Abstract: Embodiments of the present invention provide systems, devices and methods for managing skew within a polarized multi-channel optical transport system. In a DP-QPSK system, skew between polarized channels is compensated within the transport system by adding latency to at least one of the polarized channels. The amount of added latency may depend on various factors including the skew tolerance of the transport system and the amount of skew across the channels without compensation. This latency may be added optically or electrically, and at various locations on a channel signal path within a transport node, such as a terminal transmitter or receiver. Additionally, various embodiments of the invention provide for novel methods of inserting frame alignment bit sequences within the transport frame overhead so that alignment and skew compensation may be more efficiently and accurately performed at the transport receiver.

Abstract: A fiber optical system (10) for transmitting an optical signal comprises an optical fiber line (1) with a plurality of successively arranged polarization scramblers (6a to 6c) for polarization modulation of the optical signal transmitted through the optical fiber line (1) and a reference frequency signal (11) which synchronizes scrambling frequencies of all of the polarization scramblers (6a to 6c) to a common reference frequency.

Abstract: Certain exemplary embodiments comprise a method that can comprise, responsive to an instruction to change a setting of a polarization controller, automatically changing a first rotational speed of a birefringent plate associated with the polarization controller to orient the birefringent plate pseudo-randomly over time with respect to a predetermined axis.

Abstract: The invention relates to a method and a system for controlling a PMD compensator (2). For this purpose, a measuring signal (MS) is branched off from an already compensated optical data signal (ODSK) and supplied to a polarization adjuster (2). The output signal of the latter is supplied to an optical filter unit (61) and subdivided into two optical measuring signal components (OMKI, OMK2) having different polarizations. After a respective opto-electrical conversion, the spectra are compared with each other in an analysis and control unit (81) and the PMD compensator (2) is adjusted in such a manner that they are as identical as possible.

Abstract: In an optical detection method that requires a reference light such as homodyne detection, a signal light and the reference light must be equal to each other in the wavelength, and the phase relation between them must be maintained constant. In order to satisfy this requirement, the signal light and the reference light are extracted from the same light source and made equal to each other in the wavelength. The signal light and the reference light are transmitted so as to be temporally superimposed on each other with orthogonal polarizations to the same optical path, thereby making the external environments equal to each other to maintain the constant phase relation.

Abstract: A method of recovering a clock signal from an optical signal received through an optical communications system. A digital sample stream is processed to generate a dispersion compensated signal. The dispersion compensated signal is then tapped to obtain upper side band and lower side band signals of each received polarization of the optical signal. The upper side band sand lower side band signals are then processed to compensate polarization dependent impairments and the clock recovered from the resulting optimized.

Abstract: A method of a conveying data through an optical communications system. An optical signal is received through the optical communication system, the optical signal comprising data symbols and SYNC bursts, each SYNC burst having a predetermined symbol sequence. The received optical signal is oversampled to generate a multi-bit sample stream. The sample stream is partitioned into blocks of contiguous samples, wherein each block of samples partially overlaps at least one other block of samples and encompasses at least one SYNC burst and a plurality of data symbols. Each block of samples is independently processed to detect a value of each data symbol.

Abstract: Example embodiments of a near-Infrared (NIR) sensor system and methods for detecting changes in polarization are generally described herein. Other example embodiments may be described and claimed. In some example embodiments, the sensor system includes a transmit optical element to transmit optical signals with a polarization, and a receive optical element to receive optical signals with an orthogonal polarization. The transmit and receive optical elements may include nano-imprinted wire-grid polarizers configured to polarize at least infrared IR wavelengths. In some example embodiments, birefringent filter layers may be used to induce an additional polarization state on the transmitted and received optical signals.

Abstract: Embodiments include n apparatus including a color sensor including a transmitter portion and a receiver portion, the transmitter portion including a light source operable to generate and transmit a light having a particular range of wavelengths, the receiver portion including a first detector operable to receive a first portion of the light emitted from the transmitter portion and to measure a luminance of the received first portion of the emitted light, and a second detector including a polarization filter, the second detector operable to receive a second portion of the light emitted from the transmitter after the second portion has passed through the polarization filter, and operable to measure a pure color of the received second portion of transmitted light.

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: Binary signals are converted at the transmission end into two optical signals which are combined into a polarization multiplex signal and are then transmitted. The transmitted polarization multiplex signal is divided at the receiving end into two polarized signal parts which are converted in a linear manner into orthogonal electrical components and are supplied to a multidimensional filter. Said multidimensional filter replaces a polarization controller, restores the signal values that correspond to the signals at the transmission end, and compensates signal distortions.

Abstract: Digital compensation of the polarization-mode dispersion (PMD) effects experienced by an optical signal in a transmission link is achieved. A digital representation of the optical fields of two orthogonal polarization components of an optical signal, defined by a polarization beam splitter (PBS), is first obtained. The fiber transmission link is treated as a concatenation of multiple virtual PMD segments, each having two specific principle-state-of-polarization (PSP) axes and causing a differential group-delay (DGD) and a phase delay between two signal components that are polarized along the two PSP axes. The best guesses of the parameters of the PMD segments and the relative orientation between the PSP axes of the last PMD segment and the characteristic polarization axes of the PBS are dynamically obtained. The digital representation of at least one generic component of the field of the optical signal is then computed through matrix operations by using the best guesses.

Abstract: A filter conducts the round trip by using the return optical signal that has been shifted in frequency, and measures the transmission optical signal and the return signal in phase by the principle of the Michelson interferometer at the same time, independently, and splits the two optical signals. A polarization state in which transmission and reception optical signals within an optical phase shifter which enters one route of the two optical signals are made orthogonal to each other is provided, to thereby distinguish the transmission and reception signals of the round trip from each other. The light is allowed to pass the shifter in incoming and returning to remove the polarization rotation of the shifter by using the reversibility of the light. Then, the phases of the transmission signal and the return signal are measured and synchronized with each other to conduct the transmission phase compensation.

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: A high-luminance quantum correlation photon beam generator in which a laser light source (1) emits a laser pumped light and a parametric crystal (2) generates a pair of two photons of a signal photon and an idler photon on receiving the pumped light to emit two photon beams. Further, a beam splitter (5) splits a signal photon beam (6) from an idler photon beam (7), a mode inverter (10) rotates one of the signal photon beam, (6) and the idler photon beam (7) 180° around its geometric center, a phase adjusting means (8) adjusts phases of the signal photon beam (6) and the idler photon beam (7) based on an optical time delay, and a beam coupling means (14) overlays the signal photon beam (6) with the idler photon beam (7) in a common-line polarized annular shape by the mode inverter (10) to bring them into a quantum correlated state.

Abstract: An apparatus and method are provided for filtering an optical signal by wavelength. An initially polarised signal is passed through a DGD element effective to alter the polarisation state of the components of the signal according to wavelength. A polarisation filter (polariser) is then provided to attenuate light having given polarisation states from the signal, thereby attenuating the wavelengths associated with said polarisation states. The invention finds particularly utility in the domain of vestigial sideband filtering, allowing the bandwidth of signals within a wavelength division multiplexed system to be reduced without introducing the deleterious effects associated with conventional wavelength filters.

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: In the transmitting apparatus, phase modulation means phase-modulates a signal light from a signal source based on data. Polarization modulation means polarization-modulates the signal light which is phase-modulated by the phase modulation means so that the polarization directions of temporally adjacent unit data are orthogonal to each other. In the receiving apparatus, interference means causes the signal light transmitted from the transmitting apparatus to interfere with a signal light such that the signal light is delayed by an even number of unit data. Intensity detecting means detects the intensity of the signal light obtained by interference by the interference means to detect data.

Abstract: For readjusting a polarization drift in the transmission of a polarization-encoded optical signal from a transmitter via a light guide to a receiver, optical auxiliary signals having the same wavelength as the polarization-encoded signal as well as different polarizations as in correspondence with a first base and a second base are fed into the light guide on the side of the transmitter while the transmission of the polarization-encoded signal is interrupted, and the optical auxiliary signals are picked up from the light guide and checked for shifts of the different polarizations by a polariometer on the side of the receiver, whereupon, in the event of the detection of polarization shifts, the different polarizations shifted during the transmission are displaced in the sense of the polarization set values via a polarization controller associated with the light guide.

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: An optical transmitter apparatus for use in an optical communications network has a polarization dithering unit, an optical transmitter unit, and a transmission fiber. The polarization dithering unit is connected in series between an output of the optical transmitter unit and the transmission fiber.

Abstract: A squeezed light generator comprises an arbitrary optical fiber, a means for temporally separating two linearly polarized components, two Faraday rotators and a high-reflection mirror. Pulse lights that are temporally separated into two orthogonally polarized components at an intensity ratio of 50:50 are reciprocatively propagated in the optical fiber, and the polarized light is rotated by 90° in an outward transmission. Since those two polarized components pass through the optical paths which are accurately equal to each other in the outward and homeward transmissions, those two polarized components interfere with each other accurately at 50:50 after reciprocation through the fiber. The interfered beam is separated by a polarizing beam splitter that is high in an extinction ratio. When the polarized lights before inputting the fiber and after reciprocating coincide with each other, it is unnecessary to maintain the polarization in the fiber propagation, and an arbitrary fiber can be used.

Abstract: Systems and methods of polarization-time coding are disclosed. One method includes encoding information in orthogonal polarizations of light and correlated information in multiple time slots, and transmitting the information using the orthogonal polarizations in the time slots. Another method includes receiving a first input pair which specifies a first polarization state and a second input pair containing which specifies a second polarization state; transforming each input pair according to a matrix specifying a conjugate operation to produce four output pairs. The method further includes transmitting at a first time the first output pair using the first polarization state and the third output pair using the second polarization state. The method further includes transmitting at a second time the second output pair using the first polarization state and the fourth output pair using the second polarization state.

Abstract: An apparatus and method of transmitting a plurality of polarized signals having different wavelengths through a length of signal transmission cable which changes the polarization of the signals in correspondence with their amplitudes and wavelengths. A dynamic filter capable of differential adjustment of the amplitudes of the signals and a polarizing element are provided in series with the length of signal transmission cable and the amplitudes of the different wavelength signals are so adjusted that the polarization states of the signals move towards alignment with the low-loss axis of the polarizing element. An advantage provided by the apparatus and method is that the high-amplitude signals are aligned with the low-loss axis of the polarizing element while low-amplitude noise is aligned with the high-loss axis of the polarizing element, resulting in an improvement in signal-to-noise ratio.

Abstract: A transmitter subsystem generates an optical signal which contains multiple subbands of information. The subbands have different polarizations. For example, in one approach, two or more optical transmitters generate optical signals which have different polarizations. An optical combiner optically combines the optical signals into a composite optical signal for transmission across an optical fiber. In another aspect, each optical transmitter generates an optical signal containing both a lower optical sideband and an upper optical sideband (i.e., a double sideband optical signal). An optical filter selects the upper optical sideband of one optical signal and the lower optical sideband of another optical signal to produce a composite optical signal.

Abstract: A method for the adaptive adjustment of a PMD compensator in optical fiber communication systems comprises the steps of taking the signal at the compensator output and extracting the components y1(t) and y2(t) on the two orthogonal polarizations, computing the signal y(t)=[y1(t)]2+[y2(t)]2, sampling the signal y(t) at instants tk=kT with T=symbol interval to obtain samples y(tk), computing the mean square error e(k)=y(tk)?u(k) with u(k) equal to the symbol transmitted, and adjusting the parameters of the compensator to seek to minimize e(k).

Abstract: Provided are an auto-compensating quantum cryptography transceiver and method of transmitting a quantum cryptography key at a high speed. A quantum cryptography transmitter includes a wavelength converter, an optical attenuator, an optical phase modulator, and a Faraday mirror. A quantum cryptography receiver includes a polarization beam splitter, an optical coupler, an optical filter, and a photon detector. Thus, a limit of a transmission rate caused by Rayleigh scattering of an optical fiber can be overcome.

Abstract: A wavelength converter for binary optical signals includes an interferometer structure (110) for generating an output signal by modulating a received local signal (LS) according to the modulation of a fUrther received first input signal (IS 1). When such interferometer structures (110) are operated in a standard mode it is known in the art to control the power of the input signal such that the extinction ratio of the output signal is kept minimal. The invention also controls the power of the input signals to achieve the minimal extinction ratio when the wavelength converter and in particular the interferometer structure (110) is operated in a differential mode receiving two input signals.

Abstract: By using low-frequency signals, an optical transmitting unit modulates one of a wavelength, a transmission timing, and an intensity of light as a carrier wave. A polarization multiplexer synthesizes the output light signals, modulated by the optical transmitting unit, in polarization states orthogonal to each other and generates polarization-multiplexing signals. A polarization splitter splits by extracting two orthogonal polarization components from the polarization-multiplexing signals. The polarization states of the polarization-multiplexing signals are controlled by a polarization controller in an optical receiving unit. A band-pass filter extracts components transmitting through passbands from output signals of the optical receiving unit and outputs an intensity of the components.

Abstract: An optical transmitter splits a linear polarization optical carrier into a TE wave and a TM wave. One of the TE wave and the TM wave is phase-modulated with a transmission data so as to generate a phase-modulated signal. The phase-modulated signal and the other one of the TE wave and the TM wave are coupled with a linear polarization and output into an optical transmission line. An optical receiver splits a light input from the optical transmission line into the TE wave and the TM wave. The TM wave or TE wave is converted into the TE wave or TM wave to interfere with the TE wave or TM wave. The interfered signal light is converted into an electric signal for restoration of the data.

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: 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 dynamic dispersion compensation system and method are provided. The method dynamically compensates for dispersion in an optical signal by recovering a first clock and a second clock from a first polarization component and a second polarization component of the optical signal respectively, determining a delay time between the first clock and the second clock, determining the dispersion based on the delay time and dynamically compensating for the determined dispersion. The system comprises a polarization beam splitter, a clock recoverer, a dispersion determiner and a tunable dispersion compensation module and is operable to dynamically compensate for the dispersion in an optical signal.

Abstract: The invention relates to a device which is used for the spectral analysis of optical signals and which is based on the stimulated Brillouin scattering effect. The invention also relates to the associated measurement method which makes use of the optical signal amplification caused by the Brillouin scattering effect. The Brillouin scattering effect enables the selective optical amplification of a determined component of the optical spectrum of the signal to be analysed, known as the problem signal, for the measurement thereof with a determined dynamic range, sensitivity and resolution. According to the invention, the problem signal is introduced into an optical fibre together with a narrowband optical signal, known as the probe signal, with a determined wavelength. Said probe signal propagates in the opposite direction to that of the problem signal, such that both signals interact inside the fibre owing to the Brillouin effect.

Abstract: An optical clock signal regeneration device, which includes a mode-locking laser element, a signal light provision component and an optical clock signal formation component, is provided. The signal light provision component includes a birefringent medium, at which a polarization group delay time between orthogonal polarization signals, which is caused by a difference in refractive indices between orthogonal optical axes, is a natural number multiple of a signal time interval of an inputted signal light, and, on the basis of orthogonal polarization signal light obtained by passing input signal light which is inputted from outside through the birefringent medium, provides at least a signal light component with a light polarization direction that matches an oscillation polarization direction of the mode-locking semiconductor laser to the mode-locking laser element.

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: A system operable to monitor a polarization controller includes the polarization controller and a polarization controller monitor. The polarization controller polarizes the signal to yield a polarized signal comprising a first signal component and a second signal component, where the first signal component is orthogonally polarized with respect to the second signal component. The polarization controller monitor monitors a first polarization indicating waveform of the first signal component and a second polarization indicating waveform of the second signal component. The polarization controller monitor determines whether to adjust polarization of the received signal by polarization controller in accordance with the first polarization indicating waveform and the second polarization indicating waveform.

Abstract: The present invention provides a system and method of optical communications that utilize coherent detection technique and optical orthogonal frequency division multiplexing for phase encoded data transmission. In particular the invention addresses a device and method for digital polarization compensation of optical signals with up to 100 Gb/s transmission rate received via an optical link. The polarization compensation operates in two modes: acquisition mode and tracking mode. The polarization recovery is performed at the receiver side using the received digital signal conversion into frequency domain and separate reconstruction of the polarization state in each spectral component.

Abstract: This application describes optical monitoring devices and applications in optical systems for monitoring various optical parameters of light, including the signal to noise ratio, the degree of polarization, and the differential group delay (DGD).

Abstract: According to an aspect of embodiment, an optical switch comprises a signal light input unit, a control light input unit, a first polarization controller, a second polarization controller, a coupler, a nonlinear medium, a monitor and a controller. The first polarization controller controls a polarization of a signal light. The second polarization controller controls a polarization of a control light. The nonlinear medium generates an intensity correlation signal. The monitor monitors a polarization state of light outputted from the nonlinear medium. The controller controls the first polarization controller and the second polarization controller on the basis of the polarization of the signal light and the polarization of the control light.

Abstract: According to an aspect of an embodiment, an optical switch comprises: a coupler for coupling a signal light and a control pulse; a first nonlinear medium for amplifying the signal light in accordance with the polarization direction of the control pulse light by nonlinear effect; a first polarizer outputting a component light in a signal light and the control pulse light in parallel with the transmission axis of the first polarizer; a second nonlinear medium for changing status of polarization of the signal light by nonlinear effect; and a second polarizer outputting a signal light and a control pulse light in parallel with the transmission axis of the second polarizer.

Abstract: Methods, devices and/or systems are provided for reducing signal degradations in optical transmission links. A means for ensuring a flexible manipulation for the improvement of an optical signal, especially during operation, is provided in a simple and cost-effective manner. To this end, a signal degradation in an optical transmission link is reduced by at least partially compensating a chromatic dispersion and a polarization mode dispersion of an optical signal, by adapting the temperature of a dispersion compensation device coupled into the transmission link.

Abstract: The wavelength converter comprises (1) an optical multiplexer for multiplexing an amplitude-modulated first light and reference light, which is continuous light having a wavelength different from the wavelength of the first light, (2) an optical fiber for propagating the multiplexed light therethrough to generate a third light by a non-linear optical phenomenon, and (3) an optical filter having a pass wavelength range set such that a pulse time width of the third light is 20% or more narrower than a pulse time width of the first light after the third light has passed through the optical filter, or (3?) an optical filter having a pass wavelength range set such that a cross point of an eye pattern of the third light is lower than a cross point of an eye pattern of the first light after the third light has passed through the optical filter.

Abstract: Influence of polarization mode dispersion, occurring in an optical fiber is mitigated by means of polarization scrambling, differential group delay which a received optical signal has is optically suppressed; the optical signal in which differential group delay is thus suppressed is converted into an electric signal; and error correcting processing is carried out on the electric signal obtained, a jitter amplitude in the received optical signal is suppressed, influence of which to a jitter tolerance increases due to increase in speed of the polarization scrambling.

Abstract: A method for reducing intra-channel, non-linear distortions of an optical signal resulting from non-linear fiber propagation includes applying a polarization mode dispersion (PMD) pre-distortion to an optical signal such that the PMD pre-distortion produces two replica signals of the optical signal spaced by a differential group delay (DGD). The replica signals are adapted for transmission via an optical fiber. The DGD spacing is selected to reduce intra-channel, non-linear distortions imparted by the optical fiber.

Abstract: A method and apparatus for switching at least one wavelength component of an optical signal beam from a first state to a second state. The phase characterizing the optical signal component is incremented by interaction with one or more escort beams in a non-linear medium thereby switching the state of the optical signal component on the basis of its incremented phase. Multiple escort beams may also be employed to switch different wavelength components of the signal. The method may be employed to achieve high speed, and substantially transparent, switching of phase, intensity or polarization of a signal.

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: The present invention is directed to an in-passband signaling method. The method includes the steps of extracting a control component and a data component from an optical signal. The control component may be used to determine the state of an optical switch in either a packet-switched network or circuit-switched network. The state of the optical switch is switched based on the extracted control signal. The control component may also be used to provide other network functions such as network operations, administration, and management (OA&M), network monitoring, and network control and management (NC&M). The control component is erased by polarization realignment of the optical signal. The control component is updated by remodulating the polarization state of the data component.