Tutorial.pdf

Lesson 9: Design of a broadband Raman amplifier using
subsystems
Overview
The number of channels deployed in long-haul DWDM systems is rapidly increasing beyond
hundreds of channels over the C-band (1528-1563 nm) and L-band (1575-1610 nm). This
demand for more bandwidth is driving the search for new and more sophisticated fiber amplifiers
that are flattened over a very wide spectral range for maximum bandwidth transmission over the
long haul.
The specifics of the stimulated Raman scattering effect allow for an interesting technique for gainflattening
of broadband Raman amplifiers (Y. Emori, K. Tanaka and S. Namiki, Electron. Lett. 35,
1355, 1999). It requires only a suitable multiple-pump configuration and does not rely on passive
filters, gratings, etc.
Definition of Multi-line source
At an initial stage of the pump system lets set up a group of twelve pump laser diodes having
“Parameterized” signal representations and the following wavelengths and powers:
LD λ [nm] P [mW] LD λ [nm] P [mW]
1 1405.0 322 7 1450.0 122
2 1412.5 311 8 1457.5 113
3 1420.0 311 9 1465.0 110
4 1427.5 346 10 1480.0 127
5 1435.0 115 11 1495.0 126
6 1442.5 92 12 1510.0 219
After that we multiplex their outputs using, for instance, two multiplexers and a 2x1 power
combiner. The channels of the multiplexers should be accordingly adjusted to the
wavelengths of the pumps, as shown for the case of the 8x1 multiplexer:
Figure 87 -Adjusting multiplexer channels
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