Abstract

The drive for greater bandwidth from a single optical fibre has brought about the move from single wavelength transmission, to wavelength-division multiplexed (WDM) systems. Erbium doped fibre amplifiers (EDFA) have so far managed to satisfy the demand for bandwidth, giving gain in the C-band (1530–1565 nm) and L-band (1570– 1605 nm). However, the EDFA gain bandwidth is limited by the fluorescence of the erbium ion in the host material, and covers only a small proportion of the full potential bandwidth of silica transmission fibre. It is therefore necessary to employ alternative rare-earth or non-linear amplifiers in order to access this bandwidth. Stimulated Raman scattering is an inelastic process where pump photons are scattered by the vibrational modes of the glass, transferring energy to a lower frequency signal. Raman amplification has the potential to offer gain at any wavelength so long as a suitable pump laser can be found at the appropriate frequency. Multiple pump wavelengths can be used to give a large continuous gain bandwidth, ^1,2 whilst distributed amplification can increase overall system performance.³

© 2002 Optical Society of America