Optical fiber gas sensing method and sensor

Abstract

A optical fiber gas sensor employs a optical fiber Fabry-Perot interferometer constituting a low reflection cavity lens and a measurement optical fiber to detect sound pressure wave signal generated by gas after absorbing light energy, and a realization method for optical acoustic gas sense technique is provided. Pulse modulated excited light is emitted by an excitation light source, passes through a band-pass filter and enters a gas cavity from a gas cavity window; the excited light emitted into the gas cavity generates a sound pressure wave which strength corresponds to measured gas concentration in the gas cavity after absorbing by the measured gas; the sound pressure wave is transmitted to vibration of a vibrating film sheet by the vibrating film sheet which is equipped at other end of the gas cavity; a measuring light signal emitted by measuring light source driven by a first drive power supply passes through a optical fiber wave combination equipment, a transmission optical fiber and a optical fiber wave separation equipment and enters a measuring optical fiber of the Fabry-Perot interferometer; concentration value of the measured gas is obtained by optical path difference of the return light beam and the light beam directly reflected by an optical end face.

Description

technical field [0001] The invention relates to a method and a sensor for photoacoustic gas sensing, in particular to a device and a method for detecting photoacoustic signals by utilizing low-fineness optical fiber Fabry-Perot interference. The invention belongs to the technical field of optical fiber sensing, and is mainly used for sensing and detecting the concentration of gaseous substances. Background technique [0002] Gas detection, especially the detection of flammable, explosive, toxic and harmful gases, is crucial to industrial and agricultural production, people's lives, scientific research and national security. [0003] The use of gas sensors to detect the concentration of gaseous analytes using the photoacoustic effect is well known. For example, the prior art [US Patent No. 4740086] describes the use of photoacoustic gas sensors to convert the light energy of an amplitude-modulated light source into acoustic energy when a gaseous an...

AI Technical Summary

Problems solved by technology

It solves the problems that the existing optical fiber gas sensor has complex system devices, difficult control of the absorption optical path, and relatively large coupling loss of the optical path, including the light source, the optical path of the light guide gas chamber connected to the light source through ordinary optical fibers, optical splitters, and The reference light path of ordinary optical fiber, and the signal conversion part including photodiode and lock-in amplifier arranged at the other end of the light path of the light guide gas chamber and the reference light path are used to provide signals for the external gas concentration monitoring circuit. The light guide gas chamber adopts its Hollow-core photonic crystal fiber with micron-sized air-permeable pores

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