Raman gain spectrum equalization by using Polarization-diversity Loop Filter

Raman amplifier plays an important role in wavelength division multiplexing (WDM) systems. The drawback of Raman amplifier is that the Raman gain spectrum is flat for very small narrowband. So, it is necessary to equalize the Raman gain spectrum to achieve the desire performance for the WDM systems. This paper has proposed an extrinsic gain equalization technique by using polarization-diversity loop filter. It is found that by using PDLF, an equalize bandwidth of 90nm (1550nm - 1640nm) can be achieved with a gain ripple of 0.5dB.