High-speed / High-capacity Systems

82x10Gbps Dual Band Transmission using Distributed Raman Amplification

Description

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.

Typical Results

The transmission of 82x10Gbps NRZ channels (100 GHz channel spacing) over 1500km of SSMF is considered. The line consists of 10 spans, each comprising 150km 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 Figure 1. The power profile of the WDM signal in the first span is reported in Figure 2.
The eye diagrams of the channels located in the center of the C- and L-bands are reported in Figure 3 for the cases where the nonlinearities are switched off and on in the DCF. The channel power at the span input is set to -6dBm. 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 non-flat gain of the DRA. For optimal operation, the hybrid amplification scheme should be optimized for better control of the channels input power into the DCF.