Optical fiber hydrophone array structure based on compensation interference

Abstract

The invention discloses an optical fiber hydrophone array structure based on compensation interference. The structure comprises a signal input end which is used for inputting a pulse signal, a compensation interference assembly which has an unbalanced arm difference and is used for converting the pulse signal into a delayed pulse signal pair and outputting the delayed pulse signal pair, an opticalring assembly used for transmitting the pulse signal pair, a time division multiplexing array assembly which has a time division multiplexing array and is used for splitting and delaying the pulse signal pair, combining delay signals after sensing signals are obtained, and transmitting time division multiplexing interference pulse signals with the sensing signals to a second port of the optical ring assembly from an input / output port, and a signal output end used for outputting the time division multiplexing interference pulse signals with the sensing signals. According to the optical fiber hydrophone array structure, the comprehensive performance of a large-scale optical fiber hydrophone remote transmission array can be greatly improved, and the application requirements of related fieldssuch as optical fiber hydrophone seabed shore-based fixed arrays are met by the large-scale optical fiber hydrophone remote transmission array.

Description

technical field [0001] The invention relates to the technical field of optical fiber hydrophones, in particular to an array structure of optical fiber hydrophones based on compensation interference. Background technique [0002] Optical fiber hydrophone is a fiber optic sensor based on optical fiber and photoelectric technology, which uses sound waves to detect, locate and identify underwater acoustic targets. Optical fiber hydrophones have the advantages of small size and light weight, and can easily form various underwater optical fiber sensing networks, providing an ideal technical approach for solving problems related to marine development strategies such as underwater acoustic detection and oil exploration. Typical applications of fiber optic hydrophones include submarine shore-based fixed arrays, towed arrays, and snorkeling buoys. Among them, shore-based arrays have the advantages of stable formation, long-term continuous duty, and low self-noise away from ships, whic...

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Problems solved by technology

[0004] (2) In terms of long-distance transmission technology of fiber optic hydrophones, with the increase of the transmission distance of analog optical signals, it is also accompanied by coherent Rayleigh scattering noise (Rayleigh), stimulated Brillouin scattering (stimulated Brillouin scattering, SBS), four-wave The intensification of linear and nonlinear noise such as frequency mixing (Four-Wave Mixing, FWM) affects the weak acoustic signal detection capability of fiber optic hydrophones

[0008] 1. In the equi-arm compensation interference structure using heterodyne demodulation, the round-trip length of the array delay fiber length is equal to the arm difference of the horse-increasing compensation interferometer, that is, the interference delay after compensation Δτ=0, resulting in Δf 2 ×Δτ≡0, unable to satisfy the phase modulation scheme Δf 2 ×Δτ=k (k is a positive integer) requirements

Therefore, the suppression of SBS noise in remote transmission can only be achieved by controlling the optical power injected into the remote fiber below the SBS threshold.

Compared with the phase modulation stimulated Brillouin scattering suppression scheme, the total optical power budget of the system will be reduced by more than 10dB, and the long-distance transmission distance and array scale are greatly limited

[0009] 2. The equi-arm compensation interference structure of heterodyne demodulation introduces a fixed frequency difference Δf into the two beams of interference light field, and extracts signals of related frequencies to demodulate the phase information of the hydrophone. The heterodyne demodulation scheme Does not have the ability to suppress noise

However, the disadvantage of this solution is that each probe of the array is an independent Michelson interferometer, and the number of couplers, optical fibers, mirrors, and fusion points used in the time-division multiplexing array is 2 to 3 times that of the compensation interference structure.

Therefore, in the actual production process of large-scale arrays, the independent probe scheme greatly increases the complexity of the process compared with the compensation interference scheme, and also increases the optical loss and cost of the array, which has obvious disadvantages

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