分布式光纤拉曼放大器在长距离光传输系统中的优化设计

Optimal design of distributed Raman amplifiers employed in long-haul optical transmission systems

同时考虑接收光信噪比(OSNR)及非线性失真影响,对分布式光纤拉曼放大器在长距离光传输系统中的最优抽运方式进行了研究.利用变分法原理获得了在不记双瑞利背散射(DRB)影响时的最优信号功率分布函数———均匀分布,但考虑双瑞利散射影响时则不存在解析的最优分布函数.在分别考虑长、短光纤跨距的情况下,比较了三种具有代表性的分布式光纤拉曼放大方式,即双向二阶拉曼抽运、双向一阶拉曼抽运和拉曼+掺铒光纤放大器混合放大方式的性能.指出通过优化一阶抽运波长以及一阶到二阶抽运功率比,对称结构的双向二阶抽运在绝大部分情况下可以在相同的非线性条件下获得更优的OSNR性能,但当DRB影响非常大时,混合放大结构将具有更好的性能.

The optimization of pumping schemes of distributed Raman amplifiers employed in long-haul optical transmission systems is investigated in detail. Considering the received optical signal to noise ratio （OSNR） as well as nonlinear distortion and the optimal signal power distribution, i .e. uniform distribution, is achieved by using variational method. But the analytical optimal distribution does not exist when taking double Rayleigh baekseattering （DRB） into account. Comparison between three Raman amplification schemes, i.e. bidirectional dual-order, first-order pumping and Raman-plus-Erbium doped fiber amplifier hybrid amplification, is carried out at identical nonlinear phase shifts. The results show that symmetric bidirectional dual-order pumping can achieve the best OSNR performance through appropriate choice of the second-order pump wavelength and second-to-firstorder pump power ratio in most cases for both short- and long-span applications. However, hybrid amplification will be a better choice when the DRB noise is dominant. These results will be helpful for designing long-haul transmission systems.