Temperature and strain measurement method based on fiber bragg grating (FBG)and thin-core fiber

Abstract

The invention discloses a temperature and strain measurement method based on a fiber bragg grating (FBG) and a thin-core fiber. The temperature and strain measurement method includes the steps of writing the FBG on the thin-core fiber through a femtosecond laser direct writing method; modulating the FBG through a Mach-Zehnder structure which is formed by welding the FBG written thin-core fiber tomultimode fiber and welding monomode optical fiber to the tail end of the multimode fiber; acquiring variation of temperature and strain and variation matrix of resonant peak strength and wavelength;detecting the wavelength variation delta lambda and the strength variation delta P of the resonant peak of the Mach-Zehnder transmission spectrum of the thin-core fiber through a spectrograph, substituting the values to the variation matrix obtained in the third step, so as to acquire changes of environmental temperature and strain. The Mach-Zehnder transmission spectrum is modulated by FGB, wavelength and strength variation of a certain transmission resonant peak of the Mach-Zehnder transmission spectrum within the linear measurement zone is monitored and measured, and thus, discriminating measurement of temperature and strain can be achieved.

Description

technical field [0001] The invention relates to a method for measuring temperature and strain, in particular to a method for measuring temperature and strain based on fiber Bragg gratings and thin-core optical fibers. Background technique [0002] The research and application of fiber gratings in the field of fiber lasers and fiber optic sensors is very important. It is characterized by the coupling between the core fundamental mode and the cladding mode propagating in the same direction, and there is basically no back-reflected light. It belongs to the transmission-type band-stop filter. . The resonant wavelength and resonant intensity of Fiber Bragg grating (Fiber Bragg grating, FBG) are very sensitive to changes in the external environment, and have a larger temperature sensitivity coefficient, which can be used as a temperature sensor to measure high temperatures of 800°C; , the peak of the transmission spectrum can be tuned by using its sensitive characteristics, and a...

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Problems solved by technology

[0007] In 2006, N. Zhang of Nankai University and others successfully wrote FBG with an intensity of 8dB in SMF-28e silicon germanium fiber by using 800nm ​​femtosecond laser, but its transmission spectrum has only one resonant main peak near the wavelength, and the spectrum is retroreflected Greater loss

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