Abstract: A digital-electronic-to-analog-optical converter, which has a structure consistent with a super-Mach-Zehnder interferometer, and which can perform the functionalities of both a Digital to Analog Converter (DAC) and a digital modulator uses a sub-Mach-Zender modulator to modulate optical wave signals propagating through its optical waveguide in a push-pull manner. The modulation performed is phase modulation realized with electrodes positioned near the optical wave guide where such electrodes carry modulation signals in digital, analog or discrete time signal format creating electromagnetic or electric fields that engage the optical wave signals traveling through the waveguide thus imparting a phase shift onto the optical wave signals. The amount of the phase shift can be implemented through the geometry of the electrodes, the length of time the modulating signal is applied, and the amplitude of the modulating signal.

Abstract: An apparatus, e.g. an optical oscilloscope, includes an optical receiver front end, including an optical device, and an optical delay. The receiver front end is configured to receive at least one input optical signal and produce by the optical device at least first and second output optical signals. The receiver front end is further configured to gate said at least one input optical signal or said at least first and second output optical signals. An optical combiner is configured to combine said at least first and second output optical signals, and the optical delay is located in an optical path of said first optical output signal between said optical receiver front end and the optical combiner. An optical detector is configured to receive a combined optical signal from said optical combiner and to produce therefrom an analog-electrical signal representative of the combined optical signal.

Abstract: An apparatus, e.g. an optical oscilloscope, includes an optical receiver front end, including an optical device, and an optical delay. The receiver front end is configured to receive at least one input optical signal and produce by the optical device at least first and second output optical signals. The receiver front end is further configured to gate said at least one input optical signal or said at least first and second output optical signals. An optical combiner is configured to combine said at least first and second output optical signals, and the optical delay is located in an optical path of said first optical output signal between said optical receiver front end and the optical combiner.

Abstract: We disclose an optical transponder, in which one or more all-electronic feedback paths are used to obtain a relatively accurate estimate of the device-specific signal distortions in the transmitter portion thereof. The obtained estimate is used to enable the digital signal processor of the optical transponder to carry out electronic pre-distortion (EPD) that can significantly reduce or cancel these signal distortions without the use of detailed factory-calibration measurements or optics dedicated to feedback purposes. The use of all-electronic feedback paths may enable a beneficial reduction in the cost of the EPD functionality, e.g., by eliminating a significant extra cost associated with the implementation of optically generated feedback.

Abstract: A digital-electronic-to-analog-optical converter, which has a structure consistent with a super-Mach-Zehnder interferometer, and which can perform the functionalities of both a Digital to Analog Converter (DAC) and a digital modulator uses a sub-Mach-Zender modulator to modulate optical wave signals propagating through its optical waveguide in a push-pull manner. The modulation performed is phase modulation realized with electrodes positioned near the optical wave guide where such electrodes carry modulation signals in digital, analog or discrete time signal format creating electromagnetic or electric fields that engage the optical wave signals traveling through the waveguide thus imparting a phase shift onto the optical wave signals. The amount of the phase shift can be implemented through the geometry of the electrodes, the length of time the modulating signal is applied, and the amplitude of the modulating signal.

Abstract: We disclose an optical transponder, in which one or more all-electronic feedback paths are used to obtain a relatively accurate estimate of the device-specific signal distortions in the transmitter portion thereof. The obtained estimate is used to enable the digital signal processor of the optical transponder to carry out electronic pre-distortion (EPD) that can significantly reduce or cancel these signal distortions without the use of detailed factory-calibration measurements or optics dedicated to feedback purposes. The use of all-electronic feedback paths may enable a beneficial reduction in the cost of the EPD functionality, e.g., by eliminating a significant extra cost associated with the implementation of optically generated feedback.

Abstract: An optical fiber transmission system includes a series of optical fiber transmission spans and one or more all-optical signal processors. The optical fiber transmission spans are connected to form an optical communication path. Each all-optical signal processor directly connects a corresponding adjacent pair of the spans. Each all-optical signal processor includes an optical wavelength converter having input and output ports and a dispersion adjustment module connected to the input port of the optical wavelength converter of the same processor. The dispersion module is also configured to adjust cumulative dispersions of some received optical pulses to be outside of a range for the cumulative dispersions of corresponding optical pulses in the span directly preceding the same processor.

Abstract: An optical transport system having an optical add-drop multiplexer configured to reduce inter-channel crosstalk by driving Mach-Zehnder pulse carvers in its optical transmitters with electrical drive signals whose swing range is smaller than voltage 2V? of said Mach-Zehnder pulse carvers.

Abstract: An apparatus includes a non-solitonic all-optical communication path having serially connected first and second segments. The first segment end-couples to a lumped optical transmitter. The second segment end-couples to a lumped optical receiver. Each segment has a series of spans of transmission optical fibers. The all-optical communication path has an optical phase conjugator that optically end-couples the first segment to the second segment. The optical phase conjugator is positioned away from the path's midpoint.

Abstract: A method of optically equalizing a multi-level (amplitude or phase) optical signal through the effect of an optical equalizer wherein the optical equalizer (OEQ) is placed at either a transmission end or a receiver end of the optical communications link and a tap delay characteristic of the OEQ need not be determined by symbol spacing, rather it may advantageously be adjusted to desirably compensate non-linear mapping performed in the modulation process or simultaneous operation on a plurality of wavelength division multiplexed (WDM) channels.

Abstract: A polarization-diverse optical amplifier includes a polarization-sensitive optically active medium and a polarization splitter. The polarization splitter is configured to receive input light, to direct a first polarization component of the received input light to a first optical path segment, and to direct a second polarization component of the received input light to a separate second optical path segment. The active medium has first and second optical ports. The first optical port is at an end of the first optical path segment. The second port is at an end of the second optical path segment. The active medium outputs amplified light from one of the ports in response to receiving the input light at the other of the ports. In a preferred embodiment, the active medium has an internal optical axis, and the polarizations of the first and second components are oriented relative to that axis so that amplification is enhanced. The two optical path segments may include polarization-maintaining optical waveguides.

Abstract: A method of optically equalizing a multi-level (amplitude or phase) optical signal through the effect of an optical equalizer wherein the optical equalizer (OEQ) is placed at either a transmission end or a receiver end of the optical communications link and a tap delay characteristic of the OEQ need not be determined by symbol spacing, rather it may advantageously be adjusted to desirably compensate non-linear mapping performed in the modulation process or simultaneous operation on a plurality of wavelength division multiplexed (WDM) channels.

Abstract: A polarization-diverse optical amplifier includes a polarization-sensitive optically active medium and a polarization splitter. The polarization splitter is configured to receive input light, to direct a first polarization component of the received input light to a first optical path segment, and to direct a second polarization component of the received input light to a separate second optical path segment. The active medium has first and second optical ports. The first optical port is at an end of the first optical path segment. The second port is at an end of the second optical path segment. The active medium outputs amplified light from one of the ports in response to receiving the input light at the other of the ports. In a preferred embodiment, the active medium has an internal optical axis, and the polarizations of the first and second components are oriented relative to that axis so that amplification is enhanced. The two optical path segments may include polarization-maintaining optical waveguides.

Abstract: An optical transmitter includes a modulator, a dispersion adjustment module, and an optical amplifier. The optical transmitter is configured to transmit optical pulses over a free-space optical communication channel. The modulator is configured to produce an optical carrier that is amplitude and/or phase modulated by data. The dispersion adjustment module is connected between the modulator and the amplifier and is configured to substantially change temporal widths of optical pulses received from the modulator by changing dispersions of the received optical pulses.

Abstract: An optical fiber transmission system includes a series of optical fiber transmission spans and one or more all-optical signal processors. The optical fiber transmission spans are connected to form an optical communication path. Each all-optical signal processor directly connects a corresponding adjacent pair of the spans. Each all-optical signal processor includes an optical wavelength converter having input and output ports and a dispersion adjustment module connected to the input port of the optical wavelength converter of the same processor. The dispersion module is also configured to adjust cumulative dispersions of some received optical pulses to be outside of a range for the cumulative dispersions of corresponding optical pulses in the span directly preceding the same processor.

Abstract: Embodiments of the invention include system for monitoring the effectiveness of pulse shaping in a nonlinear optical fiber (40). The spectral content of the pulse, after passing through the nonlinear fiber (40), provides an indication of how effectively the pulse was regenerated. A portion of the pulse exiting the nonlinear fiber is tapped off and its pulse energy is measured in at least one selected spectral region. The selected spectral region is one in which the pulse tends to gain energy when effective regeneration is taking place. The information concerning the effectiveness of pulse shaping in a nonlinear optical fiber is fed back to dynamically change the residual dispersion at the regenerator input. The spectral measurement leads to a control signal (48) to indicate a level of performance of the system, or to improve the performance of the system by adjusting an operational parameter.

Abstract: An apparatus includes a non-solitonic all-optical communication path having serially connected first and second segments. The first segment end-couples to a lumped optical transmitter. The second segment end-couples to a lumped optical receiver. Each segment has a series of spans of transmission optical fibers. The all-optical communication path has an optical phase conjugator that optically end-couples the first segment to the second segment. The optical phase conjugator is positioned away from the path's midpoint.

Abstract: An apparatus includes an optical wavelength-converter and a polarization splitter. The polarization splitter is configured to receive input and pump light, to direct a first polarization component of the received input and pump light to a first optical path, and to direct a second polarization component of the received input and pump light to a separate second optical path. The optical wavelength-converter has first and second optical ports. The first optical port is at an end of the first optical path. The second port is at an end of the second optical path. The wavelength-converter outputs wavelength-converted light from one of the ports in response to receiving the input and pump light at the other of the ports. The two optical paths may include polarization-maintaining optical waveguides. The polarization splitter and optical paths may be configured to transmit substantially the same pump light intensity to the two optical ports.

Abstract: Embodiments of the invention include system for monitoring the effectiveness of pulse shaping in a nonlinear optical fiber (40). The spectral content of the pulse, after passing through the nonlinear fiber (40), provides an indication of how effectively the pulse was regenerated. A portion of the pulse exiting the nonlinear fiber is tapped off and its pulse energy is measured in at least one selected spectral region. The selected spectral region is one in which the pulse tends to gain energy when effective regeneration is taking place. The information concerning the effectiveness of pulse shaping in a nonlinear optical fiber is fed back to dynamically change the residual dispersion at the regenerator input. The spectral measurement leads to a control signal (48) to indicate a level of performance of the system, or to improve the performance of the system by adjusting an operational parameter.

Abstract: The invention comprises a method and apparatus for passive optical conditioning and format conversion of RZ optical signals including, but not limited to, conversion from RZ to CRZ or to CSRZ, using a nonlinear device. The invention generates signals that may be optimized to improve transmission performance, receiver performance, and/or spectral efficiency of the optical transmission system. A method for passively generating an optical carrier-suppressed return-to-zero (CSRZ) signal according to the present invention includes, propagating an optical RZ signal through a nonlinear element, the nonlinear element configured to broaden the optical RZ signal such that the optical RZ signal is phase shifted by approximately 3Π/2.