Abstract: A method and apparatus provides pump energy to an optical fiber located along an optical transmission path. The optical fiber imparts Raman amplification to an optical signal traveling therein when pumped at a pump wavelength. In accordance with the method, a first beam of pump energy is generated at the pump wavelength of the optical signal and a second beam of pump energy at a wavelength one Raman Stokes order below the pump wavelength. The first beam of pump energy is introduced to the optical fiber so that it contrapropagates with respect to the optical signal. The second beam of pump energy is introduced to the optical fiber so that it co-propagates with respect to the optical signal. The second beam of pump energy does not pump the signal (thus minimizing noise) but rather serves to pump the first pump beam by the production of Raman Stokes- shifted light.

Abstract: A method is provided for determining at least one optical transmission parameter for achieving a prescribed operating characteristic of an optical transmission system that includes at least one optical amplifier. The optical transmission parameter to be determined may include, for example, the channel wavelengths that are employed, the channel powers, and/or the spacing between adjacent channels.The method begins by transmitting through the transmission system a plurality of saturating optical wavelengths such that the optical amplifiers operate at a desired operating point within a region of gain compression. A plurality of probe wavelengths are transmitted through the transmission system. The probe wavelengths have a total power insufficient to substantially change the desired operating point of the optical amplifiers. The plurality of probe wavelengths are characterized by at least one optical transmission parameter. Next, an initial operating characteristic of the transmission system is determined.

Abstract: A method and apparatus is provided for providing pump energy to a doped optical fiber located along an optical transmission path. The doped optical fiber imparts amplification to an optical signal when pumped at a pump wavelength. In accordance with the method, pump energy is generated in the transmission fiber by introducing a power at a wavelength one Raman Stokes order below the desired pump wavelength. The pump energy is transmitted along the transmission path such that first order Raman Stokes-shifted light is applied to the doped optical fiber. For example, if the optical fiber is doped with erbium, which has a pump wavelength of about 1485 nm, pump energy is provided at a wavelength of 1390 nm.

Abstract: The disclosed optical fiber communication system comprises a remotely pumped erbium-doped fiber amplifier (EDFA). The pump radiation is de-tuned with respect to wavelength, the wavelength being selected longer than both the optimal wavelengths for pumping the EDFA and for producing Raman gain in the transmission fiber, respectively. Such de-tuning results in improved over-all system performance through reduced multi-path interference. Exemplarily, the pump radiation has wavelength in the range 1490-1510 nm.

Abstract: A Raman amplifier is provided that includes at least a portion of optical fiber in which an optical signal travels. The optical fiber portion may encompass all or part of the optical transmission path of an optical communication system. A pump energy unit is provided that includes first and second pump sources providing pump power at first and second wavelengths, respectively. The first and second wavelengths generate first and second overlapping gain profiles in the optical fiber portion. An optical circulator has a first port receiving the pump power, a second port providing the pump power to the optical fiber and receiving the optical signal, and a third port transmitting the optical signal received from the second port. As a result of this arrangement, a Raman amplifier is provided in which the bandwidth is substantially increased over the bandwidth that can be achieved by the previously mentioned Raman amplifier.