Combined C- and L-band transmission can be achieved by making use of the wide
gain spectrum provided by Raman amplification. Besides broadband amplification, distributed Raman
amplifiers (DRA) also offer enhanced noise characteristics compared to Erbium-Doped Fiber Amplifiers
(EDFA), and enable a better control of fiber nonlinearities through a reduction of power variations
in the transmission fiber.
The transmission of 82x10-Gbps NRZ channels (100 GHz channel spacing) over 1500 km
of SSMF is considered. The line consists of 10 spans, each comprising 150 km SSMF and a hybrid EDFA/DRA
dispersion compensating module. This module contains two pump lasers to perform DRA in the C- and
L-bands and two dispersion compensation fibers (DCF) adjusted for the C- and L-bands. Additional
amplification is realized with two EDFAs. Two optical filters are used to flatten the response of
the combined DR and EDF amplification. The setup of the investigated system is displayed in
. The power
profile of the WDM signal in the first span is reported in
The eye diagrams of the channels located in the center of the C- and L-bands are reported in
for the cases
where the nonlinearities are switched off and on in the DCF. The channel power at the span input is set
to -6 dBm. We can observe that the L-band channel is more affected by fiber nonlinearities than the
C-band channel. This is due to the particularly large input power of this channel into the DCF
resulting from the nonflat gain of the DRA. For optimal operation, the hybrid amplification scheme
should be optimized for a better control of the channels input power into the DCF.
Keywords: High-capacity, Dense Wavelength Division Multipexing (DWDM), C-band, L-band, Distributed Raman Amplification (DRA), Nonlinear effects
Similar demonstrations are available in VPItransmissionMaker Optical Systems and on the VPIphotonics Forum.