Abstract: An optical coupler system is described. The optical coupler system is for coupling radiation from a plurality of radiation sources. The optical coupler system comprises a first optical coupler having at least a first and a second input and a first and a second output. The optical coupler also comprises a second optical coupler having at least a first and a second input and a first and a second output, wherein the first and second outputs of the first optical coupler are connected to the first and second inputs, respectively, of the second optical coupler via first and second optical links, and wherein the first and second links provide different optical paths between the first and second optical couplers such that portions of radiation energy that is input to the first input of the first optical coupler are combined incoherently at the first output of said second optical coupler.

Abstract: A system and method of providing a transmission span that compensates for signal attenuation, dispersion, and nonlinearity of an optical signal communicated between two line units of a transmission link includes dividing the transmission span into a plurality of fiber segments and selecting a particular fiber for each of the segments. The fiber selection and arrangement of fibers within the span can be selected in accordance with the nonlinearity, dispersion conditions, and distributed gain conditions of the constituent fibers. In a three segment map, the first segment can provide low non linearity, the third segment can provide distributed gain, and the second segment can compensate for the dispersion of the first and third segments. The span can be used, e.g., for distributed Raman amplification. The span can alternatively include a two segment map, a four segment map, or a map with additional segments.

Abstract: A system for reducing gain ripple of an optical system that includes a set of spans further includes a multiplexing unit and an optical filter. The multiplexing unit multiplexes a plurality of optical signals. The optical filter filters the multiplexed optical signals, prior to transmission of the multiplexed signals over the spans of the optical system, to reduce gain ripple.

Abstract: An optical amplifier. The amplifier includes a plurality of pump radiation sources, each pump radiation source adapted to produce radiation having a set of pump wavelengths and pump powers corresponding to the respective pump wavelengths, wherein at least one set is different from at least one other set. The amplifier also includes a plurality of pump radiation combiners and a coupler. The coupler is optically coupled to the outputs of the pump radiation combiners, receives the coupled radiation from the pump radiation combiners and outputs pump radiation profiles to respective coupler outputs. The amplifier also includes pump-signal combiners, each optically coupled to a respective coupler output of the coupler outputs, which are adapted to couple an optical signal with the respective pump radiation profiles.

Abstract: A method and system for equalizing Q performance of a wideband, Raman-amplified optical communication system are disclosed. Wideband, Raman-amplifed systems suffer significant performance degradation from nonlinear effects in shorter wavelength channels. Absent compensation, the shorter wavelength channels limit system performance and restrict the amount of launch power that can be employed for the optical data signals in each wave division multiplexed channel. Careful design that employs increased channel spacing in the nonlinear region of the bandwidth can offset the increased nonlinear effects, thereby improving the worst channel's Q performance and permitting high launch power without unacceptable Q performance.

Abstract: An optical coupler system is described. The optical coupler system is for coupling radiation from a plurality of radiation sources. The optical coupler system comprises a first optical coupler having at least a first and a second input and a first and a second output. The optical coupler also comprises a second optical coupler having at least a first and a second input and a first and a second output, wherein the first and second outputs of the first optical coupler are connected to the first and second inputs, respectively, of the second optical coupler via first and second optical links, and wherein the first and second links provide different optical paths between the first and second optical couplers such that portions of radiation energy that is input to the first input of the first optical coupler are combined incoherently at the first output of said second optical coupler.

Abstract: A method and system for equalizing Q performance of a wideband, Raman-amplified optical communication system are disclosed. Wideband, Raman-amplifed systems suffer significant performance degradation from nonlinear effects in shorter wavelength channels. Absent compensation, the shorter wavelength channels limit system performance and restrict the amount of launch power that can be employed for the optical data signals in each wave division multiplexed channel. Careful design that employs increased channel spacing in the nonlinear region of the bandwidth can offset the increased nonlinear effects, thereby improving the worst channel's Q performance and permitting high launch power without unacceptable Q performance.

Abstract: A wavelength division multiplexed (WDM) optical network includes a plurality of optical transmitters, each optical transmitter generating a data signal sent over a respective one of a plurality of signal channels, the plurality of signal channels being divided into a number of sub-bands where each sub-band includes at least two signal channels, and a plurality of substitute signal transmitters, the number of substitute signal transmitters being equal to the number of sub-bands, each substitute signal transmitter generating a substitute signal which provides loading in a corresponding sub-band. The WDM optical network also includes a combining circuit which combines the data signals output from the plurality of optical transmitters and the substitute signals output from the plurality of substitute signal transmitters into a WDM signal, and an optical transmission fiber which receives the WDM signal from the combining circuit.

Abstract: A method for maintaining amplifier saturation in a wavelength division multiplexed (WDM) optical network having a plurality of sub-bands, each sub-band including at least two signal channels which carry respective data signals, and a plurality of substitute signal transmitters, each substitute signal transmitter generating a substitute signal and corresponding to a respective one of the plurality of sub-bands, includes identifying signal channels having a predetermined characteristic within each of the plurality of sub-bands. A substitute signal transmitter is turned on if the sub-band corresponding to the substitute signal transmitter includes a predetermined number of signal channels having said predetermined characteristic. The data signals and the substitute signals are combined into a WDM signal, and the WDM signal is transmitted over an optical transmission fiber.

Abstract: A system and method of providing a transmission span that compensates for signal attenuation, dispersion, and nonlinearity of an optical signal communicated between two line units of a transmission link includes dividing the transmission span into a plurality of fiber segments and selecting a particular fiber for each of the segments. The fiber selection and arrangement of fibers within the span can be selected in accordance with the nonlinearity, dispersion conditions, and distributed gain conditions of the constituent fibers. In a three segment map, the first segment can provide low non linearity, the third segment can provide distributed gain, and the second segment can compensate for the dispersion of the first and third segments. The span can be used, e.g., for distributed Raman amplification. The span can alternatively include a two segment map, a four segment map, or a map with additional segments.

Abstract: A pump assembly for an optical amplifier includes a plurality of pump radiation sources, each pump radiation source producing radiation at a respective one of a first number of pump wavelengths. A coupler is optically coupled to each of the plurality of pump radiation sources, receives each of the first number of pump wavelengths from the plurality of pump radiation sources, and outputs each of the first number of pump wavelengths to each one of a second number of outputs. The pump assembly also includes a plurality of pump signal combiners, each pump signal combiner optically coupled to a respective one of the second number of outputs of the coupler and receiving each of the first number of pump wavelengths output from the coupler. Each pump signal combiner placing each of the first number of pump wavelengths output from the coupler in co-propagation with a respective one of a plurality of data signals propagating on a respective one of a plurality of optical fibers.

Abstract: An optical amplifier having redundancy and a dynamic range of pump power is provided. The amplifier contains a plurality of optical pump sources which are adapted to emit a plurality of pumps. The amplifier also contains a P×V coupler containing P inputs and V outputs, which is adapted to receive the pumps and to output V pump profiles, where P and V are positive integers >1 and P=V or P≠V. The pump profiles include a first set of pumps having a first set of wavelengths and having a first power and a second set of pumps having a second set of wavelengths different from the first set of wavelengths and having a second power different than the first power. The amplifier optionally contains at least one spare optical pump source which is adapted to be turned off during operation of the amplifier unless at least one of the plurality of optical pump sources becomes non operational during the operation of the amplifier.

Abstract: An optical amplifier is described that can couple to and amplify optical signals along multiple fiber transmission paths. The optical amplifier includes a plurality of pump radiation sources, each pump radiation source adapted to produce radiation having a set of pump wavelengths and pump powers corresponding to the respective pump wavelengths, wherein at least one set is different from at least one other set. The optical amplifier also includes a plurality of pump radiation combiners, each pump radiation combiner coupling the radiation of a respective set of pump wavelengths of a respective source of the plurality of pump radiation sources and outputting the respective coupled radiation having coupled radiation profiles via a respective pump radiation combiner output. The optical amplifier also includes a coupler, such as a P×V coupler with P inputs and V outputs.

Abstract: An optical amplification system is described. The system includes a series of optical amplifier groups optically connected in series. Each optical amplifier group comprising multiple optical amplifiers. The optical amplifiers of a particular amplifier group each produces pump radiation having a different set of pump wavelengths and pump powers corresponding to the respective pump wavelengths. Each amplifier group provides a desired gain profile, such as a substantially flat gain profile, over a first range of optical signal wavelengths.

Abstract: A reset-free polarization controller is presented for maintaining the polarization of an incident optical signal at a fixed and known value. At least 3 controllable quarter-wavelength plates are connected in cascade to an incident optical source having a variable polarization. Each quarter-wavelength plates varies the orientation of phase retardation along the optical wavepath. The dynamic realignment of the cascaded quarter-wavelength plates with respect to the varying input polarization maintains the polarization of the output optical signal at a fixed and known value.

Abstract: Laser wavelengths used in a WDM system are stabilized using a known accurate electrical frequency standard. The laser wavelengths are stabilized using a first frequency locking circuit which individually locks each laser wavelength to a different resonant frequency of an optical interferometer and a second frequency locking circuit which locks a different resonant frequency of the optical interferometer to an accurate electrical frequency standard signal. The known accurate electrical frequency standard prevents the resonator from drifting and the resonator prevents the WDM system lasers from drifting.