Raman amplification provides an alternative to erbium-doped fiber devices

Raman amplification provides an alternative to erbium-doped fiber devices

According to Tyco Submarine Systems (Holmdel, NJ) researchers, distributed Raman amplifiers offer advantages over erbium-doped fiber amplifiers (EDFAs) because they provide direct optical amplification of the light signal and broad gain bandwidth. Researcher Karsten Rottwitt told the OFC (San Jose, CA) postdeadline audience that Raman amplification offers a potential way around some limitations of EDFA-based wavelength-division-multiplexed systems. He described a simple distributed Raman amplifier with transparency over a 92-nm bandwidth and noise performance similar to current narrow-bandwidth discrete amplifiers. To demonstrate the device, a broadband Raman amplifier was constructed by combining pum¥light at 1453 and 1495 nm. This light was coupled into a 45-km-long dispersion-shifted fiber with a zero-dispersion wavelength at 1588 nm. The pum¥light was launched counterpropagating to the signal light and measured using a pum¥tap. Results obtained within the 1550- to 1620-nm wavelength region lead Rottwitt to expect that a gain-equalized Raman amplifier will perform better than EDFAs with noise figures of 5 dB or higher.