Patent ID: 8594502

Claim:
A bidirectional optical communications network comprising: an optical transmission fiber for carrying a downstream signal at a first wavelength and a multiplicity of upstream signals at a second, different wavelength, said fiber being characterized by distributed Raman gain over at least an extended portion of the length of said optical fiber, a first terminal optically coupled to an upstream end of said fiber, said first terminal comprising: a first transmitter for generating said downstream signal, a first receiver for detecting said upstream signals, and at least two pump sources comprising a first pump source for generating pump light that counter-propagates with and provides Raman amplification to said upstream signals and a second pump source for generating pump light that co-propagates with and provides Raman amplification to said downstream signal, a multiplicity of second terminals optically coupled to a downstream end of said fiber, each of said second terminals comprising: a second transmitter for generating one of said upstream signals, and a second receiver for detecting a downstream sub-signal, and a passive optical node (i) for splitting said downstream signal into a multiplicity of said downstream sub-signals, wherein each downstream sub-signal propagates at said first wavelength to a separate one of said second terminals and (ii) for combining each of said upstream signals from each of said second terminals onto said fiber for transmission to said first terminal, wherein said downstream signal first wavelength is within the range of approximately 1480-1500 nm, said upstream signal second wavelength is within the range of approximately 1300-1320 nm, said co-propagating pump light has a wavelength within the range of approximately 1415-1435 nm, and said counter-propagating pump light has a wavelength within the range of approximately 1230-1250 mn, the wavelengths of said upstream signal and said co-propagating pump light being chosen so as to reduce depletion of the gain of said upstream signal, and wherein said node further comprises a bandpass filter for filtering out said pump light after it propagates through said fiber, so as to reduce the amount of pump light that enters said second receivers.