Abstract: A semiconductor device comprises a semiconductor die and an integrated capacitor formed over the semiconductor die. The integrated capacitor is configured to receive a high voltage signal. A transimpedance amplifier is formed in the semiconductor die. An avalanche photodiode is disposed over or adjacent to the semiconductor die. The integrated capacitor is coupled between the avalanche photodiode and a ground node. A resistor is coupled between a high voltage input and the avalanche photodiode. The resistor is an integrated passive device (IPD) formed over the semiconductor die. A first terminal of the integrated capacitor is coupled to a ground voltage node. A second terminal of the integrated capacitor is coupled to a voltage greater than 20 volts. The integrated capacitor comprises a plurality of interdigitated fingers in one embodiment. In another embodiment, the integrated capacitor comprises a plurality of vertically aligned plates.

Abstract: A bandwidth scheduling method includes receiving a bandwidth request sent by a data center, where the bandwidth request includes bandwidth required to transmit non-real-time traffic; allocating, based on historical bandwidth information, the bandwidth required by the data center to transmit the non-real-time traffic in a future time period, where the historical bandwidth information is used to predict occupation of total bandwidth by the data center in a region in which the data center is located at each moment in the future time period; and sending a bandwidth response to the data center, where the bandwidth response includes an allocation result.

Abstract: A method of equalising optical losses, at a required operating wavelength, in waveguide sections in an optoelectronic device comprising a first semiconductor waveguide section and a second semiconductor waveguide section, the method comprising determining (1301) a first optical loss through the first waveguide section for a signal with the required operating wavelength, determining (1302) a second optical loss through the second waveguide section for the signal, determining (1303) a loss difference between the first optical loss and the second optical loss, determining (1304) a first bias voltage based on the loss difference and the operating wavelength, such that the loss difference is reduced, and applying (1305) the bias voltage to the first waveguide section.

Abstract: An optical reception device including: a local light transmission unit configured to generate a plurality of local lights having different wavelengths, select a local light having a wavelength that is close to the wavelength of a received optical signal from among the plurality of generated local lights having different wavelengths, and transmit the selected local light to a coherent receiver; a demultiplexing unit configured to demultiplex a received optical signal and transmit the demultiplexed optical signal to the coherent receiver via a first path; and a wavelength detection unit configured to input the optical signal demultiplexed by the demultiplexing unit via a second path, split the input optical signal into different paths according to wavelengths by using a wavelength multiplexer/demultiplexer, and output, to the local light transmission unit, a control signal for causing the local light transmission unit to output a local light having a frequency that corresponds to a path in which the optical sig

Abstract: The purpose of the present invention is to improve signal modulation resolution. A coarse phase modulation element 62A modulates a signal into any of M1 (M1 is an arbitrary integer) patterns in a first range. Fine phase modulation elements 62B-1 through 62B-(k?1) respectively modulate the signal into any of M2 through Mk (M2 through Mk are arbitrary integers that are independent of each other and M1) patterns in a second range through k-th range (k is an integer of 2 or greater). A coarse DAC 61A and DACs 61B-1 through 61B-(k?1) perform control such that the second range through k-th range become narrower than the first range.

Abstract: An optical transmitter generates symbols for transmission by applying a predetermined coding method to each of m-valued transmission symbols generated from transmission data, generates signal light by performing optical modulation on the basis of the symbols for transmission, and transmits the signal light. An optical receiver generates a series of digital signals from the received signal light, detects coded symbols by applying predetermined digital signal processing to the series of digital signals, decodes the m-valued transmission symbols from the detected coded symbols, and restores the transmission data from the decoded m-valued transmission symbols.

Abstract: Systems and methods for an optical ternary content addressable memory (TCAM) are provided. The optical TCAM implements a time-division multiplexing (TDM) based encoding scheme to encode each bit position of a search word in the time domain. Each bit position is associated with at least two time slots. The encoded optical signal comprising the search word is routed through one or more modulators configured to represent a respective TCAM stored word. If a mismatch between at least one bit position of the search word and at least one TCAM stored word occurs, a photodetector or photodetector array will detect light.

Abstract: A packaged integrated white light source configured for illumination and communication or sensing comprises one or more laser diode devices. An output facet configured on the laser diode device outputs a laser beam of first electromagnetic radiation with a first peak wavelength. The first wavelength from the laser diode provides at least a first carrier channel for a data or sensing signal.

Abstract: A method in an electronic device, the method includes projecting infrared (“IR”) light from a plurality of light emitting diodes (“LEDs”) disposed proximate to the perimeter of the electronic device, detecting, by a sensor, IR light originating from at least two of the plurality of LEDs reflected from off of a person, and carrying out a function based on the relative strength of the detected IR light from the LEDs.

Abstract: A transimpedance amplifier includes a feedback circuit that generates a bypass current in accordance with a charging voltage of a capacitor based on a difference between a voltage signal and a reference voltage signal, a differential amplifier circuit that generates a differential signal in accordance with the difference between the voltage signal and the reference voltage signal, and a detector circuit that resets the charging voltage of the capacitor in response to a detection of end of a burst optical signal. The feedback circuit detects start of the burst optical signal based on the charging voltage, maintains a time constant at a first time constant for a predetermined period from the detection of the start of the burst optical signal, and, upon an elapse of the predetermined period, switches the time constant from the first time constant to a second time constant larger than the first time constant.

Abstract: The present invention is directed to communication systems and methods. According to a specific embodiment, FEC data streams from multiple FEC data lanes are received. First stage interleaving and inner encoding are performed on the FEC data streams to generate inner encoded data streams. A second stage interleaving process is performed to interleave the inner encoded data streams. There are other embodiments as well.

Abstract: A negative feedback inductor and a gate inductor are formed in different wiring layers of a substrate so as to be at least partially overlapped with each other in a plan view. When the lower wiring layer is thinner and the upper wiring layer is thicker, the negative feedback inductor Lc is formed in the lower wiring layer that is thinner.

Abstract: The application provides an optical network apparatus and an optical module. The optical network apparatus is configured to: convert, by a processing chip, the received N electrical signals from a board interface chip into a first electrical signal and a second electrical signal; and send the above two electrical signals to a first optical transmission component and a second optical transmission component, respectively; convert, by the first optical transmission component, the first electrical signal into a first optical signal; and convert, by the second optical transmission component, the second electrical signal into a second optical signal. The N to-be-sent electrical signals are combined, and only two optical transmission components are connected to the processing chip. Therefore, the processing chip does not need to be connected to four optical transmission components, fewer optical transmission components are required, and costs are reduced.

Abstract: Optical network devices, optical receivers, Automatic Gain Control (AGC) circuits, and power detection systems are provided for detecting power of optical signals within an optical communication system. An optical network device, according to one implementation, includes a receiver configured to receive an optical signal. The optical network device also includes a low bandwidth path configured to detect a low-band power component of the optical signal within a channel of interest and a broad bandwidth path arranged in parallel with the low bandwidth path. The broad bandwidth path is configured to detect a broad-band power component of the optical signal within broad-band channels including at least the channel of interest. A power detection output is derived from the low-band power component and the broad-band power component.

Abstract: In one embodiment, stable and controlled circuit element biasing is provided in a circuit comprising a voltage source operable to output a first voltage, a reference voltage source operable to output a reference voltage, a circuit element biased, during operation, by the first voltage at a first end and by a second voltage at a second end, a voltage controller coupled to the second end of the circuit element, wherein the voltage controller is operable to adjust the second voltage based on a gain output, a gain controller operable to receive the reference voltage as a first input and the second voltage as a second input, wherein the gain controller is operable to generate, at an output of the gain controller, the gain output based on the second voltage and the reference voltage, and a feedback loop that extends from the output of the gain controller, through the voltage controller, and to the second input.

Abstract: A light-emitting device includes a laser unit; and a first capacitive element and a second capacitive element that supply a driving electric current to the laser unit; wherein the first capacitive element has smaller equivalent series inductance than the second capacitive element, and the second capacitive element has a larger capacity and a smaller mount area than the first capacitive element.

Abstract: A method and apparatus for the increase of internal data throughput and processing capability for SSD's, to enable processing of database commands on an SSD. A front-end ASIC is provided with 256 to 512 RISC processing cores to enable decomposition and parallelization of host commands to front-end module (FM) ASICs that each in turn are coupled to multiple NVM dies, as well as processing of host database operations such as insert, select, update, and delete. Each FM ASIC is architected to increase parity bits to 33.3% of NVM data, and process parity data with 14 LDPC's. By increasing the parity bits to 33.3%, BER is reduced, power consumption is reduced, and data throughput within the SSD is increased.

Abstract: A method includes determining a first power level by performing a first series of measurements based on a first series of burst transmissions from an optical transmitter of an optical network unit (ONU) in an optical network. Bursts in the first series of burst transmissions include a first modified preamble. A second power level is determined by performing a second series of measurements based on a second series of optical burst transmissions. Bursts in the second series of burst transmissions include a second modified preamble. A first power level (P0) and a second power level (P1) are determined based on the first power level and the second power level and one or more additional parameters associated with transmissions from the optical transmitter are determined based on P0 and P1. Based on the additional parameters, it is determined whether the optical transmitter complies with specifications of the optical network.

Abstract: A clock data recovery circuit detects illegal decisions for received data, accumulates a phase gradient for the data, determines a number of the illegal decisions in a configured window for receiving the data, and if the number of the illegal decisions exceeds a pre-defend number in the window, applies a sum of the accumulated phase gradient and a phase increment having a sign of the accumulated phase gradient to a clock circuit for the data receiver.

Abstract: A transmitter can include a laser operable to output an optical signal; a digital signal processor operable to receive user data and provide electrical signals based on the data; and a modulator operable to modulate the optical signal to provide optical subcarriers based on the electrical signals. A first one of the subcarriers carriers carries first TDMA encoded information and second TDMA encoded information, such that the first TDMA encoded information is indicative of a first portion of the data and is carried by the first one of the subcarriers during a first time slot, and the second TDMA encoded information is indicative of a second portion of the data and is carried by the first one of the subcarriers during a second time slot. The first TDMA encoded information is associated with a first node remote from the transmitter and the second TDMA encoded information is associated with a second node remote from the transmitter.

Abstract: A semiconductor device comprises a semiconductor die and an integrated capacitor formed over the semiconductor die. The integrated capacitor is configured to receive a high voltage signal. A transimpedance amplifier is formed in the semiconductor die. An avalanche photodiode is disposed over or adjacent to the semiconductor die. The integrated capacitor is coupled between the avalanche photodiode and a ground node. A resistor is coupled between a high voltage input and the avalanche photodiode. The resistor is an integrated passive device (IPD) formed over the semiconductor die. A first terminal of the integrated capacitor is coupled to a ground voltage node. A second terminal of the integrated capacitor is coupled to a voltage greater than 20 volts. The integrated capacitor comprises a plurality of interdigitated fingers in one embodiment. In another embodiment, the integrated capacitor comprises a plurality of vertically aligned plates.

Abstract: Methods and systems for waveguide delay based equalization summing at single-ended to differential converters in optical communication are disclosed and may include: in an photonic circuit including a directional coupler, photodetectors, and a gain stage, receiving an input optical signal; splitting the input optical signal into first and second optical signals using the directional coupler; generating a first current from the first optical signal using a first photodetector; communicating the first voltage to a first input of the gain stage; generating a second current from the second optical signal using a second photodetector; communicating the second voltage to a second input of the gain stage; and generating a differential output voltage based on the first and second currents using the gain stage.

Abstract: Examples described herein relate to an analog front-end (AFE). The AFE includes a trans-impedance amplifier to receive an input current and generate a pair of the differential voltage signals based on the input current and a reference current. Further, the AFE includes a dynamic voltage slicer to receive the differential voltage signals at input terminals and supply digital voltages at output terminals. The dynamic voltage slicer includes a preamplifier to generate a pair of intermediate voltages based on the differential voltage signals sampled at a predetermined frequency. The dynamic voltage slicer also includes a voltage latch circuit coupled to the preamplifier, wherein the voltage latch circuit is to regenerate a pair of digital voltages based on the pair of the intermediate voltages. Moreover, the AFE includes a logic latch coupled to the dynamic voltage slicer to provide digital output states based on the pair of the digital voltages.

Abstract: A quantum receiver for decoding an optical signal includes a beamsplitter for interfering the optical signal with a local-oscillator field to generate a displaced field, and a single-photon detector for detecting the displaced field. The quantum receiver also includes a signal-processing circuit for determining, based on an electrical output of the single-photon detector, a measurement outcome. The signal-processing circuit also determines, based on the measurement outcome and a feed-forward machine-learning model, a next displacement. The quantum receiver also includes at least one modulator for modulating, based on the next displacement, one or both of the optical signal and the local-oscillator field. Like a Dolinar receiver, the quantum receiver implements adaptive measurements to reduce the error probability of the decoded symbol. The use of machine-learning reduces the latency of the signal-processing circuit, thereby increasing the number of measurements that may be performed for each received symbol.

Abstract: A passive continuous-variable quantum key distribution scheme, where Alice splits the output of a thermal source into two spatial modes, measures one locally and transmits the other mode to Bob after applying attenuation. A secure key can be established based on measurements of the two modes without the use of a random number generator or an optical modulator.

Abstract: A sampling frequency required for symbol timing recovery is made smaller than that of the related art. A receiver 1 performs visible light communication with a transmitter 8. A received signal generating unit 112 measures an intensity of an electrical signal corresponding to an optical signal received from a transmitter 8 at a predetermined time interval to generate a sequence of received signals. A parameter estimation unit 12 uses a distribution of received signals estimated from the sequence of received signals to estimate any one or more parameters of a maximum luminance value, a synchronization shift, and a steady noise level, the one or more parameters including at least the maximum luminance value.

Abstract: A logarithmic power detector includes a power distributor, a first detection circuit, a second detection circuit and an output circuit. The power distributor is used to generate a first power signal and a second power signal according to an input signal. The first detection circuit is used to attenuate the first power signal to generate a first rectified signal, filter the first rectified signal to generate a first low-pass signal, and amplify the first low-pass signal to generate a first amplification current. The second detection circuit is used to attenuate the second power signal to generate a second rectified signal, filter the second rectified signal to generate a second low-pass signal, and amplify the second low-pass signal to generate a second amplification current. The output circuit is used to receive the first amplification current and the second amplification current to generate a converted voltage related to the input signal.

Abstract: Disclosed herein are transimpedance circuits, as well as related methods and devices. In some embodiments, a transimpedance circuit may include a current source bias terminal, a current source output terminal, and a transimpedance amplifier coupled to the current source output terminal, wherein voltage signals at the current source bias terminal are correlated with voltage signals at the current source output terminal. In some embodiments, the current source may be a photodiode.

Abstract: Consistent the present disclosure, a network or system is provided in which a hub or primary node may communication with a plurality of leaf or secondary nodes. The hub node may operate or have a capacity that may be greater than that of the leaf nodes. Accordingly, relatively inexpensive leaf nodes may be deployed that receive data carrying optical signals from and supply data carrying optical signals to the hub node. One or more connections may couple each leaf node to the hub node, whereby each connection may include one or more spans or segments of optical fibers, optical amplifiers, and optical add/drop multiplexer, for example. Consistent with an aspect of the present disclosure, optical subcarriers may be transmitted over such connections. The subcarriers may be generated by a combination of a laser and a modulator, such that multiple lasers and modulators are not required, and costs may be reduced.

Abstract: A calibration method of an equalizer circuit for a memory storage device is disclosed. The calibration method includes: receiving a first signal; adjusting, by the equalizer circuit, the first signal according to a control parameter to output a second signal; generating a first sampling signal according to a first reference signal and the second signal, wherein the first sampling signal reflects data transmitted by the first signal; and generating a second sampling signal according to a second reference signal and the second signal and adjusting the control parameter according to the second sampling signal to calibrate the equalizer circuit, wherein a voltage value of the first reference signal is different from a voltage value of the second reference signal.

Abstract: A data acquisition system may include an input for receiving an input signal for the data acquisition system, a plurality of data paths including a first data path and a second data path, and a signal estimator configured to determine a magnitude of the input signal using estimation of the input signal and dynamically deactivate one of the first and second data paths based on the magnitude of the input signal.

Abstract: System and method for fiber-optic time frequency and data joint transmission, comprising local end, relay nodes, and remote end. In each local end, relay node, and remote end, multiplexing and demultiplexing of time frequency signals, optical supervisory signals, and optical communication data services are performed by CWDM modules and OSC-band wavelength multiplexer/demultiplexers, and processing (transmitting, relaying, receiving) is performed by corresponding processing modules for joint transmission. A sub-band of standard OSC band is used for transmitting time frequency signal so that transmission of optical supervisory signal is not influenced while no extra band resource is occupied with improved utilization of wavelength resources and reduced costs.

Abstract: A test system and interface circuitry for antenna-free bit error rate testing of an electronic device under test, including a pulse shaping circuit with a pulse shaping filter circuit to pulse shape a modulating signal before amplitude modulation with a carrier signal, and the amplitude modulated signal is coupled directly or via a transformer and a socket to the device under test without antennas to facilitate automated device testing with simple reconfiguration of signal generators for different device type. A method includes filtering a square wave modulating signal to create a pulse shaped modulating signal, amplitude modulating a carrier signal with the pulse shaped modulating signal to create an amplitude modulated signal, providing the amplitude modulated signal to the socket, and evaluating a bit error rate of the DUT according to receive data from the DUT and according to the BER test transmit data.

Abstract: Embodiments herein disclose receiver of coherent optical communication link and method of compensating carrier phase offset in receiver. 90° optical hybrid is configured to receive input of reference optical carrier (LO) signal and modulated optical signal (S) and carrier phase offset detection block is configured to generate output signal representing average of the phase offset at the input of the carrier phase offset detection block. Electronic control unit configured to receive output signals from the carrier phase offset detection block for generating control signals and tunable phase delay block configured to receive the control signals from the electronic control unit. 90° optical hybrid, carrier phase offset detection block, electronic control unit and the tunable phase delay block are configured in feedback loop, such that outputs of the carrier phase offset detection block are used for tuning the phase delay of the tunable phase delay block to achieve carrier phase synchronization.

Abstract: A system for generating clock signals for a photonic quantum computing system includes a pump photon source configured to generate a plurality of pump photon pulses at a first repetition rate, a waveguide optically coupled to the pump photon source, and a photon-pair source optically coupled to the first waveguide. The system also includes a photodetector optically coupled to the photon-pair source and configured to generate a plurality of electrical pulses in response to detection of at least a portion of the plurality of pump photon pulses at the first repetition rate and a clock generator coupled to the photodetector and configured to convert the plurality of electrical pulses into a plurality of clock signals at the first repetition rate.

Abstract: Techniques are described for implementing an out-of-band communication channel used to exchange control channel information in sub-carrier-based optical communication systems. In an example implementation, an apparatus includes laser operable to supply an optical signal, a digital signal processor operable to supply digital signals, a digital to analog circuitry operable to provide analog signals based on the digital signals, and driver circuitry is coupled to the digital to analog circuitry and operable to supply at least one drive signal. The apparatus also includes a modulator operable to receive said at least one drive signal, modulate the optical signal based on said at least one drive signal to provide a plurality of optical subcarriers, amplitude modulate the plurality of optical subcarriers at a first frequency to carry first control information, and modulate the plurality of subcarriers at a second frequency to carry second control information.

Abstract: Techniques are described for implementing an out-of-band communication channel used to exchange control channel information in sub-carrier-based optical communication systems. In an example implementation, a transmitter includes a laser operable to supply an optical signal, a digital signal processor operable to supply first electrical signals based on first data input to the digital signal processor and second data input to the digital signal processor, digital-to-analog conversion circuitry operable to output second electrical signals based on the first electrical signals, modulator driver circuitry is operable to output third electrical signals based on the second electrical signals, and an optical modulator operable to supply first and second modulated optical signals based on the third electrical signals. The first modulated optical signal includes a plurality of optical subcarriers carrying user data. The second modulated optical signal is polarization modulated based on the second data.

Abstract: A method and apparatus for night lapse video capture are disclosed. The apparatus includes an image sensor, an image processor, and a video encoder. The image sensor is configured to capture image data. The image data includes a first image that is temporally precedent to a second image. The image processor is configured to determine a motion estimation. The motion estimation is based on a comparison of a portion of the first image and a portion of the second image. The image processor is configured to subtract a mask from the second image to obtain a denoised image. The mask is based on the motion estimation. The video encoder is configured to receive the denoised image from the image processor. The video encoder is configured to encode the denoised image in a video format. The video encoder is configured to output a video file in the video format.

Abstract: A clock and data recovery circuit includes an equalizer configured to equalize an input signal to generate an equalization input signal, a subtractor configured to subtract a decision feedback equalization signal from the equalization input signal to generate a sampling input signal, a decision feedback equalization unit configured to generate first digital data corresponding to the sampling input signal in response to a first sampling clock signal, generate second digital data corresponding to the sampling input signal in response to a second sampling clock signal having a predetermined time difference with the first sampling clock signal, and compare the sampling input signal and a reference data level. A controller is configured to adjust the reference data level, determine a maximum eye opening and adjust a sample timing based on the reference data level.

Abstract: The present disclosure provides a method and a device for amplifying uplink light of a passive optical network, and a computer-readable storage medium. The passive optical network includes an optical network unit, an optical line terminal, and an optical amplifier provided between the optical network unit and the optical line terminal, and the method include: receiving a registration signal transmitted from the optical line terminal; determining a gain value of the optical amplifier, and performing gain value adjustment on the optical amplifier according to the determined gain value; and completing registration when an uplink optical signal transmitted to the optical line terminal through the optical amplifier reaches preset power.

Abstract: An example apparatus for correcting gaze in images includes an image receiver to receive an image comprising an eye and a target angle set to a center. The apparatus also includes a bidirectionally trained convolutional neural network (CNN) to receive the image and the target angle from the image receiver and generate a vector field and a brightness map based on the image and the target angle. The apparatus further includes an image corrector to generate a gaze corrected image based on the vector field and the brightness map.

Abstract: One example includes a digital signal conditioner (DSC) system. A sample selector bank receives a digital sample block of an input signal that is provided at a supported input oversampling factor and selects a subset of samples from the digital sample block based on a selection signal. A tap weights selector bank generates a set of tap weights based on the selection signal. A filter bank receives the subset of the samples from each of the sample selectors and a respective set of tap weights. Each filter provides a weighted sample associated with the respective subset of samples and the respective set of tap weights. A reformattor receives the weighted sample from each of the filters and provides a filtered sample block including the weighted sample from a subset of the filters at an output oversampling factor for each supported input oversampling factor based on a selected supported resampling ratio.

Abstract: In optical receivers, extending the transimpedance amplifier's (TIA) dynamic range is a key to increasing the receiver's dynamic range, and therefore increase the channel capacity. Ideally, the TIA requires controllable gain, whereby the receiver can modify the characteristics of the TIA and/or the VGA to process high power incoming signals with a defined maximum distortion, and low power incoming signals with a defined maximum noise. A solution to the problem is to provide TIA's and VGA's with reconfigurable sizes, which are adjustable based on the level of power, e.g. current, generated by the photodetector.

Abstract: Disclosed herein is an apparatus that includes a phase frequency detector configured to compare a phase difference between first and second clock signals to generate a phase detection signal, and a slew rate controller configured to lower a slew rate of the first clock signal when a selection signal is in a first state.

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: The present disclosure relates to optical receivers. One example optical receiver includes an optoelectronic detector, a transimpedance amplification (TIA) circuit, a single-ended-to-differential converter, an I/O interface, and a controller. The optoelectronic detector, having bandwidth lower than required system transmission bandwidth, converts an optical signal into a current signal. The TIA circuit compensates gain for the received current signal based on a received control signal to obtain a voltage signal, where a frequency response value of the current signal within first bandwidth is greater than that within the bandwidth of the optoelectronic detector, and any frequency in the first bandwidth is not lower than an upper cut-off frequency of the optoelectronic detector. The single-ended-to-differential converter converts the voltage signal into a differential voltage signal. The I/O interface outputs the differential voltage signal.

Abstract: A PDM-capable coherent optical receiver can be implemented using four high-bandwidth photodiodes connected in a single-ended electrical configuration. The SSBI present in the electrical output of the single-ended photodiodes is effectively canceled in the receiver DSP based on measurements of average optical power of the optical data and local-oscillator signals. In various embodiments, such measurements can be performed using relatively inexpensive circuits/components incorporated into the optical front end of the receiver. For a given signaling interval, the DSP runs an iterative algorithm to compute estimates of the in-phase and quadrature components of the optical data signal and achieve a level of performance comparable to that of a coherent optical receiver having a greater number of high-bandwidth photodiodes connected to form balanced photodetectors. The achieved reduction in the number of high-bandwidth photodiodes can advantageously be used, e.g.

Abstract: The receiving-side system (10) includes a smaller number of optical reception front ends (12) than the number of a plurality of wavelength-multiplexed subcarrier signals. Each of the optical reception front ends (12) is configured to receive two or a plurality subcarrier signals of the plurality of subcarrier signals. A frequency offset monitoring unit (22) monitors frequency offsets of the respective subcarrier signals received by the optical reception front end (12). A light source frequency control unit (24) controls at least one of a light source frequency of the transmitting-side system (2) and a light source frequency of the receiving-side system (10) based on a result of the monitoring performed by the frequency offset monitoring unit (22).

Abstract: One example includes an optical coupler. The optical coupler includes a waveguide formed in a first layer of a layered structure that is to propagate an optical signal. The waveguide includes an end portion. The optical coupler also includes a turning mirror that includes a bulk structure and a reflective material deposited on an angular face of the bulk structure to form a surface of the turning mirror. The bulk structure can have a greater cross-sectional size than a cross-sectional size of the waveguide, such that the angular face extends above the first layer of the layered structure and extends into a second layer of the layered structure below the first layer. The surface of the turning mirror can be arranged to reflect the optical signal that is provided from the end portion of the waveguide.

Abstract: Swept source optical coherence tomography (SS-OCT) systems and methods may employ down-conversion. Down-converter systems and methods may utilize a distribution element and a frequency down shifter. The distribution element may receive an output signal of a photo detection device, the output signal comprising a first frequency component at or below a maximum conversion frequency and a second frequency component above the maximum conversion frequency. The distribution element may send the first frequency component to an analog to digital (A/D) converter and send the second frequency component to a frequency down shifter. The frequency down shifter may down shift the second frequency component to a frequency at or below the maximum conversion frequency to form a down shifted second frequency component. The frequency down shifter may send the down shifted second frequency component to the A/D converter.