Patent ID: 8059334

Claim:
A multi-stage optical fiber amplifier system for amplifying an optical signal, the optical fiber amplifier system comprising: a first single-pass optical fiber amplification stage having a first optical fiber with a core doped with a first rare-earth ion and with a first gain spectral profile upon being pumped, the first optical fiber amplification stage being adapted to receive said optical signal; a second single-pass optical fiber amplification stage having a second optical fiber with a core doped with a second rare-earth ion and with a second gain spectral profile upon being pumped, the second optical fiber being optically coupled to the first optical fiber for said optical signal amplified in said first optical fiber to be coupled to the second optical fiber; the optical fiber amplification stages having a continuous wave pump light system having a first continuous wave pump light source optically coupled to the first optical fiber and a second continuous wave pump light source optically coupled to the second optical fiber, so as to store energy in the fibers for a subsequent amplification of the optical signal; and wherein the first and the second rare-earth ion are different, such that the first gain spectral profile and the second gain spectral profile are distinct while overlapping over a wavelength region including the optical signal wavelength so as to reduce energy depletion in the second optical fiber from amplified spontaneous emission when said amplified spontaneous emission generated by the first optical fiber is coupled to the second optical fiber, and with one of the first rare-earth ion and the second rare-earth ion being neodymium and the other one being ytterbium.