Patent ID: 6335820
Filing Date: 2002-01-01
Classification: H01S

Abstract:
A multi-stage optical amplifier, comprising:an optical fiber including a first length of Raman amplifier fiber and a second length of Raman amplifier fiber, the optical fiber configured to be coupled to a signal source that produces at least a signal wavelength &lgr;s and a pump source that produces a pump wavelength &lgr;p, wherein pump wavelength &lgr;p is less than signal wavelength &lgr;s, the first Raman amplifier fiber having an optical noise figure of less than 8 dB and lower noise than the second Raman amplifier fiber, and the second Raman amplifier fiber having a gain level of at least 5 dB; a signal input port coupled to the optical fiber; a signal output port coupled to the optical fiber; a pump input port coupled to the optical fiber; a first lossy member coupled to the optical fiber 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 signal input port and the signal output port.