a)A fiber based Raman amp uses SRS occurring in silica fiber when an intense pump beam propagates through it

b)The incident photon gives up its energy to create another photon of reduced energy and lower frequency

c)This scattered wave is usually referred to as the Stokes wave

3) One advantage of Raman amplifiers is that the signal gain spectrum is largely determined by the position of the pump wavelength. Large bandwidths of about 50nm can be achieved for a single pump wavelength and this can be increased by using multiple pump wavelengths.

4) The noise performance can be very good for these amplifiers especially if backward pump propagation is used inGain Saturation: When the signal power is much larger than the available power from the amplifier we reach the point where the gain has reduced to unity since the output can only be infinitesimally greater than the input.

a) EDFA has revolutionized optical communications

b) All optical and fiber compatible

c) Requires optical pumping at 980 nm or 1480 nm

d) Wide bandwidth, 20 ~ 70 nm

e) High gain, 20 ~ 40 dB

f) High output power   >   200mW

g) Bit rate, modulation format and power are wavelength insensitive

h) Low distortion and low noise (NF < 5dB)

i) Lengths of 10m to 100m

j) Long lifetimes (100 mS)