Abstract: For transmitting information on an optical fiber, a plurality of information carrier channels at different carrier frequencies and a plurality of filling channels are used. The filling channels are transmitted together with the information carrier channels along the fiber. The total optical power of the information carrier channels and the filling channels transmitted on the fiber is maintained constant by compensating every change of the optical power of the information carrier channels by an inverse change of the optical power of the filling channels. The change of the optical power of the filling channels is distributed to the individual filling channels such that a minimum displacement of the center of gravity of the common spectrum of information carrier channels and filling channels results.

Abstract: An optical transmission line monitoring device is provided including a device which calculates a management amount based on an optical intensity of returning light, a reference data storage device which stores reference management amounts beforehand, a detecting device which in response to the calculated management amount being of poorer quality than the reference management amount stored in the reference data storage device detects a distance, creates detection data based on the calculated management amount, and stores the created detection data in a detection data storage device, an alarm outputting device that creates alarm data based on the detection data created by the detecting device, and displays the created alarm data on a screen, an inputting device that inputs selection command data indicating that the alarm data displayed on the screen will not be output, and a removal data adding device that adds, to the detection data stored in the detection data storage device corresponding to the alarm data of

Abstract: A data transmission system has a light-emitting transmitter, a light-receiving receiver and a data transmission channel based on incoherent light. A pre-equalization device connected upstream of the transmitter is provided for the purpose of pre-equalizing a data signal which is to be transmitted from the transmitter to the receiver via the data transmission channel. The data transmission channel has constant transmission conditions within prescribed limits. The data signal to be transmitted is transmitted using a prescribed maximum bandwidth of the transmitter.

Abstract: A fiber optic communication system includes a first fiber optic device configured to transmit a fiber optic signal. A second fiber optic device is in fiber optic communication with and configured to receive the fiber optic signal from the first fiber optic device. The second fiber optic device includes an adjustment circuit configured to automatically adjust the fiber optic signal if the fiber optic signal is transmitted outside of a predetermined signal strength range.

Abstract: In a receiver, a skew detector detects a skew between two synchronization symbols having different wavelengths among synchronization symbols included in received signals. A skew rough adjustment calculator calculates a delay compensation amount for each received signal based on the skew and a signal delay characteristic in a transmission path. A variable delay processor deskews the received signals based on the delay compensation amount.

Abstract: A forward error correction (FEC) communication device that includes a transmitter photonic integrated circuit (TxPIC) or a receiver photonic integrated circuit (RxPIC) and a FEC device for FEC coding at least one channel with a first error rate and at least one additional channel with a second error rate, wherein the first error rate is greater than the second error rate. The TxPIC chip is a monolithic multi-channel chip having an array of modulated sources integrated on the chip, each operating at a different wavelength, wherein at least one of the modulated sources is modulated with a respective FEC encoded signal. The TxPIC also includes an integrated wavelength selective combiner for combining the channels for transport over an optical link.

Abstract: An optical transmission system is provided in which the optimum operating point of a Mach-Zehnder interferometer, matched to the optical frequency of the light source on the transmitting side, can be set.

Abstract: The present invention discloses a transmitter and receiver for optical communications system, which provide compensation of the optical link nonlinearity. M-PSK modulating is used for data embedding in an optical signal in each WDM channel using orthogonal frequency division multiplexing (OFDM) technique. At the receiver side electrical output signals from a coherent optical receiver are processed digitally with the link nonlinearity compensation. It is followed by the signal conversion into frequency domain and information recovery from each subcarrier of the OFDM signal. At the transmitter side an OFDM encoder provides a correction of I and Q components of a M-PSK modulator driving signal to compensate the link nonlinearity prior to sending the optical signal to the receiver.

Abstract: A system, method, and communication device are disclosed. The system can include an optical interrogator and a phase-modulating communication device. The communication device can include a retro-optimized lens, a phase modulator, and a processor. The retro-optimized lens can be a non-imaging optical arrangement configured to minimize deviation between an incoming signal and a reflected signal used for return link communications. The processor can be configured to calibrate a modulation path length of the communication device based on a wavelength of the communication signal and can control an operation of the phase-modulator to send phase-coded messages to the interrogator. Optionally, the processor can perform a real-time phase calibration of the communication device using feedback from the interrogator.

Abstract: In order to enhance dispersion control, the apparatus includes a dispersion controller; a quality index generator generating a quality index representing a quality of an optical signal output from the dispersion controller; and a searching unit searching for an amount of dispersion control applying to the dispersion controller which amount optimizes the quality index, wherein the searching unit includes a splitting-half searching unit roughly searching, in a splitting half method, a range in which dispersion is controllable by the dispersion controller for an amount of dispersion control such that the quality index generated by the quality index generator becomes preferable, and a sweep searching unit thoroughly searching, by sweeping, a limited range based on the amount of dispersion searched by the splitting-half searching unit for an amount of dispersion control that optimizes the quality index generated by the quality index generator.

Abstract: The present invention is directed toward a method for setting a driving voltage of a differential quadrature phase-shift modulator, this method making signal quality superior in response to an individual difference in extinction ratio due to variations in manufacture of a device. To this end, signal quality of differential quadrature phase-shift modulated light output from a differential quadrature phase-shift modulator is acquired. An average amplitude of a first or second driving voltage signal is adjusted according to the signal quality of the thus-acquired differential quadrature phase-shift modulated light.

Abstract: An economical optical network is constituted by effectively using network resources by using the minimum number of, or minimum capacity of 3R repeaters. 3R section information corresponding to topology information on the optical network to which an optical node device itself belongs is stored, and the 3R section information stored is referred so as to autonomously determine whether or not the optical node device itself is an optical node device for implementing the 3R relay when setting an optical path passing through the optical node device itself. Alternatively, when the optical node device itself is a source node, another optical node device for implementing the 3R relay among the other optical node devices through which the optical path from the optical node device itself to the destination node passes is identified, and this identified optical node device is requested to implement the 3R relay when setting an optical path in which the optical node device itself is a source node.

Abstract: A bias-control circuit that provides operating point control for a Mach-Zehnder modulator experiencing optical absorption at their interferometric arms. The bias control circuit generates compensation signals that are used to counter the thermally induced index shifts as a result of absorption. In addition, an operating point with desirable transmitter characteristics can also be arbitrarily chosen by over-compensating or under-compensating thermal effects.

Abstract: Methods and apparatus for optical-power control in an optical network employing wavelength-division multiplexed (WDM) optical-fiber links are devised to circumvent the effect of crosstalk caused by optical-power scattering. Each carrier signal is amplitude-modulated by an identifying tone, with the power of an identifying tone having a predetermined ratio to the power of its carrier signal. A fiber span within an optical-fiber link is tapped at a preferred monitoring point, and the power spectrum of the envelope of the tapped optical signal is measured. To estimate an individual carrier power, a temporary gain is applied and the power of a corresponding tone is measured. To control optical power of each wavelength carrier in several spans in the network, a network controller selects an order of processing the spans of interest, and selects the order of processing of each channel within each span.

Abstract: A method of suppressing effects of aliasing in a system for digitally processing a high speed signal having a symbol rate of 1/T. The high speed signal is sampled at a fractional multiple (N) of the symbol rate, wherein 1<N<2, to generate a corresponding sample stream, and filtered using a low-pass filter characteristic having a cut-off frequency corresponding to 1/2T. Phase distortions due to the filtering are compensated by digitally processing the sample stream.

Abstract: A system and method for dispersion compensation of an optical signal in a hybrid network includes generating optical traffic in a first set of one or more channels, wherein the traffic in the first set of channels is modulated using a first modulation technique. Optical traffic is generated in a second set of one or more channels, wherein the traffic in the second set of channels is modulated using a second modulation technique. An optical dispersion pre-compensation is applied to the second set of channels. The first set of channels and the second set of channels are combined to form an optical signal, and the optical signal is transmitted over an optical network.

Abstract: An interference-rejection coding method for an optical wireless communication system and such an optical wireless communication system are provided. The coding method uses delay modulation, block code techniques and filtering to reduce the low frequency interference from light sources. A plurality of codewords from the block codes are reserved for performing digital data recovery. The invention removes the need of analog clock data recovery circuit, and does not require complex hardware for realization. Therefore, it can be applied to a wide range of applications, such as optical WLAN, data transmission of medical facilities, wireless communication in the aircraft, encrypted data transmission network, and low-priced transmission interfaces.

Abstract: Described is a method of reducing transmitter error in an optical communications channel. An optical signal transmitted from an optical transmitter that has impairment due to transmitter error is processed to generate a digitally-equalized signal. A nonlinear characteristic of the digitally-equalized signal that relates to the transmitter error is determined. An optical control signal comprising data that are based on the nonlinear characteristic is transmitted to the optical transmitter. The optical transmitter modifies a transmitter parameter in response to the optical control signal to change the nonlinear characteristic and thereby reduce the impairment.

Abstract: Ultra-miniaturized THz spectrometer/multi-channel receiver devices are provided. THz communication devices employ a THz transmitter, a THz receiver and a modulator, wherein the THz transmitter is configured to introduce a THz signal to the modulator and the THz receiver is configured to receive the THz signal from the modulator and demodulate the signal. Communication systems and methods employing the THz spectrometer/multi-channel receiver devices enable secure communications. Portable THz emitter devices are provided employing semiconductor lasers and a nonlinear birefringent waveguide monolithically integrated on the same substrate.

Abstract: Certain aspects of a method and system for optimum channel equalization between a host Serializer-Deserializer (SerDes) and an optical module may compensate and reduce dispersion loss along an electrical transmit path of a transmitter and an optical transmit path coupled to the transmitter via pre-emphasis. The data degradation as a result of the dispersion loss along the electrical transmit path of the transmitter and the optical transmit path coupled to the transmitter may be recovered by equalizing signals received via an electrical receive path of a receiver communicatively coupled to the transmitter.

Abstract: An optical communications system for conveying traffic through an optical link between transmitting and receiving nodes. The system comprises, for each node, respective legacy and bypass paths coupled in parallel between the optical link and the node. The legacy path of each node includes an optical dispersion compensation block for compensating a respective portion of dispersion of the link. Thus the present invention provides a system architecture by which an optical communications system can be constructed using conventional modulation and optical dispersion compensation technologies. Once installed, system growth can be accommodated using next generation transmitters (with electronic compensation) without stranding the legacy equipment. Legacy channels can also be upgraded to electronic compensation, as desired.

Abstract: An optical transmission system that alleviates waveform distortions due to nonlinear effects in fibers. A transmitter sends WDM signals to a receiver over a dispersion-managed optical transmission line with in-line optical repeaters. The transmission line is divided into a plurality of dispersion compensation intervals each composed of a main segment and a compensation segment. Chromatic dispersion is managed such that the dispersion compensation intervals have a non-zero net dispersion at every boundary point between them, or such that the number of zero-dispersion boundary points is reduced. The main segment is a series of repeater sections with negative dispersion, while the compensation segment is a single repeater section with positive dispersion.

Abstract: A method for creating a logic state for teleporting quantum information using a single photon is described. The method includes receiving a photon with an initial polarization and causing a first semiconductor crystal to have a first spin orientation. The photon interacts with the first semiconductor crystal for producing a resulting polarization dependent upon the first spin orientation. Causing the photon to interact with the first semiconductor crystal generates a maximally entangled state.

Abstract: An optical correlation apparatus is described which forms first and second parallel optical signals in response to a serial input data stream. The first parallel optical signal is arranged to have bright pulses represent binary 1 and the second parallel optical signal is arranged to have bright pulses represent binary 0. A channel select means, such as an optical switch or amplitude modulators deselects or blocks channels in the first parallel optical signal which correspond to binary 1 in a reference data string and also deselects or blocks channels in the second parallel optical signal which correspond to binary 0 in the reference data string. The remaining optical signals are combined at one or more detectors. Where the input data matches the reference data string each bright pulse in the first and second parallel optical signals is deselected and the detector registers zero intensity. However when there is any mismatch at least one channel will pass a bright pulse to the detector.

Abstract: Methods and apparatus (100) for composing, generating and transmitting information-bearing optical signals are provided. An information-bearing electrical signal is composed (108) having desirable spectral properties, preferably configured to ensure that undesired interference between electrical spectral components generated in a square-law direct detection process (120) at a corresponding optical receiver (104) is substantially avoided. Predistortion (110) is advantageously applied to transmitted signals, in order to account for a nonlinear relationship arising in a modulation process (114) between electrical signal amplitude and corresponding optical field amplitude. Orthogonal frequency division multiplexing (OFDM) techniques may be applied to composed signals having the desired characteristics, and additionally may facilitate the application of frequency domain equalisation (128) in order to mitigate transmission impairments, including dispersion.

Abstract: The present invention includes a fast algorithm to compute the pre-equalized waveform for simultaneous compensation of the self-phase modulation and chromatic dispersion experienced by a high-speed optical signal, e.g., at 10 Gb/s, and shows that it is used for an automatic self-adapting pre-equalization when the knowledge on transmission link details is inaccurate or incomplete.

Abstract: Provided is a fiber ring laser capable of obtaining a back-up laser light and standard light having a wavelength continuously tuned in a single mode with equal spacing of 12.5 GHz, 25 GHz, 50 GHz or 100 GHz recommended by ITU-T Recommendation G. 692 & G. 694.1 in a C-band and an L-band using a fiber tunable etalon filter, an air gap etalon filter and a saturable absorber in an optical fiber laser resonator having a serial ring shape using a C-band optical amplifier and an L-band optical amplifier. The fiber ring laser can generate laser light having a wavelength tuned by more than 70 nm, excellent output power flatness and a source spontaneous emission ratio of more than 70 dB in 361 channels with equal spacing of 25 GHz by applying a bias voltage to a voltage-operated piezoelectric element of a tunable etalon filter. A single longitudinal mode operation of the fiber ring laser can be obtained by using a saturable absorber serving as a narrow-bandwidth filter.

Abstract: A low-cost configuration of, and at the same time to control the variable dispersion compensator at a high speed in a variable dispersion compensator for compensating the wavelength dependent accumulated dispersion resulting from the wavelength dependency of the transmission fiber and fixed dispersion compensator in a long-distance high-speed WDM transmission system. In order to achieve the object mentioned above, the wavelength dependent representative characteristic of the transmission fibers 4-1 . . . n, and the wavelength dependent representative characteristic of the DCFs 13-1 . . . n are recorded and maintained in advance in the dispersion control circuit 5-1 . . .

Abstract: An apparatus for generating a dispersion compensation signal includes a splitting module for splitting a data signal to be transmitted into N channels of data signals; N pre-processing modules for adjusting in frequency domain the phases and amplitudes of the N channels of data signals and outputting N channels of pre-warped electrical signals; an optical carrier generating module for generating N channels of coherent optical carriers; N electro-optic modulators for modulating the N channels of coherent optical carriers based on the N channels of pre-warped electrical signals and generating N channels of pre-warped optical signals; an optical coupling module for coupling the N channels of pre-warped optical signals into a dispersion compensation optical signal. By pre-processing the data signals, the present disclosure may allow the use of existing devices to generate a dispersion compensation signal so that the bandwidth requirement set by prior art on the electrical device is reduced.

Abstract: Provided are a frequency extracting apparatus and a signal extracting system employing the same. The signal extracting system can reduce the effect of an input signal pattern by extracting two frequency components and beating them to extract a desired clock signal, and improve a signal-to-noise ratio of an extracted clock signal. The frequency extracting apparatus includes: a circulator for changing an output direction of an input signal; a reflective filter for extracting a desired frequency component among frequency components of the input signal; a wavelength and amplitude controlling unit; and the frequency amplitude controller.

Abstract: Systems and methods are provided for multi-channel ITU G.709 optical transport network (OTN) transmission and receiving. The transmission method accepts a canonical ITU G.709 OTN frame including an OTU overhead (OH) section, an ODU section, and a forward error correction (FEC) parity section. A training signal wrapper is added to the ITU G.709 OTN frame, and at least a portion of a training-enhanced (TE) OTN frame is buffered in a tangible memory medium in preparation for striping. The method stripes the training-enhanced OTN frame into n parallel streams to supply n TE_OTN-PFs (Parallel Frames) at an output.

Abstract: An open-path optical communication system has either optical or laser sources and communicates between the source and a detector. In a first embodiment, the laser source includes a gas cell in the laser cavity to regulate laser wavelengths based on the minimum absorption between spectral lines of the gas in the cell. The laser is tuned close to a minimum absorption wavelength and the minimum absorption line locks the laser wavelength to the minimum position. In a second embodiment, the strong absorption lines of a gas in a gas cell positioned at a receiver site are used to provide channel isolation of the receiver. In a third embodiment, an atmospheric gas provides the channel isolation. In the fourth embodiment, individual wavelength channels are positioned between the absorption lines of atmospheric or non-atmospheric gases to prevent cross-talk between adjacent channels.

Abstract: The present invention provides an optical receiving device, in which a portion of an optical signal is deflected for optical axis detection only when the optical axis is misaligned to thereby achieve a high S/N ratio of a received signal. A condensing section 100 condenses a received optical signal. An optical element 110 includes a transmission region 111 and a deflecting region 112, and receives the optical signal, which has been condensed through the condensing section 100. A signal light receiving section 120 receives the transmitted light, which has been transmitted through the transmission region 111. A detection light receiving section 130 receives deflected light, which has been deflected through the deflecting region 112 and performs a photoelectric conversion on the received light to thereby output a detection intensity signal that indicates an intensity of the deflected light.

Abstract: A non-linear phase noise limiter device limits the non-linear phase noise that affects a phase-modulated input optical signal of constant mean amplitude conveyed over a transmission line. The device is placed at a zero dispersion point of the transmission line, and it is suitable for suppressing amplitude fluctuations about a mean value in said optical signal.

Abstract: A distortion circuit is provided for correcting the distortion from a nonlinear circuit element by generating a frequency dependent signal having a sign opposite to the distortion signal produced by the nonlinear circuit and substantially the same magnitude. The distortion circuit includes an input signal and a first nonlinear device coupled to the input signal for generating a first signal and where the first nonlinear device has a first bias level. Also included is a second nonlinear device different from same first nonlinear device and coupled to the first nonlinear device for modifying the first signal to produce an output second signal, the second nonlinear device having a second bias level. A bias control means is provided for adjusting the first and said second bias levels so that the magnitude, phase and frequency of the output second signal can be adjusted.

Abstract: A multi-level modulation receiving device for adaptively compensating for chromatic dispersion and polarization mode dispersion with high precision. Each equalizing filter has at least one variable parameter as a weight therefor and equalizes the waveform of a corresponding channel signal in accordance with an averaged variable parameter value. A signal quality monitor monitors the signal quality of the filter output signal, and a variable parameter value calculator calculates a variable parameter value to be set as the variable parameter, in accordance with the signal quality. A variable parameter averaging unit averages the variable parameter values calculated for respective channels, to generate an averaged variable parameter value, and sends the averaged variable parameter value to the equalizing filters such that the same weight is set in the equalizing filters associated with the n channels.

Abstract: By comprising a unit 2 making the adjustment related to degradation compensation of a plurality of signals with each wavelength made after multiplexing the signals, a unit 3 multiplexing the outputs of a plurality of units 2, a unit 4 compensating for the waveform degradation of the output of the unit 3, a unit 5 selecting a component with one of a plurality of wavelengths from a part of the output of the unit 4 and a unit 6 detecting the degree of signal degradation from the output of the unit 5 and controlling the adjustment by the unit 2 corresponding to the selected frequency so as to reduce the degree, components disposed for each wavelength in an optical transmission system adopting a wavelength-division multiplexing method can be shared, and the size and cost of an compensator can be reduced.

Abstract: A method of operating an optical transmission system is described. The transmission system is provided with a bit-to-bit polarization interleaved bitstream having a given bitrate. The transmission system comprises a birefringent element and/or a decision circuit. The birefringent element and/or the decision circuit are triggered by a trigger signal having a frequency of half of the bitrate.

Abstract: In order to improve a transmission speed of multilevel light transmission, increasing the number of light emitting elements is effective. However, in a method in which light outputs from a plurality of light emitting elements are added, because common mode noise contained in the light outputs is added, deterioration in transmission quality caused by the common mode noise prominently arises. Therefore, a difference between two light outputs is previously assigned to data to be transmitted. Specifically, an optical transmitter 102 converts data Dt to multilevel optical signals OSm1 and OSm2 and transmits the converted multilevel optical signals to an optical receiver 103. The optical receiver 103 restores the data Dt which is previously assigned to a difference between electrical signals ESr1 and ESr2 converted from the multilevel optical signals OSm1 and OSm2.

Abstract: In a system where a quantum channel and a classical channel are multiplexed on a single optical transmission line and information is transmitted from a transmitter to a receiver through the quantum channel, the classical channel is inhibited from affecting the quantum channel. To this end, the transmission characteristics of a transmitter-side wavelength multiplexer/demultiplexer for the classical channel, the transmission characteristics of a receiver-side wavelength multiplexer/demultiplexer for the quantum channel, and the optical power of a light source for the classical channel are designed so that crosstalk light due to spontaneous emission light and crosstalk light due to nonlinear optical effects can be suppressed, and the classical channel does not affect the quantum channel.

Abstract: There is provided an opto-electronic communication system. The opto-electronic communication system has (a) a transmitter module including an electro-optical source for converting an electrical input signal into an optical output signal, (b) a receiver module including an opto-electrical detector for converting an optical input signal into an electrical output signal, (c) a sensor for sensing a bit rate of the optical input signal, (d) an adaptation unit associated with the transmitter module for varying an operation parameter of the transmitter module, and (e) a processing unit for determining a desired operating parameter of the transmitter module based on the bit rate, and for controlling operation of the adaptation unit in order to adapt operation of the transmitter module in accordance with the desired operating parameter.

Abstract: Techniques to control an optical receiver having a control loop using Bit Error Rate (BER). In one implementation, a bit error rate (BER) associated with a received optical signal is determined. Indication of the BER to a control loop adapted is provided to adjust the optical signal in a manner tending to reduce the BER. The received optical signal is adapted in a manner tending to increase the BER such that the control loop operates within an active control region.

Abstract: In an optical transmission apparatus controlling an optical output portion by a working optical output controller and a protection optical output controller, the optical output controllers separately generate (inverted) preset value signals corresponding to a common output preset value provided from outside, and perform an analog addition of a common optical output monitoring signal and the preset value signal with an integrating circuit. An optical output portion generates an optical output signal which is an optical input signal controlled based on an output of the wired-OR of the optical output controllers, and generates the optical output monitoring signal corresponding to the optical output signal. When the optical output monitoring signal exceeds the preset value signals, the optical output controllers substantially control input terminals of the integrating circuits respectively to a ground potential by using control circuits.

Abstract: A tunable PLC optical filter having sequentially connected thermally tunable Mach-Zehnder (MZ) interferometers is described. The MZ interferometers, having free spectral ranges matching ITU frequency grid spacing, are tuned so as to have a common passband centered on the frequency of the signal being selected, while having at least one of the stopbands centered on any other ITU frequency. Any other optical channel that may be present at any other ITU frequency is suppressed as a result. The PLC chip, including a zero-dispersion lattice-filter interleaver stage, a switchable fine-resolution stage and, or a retroreflector for double passing the filter, is packaged into a hot-pluggable XFP transceiver package. A compensation heater is used to keep constant the amount of heat applied to the PLC chip inside the XFP package, so as to lessen temperature variations upon tuning of the PLC optical filter.

Abstract: In an optical transmission system in which a pulse signal is converted into an optical signal before transmission, a pulse signal demodulation device capable of correctly demodulating the pulse signal is provided. An optical-to-electrical conversion section (31) converts a received optical signal into an electrical signal, and outputs the electrical signal as a received signal. A reception waveform information calculating section (33) outputs, as reception waveform information, information about a shape of a waveform of a short-pulse signal on which a distortion occurring during the time when a short-pulse signal is converted into an optical signal to when the optical signal is converted into a received signal by the optical-to-electrical conversion section (31), is reflected.

Abstract: A method of initializing an optical communication link between nodes. Optical transmitters adapted to pre-compensate link impairments based upon an optical compensation parameters are utilized to establish an optical communications link. Pre-compensation parameter values are selected at a node for generating an optical signal. The value is selected until confirmation from the remote node is received that the optical signal transmission has been successful. The successful pre-compensation parameter value is then used to generate the optical signal for the communications link.

Abstract: The present invention relates to an apparatus and method for extracting an optical clock using filters and an amplifier. The object of the present invention is to provide an extraction of neighboring frequency components using wavelength fixed optical filters and an amplifier. In accordance with an aspect of the present invention, there is provided an apparatus for extracting an optical clock to extract a clock from the optical signal provided with plurality of peaks on a spectrum, including a first filter for extracting a central frequency component, a second filter for extracting a frequency component adjacent to the first frequency component, the amplifier for amplifying amplitude of the second frequency component until the amplitude of the second frequency component becomes the same as that of the first frequency component and the receiver for extracting a clock to do beating the first frequency component and the second frequency component.

Abstract: In exemplary embodiments, all-optical pattern recognition for an optical input signal is achieved by wavelength-converting the input signal and then passively correlating the wavelength-converted signal based on a specified data pattern. By performing wavelength conversion using a CW laser signal having wavelength stability greater than that of the input signal, errors resulting from wavelength sensitivity of the passive correlator can be reduced. By performing both wavelength conversion and OOK-to-BPSK format conversion prior to the passive correlation, limitations in the number of available OOK patterns can be avoided. By performing the passive correlation in a bi-directional manner, feedback signal can be generated to control the operations of the passive correlator and/or the laser signal source(s).

Abstract: A method and system for estimating a fraction of an optical transmission system's transmission window that is compliant with the system's polarization mode dispersion (PMD) outage specifications, the optical transmission system including Ns optical fiber segments. The method comprises the steps of: propagating a plurality of optical signals through the Ns optical fiber segments; monitoring the differential group delay (DGD) for each optical signal over time; computing a time average and variance of the monitored DGD for each optical signal; computing statistics of the time averages and variances of the monitored DGD for each optical signal; determining the number of effective PMD sections and effective hinges in the system from the statistics; and determining the size of a PMD capacity compliant fraction for a specified outage probability.

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.