-birefringence optical fiber loop mirror (fiber loop mirrors made of highly birefringent fiber, HiBi-FLM) temperature sensor. Background technique [0002] In scientific research and production, temperature measurement is an important issue. Traditional temperature sensors include thermocouples, thermal resistance temperature sensors, thermistor temperature sensors, semiconductor temperature sensors and so on. Optical fiber based temperature sensor is a new type of sensor. Compared with the traditional temperature sensor, it has the advantages of small size, light weight, easy bending, anti-electromagnetic interference, safety, etc., especially suitable for harsh environments such as flammable, explosive, narrow space, corrosive, and radioactive pollution temperature detection. [0003] Fiber optic sensors can usually detect the measurand by detecting change...

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Problems solved by technology

[0005] The purpose of the present invention is to overcome the problem of low accuracy of the HiBi-FLM sensor demodulation unit in the prior art, and provide a HiBi-FLM temperature sensor based on PCF-LPG differential demodulation. This demodulation scheme can effectively shake the light source and Interference caused by various unstable factors in the sensing system

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