A pump source for broadband amplification of a wavelength-division
multiplexed signal transmitted via an optical fiber having a number of
low-power pump lasers, whose input signal power levels are increased in a
conversion fiber. One or more high-power lasers such as Raman cascade
lasers on the one hand, and one or more monomode laser diodes with a low
output power, on the other hand, are used as the pump lasers. Pump signals
from the monomode laser diodes are subjected to Raman amplification in the
conversion fiber before providing broadband amplification of the WDM
signal in the transmission fiber by stimulated Raman scatter. The powers
required for the amplified pump signals at the output of the conversion
fiber are achieved by respective pump power increases in the pump signals
of the monomode laser diodes, and by using monomode laser diodes with
different output powers, as well as via a corresponding arrangement of the
input coupling of the output signals of the pump lasers into the
conversion fiber.
