Dispersive Raman Amplifier

Distributed Raman amplification within a dispersion compensating fiber (DCF) is useful for  long-haul optical communication links. DCF has Raman gain peak ten times greater than that of a normal single mode fiber, due to its small effective core size.  Below picture shows two DCFs with four pumps around 1480nm and a Faraday mirror (FM) to achieve the double pass Raman amplification.

A major advantage of DRA is its ability to maintain a constant signal power level throughout the dispersive element, and this important property maximizes the signal-to-noise-and distortion ratio by keeping the signal power away from low power, noisy,  and high power, nonlinear,  regimes, typically by the discrete amplifier such as EDFAs.*

*Jason Chou, Daniel R. Solli, and Baharm Jalali, Applied Physics Letters, 92, 111102 (2008)