So for this system, in order to realize long distance transmission, the optical fiber dispersion coefficient must be small.
显然，对这种系统，要实现长距离传输，必须采用较低色散系数光纤。
2
While optical fiber Raman laser (RFL) can be a good pump of FRA. The coupling coefficient between FRL and the transmission fiber is very small, so the pump and the amplifier can be compatible easily.