Patent ID: 7692850
Filing Date: 2010-04-06
Classification: H01S,H04B

Abstract:
1. A method comprising: providing an input signal to be optically amplified, the input signal having first and second non-overlapping bands of active wavelengths; amplifying said input signal in a first stage having substantially greater gain in said first band than in said second band; amplifying said input signal in a second stage following said first stage, said second stage having substantially greater gain in said second band than in said first band; amplifying said input signal in a third stage following said second stage, said third stage having substantially greater gain in said first band than in said second band; amplifying said input signal in a fourth stage between said second stage and said third stage, said fourth stage having substantially greater gain in said second band than in said first band; directing first pump light into said first stage and said third stage at wavelengths selected to induce Raman amplification of said first band; directing second pump light in a counter-propagating direction relative to the input signal into the second stage and the fourth stage at wavelengths selected to induce Raman amplification of said second band; and coupling residual second pump light from the second stage into the first stage in a co-propagating direction relative to the input signal.