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提出了在光纤水听器时分复用系统中采用3×3耦合器解调信号的一种新算法。在该方案中,光纤水听器仍为2×2耦合器结构,3×3耦合器作为匹配干涉仪,利用其三路输出的线性组合和数字反正切技术实现信号解调,解调中使用的参数通过奇异值分解和椭圆拟合得到。该方案不需要载波调制,可实现光纤水听器近似等臂干涉,有利于抑制系统相位噪声。算法的运算量小且适用于一般的非对称3×3耦合器,解调的动态范围很大。最终利用该方案实现了两路光纤水听器时分复用的实验系统,在1 kHz时,系统的噪声本底为31μrad/Hz,动态范围超过125 dB,串扰小于64 dB。
A new algorithm of demodulating signal using 3 × 3 couplers in fiber hydrophone TDM system is proposed. In this scheme, the fiber optic hydrophone still has a 2 × 2 coupler structure, and the 3 × 3 coupler acts as a matching interferometer. The signal is demodulated using the linear combination of the three outputs and the digital arctangent technique The parameters are obtained by singular value decomposition and ellipse fitting. The scheme does not require carrier modulation and can achieve approximate isobaric interference of the fiber hydrophone, which is beneficial for suppressing system phase noise. The algorithm is computationally intensive and suitable for the general asymmetric 3 × 3 coupler, the demodulation has a large dynamic range. Finally, the scheme is used to realize the experimental system of time division multiplexing for two fiber hydrophone. The system noise floor is 31μrad / Hz at 1 kHz, the dynamic range is over 125 dB and the crosstalk is less than 64 dB.