Abstract: Embodiments relate to methods, devices, and computer-implemented methods for receiving a modulated signal transmitted from at least one signal emitter. The method can include receiving at least one image that comprises image data representing the modulated signal received as radiation emitted from the at least one signal emitter, wherein the radiation represented in the image data comprises at least one period of the modulated signal and wherein the at least one image was captured by a camera of a computing device while a field of view of the camera was moving relative to the at least one signal emitter; analyzing, by at least one processor, the at least one image; extracting, based on the analyzing, the image data representing the radiation; and determining, from the image data that was extracted, the modulated signal transmitted by the at least one signal emitter.

Abstract: Described herein is a hybrid III-V Silicon laser comprising a first semiconductor region including layers of semiconductor materials from group III, group IV, or group V semiconductor to form an active region; and a second semiconductor region having a silicon waveguide and bonded to the first semiconductor region via direct bonding at room temperature of a layer of the first semiconductor region to a layer of the second semiconductor region.

Abstract: An optical receiver including: a preamplifier capable of changing a conversion gain in accordance with a reception level of a received burst signal; a gain control circuit capable of switching between a fast time constant and a slow time constant; and a convergence determination circuit for outputting a time constant switching signal in accordance with a state of the gain control circuit (transient state or steady state) and a reset signal between the burst signals. This configuration can switch the time constant of the gain control circuit at an appropriate timing.

Abstract: An optical receiver system includes a power adjustment device, an optical receiver, and a controller. The power adjustment device adjusts the power of an optical input signal in accordance with adjustment instructions. The optical receiver converts the power-adjusted optical input signal into an electrical signal that corresponds to a desired channel of the optical input signal. The optical receiver includes an electronic amplifier that amplifies the electrical signal using a gain value, and the amplified electrical signal preferably operates around a voltage value Vopt. The controller determines adjustment instructions such that the power adjustment device adjusts the optical input signal to a target optical power level that corresponds to Vopt for the amplified electrical signal, wherein the adjustment instructions are derived from the amplified electrical signal.

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: A method (10) of compensating phase noise in a coherent optical communications network. The method comprises: receiving a traffic sample (12); receiving an optical carrier and determining a phase noise estimate for the optical carrier (14); and removing the phase noise estimate from the traffic sample to form a phase noise compensated traffic sample (16).

Abstract: An ALC processing unit to adjust the signal level of outputs from an adaptive equalizer to a target value is provided in a stage later than the adaptive equalizer and earlier than a frequency offset estimation/compensation unit in an optical digital coherent receiver. The ALC processing unit generates a histogram that counts the number of samples for discrete monitored values corresponding to amplitude values of outputs from the adaptive equalizer, and determines a level adjustment coefficient that is to be multiplied by an output from the adaptive equalizer so as to multiply the determined coefficient by the output from the adaptive equalizer so that the monitored value of the peak value of the histogram is the target value.

Abstract: An optical transmission circuit device generates first and second optical signals from differential set and reset signals each time digital electric input signals of N bits are received. The differential set signal indicates an increase in signal strength relative to immediately preceding N bits of the digital electric input signals and the differential reset signal indicates a decrease in signal strength relative to the immediately preceding N bits. An optical reception circuit device generates first and second digital signals from the first and second optical signals and a third digital signal from the first and second digital signals, a magnitude of the third digital signal being increased by the first digital signal and decreased by the second digital signal. The optical reception circuit further generates a digital output signal of N bits from the third digital signal and an immediately preceding N bits of the digital output signal.

Abstract: A photonic implementation of the modulated wideband converter (MWC) is described. The highly scalable compressive sensing receiver architecture uses photonic components for analog front-end compression and downconversion, allowing scalable data conversion over an extremely wide instantaneous surveillance bandwidth, limited only by the peak anticipated signal occupancy and application-dependent size, weight, and power constraints.

Abstract: A nodal system (10) includes a unit (D) having a memory (42) and an optical data receiver (36), and a common control unit (12) in communication with the unit. A method of commissioning the system comprises the steps of activating the optical data receiver on the unit, and transmitting an optical data signal to the unit, thereby commissioning the unit.

Abstract: An optical phase conjugator that can be deployed within a long-haul fiber-optic link of an optical WDM system to improve the system's tolerance to intra- and inter-channel nonlinear effects. In one embodiment, the optical phase conjugator has a digital signal processor configured to perform, in the digital electrical domain, a phase-conjugation transformation for various components of a WDM signal so that certain signal distortions imposed on that signal in the front portion of the fiber-optic link are reduced in the back portion of the link. Advantageously, the optical phase conjugator is flexibly configurable to employ an input-to-output carrier-frequency-mapping configuration that is most beneficial under particular operating conditions. mapping configuration that is most beneficial under particular operating conditions.

Abstract: Systems and methods for optical communication that use a transmitter/receiver. The systems and methods include receiving a modulated, encoded input stream. Channel memory is reduced using coarse digital backpropagation and other channel impairments are removed using turbo equalization. Symbols are detected in the input stream that conform to a non-uniform, polar constellation having a Gaussian source distribution to produce a stream of encoded data. The stream of encoded data is decoded with one or more low density parity check (LDPC) decoders.

Abstract: An optical 90-degree hybrid circuit includes a first demultiplexing optical coupler having two or more first input ports and two or more first output ports, a second demultiplexing optical coupler having two or more second input ports and two or more second output ports, two first arm waveguides connected to the first output ports, two second arm waveguides connected to the second output ports, a 90-degree phase shift section installed in one of the four arm waveguides, a first optical coupler and a second optical coupler connected to the first arm waveguides and the second arm waveguides, a first optical waveguide for connecting an optical splitter and the first input ports, and a second optical waveguide for connecting the optical splitter and the second input ports, wherein an optical length of the first optical waveguide is different from that of the second optical waveguide.

Abstract: According to one embodiment, a receiving circuit is provided. The receiving circuit has a first light receiving element, a signal voltage generator, a second light receiving element, a delay element and a comparator. The first light receiving element receives a light signal and converts the light signal into a first current. The signal voltage generator converts the first current into a signal voltage. The second light receiving element receives the light signal and converts the light signal into a second current. The reference voltage generator converts the second current into a voltage and outputs the voltage as a reference voltage. The delay element delays and reduces a signal component of the reference voltage. The comparator compares the signal voltage from the signal voltage generator with a threshold voltage based on an output voltage of the delay element.

Abstract: A optical detection apparatus includes: an optical splitting unit configured to split a seed lightwave and split upward signal light generated by an optical network unit, based on the seed lightwave; a first control unit configured to control polarizations of the split seed lightwaves based on a first electrical signal; a second control unit configured to control phases of the split seed lightwaves based on a second electrical signal; an optical coupling and signal conversion unit configured to couple the seed lightwaves, of which the polarization and phase are controlled, and the split upward signal lights, convert the coupled optical signals into the first and second electrical signals, and transfer the first and second electrical signals to the first and second control units, respectively; and a signal detection unit.

Abstract: From an real valued OFDM signal (S0(t)) is a baseband signal (SB(t)) derived and converted into a complex single sideband modulation signal (n(t)). This is modulated onto an optical carrier (fOC) to generate a SSB transmission signal (SOT) having a small bandwidth an carrying the information in the envelope or in the power of the envelope. According to the modulation direct detection is possible. Only a small bandwidth is necessary for the transmission.

Abstract: An optical receiver is described. This optical receiver has two operating modes: a calibration mode and a normal mode. During the normal mode, switches are used to electrically couple an input of a transimpedance amplifier (TIA) to an optical-to-electrical (OE) converter that receives an optical signal and provides a corresponding analog electrical signal. Moreover, during the calibration mode, the switches are used to electrically isolate the input of the TIA from the OE converter while maintaining a feedback path from an output of the TIA to the input of the TIA, thereby ensuring proper bias of the TIA during calibration. Furthermore, a frequency response of the TIA during the normal mode is substantially unchanged over an operating bandwidth of the TIA by the capability to electrically isolate the input of the TIA from the OE converter during the calibration mode.

Abstract: Broadband access networks are driving the upgrade of DWDM networks from 10 Gb/s per channel to more spectrally-efficient 40 Gb/s or 100 Gb/s. Signal quality degradation due to linear and non-linear impairments are significant and error control coding and signal processing solutions play increasingly key roles in meeting increasing demand, providing improved quality of service, and reduced cost. It would be beneficial to reduce the power consumption of optical receivers for optical links exploiting for example LPDC encoding. Accordingly, the inventors have established a low complexity soft-decision front-end compatible with deployable LDPC codes in next-generation optical transmission systems. Beneficially the optical receiver design can be retro-fitted into deployed hard-decision based optical systems and replaces the 3-to-2 encoder of the prior art in the electrical portion of the receiver with a single gate design. Further, the design may act as a 2-bit Flash ADC in multimode fiber based optical receivers.

Abstract: Provided is an optical receiver which accurately demodulates an optical signal obtained by the differential phase shift modulation method. The optical receiver includes: an interferometer which branches the inputted optical signal into two parts and gives a one-bit phase difference to the resultant two optical signals so that the two optical signals after addition of the phase difference are made to interfere each other to output two output lights; reflection means which reflects one of the output lights from the interferometer so as to return to the interferometer; detection means which detects the return light which has been reflected by the reflection means and propagates through the interferometer in the different direction from the inputted optical signal, for output; and phase difference control means which adjusts the phase difference given by the interferometer according to the intensity of the return light detected by the detection means.

Abstract: A method for enabling AC coupling or DC coupling when receiving burst data signals comprises generating a hold-over pattern, wherein the hold-over pattern is a AC balanced pattern when an AC coupling is required and a low-logic value signal when a DC coupling is required; inputting the generated hold-over pattern to an AC coupling circuit, when no burst data signal is received; inputting only a received burst data signal to the AC coupling circuit, during the reception of such signal; and upon receiving of the entire burst data signal, generating a reset signal causing to input the generated holdover pattern to an AC coupling circuit.

Abstract: An optical system may include: a demultiplexer to receive an optical signal and to demultiplex the optical signal into a plurality of optical channels; a detector circuit to: receive the plurality of optical channels, and identify a predetermined channel identification trace tone frequency for an optical channel of the plurality of optical channels; and a receiver to: receive the optical channel with the identified predetermined channel identification trace tone frequency from the detector circuit, and process the optical channel.

Abstract: A burst transmission method and a receiver resetting method and apparatus in a Passive Optical Network (PON) are provided. A burst receiver resetting method in a PON includes: receiving a preamble sequence and synchronizing data; after synchronizing the data, continuing to receive the data, and matching a Burst Terminator (BT); and resetting a receiver after successfully matching the BT. Meanwhile, an apparatus for implementing the method and a corresponding burst data transmission method are provided. By using the burst receiver resetting method and apparatus in the PON and the corresponding burst transmission method at an Optical Network Unit (ONU) burst transmission end, a Reach Extender (RE) does not need to unpack upstream burst bandwidth allocation information carried in downstream data. Therefore, the complexity of the implementation of the RE is reduced, and the method is simple and effective.

Abstract: An apparatus for receiving optical signals in DQPSK and method of controlling a phase offset in receiving optical signals for DQPSK is provided. An original optical signal modulated in DQPSK is received. The original optical signal is delayed by one bit to make a delay optical signal such that an interference on the original optical signal and the delay optical signal is performed. A control signal is generated by use of an interference result between the original optical signal and the delay optical signal. A phase offset for the interference between the original optical signal and the delay optical signal is controlled by use of the generated control signal. In receiving optical signals, the phase offset between the delay optical signal and the original optical signal is precisely controlled, thereby optimizing the transfer characteristics of an optical delay interferometer.

Abstract: Method and apparatus for optimizing a decision threshold of an optical receiver is used to solve a problem of affecting system stability and reliability. The method comprises: determining a maximum value and a minimum value of an adjustment range of the decision threshold, and determining an adjustment step of the decision threshold (10); adjusting a decision threshold value within the adjustment range of the decision threshold, and separately detecting pre-FEC BERs corresponding to different decision threshold values (11); and searching for a minimum value in the detected pre-FEC BERs, a decision threshold value corresponding to the minimum value being an optimal decision threshold value (12). The apparatus comprises a decision threshold adjusting unit, a pre-FEC BER detecting unit, a decision threshold control unit and an optimal decision threshold determining unit.

Abstract: A universal infrared receiving apparatus is provided. The universal infrared receiving apparatus includes a slicer, a non-volatile memory, a volatile memory and a comparison apparatus. The slicer slices a remote control command waveform into digital waveform data. The non-volatile memory pre-stores target waveform data. The volatile memory stores the digital waveform data and the target waveform data. The comparison apparatus, coupled to the volatile memory, compares the digital waveform data and the target waveform data to generate a comparison result.

Abstract: An optical device comprising a sealed/closed housing; a light source and/or a detector within the housing; a window through the housing that is transparent to light transmitted from the light source or to the detector and a fixing for fixing an optical fiber or bundle of such fibers into a coupling position adjacent to the window to allow light to pass between the housing and the fiber or fiber bundle, wherein the fixing is adapted to allow connection and/or disconnection of the fiber or fiber bundle without opening or breaking a seal of the sealed housing.

Abstract: Introduced herein is an optical network device employing three-level duobinary modulation and a method of use thereof. One embodiment of an optical network receiver module includes: (1) an optical input configured to receive an optical non-return-to-zero (NRZ) signal having a data rate, and (2) an encoder having a maximum bandwidth, coupled to the optical input and configured to receive and encode the optical NRZ signal into an electrical three-level duobinary signal, the maximum bandwidth being related to, but substantially less than, the data rate.

Abstract: A complex orthogonal code in the present invention is one in which each row of a square matrix of N rows and N columns in which an element of an mth row and nth column is exp[2?j(m?1)(n?1)/N] (where j is an imaginary unit) is adopted as a code word. An optical orthogonal code for Optical Code Division Multiplexing/Optical Code Division Multiple Access (OCDM/OCDMA) is realized by a train of N-number of optical pulses corresponding to the argument (phase) of the code elements. An optical transmitter or optical receiver includes an optical correlator provided with a sampled Bragg grating having a plurality of Bragg gratings disposed serially at regular intervals inside an optical waveguide. The optical correlator is allocated any one of the code words. In the optical transmitter, an optical signal to be transmitted is encoded by the optical correlator. In the receiver, a received optical signal is decoded by the optical correlator.

Abstract: In accordance with some embodiments of the present disclosure a method for receiving and processing an optical orthogonal frequency-division multiplexed signal containing a plurality of traffics comprises receiving the optical orthogonal frequency-division multiplexed signal.

Abstract: A system and method for improving receiver sensitivity of an DD-OFDM system without using frequency guard band. The method having: interleaving input data to the DD-OFDM system to generate interleaved data; encoding the input data with a first recursive systematic convolutional code to generate a first recursive systematic convolutional encoded data; encoding the interleaved data with a second recursive systematic convolutional code to generate a second recursive systematic convolutional encoded data; puncturing the first recursive systematic convolutional encoded data and the second recursive systematic convolutional encoded data to generate a parity sequence; and combining the input data with the parity sequence to generate coded DD-OFDM data; wherein the parity sequence is generated by using different puncturing rates for different OFDM subcarriers, so as to obtain higher spectral efficiency.

Abstract: An analog signal receiver includes photonic sampling and electronic quantization. The receiver includes timing control circuitry configured to receive a series of optical pulses and output a plurality of timing signals based on the series of optical pulses to synchronize optical switches that receive a sampled optical signal to time deinterleave the optically sampled signal. The time deinterleaved signals are then sent to a plurality of demodulators wherein each demodulator receives at least one time deinterleaved optically sampled signal and at least one time deinterleaved optical reference signal to produce electrical signals based on the demodulated optical signals.

Abstract: A receiving apparatus and method for processing a differential phase shift keying signal carrying a plurality of symbols are disclosed to provide for improved compensation of linear and non-linear noise in phase modulated optical transmission. The receiving apparatus comprises an input unit for receiving electrical signals derived from an optical signal and a calculation unit for calculating a current value of a decision variable. The current value is indicative of a differential phase shift in the optical signal between a currently received symbol and a previously received symbol as a function of the optical signal power of the optical signal for the currently received symbol and at least one previous value of the decision variable. The receiving apparatus also comprises a decision unit for determining the differential phase shift from the current value of the decision variable obtained from the calculation unit to obtain the currently received symbol.

Abstract: A device may include a group delay monitor and a signal receiver. The group delay monitor may be configured to obtain group delay data corresponding to group delay of an optical signal and provide the group delay data to a signal receiver. The signal receiver configured to obtain a time-domain digital signal corresponding to the optical signal, convert the time-domain digital signal into a frequency-domain signal, apply a digital filter constructed based on the group delay data to the frequency-domain signal to obtain an output signal, and transmit the output signal.

Abstract: Technology for detecting an optical data signal carried in a combined optical signal that comprises a carrier optical signal modulated by the optical data signal and also comprises ASE noise. The proposed optical data detector/receiver is provided with an SHG device adapted to generate a second harmonic optical signal of the carrier optical signal modulated by the data signal. In the signal, generated by the SHG, the ASE noise will be essentially reduced.

Abstract: An apparatus comprising an optical receiver configured to receive an optical signal, and a combined level and clock recovery circuit coupled to the optical receiver and configured to update a signal threshold and a clock phase substantially simultaneously. Also included is an apparatus comprising at least one processor configured to implement a method comprising recognizing reception of a signal, and adjusting a threshold and a clock phase associated with the signal using a rising time for the signal and a falling time for the signal. Also included is a method comprising receiving a signal, and adjusting a threshold level of the signal to establish level recovery using a clock recovery scheme.

Abstract: According to one embodiment, a visible-light communication apparatus includes an image input unit, a calculation unit, a preamble detection unit, a bit train detection unit, and a reception unit. The image input unit is configured to input image data generated by photographing a source of visible light carrying data. The calculation unit is configured to generate, from the image data, luminance data about an image at a designated position. The preamble detection unit is configured to detect a preamble at the head of the data, on the basis of the luminance data. The bit train detection unit is configured to detect the data bit train from the image data, in accordance with the preamble. The reception unit is configured to reproduce the data from the data bit train.

Abstract: An apparatus for receiving optical signals in DQPSK and method of controlling a phase offset in receiving optical signals for DQPSK is provided. An original optical signal modulated in DQPSK is received. The original optical signal is delayed by one bit to make a delay optical signal such that an interference on the original optical signal and the delay optical signal is performed. A control signal is generated by use of an interference result between the original optical signal and the delay optical signal. A phase offset for the interference between the original optical signal and the delay optical signal is controlled by use of the generated control signal. In receiving optical signals, the phase offset between the delay optical signal and the original optical signal is precisely controlled, thereby optimizing the transfer characteristics of an optical delay interferometer.

Abstract: An optical receiver includes a photo-detector that converts a received optical signal into an electric signal and outputs the electric signal, a converter that converts the electric signal into a parallel data signal and outputs the parallel data signal, and parallel-number changer changing a parallel number of the parallel data signal in accordance with a bit rate of the optical signal and outputting the parallel data signal having the changed parallel number.

Abstract: A stream of wavelength division multiplexed optical signals can be converted into the electrical domain and processed electrically to discriminate the information on each optical signal. An optical medium can transmit multiple optical communication signals, each having a different wavelength and each imprinted with different information. Detectors can receive the optical communication signals, with each detector receiving some of each communication signal. Thus, any one of the detectors can output an electrical signal according to a composite of multiple optical communication signals. Accordingly, each output electrical signal can include features or energy of each of the optical communication signals. An electrical circuit can process the electrical signals output by the detectors.

Abstract: A PPM transmitter includes an optical clock generator for generating equally-spaced optical pulses with a sampling period T; an encoder for transforming an incoming waveform U(t) into a linear combination V(t) of U(t) and a delayed output V(t?kT) according to a rule V(t)=U(t)+aV(t?kT), where k is a positive integer, V(t) is voltage generated by the encoder and a is a coefficient; and an optical delay generator for delaying optical pulses generated by the optical clock generator in proportion to the voltage V(t), such that ?tn=bV(t), where b is another coefficient and where ?tn is the amount of delay imposed by the optical delay generator. The PPM transmitter functions with a PPM receiver for communicating data without the need to transmit or otherwise provide a clock signal. The PPM receiver decodes an original series of the delayed optical pulses Q(t) and a second series Q(t?ckT) delayed by ckT where c is a coefficient.

Abstract: A receiver receiving a phase-modulated optical frequency division multiplexed signal is provided. The receiver includes a light spectrum shaper configured to extract a carrier wave and a modulated light component contained in either one of a short-wavelength-side waveband or a long-wavelength-side waveband with respect to the carrier wave, to output a spectrum-shaped light signal; and an optical-to-electric converter configured to convert the spectrum-shaped light signal into an electric signal.

Abstract: A method of analyzing an input signal, the method including the steps of: (a) dividing a first input signal into first and second orthogonal signal polarization components; (b) dividing a second input signal into orthogonal first and second orthogonal local polarization components; (c) mixing the first orthogonal signal component with the second orthogonal local polarization component to provide a first mixed signal; (d) mixing the second orthogonal signal component with the first orthogonal local polarization component to provide a second mixed signal; (e) analyzing the first and second mixed signal to determine the polarization or phase information in the input signal.

Abstract: Visible light data communication with a sufficient transmission speed is performed using a general-purpose and cost-advantageous blue-light-excitation-type white LED without using a blue color filter while preventing the element from being damaged. When transmission data is inputted to a driving waveform generation unit (110) in a transmitter (100), the driving waveform generation unit (110) and a multi-gray scale driving unit (120) generate a multi-gray scale driving signal, which is supplied to the blue-light-excitation-type white LED (140) and allows the blue-light-excitation-type white LED (140) to emit light. A light signal outputted from the blue-light-excitation-type white LED (140) is collected by a lens or the like, is made incident into a PD (210) in a receiver (200), and is converted to a current signal. The current signal is converted into a voltage signal in a trans-impedance amplifier (212).

Abstract: The present invention relates to a method for determining a signaling set, comprising: selecting a first basis function in the form of a symmetric pulse represented by an even function; selecting a second basis function orthogonal to the first basis function; wherein the second basis function is represented by an odd function having a shape determined by a variable parameter; and determining a signaling set comprising a plurality of data signals formed by linear combinations of the first and second basis functions based on a predetermined requirement of the signaling set. The invention also relates to a modulation and demodulation method using the signaling set, a device performing the modulation and demodulation method and to a system incorporating such a device.

Abstract: A system and method for blind equalization of a QAM signal. Equalization is achieved using an algorithm characterized by cost function that is a function the Euclidian distance, e.g. the minimum Euclidian distance, between points of the constellation associated with the QAM signal, i.e. the distance between symbols.

Abstract: A coherent optical receiver for a data-frame format in which a data frame has two or more pilot-symbol blocks, each having a cyclic prefix or suffix, and one or more payload-symbol blocks, each of which is concatenated with at least one adjacent block without a guard interval between them. The receiver uses optical signals corresponding to the pilot-symbol blocks to perform data-frame synchronization, frequency-offset correction, and channel-estimation procedures, which are robust even in the presence of certain transmission impairments. The receiver applies block-overlap processing with a sliding window to recover the payload data in a manner that substantially cancels the adverse effects of inter-block interference caused by the absence of guard intervals in the payload portion of the data frame.

Abstract: Methods and systems for normalized least mean square phase estimation are shown that include receiving optical transmissions that include a modulated signal, determining a step size based on a signal-to-noise ratio (SNR) and a laser linewidth that provides a balance between convergence speed and precision, estimating phase error using the determined step size, derotating the modulated signal to remove the estimated phase error, and demodulating the derotated signal to produce a bitstream.

Abstract: The light receiving device includes a pixel array, such as a two-dimensional pixel array, of pixels each having a light-receiving element for receiving input signal light, an output selecting unit for selecting the outputs of pixels within the pixel array, a selected output adding unit for adding and outputting the selected outputs of the pixels, and an amplifying unit for amplifying the output of the selected output adding unit.

Abstract: A transmitter in an optical communications system includes a digital signal processor for processing a data signal to generate a sample stream encoding successive symbols in accordance with a constrained phase modulation scheme having a constellation of at least two symbols and a modulation phase constrained to a phase range spanning less than 4?. A digital-to-analog converter converts the sample stream into a corresponding analog drive signal. A finite range phase modulator modulates a phase of a continuous wavelength channel light in accordance with the analog drive signal, to generate a modulated channel light for transmission through the optical communications system. A receiver in the optical communications system includes an optical stage for detecting phase and amplitude of the modulated channel light and for generating a corresponding sample stream, and a digital signal processor for processing the sample stream to estimate each successive symbol of the modulated channel light.

Abstract: A demodulating delay circuit with a planar lightwave circuit includes: an optical interferometer including input and output couplers, and a first arm waveguide connecting the couplers, and a shorter second arm waveguide. The interferometer delays each bit of a signal by one bit such that the delayed bit interferes with its adjacent bit, and has a bent form such that propagation directions of light in the couplers are different by 180 degrees. The couplers each include first and second waveguides. The first waveguide is longer and the waveguides are closely arranged in parallel at two positions thereby forming directional couplers. The input and output couplers are each configured as a wavelength insensitive coupler having a coupling ratio of 50 percent in a bandwidth used. The first waveguide of the input coupler is arranged on the same side as that on which the first waveguide of the output coupler is arranged.