Patent ID: 6624927
Filing Date: 2003-09-23
Classification: H01S

Abstract:
Apparatus for amplifying optical signals in a wavelength-division-multiplexing fiber-optic communications link including optical fiber on which a plurality of channels at different wavelengths are carried, comprising:a first Raman pump that produces pump light for the optical fiber at a first wavelength; a second Raman pump that produces pump light for the optical fiber at a second wavelength, wherein the pump light at the first wavelength propagates in the same direction in the optical fiber as the pump light at the second wavelength, wherein the pump light at the second wavelength is located at a wavelength that is a Stokes shift shorter than at least some of the wavelengths of the channels so that the pump light at the second wavelength produces Raman gain for the channels, and wherein the pump light at the first wavelength is located at a wavelength that is a Stokes shift shorter than the second wavelength so that the pump light at the first wavelength produces Raman gain for the pump light at the second wavelength; an optical monitor that monitors the optical signals on the link; and a control unit that receives information on the monitored optical signals from the optical monitor, wherein the control unit uses the information to control at least the second Raman pump to prevent Raman gain transients in the optical fiber due to fluctuations in the optical signals.