Abstract: A scheme is described for mitigating the effects of polarization-mode dispersion (PMD) in a wave-division multiplex (WDM) optical communication system having one or more transmission links with one or more quasi-static waveguide sections coupled by one or more non-static coupling sections. A transmitter is coupled to the transmission link and is adapted to transmit optical signals through the transmission link with wavelength channel spacing of the optical signals greater than about the PMD correlation bandwidth of at least one of the one or more quasi-static waveguide sections, so that the PMD induced outage probability for the system is optimized.

Abstract: A polarization scrambler has a polarization state rotating unit rotating the polarization state of a signal light, and a rotation speed controlling unit controlling the rotation speed of the polarization state in the polarization state rotating unit on the basis of the speed and scheme of modulation of the signal light, and the value of polarization mode dispersion of a transmission path on which the signal light is to be transmitted. Degradation of the transmission quality due to PMD is more mitigated than the known techniques.

Abstract: Systems and method of compensating for transmission impairment are disclosed. One such method comprises: receiving an optical signal which has been distorted in the physical domain by an optical transmission channel; and propagating the distorted optical signal backward in the electronic domain in a corresponding virtual optical transmission channel.

Abstract: A method includes modulating lightwaves to provide first and second OFDM signal sidebands at a first polarization direction and first and second OFDM signal sidebands at a second polarization direction, and combining sidebands that are oppositely positioned and joined from the first and second OFDM signal sidebands at each polarization direction to provide a polarization multiplexing OFDM signal.

Abstract: There is provided a method for detecting optical signals comprising employing a photo diode to both directly detect a received optical signal and convert it into an electrical signal for recovery of data bit stream information in the received optical signal, the received optical signal being derived from a separation of two polarization multiplexed optical signals that were combined before being received.

Abstract: In the optical reception apparatus, a DQPSK polarization multiplexed signal light (S) input thereto is split into horizontally/vertically polarized signal lights (SH, SV) by a polarization beam splitter (3), and the signal lights (SH, SV) each is branched into two by each of optical couplers (4H, 4V). Then, one branched lights (SH1, SV1) by each of the optical couplers (4H, 4V) are supplied to a delay interferometer (5I) on the I branch via optical circulators (10I1, 10I2) to be propagated in bidirectional, and the other branched lights (SHQ, SVQ) by each of the optical couplers (4H, 4V) are supplied to a delay interferometer (5Q) on the Q branch side via optical circulators (10Q1, 10Q2) to be propagated in bidirectional, so that a set of delay interferometers (5I, 5Q) is commonly used for horizontally polarized waves and vertically polarized waves.

Abstract: The present invention relates generally to the transport and processing of optical communication signals. More specifically, the present invention relates to systems and methods for the polarization insensitive coherent detection of optical communication signals with Brillouin amplification of the associated signal carrier and the polarization division multiplexed transmission of optical communication signals without polarization tracking at the associated receiver(s).

Abstract: A signal equalizer for compensating impairments of an optical signal received through a link of a high speed optical communications network. At least one set of compensation vectors are computed for compensating at least two distinct types of impairments. A frequency domain processor is coupled to receive respective raw multi-bit in-phase (I) and quadrature (Q) sample streams of each received polarization of the optical signal. The frequency domain processor operates to digitally process the multi-bit sample streams, using the compensation vectors, to generate multi-bit estimates of symbols modulated onto each transmitted polarization of the optical signal. The frequency domain processor exhibits respective different responses to each one of the at least two distinct types of impairments.

Abstract: Disclosed is an optical packet communication system using a wavelength-offset polarization-division multiplexing labeling. An optical signal transmitter which is provided at an ingress node positioned at a sending end in an optical packet switching network, generates and combines packet data and a label, and transmits the combined packet data and label to a core node, wherein the packet data and label have polarization directions perpendicular to each other and maintain a predetermined wavelength interval. A label swapping device detects the label from the combined packet data and label received from the optical signal transmitter, detects next moving position information of the packet data, for generating a new label, substitutes the detected label by the new label, combines the new label with the packet data, and transmits the combined packet data and new label to a next moving position.

Abstract: Provided herein are at least one embodiment of a system and method for reducing or eliminating crosstalk and associated distortion in a wavelength-division multiplexed optical signal transmitted over a fiber optic network by inversion of the RF signals that are inputs to the system.

Abstract: A simplified optical receiver architecture capable of tracking and demultiplexing polarization-multiplexed signals, dynamically compensating for PMD using a variety of polarization controller technologies, and reducing the number of delay line demodulators by two for both DPSK and DQPSK modulation is illustrated. Once polarization is stabilized at the first stage of the cascaded system of the present invention, subsequent stages can be simplified and cost reduced.

Abstract: Exemplary embodiments of detection and transmission arrangements are disclosed herein. For example, some of the disclosed embodiments comprise a splitter, a detector, first and second paths defined between the splitter and the detector, and a manipulation arrangement. In certain embodiments, the splitter is arranged to direct an incoming particle along the first or second path depending upon the value of a parameter of the incoming particle. In particular embodiments, the manipulation arrangement is located on at least one of the first and second paths, so that, if a particle in a superposition of values of the parameter impinges on the splitter and a wavefunction of the particle is directed along both the first and second paths, the manipulation arrangement will act on the wavefunction to allow interference, at or near the detector, between the portions of the wavefunction that were directed along the first and second paths.

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: A polarization multiplexing and transmitting apparatus generates polarization multiplexed light by multiplexing modulated signal components that having varying intensities and are in polarization states orthogonal to each other. The polarization multiplexing and transmitting apparatus includes a converting unit that converts light generated by a light source into signal components having a varying intensity synchronized with a clock signal input thereto and a varying intensity inversely synchronized with the clock signal, respectively; a modulating unit that modulates the signal components, respectively; and a polarization adjusting unit that orthogonalizes polarization states of the signal components.

Abstract: An optical switch includes an optical waveguide to route an input optical beam. At least one polarization switch receives the input optical beam from the optical waveguide. At least one birefringent wedge is associated with the at least one polarization switch. The at least one polarization switch and at least one birefringent wedge operate to direct the input optical beam to two or more output locations through control of the polarization switch.

Abstract: An optical switching apparatus includes at least one optical waveguide to deliver at least one input optical beam. A dispersion device spatially separates the at least one input optical beam into individual wavelength channels. An optical power device aligns the individual wavelength channels. An optical switch has at least one transflective polarizing element, at least one birefringent wedge and at least two polarization switches. The individual wavelength channels are directed to independently addressable regions of the polarization switches for wavelength selective switching. A second optical power device aligns the individual wavelength channels from the optical switch. A second dispersion device spatially combines individual wavelength channels from the second optical power device. At least one output optical waveguide receives at least one of the individual wavelength channels from the second dispersion device.

Abstract: A polarization duobinary optical transmitter is disclosed. The transmitter includes a precoder for coding an electric signal and a light source for generating continuous light. The transmitter also includes a chirped-free modulator for generating an NRZ signal including first and second polarization light beams orthogonal to each other by modulating the light with the electric signal and a band-pass filter for limiting neighbor frequency bands between the first and second polarization light beams.

Abstract: The present invention includes apparatus and method of a variable step size dithering control algorithm for polarization mode dispersion controllers (PMDCs). The dithering step size of the PCs is adjusted according to the feedback signal including degree of polarization (DOP).

Abstract: A receiver (10) for an optical signal containing a time jitter and a time-varying distortion caused by a periodic polarization scrambled signal comprises at least one decision gate (11) and a clock recovery module (13) providing a clock signal (C) recovered from the optical signal to the at least one decision gate (11). The receiver (10) further comprises a scrambling frequency generator (16) synchronized to the scrambling frequency and phase of the polarization scrambled signal, a jitter function generator (17) generating a clock phase control signal (??b) reproducing the time jitter, and at least one clock phase modulator (14) modulating the phase of the clock signal (C) according to the clock phase control signal (??b).

Abstract: An optical transmission/reception device includes at least one light emitting portion and at least one light receiving portion on the same substrate. The light emitting portion includes at least a lower multilayer reflector and an active layer provided on the lower multilayer reflector. A metal layer including a plurality of opening portions is provided in an upper portion of the light emitting portion. Each of the opening portions has a size smaller than a light emission wavelength of the light emitting portion.

Abstract: A receiver for an OTDM/PDM pulse train (10) in which the pulses (12) have alternating polarizations (P1, P2) has a polarization insensitive optical switch (16; 161, 162, 163, 164) for isolating optical pulses (10?) within the pulse train (10), and a polarization selective element (17) for separating from the isolated pulses (10?) at least one component that has a single polarization. This allows to considerable relax the constraints posed on the switch since components in the isolated pulses that result from interchannel interference can, at least to a large extent, be eliminated by the subsequent polarization selective element (17).

Abstract: Methods and systems for PMD compensation in an optical communication system are implemented by transmitting multiple optical signals through a common optical conduit to an optical compensator that adjustably rotates the polarization states of the multiple optical signals and transmits the rotated optical signals to an optical receiver. The receiver, upon sensing an excessive error condition, commands the optical compensator to change the polarization state of rotation, which changes the PMD profile of the received optical signals.

Abstract: The present invention provides an optical switch in which a switching operation is not affected even when the polarization state of a control light varies. The optical switch includes a loop-form optical waveguide loop circuit formed from an optical nonlinear medium, a control light input arrangement for inputting the control light into the optical waveguide loop circuit and serving as a phase control arrangement, a wavelength demultiplexing/multiplexing circuit, and a phase bias circuit.

Abstract: A device for processing a digital signal of an optical transmission system is described. The device comprises: a polarization beam splitter for receiving the signal, a phase shifter for shifting the phase of the signal at the orthogonal output of the polarization beam splitter, and means for combining the signal at the parallel output of the polarization beam splitter and the shifted signal.

Abstract: There is provided a filter assembly for combining a wavelength multiplexed optical signal by multiplexing optical signals of different wavelength emitted from respective optical devices, and/or for dividing a wavelength multiplexed optical signal into optical signals of different wavelength and causing the optical signals of different wavelength to enter respective optical devices. This filter assembly comprises: a light transmitting member within which each optical signal propagates; plural optical filters disposed on an upper face of the light transmitting member at a predetermined spacing wherein each optical signal passes through the optical filters; upper reflective layers respectively provided between adjacent ones of the optical filters; and a lower reflective layer provided on a lower face of the light transmitting member, and wherein the wavelength multiplexed optical signal propagates along the same optical path within the light transmitting member.

Abstract: Method and apparatus for compensating for first-order Polarization Mode Dispersion in an optical transmission system. An apparatus has a polarization controller for transforming polarization components of an optical signal carried by the optical fiber into orthogonal polarization states, a variable delay line for introducing a variable differential time delay between the polarization states and for producing an output optical signal that is compensated for PMD in the optical fiber, and a feedback unit for adjusting the polarization controller and the variable delay line to compensate for variations in the PMD of the optical fiber, the feedback unit including apparatus for generating a plurality of independent control signals to independently control actuators of the polarization controller and the variable delay line. The invention provides for a reduction in response time of the actuators and a reduction in complexity of an algorithm used to control the apparatus.

Abstract: In order to reduce mutual interferences between POLMUX and signals, the signals are transmitted with differed to each other carrying signals, thereby making it possible to obtain the circular polarization of each resulting POLMUX signal. Each second POLMUX signal is transmissible with an opposite circular polarization. In order to reduce also interferences when only one modulated data signal is transmitted through a POLMUX channel, a polarization plane of modulated data signals of each second POLMUX channel is turned at 45°. In a variant, polarization multiplex signals are produces and the resulting polarizations thereof in adjacent channels are perpendicular to each other.

Abstract: Apparatus, systems and techniques for optical communication based on polarization division multiplexing (PDM) using an optical monitor channel to facilitate the effective demultiplexing of the two orthogonal signal channels through automatic feedback control on a dynamic polarization controller and a polarization beam splitter.

Abstract: An orthogonal polarization multiplexing transmission apparatus capable of performing dispersion compensation considering a short wavelength side and a long wavelength side of a zero dispersion wavelength. A plurality of light signals of different wavelengths are divided into two orthogonal polarization multiplexing portions, and the light signals of an oddnumber array polarization multiplexing portion and an even-number array polarization multiplexing portion are orthogonal-polarization-multiplexed in each orthogonal polarization multiplexing portions. Adjacent light signals of the two orthogonal polarization multiplexing portions have their mutual planes of polarization rendered non-orthogonal when multiplexed by an optical multiplexer so that, for the purpose of deterring inter-symbol interference, a guard hand having the wavelength spacing rendered wider than that on orthogonal polarization multiplexing is provided in advance.

Abstract: A method and apparatus for utilizing tunable differential group delay with at least a component of a fiber optic transmission system includes providing a tunable differential group delay system that is optically connected to a component of the fiber optic transmission system. The tunable differential group delay system is then controlled to insert differential group delay into the component of the fiber optic transmission system.

Abstract: A method and system is provided for compensating polarization mode dispersion (PMD) in an optical communications system includes a controller designed to control a broadband PMD compensator to differentially delay light at each one of a plurality of selected wavelengths. At least one of the selected wavelengths lies between an adjacent pair of channel wavelengths of the optical communications system. A performance parameter value indicative of PMD is measured at each channel wavelength of the optical communications system. An estimated performance parameter value is then calculated at each selected wavelength, and an error function calculated as a function of wavelength based on the estimated performance parameter values. The broadband PMD compensator is then controlled to minimize the value of the error function.

Abstract: This application describes techniques for optical multiplexing and demultiplexing in optical communication systems based on polarization multiplexing of different signal channels.

Abstract: An optical packet switch switches optical packets according to bit-rates at which the optical packets are provided. For example, optical packets that are received at similar bit-rates may be routed to a destination at separate time slots over a single channel wavelength, and optical packets that are received at different bit-rates may be routed to the destination over separate channel wavelengths. When optical packets are provided at different bit-rates on a plurality of input paths, optical packets provided at low bit-rates may be compacted before switching to the destination. Alternatively or additionally, the bit-rates of the optical packets may be balanced before switching to the destination. Bandwidth contention among optical packets may be resolved by polarizing optical packets originating from separate input paths in different polarization directions, and merging optical packets having different polarization directions onto a single switched channel wavelength.

Abstract: A cross connector for the transparent switching of optical signals is disclosed, comprising a first switching module with one or several switching modules of varying granularity, such as patch panel, wavelength groups or/and wavelengths. A second switching device is connected in series with the first switching device and comprises a polarisation multiplex switching granularity.

Abstract: A method is provided for an equalization strategy for compensating channel distortions in a dual-polarization optical transport system wherein the received signal includes a complex signal of a first transmitted polarization component and a complex signal of a second transmitted polarization component. In a first step, a blind self recovery mode used a blind adaptation algorithm in calculating and modifying multiple complex equalizer transfer function coefficients to enables recovery of only the complex signal of the first transmitted polarization component. In a second step, equalization is performed in a training mode for recovery of the complex signals of the first and second transmitted polarization components. In a third step, equalization is performed in a data directed mode. The method is suited for a digital signal processing implementation in a coherent receiver.

Abstract: A method and system enables measurement of polarization dependent loss (PDL) in an optical communications system including a plurality of cascaded optical components. An optical signal having a predetermined initial polarization state is launched into the optical communications system. A polarization state of the signal is detected at a selected detection point downstream of the launch point. The PDE is evaluated using the predetermined initial polarization state and the detected polarization state.

Abstract: A dynamic equalizing optical channel router includes an input port for receiving a wavelength division multiplexed composite optical signal comprising a plurality of channels; at least one output port; a diffraction grating optically coupled to the input and output ports; a lens optically coupled to the diffraction grating at a side opposite to the input and output ports; an array of steering devices optically coupled to the lens at a side opposite to the diffraction grating, wherein each channel is reflected by a different steering device of the array; and a plurality of attenuators, wherein each channel reflected by the array traverses one of the attenuators and the diffraction grating to the at least one output port. The router is able to dynamically adjust optical intensity of each wavelength channel by a different amount while also performing the function of wavelength routing.

Abstract: Methods and systems for PMD compensation in an optical communication system are implemented by transmitting multiple optical signals through a common optical conduit to an optical compensator that adjustably rotates the polarization states of the multiple optical signals and transmits the rotated optical signals to an optical receiver. The receiver, upon sensing an excessive error condition, commands the optical compensator to change the polarization state of rotation, which changes the PMD profile of the received optical signals.

Abstract: A method and a system to produce, either in numerical simulations or in experiments, specified amounts of first, second and higher order PMD in a controlled manner, in particular large amounts. Parameters can be adjusted to obtain specific ranges of first, second and higher order PMD, and importance sampling can be used to determine the probability that the resulting PMD events can be obtained in realistic situations. Individual results obtained using specific parameter values can be combined to produce even larger ranges of PMD.

Abstract: A laser apparatus is disclosed combining polarized light beams from two optical emitters into a combined beam of light with controllable degree of polarization (DoP). The laser apparatus includes a polarization combiner for combining the polarized beams into the combined beam, an optical tap for separating out a portion of the combined beam, and a photodetector electrically coupled to a laser controller for providing a feedback signal. The controller distinctively modulates the polarized radiation of each of the emitters, detects modulation signals in the photodetector output and adjusts an output power ratio of the optical emitters for maintaining the DoP of the combined beam at a pre-determined level. The invention can be used for minimizing the DoP of pump radiation in Raman and EDFA pump laser modules combining multiple pump laser diodes.

Abstract: Method and system for flattening tilt gain with a digital title gain equalizer (“DTGE”) constructed with a linear tilt optical filter (“LTOF”). In a first embodiment, a DTGE flattens tilt gain with a combination of LTOF and a rotative half-wave plate. In a second embodiment, a DTGE flattens tilt gain with a combination of LTOF and variable Faraday rotators.

Abstract: An object of the present invention is to provide at low cost, a highly functional and small size optical amplifier, which realizes a polarization mode dispersion (PMD) compensation function and an optical amplifying function, with a simple construction.

Abstract: A polarization mode dispersion compensation apparatus using a photonic crystal structure includes an optical signal splitter for splitting and outputting incident optical signals into optical signals of a first and second polarization state; an optical signal combiner for combining and outputting the optical signals of the first and second polarization states; an optical signal guide having a photonic crystal structure having a first waveguide and a longer and variable second waveguide; a signal tab for externally outputting a portion of the optical signals and for outputting a portion of the optical signals to a feedback unit; a feedback unit for measuring a dispersion degree of the first and second polarization states inputted from the signal tab, and for outputting a feedback signal for removing the polarization mode dispersion; and an effective optical path length variation unit for varying an effective optical path length of the second waveguide.

Abstract: For setting the optical gain of an optical amplifier such as a Raman amplifier that is connected in a wavelength division multiplexing (WDM) system, the gain of the amplifier is made dependent on the states of optical polarizers connected to individual inputs of a WDM multiplexer. The polarizers can be actively controlled by a device connected to sense the output power of the Raman fiber at different wavelengths. For an appropriate control the optical gain can be given any desired shape such as for example a reasonable flatness. The control of the polarization states of the WDM-channels allows for the use of a single wavelength pump source of the amplifier, instead of the conventionally used multiwavelength source.

Abstract: An optical interleaver for use in a range of telecommunications applications including optical multiplexers/demultiplexers and optical routers. The optical device includes an optical processing loop which allows multi-stage performance characteristics to be achieved with a single physical filtration stage. Optical processing on the first leg and second legs of the loop is asymmetrical thereby improving the integrity of the optical signals by effecting complementary chromatic dispersion on the first and second legs. A fundamental filter cell within the interleaver filters optical signals propagating on each of the two legs of the optical loop which intersects the fundamental filter cell.

Abstract: A method and apparatus for transferring information of an optical information-bearing signal from a first wavelength to a second wavelength. The method is implemented in an all-optical wavelength converter circuit which includes a laser diode in communication with a polarization controller. An information-bearing signal having a first wavelength is input to the circuit. A polarization controller adjusts the polarization of the information-bearing signal. The laser diode receives the polarization-adjusted information-bearing signal and generates a converted information-bearing signal by transferring the information of the polarization-adjusted information-bearing signal from the first wavelength to the second wavelength. The polarization controller receives the converted information-bearing signal from the laser diode, and polarizes the converted information-bearing signal.

Abstract: An operation unit of a PMD compensation module includes a PBS (polarization beam splitter), a compensating part and a combiner. The PBS separates an optical input into a first polarized signal and a second polarized signal. The compensating part includes a fixed prism and a movable prism. The first polarized signal outputted from the PBS travels through the fixed prism and the movable prism in series. The light path of the first polarized signal in the movable prism is elongated or shortened according to a position of the movable prism. A continuously variable delay can thus be applied between the first and second polarized signals. The combiner recombines the first polarized signal received from the compensating part and the second polarized signal received from the PBS into an optical output signal.

Abstract: Method and system for flattening tilt gain with a digital title gain equalizer (“DTGE”) constructed with a linear tilt optical filter (“LTOF”). In a first embodiment, a DTGE flattens tilt gain with a combination of LTOF and a rotative half-wave plate. In a second embodiment, a DTGE flattens tilt gain with a combination of LTOF and variable Faraday rotators.

Abstract: A optical polarization encoding device (16) provides wavelength dependent processing of polychromatic optical signals without prior separation into narrow wavelength bands. Embodiments of the encoding device include a wavelength dependent tunable optical switch (400, 500) and a wavelength tunable optical level controller (600). An encoded signal is processed, (e.g., rerouted or attenuated), as a function of wavelength using polarization dependent devices (18). Desired states of polarization are imparted to optical signals to either direct selected wavelengths to selected output ports (optical switch), or to adjust the level of selected channels or wavelengths (level controller). Desired polarizations are achieved simultaneously at all wavelengths contained within the incoming signal by independently varying the birefringence and/or crystallographic orientation of each variable element within the stack.

Abstract: In an optical transmission system, a first modulated signal with a first transmission bit rate is generated at the transmitting end by modulating a first carrier signal with the first data signal, using a nonreturn to zero coding, and a second modulated signal with a second transmission bit rate is generated by modulating a second carrier signal with the second data signal, using a return to zero coding. The first and second modulated signal are polarized orthogonally with respect to one another and combined to form an optical multiplex signal and transmitted. At the receiving end, the optical multiplex signal is conducted via a polarization control element to a polarization splitter which splits the optical multiplex signal into the first and second modulated signal.