Patent ID: 7253944
Filing Date: 2007-08-07
Classification: H01S,H04B

Abstract:
1. A method for amplifying an optical signal having frequency in a signal frequency range, comprising: introducing said optical signal respectively into at least a first and a second optical path disposed in series with each other, each comprising a Raman-active material having a predetermined Raman shift; introducing into said first optical path a first pump portion, said first pump portion including a first group of pump frequencies between a first minimum pump frequency and a first maximum pump frequency; and introducing into said second optical path a second pump portion, said second pump portion including a second group of pump frequencies between a second minimum pump frequency and a second maximum pump frequency, a whole of said first and second group of pump frequencies extending over a pump frequency range having a width of at least 40% of said Raman shift; at least a portion of said first group of pump frequencies being excluded from said second group of pump frequencies and at least a portion of said second group of pump frequencies being excluded from said first group of pump frequencies; said steps of introducing said first and second pump portions into said first and second optical paths being performed such that a residual of said second pump portion entering into said first optical path has a power lower by at least 10 dB than said first pump portion, and such that a residual of said first pump portion entering into said second optical path has a power lower by at least 10 dB than said second pump portion; said first minimum pump frequency and said first maximum pump frequency differing from each other by at most 70% of said Raman shift; and said second minimum pump frequency and said second maximum pump frequency differing from each other by at most 70% of said Raman shift.