available. Raman amplifiers have the big advantage that the gain is not limited to
any specific spectral band and that amplification works also outside the EDFA C
and L bands. With the availability of high-power 14xx-nm pump laser diodes and
the requirement for ever higher capacity, transmission systems based on Raman
were investigated in detail, and it was demonstrated that record capacity distance
products are achieved with Raman amplification [3].
As a consequence of the Raman process, the requirements on the 14xx-nm
pump diode with respect to power and noise are quite challenging [3], unlike 1480
or 980-nm pump lasers, where the noise is reduced by the long spontaneous
lifetime of the erbium gain. Much progress has been made toward the required ...