Abstract: A pluggable module is provided for converting an optical signal to a plurality of electrical signals. The pluggable module may include a printable circuit board (PCB) and an optical connector disposed on a first side of the PCB. The optical connector may route any received optical signal to an optical to electrical transceiver. The optical to electrical transceiver may convert the optical signal to an electrical signal and route the electrical signal to an electrical connector mounted on a second, opposite side of the PCB.

Abstract: A free space optical communication system includes an optical receiver configured to receive a light beam from an optical transmitter wirelessly in free space. The optical receiver includes an array of photodetectors and an electrical circuit. The array of photodetectors is configured to receive the light beam and convert optical signals of the light beam into electrical current. The electrical circuit is electrically coupled to the array of photodetectors and is configured to combine electrical current from the photodetectors and output a voltage or current signal.

Abstract: An apparatus for determining an eye mask of a device under test (DUT) which is configured to receive a data bit stream signal including a threshold level value and output a data bit stream output signal. The apparatus includes an input unit configured to receive the data bit stream output signal provided by the DUT, an evaluation unit configured to evaluate the received data bit output signal and provide an evaluation result, and a controller configured to change the threshold level value in response to the evaluation result. The apparatus is integrated into the DUT and can operates autonomously without multiple interactions with a tester.

Abstract: Systems and methods for transmission filtering are provided. A receiver includes an input coupled to a transmission line to receive distorted optical symbols. A distortion filter is coupled to the input to replace the distorted optical symbols with predicted symbols using a trained neural network. A decoder is coupled to the distortion filter to decode the predicted symbols.

Abstract: An optical transceiver includes an optical transmitter and an optical receiver. The optical transmitter includes a laser diode configured to convert a current signal into an optical signal; a main driver comprising first and second output terminals that have a differential structure, the main driver configured to drive the first and second output terminals in response to differential input signals and to provide the current signal to the laser diode through the first output terminal; and an impedance balancer configured to match impedances of the first and second output terminals by adjusting the impedance of the second output terminal according to signal states of the first and second output terminals.

Abstract: Embodiments of this disclosure provide an impairment monitoring apparatus, impairment monitoring and compensating system and method. As a parameter of a impairment of a receiver end and/or a parameter of an impairment of a transmitter end is/are determined according to a preset period or a preset condition to perform compensation or calibration, complexity of calculation and power consumption of the system may be efficiently lowered. And as the parameter of the impairment of the receiver end and the parameter of the impairment of the transmitter end are not changed rapidly, determining these parameters according to the preset period or the preset condition to perform compensation or calibration will not affect an effect of the compensation or calibration, thereby ensuring a performance of the system.

Abstract: In optical receivers, cancelling the DC component of the incoming current is a key to increasing the receiver's effectiveness, and therefore increase the channel capacity. Ideally, the receiver includes a DC cancellation circuit for removing the DC component; however, in differential receivers an offset may be created between the output voltage components caused by the various amplifiers. Accordingly, an offset cancellation circuit is required to determine the offset and to modify the DC cancellation circuit accordingly.

Abstract: An optical communication device, reception apparatus, transmission apparatus and transmission and reception system are disclosed. The optical communication device includes a drive circuit substrate. A first through via extends through the drive circuit substrate and is configured to electrically connect an optical element disposed on a first surface side of the drive circuit substrate to a drive circuit disposed on a second surface side of the drive circuit substrate. A positioning element is attached to an interposer substrate and is configured to align optical axes of a first lens that is attached to a lens substrate and that faces a second lens that is disposed on the first surface side of the drive circuit substrate. A second through via extends through the interposer substrate and electrically connects the drive circuit to a signal processing circuit disposed on a signal processing substrate positioned above the interposer substrate.

Abstract: Methods and systems for accurate gain adjustment of a transimpedance amplifier using a dual replica and servo loop is disclosed and may include, in a transimpedance amplifier (TIA) circuit comprising a first TIA, a second TIA, and a third TIA, each comprising a configurable feedback impedance, and a control loop, where the control loop comprises a gain stage with inputs coupled to outputs of the first and second TIAs and an output coupled to the configurable feedback impedance of the second and third TIAs: configuring a gain level of the first TIA by configuring its feedback impedance, configuring a gain level of the third TIA by configuring a reference current applied to an input of the first TIA, and amplifying a received electrical signal to generate an output voltage utilizing the third TIA. The reference current may generate a reference voltage at one of the inputs of the gain stage.

Abstract: An optical receiver is configured so as to be as less susceptible to noise as possible even in the case where high noise occurs inside an optical transceiver. The optical receiver includes a connection part that connects two photodiodes (PDs) constituting a dual photodiode and a transimpedance amplifier (TIA), wherein signal lines from the dual photodiode are surrounded by a conductor pattern that is not connected to each of the signal lines for each channel, and the conductor pattern is connected to a ground pattern on the transimpedance amplifier or a power source pattern for the PDs.

Abstract: An optical module includes an optoelectronic transceiver. The optical modules includes a heat sink. The heat sink includes a heat radiating element aligned along a length of the heat sink. The heat sink radiates heat received from the optoelectronic transceiver. The optical modules includes a housing. The optoelectronic transceiver is encapsulated by the heat sink and the housing.

Abstract: An optical signal modulator comprising a modulator unit, a photodetector and an electrical signal combiner. The modular unit having an optical ingress port for optical radiation, a first and second optical output port each for modulated optical radiation, and an electrical ingress port for an electrical modulation signal. The optical radiation is modulated in response to the electrical modulation signal. The photodetector is connected to the second optical output port and configured to measure the modulated optical radiation that is emitted, and to provide a monitor signal. The electrical signal combiner having a first input port for an external electrical data signal, a second electrical input port for a correction signal based on the monitor signal, and an electrical output port that is connected to the electrical ingress port. The combiner generates the electrical modulation signal by combining the external electrical data signal and the correction signal.

Abstract: A method and structure for a coherent optical receiver device. Timing recovery (TR) is implemented after channel dispersion (i.e., chromatic dispersion (CD) and polarization mode dispersion (PMD)) compensation blocks. This architecture provides both improves performance and reduces power consumption of the device. Also, a TR loop is provided, enabling computing, by an error evaluation module, a first sampling phase error (SPE) and computing, by a timing phase information (TPI) module coupled to the error evaluation module, a second SPE from a plurality of CD equalizer taps PMD equalizer taps. The first and second SPE are combined into a total phase error (TPE) in a combining module, and the resulting TPE is filtered by a timing recovery (TR) filter coupled to an interpolated timing recovery (ITR) module and the combining module. The ITR module then synchronizes an input signal of the coherent optical receiver according to the TPE.

Abstract: When a frequency deviation compensation amount is compensated for by use of frequency shift, a phase offset occurs between adjacent input blocks included in a plurality of input blocks as divided, with the result that an error occurs in a reconstructed bit sequence. A frequency deviation compensation system of the invention is characterized by comprising: a frequency deviation compensation means for compensating for a frequency deviation occurring in a signal by use of frequency shift; and a phase offset compensation means for compensating for a phase offset occurring, in the signal, due to the frequency shift.

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 optoelectronic receiver including a directional coupler, photodetectors, transimpedance amplifiers (TIAs), 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; generating a first voltage from the first current using a first TIA; 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; generating a second voltage from the first signal using a second TIA; communicating the second voltage to a second input of the gain stage; and generating a differential output voltage from the first and second voltages using the gain stage.

Abstract: A method of generating a probabilistically shaped (PS), multi-level modulation signals includes encoding information bits into coded bits to which probability values are assigned according to a probability mass function, and mapping, based on a Gray coding scheme, the coded bits into symbols to which the probability values are assigned. The probability mass function is implemented by determining probabilities of the coded bits so that the probabilities of the coded bits in ascending or descending order have a Gaussian distribution, and performing a probability distribution pre-adjustment by redistributing probabilities of the coded bits corresponding to symbols probabilities of which are outside Gaussian distribution so that the symbols mapped based on the Gray coding scheme have the Gaussian distribution.

Abstract: The differences in the power received from multiple optical network units connected to an optical hub may exceed an allowable dynamic range. The dynamic range may be reduced by determining the power received at the optical hub from each optical network unit and adjusting the power transmitted from one or more optical network units to reduce the overall dynamic range. For each optical network unit, the hub may determine the received optical power in an upstream signal from the optical network unit and receive a digital representation of the transmitted power. The hub may determine to adjust the optical power sent from one or more of the optical network units to reduce the dynamic range. The adjustments to the optical powers at the optical network units may be performed by sending commands from the optical hub to each adjusted optical network unit via a downstream signal.

Abstract: A digital optical receiver capable of adaptively correcting the linearity of an analog front end unit is provided.

Abstract: An optical communication system having a data transmitter which includes: at least one optical emission device to output light energy as an optical beam having an operating bandwidth; a beam dividing device to receive and divide the operating bandwidth into plural communication bands; a frequency presence modulation unit to: spectrally segregate the bandwidth of at least one communication band into plural channels, and modulate the bandwidth to selectively produce an optical output signal with wavelengths that correspond to one or more of the channels, wherein presence and absence of energy within channels constitute an information packet for data communication; a controller for providing a control signal to the frequency presence modulation unit to spectrally segregate the bandwidth of the at least one communication band into the plural channels; and a telescope to transmit the optical output signal.

Abstract: An optical communication system that includes a data transmitter which includes: at least one ultraviolet laser source configured to output ultraviolet light energy as an optical beam having an operating bandwidth with at least one communication band; a frequency presence modulation unit including at least one optical component having an ultraviolet coating, the frequency presence modulation unit being configured to: spectrally segregate the bandwidth of the at least one communication band into plural channels, and modulate the bandwidth to selectively produce an ultraviolet optical output signal with wavelengths that correspond to one or more of the channels, wherein a presence and absence of energy within channels of the communication band will constitute an information packet for data communication; and a controller for providing a control signal to the frequency presence modulation unit to spectrally segregate the bandwidth of the at least one communication band into the plural channels.

Abstract: A method that may include receiving a block of signals from a certain wavelength division multiplex (WDM) channel out of a set of WDM channels; analyzing at least a first sub-block of signals of the block of signals to provide analysis results indicative of interferences that affect the first sub-block of signals and result from transmissions over other WDM channels of the set of WDM channels; and mitigating interferences that affect the block of signals in response to the analysis results.

Abstract: A SDH receiver which comprises a first polarization beam splitter 11, a second polarization beam splitter 13, a first separator 15, a second separator 17, a third separator 19, a fourth separator 21, a first 90-degree polarization rotor 23, a second 90-degree polarization rotor 25, a first hybrid detector 31, a second hybrid detector 33, a third hybrid detector 35, a fourth hybrid detector 37, and a signal processor 39.

Abstract: A transmission apparatus including: a branch circuit that branches a signal including first data and second data superimposed on the first data into two signals; a limiting amplifier that amplifies one signal in the two signals; a linear amplifier that amplifies another signal in the two signals; a first detector that detects the first data from the amplified one signal; and a second detector that detects the second data from the amplified another signal and the amplified one signal.

Abstract: Methods and apparatus to realize high spectral efficiency in optical signals transmitted over long distances.

Abstract: An optical receiver that receives a wavelength-multiplexed optical signal is disclosed. The optical receiver implements two or more PD elements each receiving an optical signal contained in the wavelength-multiplexed optical signal, a switch that selects one of photocurrents output from the PD elements, an I/V converter that converts the photocurrent into a voltage signal by a variable resistor whose resistance is adjusted for respective photocurrent, and a digital-to-analog converter. The optical receiver estimates the power of the optical signals from look-up-tables correlating the power of the optical signals with the digitally converted photocurrents at the selected resistance of the variable resistor.

Abstract: A voltage controlled oscillator (“VCO”) circuit is disclosed. The VCO includes a switch module comprising a first transistor and a second transistor; a first LC-tank module, the first LC-tank module is operatively connected between the drain of the first transistor and the drain of the second transistor; and a second LC-tank module, the second LC-tank module is operatively connected between the gate of the first transistor and the gate of the second transistor, the source of the first transistor and the source of the second transistor are operatively connected.

Abstract: A method and apparatus for measuring a filtering characteristic, pre-equalizer and communication equipment. The apparatus for measuring a filtering characteristic includes: a first processing unit configured to determine a filtering characteristic of a receiving end according to an amplitude of a receiving signal obtained after a measurement signal passes through a transmitting end filtering module and a receiving end filtering module at provided different frequency offsets of a transmitting laser of a transmitting end and a local laser of the receiving end.

Abstract: Apparatus and method for transmitter alignment in an optical communication system are provided. In certain configurations, a method of correcting for transmitter skew is provided. The method includes generating an optical signal using a transmitter based on an in-phase (I) component and a quadrature-phase (Q) component of a transmit signal, the optical signal having a baud rate that is based on a timing tone. The method further includes receiving the optical signal as an input to a receiver, and generating a signal vector representing the optical signal using the receiver. The signal vector includes an I component and a Q component. The method further includes calculating a power of the timing tone based on processing the signal vector using a tone power calculator of the receiver, and correcting for a skew of the transmitter based on the calculated power.

Abstract: A power converter includes an energy transfer element and a circuit coupled to the input of the power converter. The circuit includes a switch and a control circuit capable of detecting whether an AC voltage source is coupled to the input, or uncoupled from the input within a first predetermined time. The control circuit is coupled to drive the switch in a first operating mode when the AC voltage source is coupled, drive the switch in a second operating mode when the AC voltage source is uncoupled, and is capable of discharging a capacitance coupled between input terminals of the power converter to a threshold voltage level through a discharge path and through the switch within a second predetermined time. An RC time constant of the discharge path is less than or equal to one second and the threshold voltage level is less than or equal to ten volts.

Abstract: Methods and systems for accurate gain adjustment of a transimpedance amplifier using a dual replica and servo loop is disclosed and may include, in a transimpedance amplifier (TIA) circuit comprising a first TIA, a second TIA, and a third TIA, each comprising a configurable feedback impedance, and a control loop, where the control loop comprises a gain stage with inputs coupled to outputs of the first and second TIAs and an output coupled to the configurable feedback impedance of the second and third TIAs: configuring a gain level of the first TIA by configuring its feedback impedance, configuring a gain level of the third TIA by configuring a reference current applied to an input of the first TIA, and amplifying a received electrical signal to generate an output voltage utilizing the third TIA. The reference current may generate a reference voltage at one of the inputs of the gain stage.

Abstract: A comparator includes a current mirror module, a comparison module and a buffering and outputting module. The current mirror module provides a bias current to the comparison module. The comparison module comprises a positive input end, a first negative input end and a second negative input end, the positive input end connects to an external terminal, the first negative input end and the second negative input end input a low threshold voltage and a high threshold voltage, respectively. The comparison module compares a voltage of the positive input end to the low threshold voltage and the high threshold voltage, and outputs a comparison result to the buffering and outputting module.

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.

Abstract: A transceiver (4) comprising a receive part (70) configured to receive and detect a first signal carried on an optical carrier, wherein the signal is in a first part of a RF spectrum. The transceiver (4) further comprises a modulator (68) configured to modulate the same optical carrier with a second signal in a second part of the RF spectrum. The transceiver comprises a transmit part (60) configured to transmit the optical carrier modulated with the second signal. The first part of the RF spectrum is separate to the second part of the RF spectrum. The first signal and/or second signal are spectrally compressed signals.

Abstract: An Optical Line Termination (OLT) module and an OLT are disclosed. According to an embodiment of the OLT optical module, an optical signal receiver connects with a trans-impedance amplifier of which differential outputs connect with a limiting amplifier. An SD output of the limiting amplifier connects with a clock input of a D trigger and an input of a micro control unit. The D trigger connects with a control signal input of a first switch tube and may cause the first switch tube to be in conducting state when outputting high level. When the optical signal receiver detects an uplink burst signal, the limiting amplifier may generate the SD signal, the D trigger may output high level according to the SD signal and the first switch tube will be in conducting state, so that the micro control unit may detect the received optical power of the uplink burst signal.

Abstract: An optical network system comprising an optical line terminal (OLT) and an optical network unit (ONU) coupled to the OLT and configured to communicate with the OLT via an optical signal. At least one of the OLT or the ONU comprises a closed-loop gain controlled transimpedance amplifier (TIA) comprising a first amplifier configured to receive an input signal, generate a main output signal by amplifying the input signal according to a gain factor of the first amplifier, and generate an auxiliary output proportional to the input signal, an average detector coupled to the first amplifier and configured to receive the auxiliary output, and determine an average of the input signal according to the auxiliary output, and a feedback loop coupled to the first amplifier and the average detector and configured to control the gain factor of the first amplifier according to the average of the input signal.

Abstract: An optical data transmitter includes vertical cavity surface-emitting lasers and an all-optical spatial mode multiplexer. Each vertical cavity surface-emitting laser is configured to output a data modulated optical carrier at a center wavelength of less than one micrometer. The all-optical spatial mode multiplexer has an optical output and optical inputs. Each vertical cavity surface-emitting lasers is optically connected to one or more of the optical inputs of the all-optical spatial mode multiplexer. The all-optical spatial mode multiplexer is configured to cause at least two of the vertical cavity surface-emitting lasers to excite linearly independent combinations of one or more optical spatial propagating modes of an optical fiber in response to the optical output being coupled to a near end of the optical fiber.

Abstract: A method of controlling a parameter in the generation of a coherent optical signal, the method comprising the steps of: receiving a set of signal samples relating to detection of a coherent optical signal; transforming the set of signal samples into a set of spectrum samples in the frequency domain, the set of spectrum samples being an estimation of the spectrum of the coherent optical signal; calculating at least one feedback variable based on the spectrum samples; and adjusting the parameter based on the at least one feedback variable.

Abstract: An optical receiver includes an APD that converts an input optical signal into a current signal, a TIA that converts the current signal output from the APD into a voltage signal, an LIA that shapes a waveform of the voltage signal output from the TIA, an AOC having a time constant switching function, the AOC automatically compensating for an offset voltage between differential outputs from the TIA, and a convergence-state detection circuit that outputs, after detecting convergence completion of the automatic compensation in the AOC, to the AOC, a time constant switching control signal for switching a time constant from a high-speed time constant to a low-speed time constant.

Abstract: A method for operating an electronic device is provided. The method includes converting received infrared into an electrical signal, amplifying the electrical signal and outputting an analog signal, converting the analog signal into digital data, determining whether the digital data is valid, and activating an application program in a freeze state to be in an unfreeze state.

Abstract: An optical transmitter includes an optical modulator to modulate light having a predetermined wavelength into an optical signal based on a data signal, a memory, and a processor coupled to the memory and the processor configured to modulate an input signal into a multi-carrier signal so as to generate the data signal, the multi-carrier signal including a plurality of subcarriers each to which a transmission capacity is allocated, acquire a first frequency distribution of an intensity of the multi-carrier signal, acquire a second frequency distribution of an intensity of the optical signal, control the modulating of the input signal into the multi-carrier signal to change a number of subcarriers of the multi-carrier signal, and control the optical modulator to adjust a modulation characteristic of the optical modulator so that a divergence between the first frequency distribution and the second frequency distribution is equal to or less than a predetermined value.

Abstract: A method for detecting a dispersed pulse in a received signal that has been dispersed by a dispersive medium includes obtaining an input array of cells, each indicating an intensity of a frequency component of the signal at a representative time. A fast dispersion measure transform (FDMT) is applied to concurrently sum the cells of the input array that lie along different dispersion curves, each curve defined by a known non-linear functional form and being uniquely characterized by a time coordinate and by a value of the dispersion measure. Application of FDMT includes initially generating a plurality of sub-arrays, each representing a frequency sub-band and iteratively combining pairs of adjacent sub-arrays in accordance with an addition rule until all of the initially generated plurality of sub-arrays are combined into an output array of the sums, in which a cell of the output array that is indicative of a transmitted pulse is identified.

Abstract: An apparatus comprises a polarization-diversity optical hybrid that converts an optical signal into a plurality of optical signals comprising a first polarization component and a second polarization component orthogonal to the first polarization component, one or more detectors that convert the plurality of optical signals into a plurality of first analog electrical signals, DC blocking elements that remove DC signal components to output a plurality of second analog electrical signals, analog to digital converters (ADCs) coupled to the DC blocking elements that convert the plurality of second analog electrical signals into a plurality of digital signals, and a digital signal processing (DSP) unit coupled to the ADCs. The DSP is configured to perform a fiber dispersion compensation on the plurality of digital signals and add DC offsets to output a plurality of DC-restored compensated digital signals.

Abstract: Methods and systems for a distributed optoelectronic receiver are disclosed and may include an optoelectronic receiver having a grating coupler, a splitter, a plurality of photodiodes, and a plurality of transimpedance amplifiers (TIAs). The receiver receives a modulated optical signal utilizing the grating coupler, splits the received signal into a plurality of optical signals, generates a plurality of electrical signals from the plurality of optical signals utilizing the plurality of photodiodes, communicates the plurality of electrical signals to the plurality of TIAs, amplifies the plurality of electrical signals utilizing the plurality of TIAs, and generates an output electrical signal from coupled outputs of the plurality of TIAs. Each TIA may be configured to amplify signals in a different frequency range. One of the plurality of electrical signals may be DC coupled to a low frequency TIA of the plurality of TIAs.

Abstract: Embodiments of the present disclosure disclose a coherent receiver, including: a frequency offset estimation unit and a frequency offset compensation unit, where the frequency offset estimation unit is configured to receive signal light and local oscillator light, where the signal light is received by a first photoelectric detector, and a first intensity value is obtained, the signal light is received by a second photoelectric detector, and a second intensity value is obtained, the local oscillator light is received by a third photoelectric detector, and a third intensity value is obtained, and the local oscillator light is received by a fourth photoelectric detector, and a fourth intensity value is obtained; and the frequency offset compensation unit is configured to obtain a frequency offset value between the signal light and the local oscillator light according to a difference between a first ratio and a second ratio.

Abstract: An optical module is disclosed. According to one implementation, the optical module comprises an optical receiver, a diode, a first resistor, a first capacitor, a comparator, and a control chip. The diode anode connects electrically with a triggering signal output end of the optical receiving module, the cathode of the diode connects with one end of the first capacitor and one input end of the comparator. Another end of the first capacitor connects with the ground; the first resistor is connected in parallel with both ends of the first capacitor. A pre-set reference voltage is connected with another input end of the comparator. The optical receiver generates a first triggering signal in response to a burst mode optical signal. After inputting the first triggering signal into the diode anode, the comparator outputs a second triggering signal from the output end, triggering the control chip to generate a reset signal input into the optical receiver.

Abstract: A module for a hybrid fiber coax network includes a quad-output amplifier module that can include a port to couple to upstream devices, four ports to couple to downstream devices, and a configured port. The configured port can optionally couple to one of a radio frequency (RF) pre-amplifier or one or more optical transmitter modules or receiver modules. The module is initially provided in a default configuration as an optical node module. However, it can be pre-configured as a RF amplifier. When the configured port is coupled to the one or more optical transmitter modules or receiver modules in the default configuration, the module is operable as an optical node module. When the configured port is coupled to the RF pre-amplifier, the module is transformed to be operable as an RF amplifier.

Abstract: When necessary process times in a reception apparatus for a determination on a change area, a determination on the color of the change area, and a decoding of bit data stream exceed a predetermined time from a frame acquiring timing, and a process delay would occur, an image generator acquires a frame. In addition, a decoder temporarily stores the frame in a memory, and thereafter at a predetermined timing performs the determination on the change area, the determination on the color of the change area, and the decoding of the bit data stream.

Abstract: An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at two phase-locked modulation frequencies F1 and F2. COR performance parameters are determined by comparing two frequency components of the COR output. The group delay variation (GDV) information is obtained by comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two modulation frequencies shifted by the optical frequency offset f.

Abstract: In an embodiment, method of controlling an illumination device by an output signal of a DC-DC converter is disclosed. The output signal is controlled by a PWM signal. The method includes receiving a feedback signal corresponding to variation in the output signal with respect to a pre-determined output signal, and determining a target duty cycle of the PWM signal based on the feedback signal. The PWM signal of the target duty cycle is capable of enabling the DC-DC converter to generate the pre-determined output signal. The method includes providing the PWM signal of an effective duty cycle equal to the target duty cycle over N switching pulses of the PWM signal to the DC-DC converter. The method provides the PWM signal by providing M switching pulses of a first PWM signal of a first duty cycle, and N?M switching pulses of a second PWM signal of a second duty cycle.

Abstract: An optical receiver includes an equalizer to generate a plurality of equalization coefficients corresponding to a plurality of frequencies of an optical signal received by the optical receiver. The equalizer zeroes out a first subset of the equalization coefficients corresponding to a first subset of the plurality of frequency components and applies a second subset of non-zero equalization coefficients to the first signal. The optical receiver may also include a chromatic dispersion compensator to generate inverse chromatic dispersion coefficients corresponding to the plurality of frequency components, and to zero out a first subset of the inverse chromatic dispersion coefficients corresponding to the first subset of the plurality of frequency components and further to apply a second subset of non-zero inverse chromatic dispersion coefficients to a second optical signal.