Low coherence multiplex optical fiber interferometer based on non-balanced Mach-Zehnder optical autocorrelator

Abstract

The invention provides a low coherence multiplex optical fiber interferometer based on a non-balanced Mach-Zehnder optical autocorrelator. The optical fiber interferometer is formed by successively connecting a wide-spectrum light source (1), the non-balanced Mach-Zehnder optical autocorrelator (2), an optical distance autocorrelation detection unit (3), a transmission optical fiber (4) and an optical fiber sensor array (5) from end to end, wherein the non-balanced Mach-Zehnder optical autocorrelator (2) is composed of a first optical fiber coupler (21), a three-port optical circulator (23), an optical fiber collimator (24), a moveable optical reflector (25) and a second optical fiber coupler (26); and the optical distance autocorrelation detection unit (3) is composed of a three-port optical circulator (31) or (33), a photodetector (32) or (34). The optical fiber interferometer can be applied to the fields such as real-time monitoring and measurement of multipoint strain or temperature and other physical quantities, monitoring of large-sized intelligent structures and the like.

Description

technical field [0001] The invention belongs to the field of optical fiber technology, and in particular relates to a low-coherence multiplexing optical fiber interferometer based on a Mach-Zehnder optical autocorrelator. Too low and increase system stability and other issues. 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 b...

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 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 a secondary (or multiple) optical path matching relationship in the white light interference signal. Second) the optical path matching noise makes the sensor autocorrelation peak no longer unique in the spatial position, which makes it difficult to identify and measure the sensor; thirdly, there is symmetry in the optical path topology, and the light source and the detector are symmetrical in the optical path. Reciprocal, theoretically 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 sensitive to feedback, but the excessive signal Power feedback will cause the resonance of the light source (such as the light source ASE based on the fiber spontaneous super-radiation type, etc.), which will lead to a reduction in the power of the light signal generated by the light source, especially in the case of white light interference, large interference signal power fluctuations will affect the use of the light source It will cause extremely adverse effects and reduce the measurement accuracy of the optical self-coherence peak amplitude

Images