CASCADED PUMPING SYSTEM FOR DISTRIBUTED RAMAN AMPLIFICATION IN OPTICAL FIBER TELECOMMUNICATION SYSTEMS

摘要

A pumping scheme for distributed Raman amplification (DRA) in optical fiber telecommunication systems is disclosed in which pump energy at the wavelength(s) required for DRA of the transmitted optical signal(s) is developed within the transmission fiber from a primary pump source through a series, n, where n >=1, of Raman conversions resulting from the launch into the fiber of a primary pump source along with low-power seed sources. Alternatively, seed sources can be replaced by reflecting means to return, into the fiber, backward-travelling amplified spontaneous Raman scattered light resulting from high power in the fiber at a wavelength one Raman shift below the desired seed wavelength. The peak Raman gain thus occurs some distance from the primary pump launch terminal and leads to improved amplifier noise performance. Dynamic control of the magnitude and/or the spectral profile of the distributed Raman gain at, or near, a signal launch terminal can also be provided.