Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: An interferometer includes an optical beam splitter that splits an input optical signal into a first optical signal propagating in a first optical path comprising free space and a second optical signal propagating in a second optical path comprising a dielectric medium. A differential delay delays the second optical signal relative to the first optical signal by a differential delay time that is proportional to at least one of a temperature and a refractive index of the dielectric medium. A temperature controller in thermal contact with the dielectric medium changes the temperature of the dielectric medium to control at least one of thermal expansion/contraction and a temperature dependent change in the refractive index of the dielectric medium, thereby changing the differential phase delay.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: An interferometer includes an optical beam splitter that splits an input optical signal into a first optical signal propagating in a first optical path comprising free space and a second optical signal propagating in a second optical path comprising a dielectric medium. A differential delay delays the second optical signal relative to the first optical signal by a differential delay time that is proportional to at least one of a temperature and a refractive index of the dielectric medium. A temperature controller in thermal contact with the dielectric medium changes the temperature of the dielectric medium to control at least one of thermal expansion/contraction and a temperature dependent change in the refractive index of the dielectric medium, thereby changing the differential phase delay.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: System and methods for all-optical signal regeneration based on free space optics are described. In one exemplary embodiment, a method for regenerating an optical signal comprises counter-propagating an input signal and a regenerating signal within an all-optical signal regenerator based on free space optics, where the all-optical signal regenerator based on free space optics comprises a Sagnac loop interferometer, and extracting a regenerated output signal from the Sagnac loop interferometer. In another exemplary embodiment, an all-optical signal regenerator based on free space optics comprises a Sagnac loop interferometer, an optical signal input path coupled to a semiconductor optical amplifier of the Sagnac loop interferometer, a regenerating optical signal path coupled to the semiconductor optical amplifier of the Sagnac loop interferometer, and a regenerated optical output path coupled to the Sagnac loop interferometer.

Abstract: In one exemplary embodiment, a method comprises transmitting an optical signal via the optical line, measuring a relative change in spectral intensity of the optical signal near a clock frequency (or half of that frequency) while varying a polarization of the optical signal between a first state of polarization and a second state of polarization, and using the relative change in spectral intensity of the optical signal to determine and correct the DGD of the optical line. Another method comprises splitting an optical signal traveling through the optical line into a first and second portions having a first and second principal states of polarization of the optical line, converting the first and second portions into a first and second electrical signals, delaying the second electrical signal to create a delayed electrical signal that compensates for a DGD of the optical line, and combining the delayed electrical signal with the first electrical signal to produce a fixed output electrical signal.

Abstract: Optical transponders with reduced sensitivity to PMD and CD are described. In one embodiment, an optical transponder comprises a differential group delay (DGD) mitigator integrated within the transponder and optically coupled to an optical input port of the optical transponder, an optical receiver integrated within the optical transponder and optically coupled to the DGD mitigator and to an electrical output port of the transponder, and a multi-level transmitter integrated within the optical transponder, where the multi-level transmitter is electrically coupled to an electrical input port and optically coupled to an optical output port of the transponder.

Abstract: A high efficiency, high performance optical amplifier includes an amplification stage comprised of two Erbium doped fiber (EDF) gain sections separated by a variable optical attenuator (VOA). A single pump serves to pump both EDF sections. A high dynamic gain range is achieved by an interplay between the action of the VOA, and the pump energy absorption mechanisms in each gain section, which are dominated by the saturation characteristics of each of the EDFs. In a preferred embodiment of the method, input signals are coupled with a pump signal into a first EDF gain section in which the energy absorption mechanisms provide first amplified signals that are correlated with a residual pump signal. At the first EDF gain section output, the combined amplified signals and residual pump signal are decoupled, the amplified signals being attenuated in the VOA while the residual pump signal being routed around the VOA.

Abstract: A method and apparatus for optical amplification with a large dynamic gain range in both the non-linear (1530-1540 nm) and linear (1540-1565 nm) regimes of the C-Band. The large dynamic gain range is achieved by the synergistic operation of a dual-stage Erbium-doped Fiber Amplifier (EDFA) having a self-saturating Thulium-doped fiber inserted between the two stages. The Thulium-doped fiber saturation is determined by the output power of the first EDFA stage, and the synergistic, combined operation of both EDFA stages and the self-saturating absorber is controlled by appropriate algorithms and software.

Abstract: A high efficiency, high performance optical amplifier includes an amplification stage comprised of two Erbium doped fiber (EDF) gain sections separated by a variable optical attenuator (VOA). A single pump serves to pump both EDF sections. A high dynamic gain range is achieved by an interplay between the action of the VOA, and the pump energy absorption mechanisms in each gain section, which are dominated by the saturation characteristics of each of the EDFs. In a preferred embodiment of the method, input signals are coupled with a pump signal into a first EDF gain section in which the energy absorption mechanisms provide first amplified signals that are correlated with a residual pump signal. At the first EDF gain section output, the combined amplified signals and residual pump signal are decoupled, the amplified signals being attenuated in the VOA while the residual pump signal being routed around the VOA.

Abstract: A method and apparatus for optical amplification with a large dynamic gain range in both the non-linear (1530-1540 nm) and linear (1540-1565 nm) regimes of the C-Band. The large dynamic gain range is achieved by the synergistic operation of a dual-stage Erbium-doped Fiber Amplifier (EDFA) having a self-saturating Thulium-doped fiber inserted between the two stages. The Thulium-doped fiber saturation is determined by the output power of the first EDFA stage, and the synergistic, combined operation of both EDFA stages and the self-saturating absorber is controlled by appropriate algorithms and software.