Abstract: According to one embodiment, a photo detector-combined illuminance sensor includes a circuit for a Photo Detector (PD) function to detect the illuminance of the ambient environment. The illuminance sensor operates under the control of a controller in a visible light communication terminal. When an optical signal detected by the illuminance sensor is a visible light communication signal, the controller switches to cause the illuminance sensor to operate as the photo detector for the visible light communication in a visible light communication mode.

Abstract: A coherent optical communication device includes a demodulator configured to demodulate a reception signal; a local oscillator light optical source configured to generate local oscillator light used for demodulating the reception signal; a memory configured to store wavelength information; and a controller configured to control the local oscillator light optical source when the demodulator cannot receive the reception signal, so that a wavelength of the local oscillator light generated in the local oscillator light optical source is changed to a wavelength specified by the wavelength information stored in the memory.

Abstract: An optical receiver, a method of operating an optical receiver, a correction based transimpedance amplifier circuit, and a method of adjusting an output of a transimpedance amplifier. In one embodiment, the optical receiver comprises an optical-to-electrical converter, a transimpedance amplifier, and a correction circuit. The optical-to-electrical converter is provided for receiving an optical signal and converting the optical signal to an electrical signal. The transimpedance amplifier is provided for receiving the electrical signal from the converter and for generating from the electrical signal an amplified electrical signal. The amplified electrical signal has inter symbol interference resulting from a reduced bandwidth of the transimpedance amplifier.

Abstract: In part, aspects of the invention relate to methods, apparatus, and systems for intensity and/or pattern line noise reduction in a data collection system such as an optical coherence tomography system that uses an electromagnetic radiation source and interferometric principles. In one embodiment, the noise is intensity noise or line pattern noise and the source is a laser such as a swept laser. One or more attenuators responsive to one or more control signals can be used in conjunction with an analog or digital feedback network in one embodiment.

Abstract: An Ethernet adapter system may include a transmitter to insert a payload type identifier sequence in a generic frame procedure header to indicate that a network is a converged enhanced Ethernet network. The transmitter may insert idle sequences in a stream of data frames transmitted along a link. The system may include a receiver to recognize a condition and to force a loss of synchronization condition on the link that will be converted by the receiver into a loss of light condition. The receiver may scan the transmitted stream of data frames for invalid data frames and introduce a code into the stream of data frames whenever an invalid data frame is detected.

Abstract: A scheme is described of remote control of the slicing level of a receiver in a smart SFP (or SFP+, or XFP) duplex (or BiDi, or SWBiDi) transceiver in a communication system using an operating system with OAM and PP functions, an OAM, PP & Payload Processor, a transceiver, a BERT, and an optical link in the field.

Abstract: A signal processing device includes: a phase controller configured to control respective phases of an in-phase signal and an quadrature signal, which are obtained by converting an analog signal into a digital signal when a multi-value phase modulation light is demodulated, by digital signal processing; and a control amount provider configured to provide a control amount to the phase controller based on an output of the phase controller.

Abstract: An optical receiving device includes: an optical amplifier configured to amplify a wavelength multiplexed optical signal; a demultiplexer configured to demultiplex the amplified wavelength multiplexed signal into optical signals of a plurality of wavelengths; optical receivers configured to regenerate the demultiplexed optical signals; error correction units configured to correct a bit error in the regenerated optical signals; and main control unit. The control unit adjusts RXDTV of the optical receiver for receiving optical signals of a given wavelength to the optimal value in the state where the gain of the optical amplifier is lowered from that of a normal operation such that the occurrence of bit errors in the optical signals of the other wavelengths does not exceed the correction capability of the error correction unit.

Abstract: A polarization-multiplexed signal receiver includes a polarization adjustment unit to adjust a polarization state of inputted polarization-multiplexed signal, which is carrying signal data on each of two polarized waves being inputted, based on a control signal and to output the adjusted polarization-multiplexed signal, an optical signal reception unit to convert the polarization-multiplexed signal having the adjusted polarization state into an analog electric signal and output the analog electric signal, an A/D conversion unit to convert the analog electric signal into a digital electric signal and output the digital electric signal, a digital signal processing unit to perform digital coherent processing to the digital electric signal and take out the signal data and a feedback control unit to generate the control signal based on quality of the signal data and output the signal data to the polarization adjustment unit.

Abstract: A system may include one or more devices that may be used to simultaneously measure and modulate phases of a many-channel optical system relative to a high frequency optical carrier. This device may be constructed using analog-to-digital converters, comparators, and distributed timers. A digital processor may be used to recover phase information from the measurements and to calculate an error compared to desired phase. The processor may then apply feedback to a phase modulator to correct the phase.

Abstract: An optical transport system in which (i) an optical transmitter is configured to adaptively change an operative constellation to use a constellation that provides optimal performance characteristics for the present optical-link conditions and/or (ii) an optical receiver is configured to change shapes of the decision regions corresponding to an operative constellation to adapt them to the type of signal distortions experienced by a transmitted optical signal in the optical link between the transmitter and receiver. Under some optical-link conditions, the optical receiver might use a decision-region configuration in which a decision region corresponding to a first constellation point includes an area that is closer in distance to a different second constellation point than to the first constellation point.

Abstract: Provided is a pulse receiver capable of receiving a burst signal and decoding the burst signal with a bit error rate reduced to a target value or less by controlling a determination threshold such that decoding success rate is equal to or less than a predetermined value. A decode unit 140 decodes a pulse train 20 to information 30, counts the number of decoding successes for a predetermined time period and outputs the counted number (decoding success rate DR) to a control unit 150. The control unit 150 uses as a basis the decoding success rate DR communicated from the decode unit 140 to control the set value of reference voltage Vth used in the comparator 130.

Abstract: Methods, systems, and devices are described for a digital demodulator device for processing received optical signals. The device may include a quadrature error filter that receives a digitized version of an optical signal, and removes quadrature errors to generate a filtered series of data samples. The device may also include a frequency offset removal module for performing frequency rotation on the filtered series of data samples. The device may include a chromatic dispersion compensation module which removes chromatic dispersion from horizontal and vertical polarization channels. The device may include a polarization mode dispersion (PMD)/polarization dependent loss (PDL) compensation module which compensates for interference caused by PMD and PDL. The device may also include a phase recovery module configured to track and correct phase.

Abstract: A photon detection system including a photon detector configured to detect single photons, a signal divider to divide the output signal of the photon detector into a first part and a second part, wherein the first part is substantially identical to the second part, a delay mechanism to delay the second part with respect to the first part, and a combiner to combine the first and delayed second parts of the signal such that the delayed second part is used to cancel periodic variations in the first part of the output signal.

Abstract: At least one cell implementing a sensor array embraces a photoelectric-conversion accumulation element configured to generate and accumulate signal charges, a potential detection circuit configured to detect the signal charges generated by the photoelectric-conversion accumulation element as a potential change, and an amplification circuit configured to amplify the potential change and to transmit to an output-signal line. The photoelectric-conversion accumulation element and the potential detection circuit are connected in series between a first potential terminal and a second potential terminal, and the potential detection circuit has an insulated-gate transistor, which detects the potential change in a weak inversion state, in a period when an optical-communication signal is received.

Abstract: Compensation for in-phase (I) and quadrature (Q) timing skew and offset in an optical signal may be achieved based on the correlation between derivatives of I and Q samples in the optical signal. The magnitude of the correlation between derivatives is measured to determine the presence of skew. Correlation between derivatives may be coupled with frequency offset information and/or with trials having additional positive and negative skew to determine presence of skew. Correlations are determined according to pre-defined time periods to provide for continued tracking and compensation for timing skew that may result from, for example, thermal drift.

Abstract: An optical receiver, a method of operating an optical receiver, a correction based transimpedance amplifier circuit, and a method of adjusting an output of a transimpedance amplifier. In one embodiment, the optical receiver comprises an optical-to-electrical converter, a transimpedance amplifier, and a correction circuit. The optical-to-electrical converter is provided for receiving an optical signal and converting the optical signal to an electrical signal. The transimpedance amplifier is provided for receiving the electrical signal from the optical-to-electrical converter and for generating from the electrical signal an amplified electrical signal. The amplified electrical signal has inter symbol interference resulting from a reduced bandwidth of the transimpedance amplifier.

Abstract: An embodiment of the invention is a technique to equalize received samples. A coefficient generator generates filter coefficients using an error vector and input samples. A filter stage generates equalized samples from input samples using the filter coefficients. The received samples are provided by a receiver front end in an optical transmission channel carrying transmitted symbols. Other embodiments are also described.

Abstract: A light receiving device includes: a converter digitalizing an analog signal with a given sampling clock frequency, the analog signal being obtained through a photoelectric conversion of a received optical signal; a plurality of fixed distortion compensators compensating an output signal of the converter for waveform distortion with a fixed compensation amount that is different from each other; a plurality of phase shift detector circuits detecting a sampling phase shift from an output signal of the plurality of the fixed distortion compensators; a phase-adjusting-amount determiner determining a sampling phase adjusting amount with use of an output signal of the plurality of the phase shift detector circuits; and a phase adjusting circuit reducing a phase difference between the sampling clock frequency and the received optical signal based on a determination result of the phase-adjusting-amount determiner.

Abstract: An optical receiver has an adaptive optical compensator and/or an adaptive electrical equalizer for compensating signal distortion in a received optical signal. In order to achieve a very fast adaptation of the receiver to the actual signal distortion, which is important for example for bursts mode optical signals in a packet-switched optical transmission network, at least one predetermined trainings sequence is provided in the optical signal, which is known at the receiver and thus enables fast adaptation of the compensator and/or equalizer to the actual signal distortion.

Abstract: A method for recovering an OTUk frame includes: receiving an optical signal sent by using a method of multi-lane distribution from the OTUk frame to an interface of an optical module; converting the optical signal into an electrical signal, performing electrical equalization and demodulation on the electrical signal, and recovering multi-lane data from the demodulated signal; aligning and rearranging the data on each lane, according to a lane sequence identifier included in an overhead frame header of the data on each lane; and recovering the OTUk frame according to the aligned and rearranged data. According to the present invention, lane rearrangement is performed by detecting the lane sequence identifier, and the recovery of the OTUk frame is achieved. Therefore, a training sequence overhead does not need to be additionally introduced, and the influence on the system performance is avoided.

Abstract: An apparatus comprising a frequency-domain equalizer that has been iteratively generated to compensate for filtering effects of a wavelength selective switch, wherein the FDEQ is configured to process in a frequency domain digital samples of a polarization multiplexed phase-shift-keying signal that has been transported over an optical channel.

Abstract: A method for an optical transmitter, receiver or transceiver allowing determination of a signal property of a first binary signal such as the modulation amplitude. The method applies a reference stage which is modulated by the signal content of the first binary signal to allow the determination.

Abstract: A photon detection system including a photon detector configured to detect single photons, the photon detector being gated such that it produces a periodic output signal and the gating signal having a frequency of at least 50 MHz. The system further includes a combiner for combining the signal from one period with signals from other periods such that periodic variations in the output signal of the detector are suppressed.

Abstract: The present invention discloses an apparatus and method for adaptive dispersion compensation, the apparatus comprising: a coarse-grain tunable dispersion compensator, a receiver with electric adaptive dispersion compensator, and a control logic unit. In the method, firstly it is to perform optical dispersion compensation for the input optical signals; then to perform electric dispersion compensation for the optical signals for which the optical dispersion compensation is performed; it is to detect the performance parameters of the receiving of the optical signals for which the electric dispersion compensation has been performed, and based on the performance parameters, it is to perform optical dispersion compensation adjustment for said input optical signals. With an optical de-multiplexer further, said apparatus can perform adaptive dispersion compensation for the multi-channel system.

Abstract: A system may receive a group of electrical signals from an optical receiver and via a group of channels; identify a first signal, as a reference signal, that is received via a first channel; and identify a second signal, as an orthogonal signal, that is received via a second channel, where the second signal may be orthogonal to the first signal. The system may further measure a group of skew values based on a difference in arrival times between one or more other signals, of the group of electrical signals, and the reference signal or the orthogonal signal; generate a group of de-skew values based on at least a portion of the skew values; and transmit the de-skew values, to the optical receiver, where transmitting the de-skew values allows the optical receiver to de-skew signals on the group of channels.

Abstract: Consistent with the present disclosure, a coherent detector is provided that includes an optical hybrid that supplies optical signals including local oscillator light to a balanced detector. The amount of imbalance or “balance error” in the balanced detector is identified by comparing an output of the balanced detector and an output of a photodiode that receives a portion of an input optical signal provided to the optical hybrid. Based on the balance error, electrical signals generated by the balanced detector or the power of optical signals passing through (or output from) the optical hybrid circuit can be adjusted so that the balance error is minimized or reduced to zero. As a result, imbalance associated with the balanced detector is corrected so that unwanted currents and/or related electrical signals are cancelled out or substantially cancelled out.

Abstract: Methods, apparatuses, and systems are presented for performing adaptive equalization involving receiving a signal originating from a channel associated with inter-symbol interference, filtering the signal using a filter having a plurality of adjustable tap weights to produce a filtered signal, and adaptively updating each of the plurality of adjustable tap weights to a new value to reduce effects of inter-symbol interference, wherein each of the plurality of adjustable tap weights is adaptively updated to take into account a constraint relating to a measure of error in the filtered signal and a constraint relating to group delay associated with the filter. Each of the plurality of adjustable tap weights may be adaptively updated to drive group delay associated with the filter toward a target group delay.

Abstract: A control apparatus for controlling an optical receiver having delay paths comprises an optical variable attenuator configured to generate a variable signal and provide the variable signal to the optical receiver; a fine control voltage controller configured to generate a variable fine control voltage and input the variable fine control voltage to one path of the delay paths of the optical receiver; a photo-diode voltage monitor configured to detect a first voltage value and a second voltage value; a bit error rate (BER) checker configured to estimate a bit error rate (BER) according to a signal output from the optical receiver; and a controller configured to set a value of the variable signal and a value of the variable fine control voltage and to estimate the fine control voltage that makes the bit error rate a minimum according to the first voltage value and the second voltage value.

Abstract: Techniques are provided for estimation of the chromatic dispersion (CD) in an optical signal received by an optical receiver. The techniques involve iteratively adjusting dispersion compensation coefficients of one or more filters configured to compensate for the CD in the received optical signal. At each iteration of the dispersion compensation coefficient adjustment, electrical domain signals are filtered to generate digitally-filtered signals. The electrical domain signals are generated based on the received optical signal. Also at each iteration of the dispersion compensation coefficient adjustment, an amplitude histogram of the digitally-filtered signals is generated. The amplitude histograms generated at each iteration are evaluated to generate an estimate of the chromatic dispersion in the received optical signal.

Abstract: Polarization mode dispersion (PMD) in a dual-pole optical communications network is compensated for using an adaptive PMD equalizer. The PMD equalizer may include a number of substantially identical filter modules that provide partial outputs which may be combined to form a PMD compensated output. A constant modulus algorithm (CMA)-based equalizer may track PMD across both poles and generates an error signal. The CMA-based equalizer includes a filter bank, and uses an update algorithm and tap/output adjustments based on a difference between combined tap energies and an index, and feedback from a forward error correction code frame synchronizer.

Abstract: An optical homodyne communication system and method in which a side carrier is transmitted along with data bands in an optical data signal, and upon reception, the side carrier is boosted, shifted to the center of the data bands, and its polarization state is matched to the polarization state of the respective data bands to compensate for polarization mode dispersion during transmission. By shifting a boosted side carrier to the center of the data bands, and by simultaneously compensating for the effects of polarization mode dispersion, the provided system and method simulate the advantages of homodyne reception using a local oscillator. The deleterious effects of chromatic dispersion on the data signals within the data bands are also compensated for by applying a corrective function to the data signals which precisely counteracts the effects of chromatic dispersion.

Abstract: An optical receiver includes: an optical amplifier amplifying an optical signal fed thereinto according to an operating current fed thereinto, the optical signal being a wavelength-multiplexed optical signal, a demultiplexer demultiplexing an optical signal output from the optical amplifier; and an operating-current control circuit selecting a monitoring target from a plurality of wavelength signals output from the demultiplexer and controlling the operating current of the optical amplifier so that optical power of the monitoring target is controlled to be a predetermined value.

Abstract: An apparatus and method for performing joint equalization and timing recovery in coherent optical systems. The method includes equalizing signals to generate compensated polarization signals, wherein timing error in a distorted optical signal is calculated based on one of the compensated polarization signals. The method further includes performing resampling polarization signals to correct timing offset in an optical signal based on the calculated timing error. The calculated timing error may also be used to adaptively control one or more operating parameters of an external device.

Abstract: Methods and systems for split voltage domain receiver circuits are disclosed and may include amplifying complementary received signals in a plurality of partial voltage domains. The signals may be combined into a single differential signal in a single voltage domain. Each of the partial voltage domains may be offset by a DC voltage from the other partial voltage domains. The sum of the partial domains may be equal to a supply voltage of the integrated circuit. The complementary signals may be received from a photodiode. The amplified received signals may be amplified via stacked common source amplifiers, common emitter amplifiers, or stacked inverters. The amplified received signals may be DC coupled prior to combining. The complementary received signals may be amplified and combined via cascode amplifiers. The voltage domains may be stacked, and may be controlled via feedback loops. The photodetector may be integrated in the integrated circuit.

Abstract: An amplifier implementing with a common base circuit is disclosed. The amplifier includes the common base circuit, a current shunt, and a current supplement. The common base circuit receives an input current. The current shunt shunts the input current based on the average of the output of the pre-amplifier. The current supplement supplements a current shunted by the current shunt.

Abstract: A photodetector receiver circuit for an optical communication system includes an optical photodetector which receives optical signals and converts them into an electrical current. In one illustrative embodiment, a dynamic impedance module which switches the receiver circuit between a high impedance state and a low impedance state and a buffer stage which receives the electrical current and converts the electrical current into a voltage signal compatible with a digital circuit. A method for receiving an optical signal includes, receiving the optical signal and converting it into an electrical pulse train, switching a dynamic impedance module between a high impedance state and a low impedance state, transforming the electrical pulse train into an output voltage signal using a buffer stage, and receiving the output voltage signal by a digital circuit.

Abstract: Systems and methods for processing an optical signal are disclosed. The optical signal is converted to a voltage signal and the voltage signal is amplified. In addition, a signal strength and/or a signal quality parameter is monitored and an indication of the signal strength and/or a signal quality parameter is generated. Further, a gain and/or an operating bandwidth on the conversion or the amplification can be adjusted based on the indication to reduce power consumption of an optical receiver.

Abstract: In a coherent optical receiver receiving a polarization multiplexed optical signal through an optical communications network, a method of compensating noise due to polarization dependent loss (PDL). A Least Mean Squares (LMS) compensation block processes sample streams of the received optical signal to generate symbol estimates of symbols modulated onto each transmitted polarization of the optical signal. A decorrelation block de-correlates noise in the respective symbol estimates of each transmitted polarization and generating a set of decorrelated coordinate signals. A maximum likelihood estimator soft decodes the de-correlated coordinate signals generated by the decorrelation block.

Abstract: It is provided an optical receiver comprising a compensator, a compensation controller and a clock extractor. The optical receiver selects first and second values, and obtains a stabilization time necessary to change the dispersion value and a transition time shorter than the stabilization time, compensates the received optical signal using the selected first value, changes the dispersion value from the first value into the second value, compensates the received optical signal using the dispersion value when the transition time has passed since starting to change the dispersion value, creates second extraction information of the dispersion value after the transition time, compensates for dispersion of the optical signal using an dispersion value calculated based on the second value and the difference between the dispersion value after the transition time and the second value in a case where the created second extraction information indicates that the clock extraction is available.

Abstract: An optical line terminal (OLT) includes an optical receiving assembly and a processor (4). A current mirror (1), a current-voltage conversion circuit (2) and a switching circuit (3) are connected in sequence between the optical receiving assembly and the processor (4). An energy storage circuit connected to ground is connected between the switching circuit (3) and the processor (4). The optical receiving assembly generates a response current according to the optical signal received. The current mirror (1) processes the current and then transmits it to the current-voltage conversion circuit (2). The conversion circuit (2) converts the current into a voltage signal and transmits the voltage signal to the switching circuit (3). The switching circuit (3) transmits the voltage signal outputted by the conversion circuit (2) to the energy storage circuit. The voltage signal is sampled and held by the energy storage circuit and then outputted to the processor (4).

Abstract: An optical transmission apparatus including a variable optical attenuator is provided. The optical transmission apparatus includes a module detection portion for detecting a type of module that receives light attenuated by the variable optical attenuator; and a variable optical attenuator control portion for controlling so as to change control parameters of the variable optical attenuator in accordance with the type of module detected by the module detection portion.

Abstract: A method and an optical receiver implementing this method suitable for robustly receiving unencoded optical data. The method sets the threshold for the receiver using values relating to the high and low values of a binary signal. However, for some data patterns these values may not be accurately determined, such as for extended periods of constant high or low values being transmitted. In this case the method, in one embodiment, assumes that the extinction ratio of the signal is substantially constant and is thereby able to track the threshold for the signal.

Abstract: An adaptive equalizer includes a finite impulse response filter with a predetermined number of taps; and a tap coefficient adaptive controller having a register to hold tap coefficients for the filter, a weighted center calculator to calculate a weighted center of the tap coefficients, and a tap coefficient shifter to shift the tap coefficients based on a calculation result of the weighted center. During an initial training period, the tap coefficient shifter shifts the tap coefficients on a symbol data basis such that a difference between the calculated weighted center of the tap coefficients and a tap center defined by the number of taps is minimized.

Abstract: Methods, systems, and devices are described for a digital demodulator device for processing received optical signals. The device may include a quadrature error filter that receives a digitized version of an optical signal, and removes quadrature errors to generate a filtered series of data samples. The device may also include a frequency offset removal module for performing frequency rotation on the filtered series of data samples. The device may include a chromatic dispersion compensation module which removes chromatic dispersion from horizontal and vertical polarization channels. The device may include a polarization mode dispersion (PMD)/polarization dependent loss (PDL) compensation module which compensates for interference caused by PMD and PDL. The device may also include a phase recovery module configured to track and correct phase.

Abstract: Compensation for in-phase (I) and quadrature (Q) timing skew and offset in an optical signal may be achieved based on the correlation between derivatives of I and Q samples in the optical signal. The magnitude of the correlation between derivatives is measured to determine the presence of skew. Correlation between derivatives may be coupled with frequency offset information and/or with trials having additional positive and negative skew to determine presence of skew. Correlations are determined according to pre-defined time periods to provide for continued tracking and compensation for timing skew that may result from, for example, thermal drift.

Abstract: An OSNR measuring device n OSNR measuring device includes an input port to which a signal light is given; a wavelength filter which includes a variable passband, and selectively takes out an optical component corresponding to a signal optical wavelength to be measured from the signal light; a wavelength control circuit which controls the passband of the wavelength filter; a delay interferometer which branches a light output from the wavelength filter and delays one of the branched lights with respect to the other branched light and in which the branched lights are made to interfere with each other; a photodetector which detects a power of a delay interference light output; and an OSNR calculation circuit which calculates, based on a bandwidth of a passband of the wavelength filter and the power of the delay interference light, an optical signal to noise ratio of a signal optical wavelength to be measured.

Abstract: Methods and systems for split voltage domain transmitter circuits are disclosed and may include amplifying a received signal in a plurality of partial voltage domains. Each of the partial voltage domains may be offset by a DC voltage from the other partial voltage domains. A sum of the plurality of partial domains may be equal to a supply voltage of the integrated circuit. A series of diodes may be driven in differential mode via the amplified signals. An optical signal may be modulated via the diodes, which may be integrated in a Mach-Zehnder or a ring modulator. The amplified signals may be communicated to the diodes, connected in a distributed configuration, via even-mode coupled transmission lines. The partial voltage domains may be generated via stacked source follower or emitter follower circuits. The voltage domain boundary value may be at one half the supply voltage due to symmetric stacked circuits.

Abstract: For an optical network link, a receiving node monitors optical performance and upon determination of lowered optical performance for an extended period of time, the node can signal a transmitting node to lower bit transfer rate from a nominal bit transfer rate. The receiving node has a transponder which has a digital electronic variable bandwidth filter to process the digitized signals at the lowered bit transfer rate to increase the SNR of the signals. Optical performance of the link is optimized although at the lowered bit transfer rate.

Abstract: A digital coherent receiver converts signals and local light respectively detected, as detection results, in signal light from an optical transmission line, into digital signals and that further applies digital processing to the digital signals. The receiver includes a skew detecting unit that detects skew between the digital signals; a skew control unit controls the skew of each of the signals so that the skew to be detected by the skew detecting unit will be reduced; and a demodulating unit that demodulates each signal controlled for skew by the skew control unit.