High precision optical fiber grating wave length demodulation system

Abstract

An optical fiber grating wave length demodulation system belongs to the technical field of optical fiber sensing and optical measurement. The demodulation system comprises a broad band light source (1), a tunable filter (2), a 1x2 coupler, a wave length calibration module, a photodetector, a 1xN optical switch (5) and a signal processing system. The inside connection of the wave length calibrationmodule is that: one end of a standard tool filter (6) is connected with an output end of a third 1x2 coupler (11)m the other end of the standard tool filter is connected with a reference grating (10), an input end of the third 1x2 coupler is connected with an output end of a first 1x2 coupler; the other output end of the third 1x2 coupler is connected with a signal processing system (9) by a second photodetector (4) to implement the wave length calibration. The calibration of the reflected optical fiber grating wave length can be implemented rapidly and accurately by the standard tool filterand the reference grating, the signal can be effectively demodulated for high precision. The system also can be used for monitoring temperature and stress and so on physical quantities.

Description

technical field [0001] The invention belongs to the technical fields of optical fiber sensing and optical measurement, and relates to a fiber grating wavelength demodulation system. Especially suitable for high-precision, broadband demodulation, combined measurement of dynamic and static parameters. Background technique [0002] Fiber Bragg grating sensor has the characteristics of high reliability, anti-electromagnetic interference, anti-corrosion, etc. Its wavelength coding characteristics and the advantages of quasi-distributed measurement on a single optical fiber are unmatched by other sensors, and it has broad application prospects. One of the most important obstacles restricting the large-scale practical application of FBG sensors is the demodulation of the wavelength signals of FBG sensors. [0003] In the fiber grating sensing system, the external physical quantity is transmitted by the reflection wavelength of the fiber grating. Therefore, the wavelength demodulat...

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Problems solved by technology

The accuracy of this method is limited by the stability of the light source and external interference, and it requires high stability of the FBG spectrum at the detection end; S.M.Melle et al. proposed the edge filter method in 1992, that is, a filter with a larger line width and higher transmittance The linearly changing filter is convoluted with the reflected light wavelength of the sensor FBG, and the obtained signal is proportional to the position of the FBG peak wavelength, so the FBG wavelength position can be inferred from the signal size. This method requires the edge of the demodulation filter It must be very steep and linear, requiring stable parameters of each component of the system, so it is difficult to design, manufacture and use

In 2004, Jauregui et al. proposed a demodulation method using an inclined chirped grating. The demodulator made by this method is simple in structure and small in size, but the accuracy and signal-to-noise ratio are not high

[0009] There are many fiber grating wavelength demodulation methods, but due to the respective limitations of these technologies, there are not many products put into practical application, and there is no demodulation solution that can simultaneously meet the requirements of high frequency, large bandwidth, combined measurement of dynamic and static parameters and Inexpensive requirements

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