Michelson interferometric optical-fiber hydrogen sensor based on PM-PCF

Abstract

The invention discloses a Michelson interferometric optical-fiber hydrogen sensor based on a PM-PCF. The Michelson interferometric optical-fiber hydrogen sensor is composed of a broadband laser source, a polarization controller, a first transmission optical fiber, a 3-dB coupler, a second transmission optical fiber, the PM-PCF plated with a Pd / Ag thin film, a third transmission optical fiber, a fourth transmission optical fiber, a spectrograph and a constant-temperature air chamber. Lasers emitted by the broadband laser source pass through the polarization controller, and a linearly-polarized laser beam is obtained and divided by the 3-dB coupler into two same laser beams which enter the PM-PCF plated with the Pd / Ag thin film and the third transmitting optical fiber respectively. As the Pd / Ag thin film absorbs hydrogen, swells and presses an air hole in the PM-PCF, the phase of a transmission mode in a film plating area is changed, and the two laser beams are reflected through the end faces and then gathered at the transmitting end of the 3-dB coupler; as the constant phase difference exists and interference occurs, an interference spectrum is received by the spectrograph. As the corresponding relationship exists between the drifting amount of the interference spectrum and the concentration of the hydrogen, the concentration of the hydrogen is accurately measured. The Michelson interferometric optical-fiber hydrogen sensor is simple in structure, high in sensitivity and small in temperature drifting. A feasible scheme is provided for online monitoring of the concentration of the hydrogen.

Description

technical field [0001] The invention belongs to the technical field of optical fiber hydrogen sensing, in particular to a PM-PCF-based Michelson interference optical fiber hydrogen sensor. Background technique [0002] Hydrogen (H 2 ) has two outstanding advantages of high energy density and non-toxic and harmless combustion products, and is recognized as the most promising secondary energy source in the 21st century. Under the conditions of room temperature and standard atmospheric pressure, the explosive concentration range of hydrogen is very wide (4%~74.2%), the ignition energy is extremely small (0.02mJ), and the strong flammability and explosiveness have great influence on the safety and reliability of the hydrogen detection device itself. And the ability to respond to ultra-low concentrations of hydrogen puts forward higher requirements. [0003] Optical hydrogen sensors, especially optical fiber hydrogen sensors, use light as a medium for hydrogen concentration sen...

AI Technical Summary

Problems solved by technology

The common fiber Bragg grating type hydrogen sensor needs temperature compensation measures to suppress the central wavelength drift caused by the fluctuation of ambient temperature. The detection accuracy is not high and there is a problem of cross sensitivity to temperature.

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