Specialty Optical Fibers Handbook

5.5.6 Impairments Affecting Raman Amplification

The advent of Raman amplification has drawn attention to the importance of

FWM effects between the high-power Raman pumps and between the DWDM

signals and high-power Raman pumps. Essentially, it is desirable to place l

0

at a

shorter wavelength than any signal or pump wavelength used in the system. For

example, studies of Raman amplification led to the observation of FWM prod-

ucts between counter-propagating high-power pumps at 1429, 1447, and

1465 nm and C- and L-band signals when l

0

of the Tx fiber is very close to

1500 nm. Significant noise peaks due to FWM were observed near 1528, 1548,

and 1568 nm [35], causing OSNR degradation. These deleterious features did not

appear for a Tx fiber with l

0

< 1405 ...