Abstract: An optical communication amplification system may include a number of amplification stages for an optical signal that includes a first optical wavelength band signal portion and a second optical wavelength band signal portion. Each amplification stage may separate the first optical wavelength band signal portion from the second optical wavelength band signal portion. The separated first optical wavelength band signal portion is amplified using one or more first optical wavelength band amplifiers and the separated second optical wavelength band signal portion are amplified using one or more second optical wavelength band amplifiers. The amplified first optical wavelength band signal portion is filtered and a reflected portion of the first optical wavelength band signal portion may be used to provide energy to the one or more second optical wavelength band amplifiers to increase the power or gain of the separated second optical wavelength band signal portion.

Abstract: An optical communication amplification system may include a number of amplification stages for an optical signal that includes a first optical wavelength band signal portion and a second optical wavelength band signal portion. Each amplification stage may separate the first optical wavelength band signal portion from the second optical wavelength band signal portion. The separated first optical wavelength band signal portion is amplified using one or more first optical wavelength band amplifiers and the separated second optical wavelength band signal portion are amplified using one or more second optical wavelength band amplifiers. The amplified first optical wavelength band signal portion is filtered and a reflected portion of the first optical wavelength band signal portion may be used to provide energy to the one or more second optical wavelength band amplifiers to increase the power or gain of the separated second optical wavelength band signal portion.

Abstract: An adaptive equalizer with coefficients determined by averaging an estimated filter coefficient over a number, N, of past and future symbols. Estimated filter coefficients may be optimized by optimization of the number N, an averaging window function and a scaling factor using a metric. The metric also allows estimation of the amount of noise that may be compensated by an adaptive equalizer consistent with the present disclosure.

Abstract: An adaptive equalizer with coefficients determined by averaging an estimated filter coefficient over a number, N, of past and future symbols. Estimated filter coefficients may be optimized by optimization of the number N, an averaging window function and a scaling factor using a metric. The metric also allows estimation of the amount of noise that may be compensated by an adaptive equalizer consistent with the present disclosure.

Abstract: An optical transmission link pumped with multiple orders Raman pumps on both ends of the link is disclosed. At least one first-order Raman pump and at least two higher-order Raman pumps are provided on each end for reducing optical power variation of the optical signal along the optical transmission link. Wavelengths and optical power levels of the multiple-order Raman pumps and the additional Raman pump(s) can be selected by computer simulation to lessen the spatial optical power variation of the optical signal.

Abstract: An optical transmission link pumped with multiple orders Raman pumps on both ends of the link is disclosed. At least one first-order Raman pump and at least two higher-order Raman pumps are provided on each end for reducing optical power variation of the optical signal along the optical transmission link. Wavelengths and optical power levels of the multiple-order Raman pumps and the additional Raman pump(s) can be selected by computer simulation to lessen the spatial optical power variation of the optical signal.

Abstract: A polarized light beam having a coherence length L can be depolarized by splitting the beam into orthogonally polarized sub-beams and delaying one of the sub-beams relative to the other by a length larger than L. This spatial delay is created by splitting the beam in a walk-off crystal and disposing in the optical path of one of the sub-beams a slab of an optically dense material, while allowing the other sub-beam to propagate outside and near the slab. The sub-beams remain parallel to each other, allowing another walk-off crystal to be used to recombine the sub-beams. A dual-core fiber ferrule and a microlens array can be used to combine fiber-coupled output beams of two laser diodes in a single compact walk-off crystal.

Abstract: A change in loading conditions of fiber amplifiers in an optical communications network causes rapid variations in the gain profile of the amplifiers due to spectral hole burning and stimulated Raman scattering. An apparatus for reducing such gain profile variations is described which monitors optical signal perturbations and reacts by adjusting pump powers of the amplifiers and, or fast variable optical attenuator according to a pre-determined function stored in the form of constants in controller's memory. The optical signal is monitored as total power, and the power of light after passing through one or more optical filters. The light detection is relatively fast, whereby the gain profile variations are compensated by fast controlled variable optical attenuator and pump power adjustment upon the change in loading conditions.

Abstract: A reconfigurable optical amplifier is formed of a plurality of optical switches and a plurality of fiber amplifier sections to provide a switchable amplifying network. A variable pump splitter provides pump light from an optical pump source to two or more fiber amplifier sections. The optical switches and variable pump splitters are formed in a planar lightwave circuit, which may further include pump WDM combiners, variable optical attenuators, tap couplers and other optical components, and to which monitoring photodiodes and the fiber amplifier sections are coupled. A same PLC can be used for a wide variety of reconfigurable optical amplifiers.

Abstract: A polarized light beam having a coherence length L can be depolarized by splitting the beam into orthogonally polarized sub-beams and delaying one of the sub-beams relative to the other by a length larger than L. This spatial delay is created by splitting the beam in a walk-off crystal and disposing in the optical path of one of the sub-beams a slab of an optically dense material, while allowing the other sub-beam to propagate outside and near the slab. The sub-beams remain parallel to each other, allowing another walk-off crystal to be used to recombine the sub-beams. A dual-core fiber ferrule and a microlens array can be used to combine fiber-coupled output beams of two laser diodes in a single compact walk-off crystal.

Abstract: An optical amplifier having two erbium doped fiber coils and a pump laser diode is described. A tunable optical power splitter is used for variably splitting the optical pump power for the laser diode between the two erbium doped fiber coils, and variable tilters can be used for correcting the gain tilt of the amplifier. The variable splitter and the tilters can include thermally tunable Mach-Zehnder interferometers.

Abstract: An optical amplifier having two erbium doped fiber coils and a pump laser diode is described. A tunable optical power splitter is used for variably splitting the optical pump power for the laser diode between the two erbium doped fiber coils, and variable tilters can be used for correcting the gain tilt of the amplifier. The variable splitter and the tilters can include thermally tunable Mach-Zehnder interferometers.

Abstract: A fiber amplifier having two erbium doped fiber coils and a pump laser diode optically coupled, through a fiber array, to a planar lightwave circuit, is described. A photodetector array, a multiport free-space optical isolator, and a strip of thin-film gain flattening filter are attached to a side surface of the planar lightwave circuit, which has a tunable optical power splitter for variably splitting the optical pump power for the laser diode between the two erbium doped fiber coils, and variable tilters for correcting the gain tilt of the amplifier. The variable splitter and the tilters are thermally tunable Mach-Zehnder interferometers.

Abstract: A change in loading conditions of fiber amplifiers in an optical communications network causes rapid variations in the gain profile of the amplifiers due to spectral hole burning and stimulated Raman scattering. An apparatus for reducing such gain profile variations is described which monitors optical signal perturbations and reacts by adjusting pump powers of the amplifiers and, or fast variable optical attenuator according to a pre-determined function stored in the form of constants in controller's memory. The optical signal is monitored as total power, and the power of light after passing through one or more optical filters. The light detection is relatively fast, whereby the gain profile variations are compensated by fast controlled variable optical attenuator and pump power adjustment upon the change in loading conditions.

Abstract: A change in loading conditions of fiber amplifiers in an optical communications network causes rapid variations in the gain profile of the amplifiers due to spectral hole burning and stimulated Raman scattering. An apparatus for reducing such gain profile variations is described which monitors optical signal perturbations and reacts by adjusting pump powers of the amplifiers and, or fast variable optical attenuator according to a pre-determined function stored in the form of constants in controller's memory. The optical signal is monitored as total power, and the power of light after passing through one or more optical filters. The light detection is relatively fast, whereby the gain profile variations are compensated by fast controlled variable optical attenuator and pump power adjustment upon the change in loading conditions.

Abstract: A reconfigurable optical amplifier is formed of a plurality of optical switches and a plurality of fiber amplifier sections to provide a switchable amplifying network. A variable pump splitter provides pump light from an optical pump source to two or more fiber amplifier sections. The optical switches and variable pump splitters are formed in a planar lightwave circuit, which may further include pump WDM combiners, variable optical attenuators, tap couplers and other optical components, and to which monitoring photodiodes and the fiber amplifier sections are coupled. A same PLC can be used for a wide variety of reconfigurable optical amplifiers.

Abstract: Raman tilt is induced by the propagation of optical signals in optical communication fibers during and after transient events. Certain characteristics of the light are monitored at each amplification node and Raman tilt correction is achieved by spectral tilt control optics. The light is monitored either as total power, and/or the power of light after passing through one or more optical filters. In the case of EDFA (Erbium Doped Fiber Amplifier) the correction is performed by adjusting stage gains and VOA loss distribution within the amplifier. The light detection is relatively fast, whereby the tilt is compensated by fast controlled VOA and pump power adjustment during a transient event.

Abstract: A fiber amplifier having two erbium doped fiber coils and a pump laser diode optically coupled, through a fiber array, to a planar lightwave circuit, is described. A photodetector array, a multiport free-space optical isolator, and a strip of thin-film gain flattening filter are attached to a side surface of the planar lightwave circuit, which has a tunable optical power splitter for variably splitting the optical pump power for the laser diode between the two erbium doped fiber coils, and variable tilters for correcting the gain tilt of the amplifier. The variable splitter and the tilters are thermally tunable Mach-Zehnder interferometers.

Abstract: A change in loading conditions of fiber amplifiers in an optical communications network causes rapid variations in the gain profile of the amplifiers due to spectral hole burning and stimulated Raman scattering. An apparatus for reducing such gain profile variations is described which monitors optical signal perturbations and reacts by adjusting pump powers of the amplifiers and, or fast variable optical attenuator according to a predetermined function stored in the form of constants in controller's memory. The optical signal is monitored as total power, and the power of light after passing through one or more optical filters. The light detection is relatively fast, whereby the gain profile variations are compensated by fast controlled variable optical attenuator and pump power adjustment upon the change in loading conditions.

Abstract: Raman tilt is induced by the propagation of optical signals in optical communication fibers during and after transient events. Certain characteristics of the light are monitored at each amplification node and Raman tilt correction is achieved by spectral tilt control optics. The light is monitored either as total power, and/or the power of light after passing through one or more optical filters. In the case of EDFA (Erbium Doped Fiber Amplifier) the correction is performed by adjusting stage gains and VOA loss distribution within the amplifier. The light detection is relatively fast, whereby the tilt is compensated by fast controlled VOA and pump power adjustment during a transient event.