Patent ID: 6954303

Claim:
A multi-stage optical amplifier, comprising: one or more optical fibers comprising a first length of Raman amplifier fiber and a second length of Raman amplifier fiber, the one or more optical fibers configured to be coupled to one or more signal sources producing a plurality of signal wavelengths λ s and one or more pump sources that produce one or more pump wavelengths λ p , wherein the one or more pump wavelengths λ p are less than at least a portion of the plurality of signal wavelengths λ s , wherein the first length of Raman amplifier fiber is configured to introduce an effective optical noise figure to at least a portion of the plurality of signal wavelengths λ s of less than 8 dB and less than an effective optical noise figure introduced by the second length of Raman amplifier fiber, and wherein the second length of Raman amplifier fiber is capable of introducing a gain level to at least some of the plurality of wavelengths λ s of at least 5 dB; a signal input port coupled to the one or more optical fibers; a signal output port coupled to the one or more optical fibers; a pump input port coupled to the one or more optical fibers; a first lossy member coupled to the one or more optical fibers and positioned between the first and second lengths of Raman amplifier fiber, the first lossy member being lossy in at least one direction; and a pump shunt coupled to the one or more optical fibers, wherein at least a portion of the one or more pump wavelengths λ p is coupled between the first length of Raman amplifier fiber and the second length of Raman amplifier fiber.