Patent ID: 6259555
Filing Date: 2001-07-10
Classification: H04J

Abstract:
An optical communication system for transmitting optical channels between a transmitter and a receiver using wavelength division multiplexing, comprising:a wavelength multiplexer optically coupled to the transmitter for multiplexing individual optical channels;a transmitter power amplifier optically coupled to the wavelength multiplexer for amplifying the multiplexed optical channels;at least one optical line amplifier being optically coupled to the transmitter power amplifier via an optical transmission fiber;a receiver pre-amplifier optically coupled to the at least one line amplifier via another optical transmission fiber; anda wavelength demultiplexer optically coupled to the receiver pre-amplifier for separating the multiplexed optical channels into the individual optical channels for passage to the receiver;said optical communication system characterized in that the at least one optical line amplifier includes:a first stage of a first fiber amplifier for amplifying the multiplexed optical channels;a first band separation filter optically coupled to an output of the first stage for splitting the multiplexed optical channels into a first band of wavelengths and a second band of wavelengths, each of said bands covering a range of at least 6 nm;a second stage of the first fiber amplifier optically coupled to the band separation filter;a second fiber amplifier optically coupled to the band separation filter and having a first wavelength response characteristic for amplifying the first band;an equalizing filter, positioned between the band separation filter and the second amplifier, for equalizing the amplification of signals in the first band;a third fiber amplifier optically coupled to the second stage and having a second wavelength response characteristic, different from the first wavelength response characteristic, for amplifying the second band; anda combiner for multiplexing the first amplified band and the second amplified band back into the multiplexed optical channels.