光纤水听器200km无中继传输系统噪声研究

Noise Analysis of Repeaterless Long-Haul Fiber-Optic Hydrophone Systems with the Fiber Length Up to 200 km

研究了影响干涉型光纤水听器远程无中继传输系统性能的各种噪声,分析了分布式拉曼光纤放大(DFRA)与掺铒光纤放大(EDFA)混合放大方案对光放大相位噪声抑制的效果,并通过实验得到了与仿真分析一致的结果。研究了相位产生载波(PGC)调制解调对相干双重瑞利散射(DRS)噪声的抑制原理,并对不同距离的DRS噪声抑制效果进行了讨论。远程实验结果表明,PGC技术可使相干DRS噪声降低19dB,混合放大可使光放大噪声降低7.2dB。经噪声综合抑制后,100km传输系统的相位噪声降至-113.2dB(即2.2μrad/Hz1/2),与短程系统噪声基本相当;200km传输后噪声降至-104dB(即6.3μrad/Hz1/2),相比短程系统增加的部分主要为残留的DRS噪声。

The noises affecting the performance of a repeaterless long-i^aul Ilber nyclropnone system are investigated. For the noise due to pre-amplifier, distributed Raman amplifier （DFRA） and erbium-doped fiber amplifier （EDFA） are combined to decrease the noise and the experimental results in noise reduction agree well with the simulated results. The suppression of double-Rayleigh-scattering （DRS） inducing coherent noise by employing the phase generated carrier （PGC） modulation/demodulation technique is demonstrated and the suppression of DRS in systems with different fiber lengths is also discussed. The experimental results show that PGC technique scheme can suppress the DRS noise by 19 dB and the DFRA/EDFA hybrid scheme can decrease the pre-amplifier noise by 7.2 dB. In the end, the phase noise level of a hydrophone system with 100 km long-haul fiber reduces to -113.2 dB （namely 2, 2 9μrad/Hz^1/2）, which is identical to the level of a short-haul system. In the system with 200 km fiber, the noise level decreases to -104 dB （namely 6.3 μrad/Hz^1/2） and the little increase of the noise is mainly due to the DRS which has not been completely suppressed.