Patent ID: 7876498

Claim:
A method comprising: providing a first gain fiber; optically pumping the first gain fiber using pump light; amplifying seed-signal light pulses having a signal wavelength using the first gain fiber to obtain amplified light pulses; automatically limiting a gain of the first gain fiber by outputting light at non-signal wavelengths; providing at least a second gain fiber; coupling output light of the first gain fiber, including the amplified light pulses of the signal wavelength, into the second gain fiber; optically pumping the second gain fiber using pump light; further amplifying the output light of the first gain fiber using the second gain fiber to obtain further-amplified output light; automatically limiting a gain of the second gain fiber by outputting, from the second gain fiber, light at non-signal wavelengths; and filtering the output light of the second gain fiber to reject the light at the non-signal wavelengths from the output light of the second gain fiber in order to provide filtered further-amplified output light pulses at the signal wavelength.