Imbalanced-Mach-Zehnder-based demodulation device for multiplexing optical fiber interferometer

Abstract

The invention provides an imbalanced-Mach-Zehnder-based demodulation device for a multiplexing optical fiber interferometer. The device consists of a broadband light source, an optical circulator, an optical divider, a sensor array switching and transmitting optical fiber, an optical fiber sensor array, an imbalanced-Mach-Zehnder optical autocorrelator and an interference signal detecting unit inconnection, wherein the imbalanced-Mach-Zehnder interferometer forms an optical path correlator, narrow linewidth laser complexed in the correlator evaluates scanning amplitude and uniformity of the optical path, the optical path scanning error is compensated, and the measuring accuracy of the sensor is improved; the interference beating noise of the interferometer can be reduced, and multiplexing number of interferometers is improved; the optical autocorrelator demodulates signals of a multiplexing optical fiber sensor; and the unique optical path matching condition suppresses interference noise of secondary optical path matching. The device can be applied in the fields of real-time monitoring and measuring of multi-point stress or temperature and other physical quantities, monitoring oflarge-scale intelligent structures and the like.

Description

technical field [0001] The invention relates to a demodulation device of an optical fiber interferometer, in particular to a demodulation device of a multiplexing optical fiber interferometer based on an unbalanced Mach-Zehnder optical autocorrelator. Background technique [0002] Fiber-optic interferometers driven by low-coherence, broadband light sources such as light-emitting diodes (LEDs), superspontaneous emission sources (ASEs) or superluminescent laser diodes (SLDs) are often referred to as white-light fiber interferometers. The structure of a typical fiber optic white light interferometer is as follows: figure 1 As shown, the Michelson-type interferometer built by single-mode optical fiber uses a wide-spectrum light source LED or ASE as the light source, and realizes the measurement of the physical quantity to be measured through the white light interference fringes detected by the detector. Its working principle is as follows, after the broadband light emitted by t...

AI Technical Summary

Problems solved by technology

Due to the light-splitting characteristics and optical path symmetry characteristics of the N×M fiber coupler, the above-mentioned optical autocorrelators have three problems without exception: one is that the optical path topology has a large attenuation of the light source power and low light source utilization

Taking the 2×2 fiber optic coupler as an example, only half of the optical signal generated by the light source reaches the sensor array, and half of the optical signal reflected by it is attenuated, so that image 3 As far as the light path structure disclosed by W.V.Sorin is concerned, theoretically at most only 1 / 4 of the light source power participates in the optical correlation process, and other power is attenuated. If a 3×3 or 4×4 fiber coupler is used, its Power attenuation is (1 / 3) 2 or (1 / 4) 2 , it is even more serious; the second is certain optical path structures, the optical signal passes through the optical path autocorrelator twice (or multiple times) before and after, such as: Chinese patent application No. The technical solution in the patent document of the network sensing demodulation device (Chinese patent application number: 200810136821.2) makes the optical signal correlation between the optical fiber sensor and the optical path autocorrelator have more than two optical path matching relationships, resulting in white light interference signal There are secondary (or multiple) optical path matching noises in the sensor, which makes the sensor autocorrelation peak no longer unique in the spatial position, which makes it difficult to identify and measure the sensor; the third is the symmetry in the optical path topology, the light source and the detection The detector is symmetrical and reciprocal in the optical path. In theory, at least the optical signal with the same value as the received power of the detector is fed back to the light source. Although the type of light source is wide-spectrum light, compared with the laser light source, it is not very good for feedback. Sensitive, but excessive signal power feedback will cause the resonance of the light source (such as the light source ASE based on the fiber spontaneous superradiation type, etc.), which will lead to a reduction in the power of the optical signal of the light source, especially in the case of white light interference, large interference Signal power fluctuations will have extremely adverse effects on the use of light sources and reduce the measurement accuracy of optical self-coherence peak amplitude

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