Abstract: An apparatus and method for transmitting information bits via an optical communication system, the apparatus including a distribution matcher (DM) configured to receive information bits and to generate shaped symbols relating to the information bits; a pre-deinterleaver (PDI) coupled to the DM and configured to apply a perturbation function q(n) to the shaped symbols to produce pre-deinterleaved symbols; an error reduction processor (ERP) coupled to the PDI and configured to receive computer instructions which, when executed, prompt the ERP to produce error reduction symbols from the pre-deinterleaved symbols, the error reduction symbols being perturbed from the pre-deinterleaved symbols by a perturbation function p(n), q(n) being an inverse of p(n); and a modulator coupled to the ERP and configured to convert the error reduction symbols into optical signals configured for transmission via an optical communication system.

Abstract: An IC-TROSA point-to-multipoint optical network system includes a point-to-multipoint optical network that is coupled to subscriber devices, and that is coupled to a hub device via a hub IC-TROSA device included in a hub coherent optical transceiver device coupled to the hub device. The hub IC-TROSA device includes a quadrature optical modulator subsystem, and an optical directional coupler device in the quadrature optical modulator subsystem provides a first transmit connection and a second transmit connection to the point-to-multipoint optical network.

Abstract: Optical transmitter includes: signal processing circuit, optical modulator, optical filter, and delay circuit. The signal processing circuit generates N drive signals for generating a modulated optical signal. Symbol rate of the modulated optical signal is fs and each symbol of the modulated optical signal transmits N bits. The optical modulator includes Mach-Zehnder interferometer and N phase-shift segments each of which shifts a phase of light propagating through an optical path of the Mach-Zehnder interferometer according to the N drive signals. The optical filter removes, from output light of the optical modulator, a frequency component in a range of ±fs/2 with respect to a center frequency of the modulated optical signal, and extracts at least a part of other frequency components. The delay circuit controls timings of the N drive signals so as to reduce optical power of the frequency component extracted by the optical filter.

Abstract: A transmitter circuit, an optical module, and a communications device is disclosed. A transmitter circuit includes a driver and a directly modulated laser DML. A positive electrode of the driver is connected to a positive electrode of the DML, a negative electrode of the DML is connected to a voltage terminal, and the negative electrode of the DML is connected to a ground terminal through a capacitor. The driver is configured to generate a drive current based on an input signal, and output the drive current to the DML through the positive electrode of the driver. The DML inputs a first part of current of the drive current to the ground terminal through the capacitor, and the DML inputs a second part of current of the drive current to the voltage terminal.

Abstract: A Wavelength Division Multiplexing (WDM) for an optical fibre comprising a set of optical inputs, one for each wavelength of a WDM optical signal to be transmitted, a graphene electro-absorption modulator (EAM) for each optical input to modulate light from the optical input, and one or more drivers to drive each graphene electro-absorption modulator. The drivers have a data input, a low pass filter to low-pass filter data from the data input to provide low pass filtered data, and an output to drive each graphene electro-absorption modulator with a combination of the low pass filtered data and a bias voltage. The bias voltage is configured to bias the graphene EAM into a region in which, e.g., when the transmission of the graphene electro-absorption modulator increases the effective refractive index for the modulated light decreases and vice-versa to pre-chirp to the modulated light to compensate for dispersion in the fibre.

Abstract: Provided are a data transmission method and apparatus, a terminal device, and a storage medium. The method includes determining a basic unit carrying client data, where the rate of the client data is smaller than the set value, the set value is determined according to the bandwidth of a flexible Ethernet (FlexE) slot, and the basic unit is a basic unit included in a basic unit set; mapping the client data to the basic unit; and sending, through the FlexE slot, the basic unit set to which the client data is mapped.

Abstract: A coherent Ising machine based on on-chip whispering gallery mode optical microcavity mainly adopts an optical microcavity integrated with a second laser processing apparatus (a nonlinear crystal), so as to archive an on-chip structure, which, compared with the fiber loop structure in the prior art, has the integration level optimized significantly.

Abstract: Disclosed herein is a phased antenna array which is configured to provide a signal through multiple antennas. The phased antenna array may include a plurality of sub-arrays. Each sub-array may include a complete and functional optically synchronized integrated circuit including an integrated photo diode. Advantageously, integrating the photo diode into the integrated circuit may reduce the size of the sub-array and decrease the length the high frequency timing signal is passed.

Abstract: An optical transmission device includes: an IQ optical modulator to modulate incident light with a modulation signal, and adjust a phase of the modulated light with a phase bias, or adjust a phase of the incident light with the phase bias, and modulate the phase adjusted light with the modulation signal, a light intensity detector to detect light intensity of modulated light, a synchronous detection circuit to synchronously detect a light intensity signal and a dither signal, and a bias signal generating unit to monitor a change in amplitude of the modulation signal, generate the bias signal according to the synchronous detection signal when a range of the change is equal to or less than a first threshold, and generate a bias signal maintaining a phase bias before the range of the change becomes larger than the first threshold as the bias signal.

Abstract: The present invention provides a wireless optical communication data transmission apparatus and method, including a transmit module and a receive module, where the transmit module includes a transmission gate, and the transmit module is configured to convert serial data into multipath control signals to control the transmission gate to output an electrical signal, convert the electrical signal into an optical signal, and transmit the optical signal to the receive module; and the receive module includes a peak value detector and a comparator group, and the receive module is configured to convert the received optical signal into the electrical signal and output the serial data after threshold determination by the comparator group, where the peak value detector provides a reference voltage to the comparator group according to the received electrical signal, and the comparator group performs voltage division according to the reference voltage to determine a threshold.

Abstract: A predistorter for an electro-optical converter includes a plurality of low noise RF amplifiers distributed along a transmission line that receive an RF input. Second order intermodulation injection (IM2) circuitry includes an inductively-degenerated frequency doubler to square and filter IM2 products of the RF input. A Mach-Zehnder Modulator (MZM) is used for electro-optical conversion. Feed forward circuitry injects IM2 to independently propagate RF intermodulation components with velocity matching to the MZM. At least one driver injects the RF input and RF intermodulation components into the MZM.

Abstract: In an optical transmitter having an electro-optic modulator with first child MZI and a second child MZI nested to form a parent MZI, and a processor that controls the bias voltages of electro-optic modulator. In the first section of a control loop, the processor simultaneously superimposes different dither signals onto the first bias voltage of the first child MZI and the second bias voltage of the second child MZI, and extracts the first phase error information for the first child MZI and the first-round third phase error for the parent MZI from a first monitoring result. In the second section of the control loop, the processor simultaneously superimposes different dither signals onto the first and second bias voltages, and extracts the second phase error information for the second child MZI and the second-round third phase error for the parent MZI from a second monitoring result.

Abstract: A method of controlling power in a transmission system may include determining a first transmit power of a first transmit path, determining a second transmit power of a second transmit path, and controlling the first transmit path and the second transmit path based on a combination of the first transmit power and the second transmit power. The combination of the first transmit power and the second transmit power may include a sum of the first transmit power and the second transmit power. Controlling the first transmit path and the second transmit path may include determining a first effective power target for the first transmit path based on the first transmit power and the second transmit power, and determining a second effective power target for the second transmit path based on the first transmit power and the second transmit power.

Abstract: First data is received from a first host system and second data is received from a second host system. A composite signal is generated to represent both the first data received from the first host system and the second data received from the second host system. The composite signal comprises a series of signal pulses at multiple levels. A first level and a second level in the composite signal represent values from the first data received from the first host system. A third level and a fourth level in the composite signal represent values from the second data received from the second host system. The composite signal is provided to the memory device.

Abstract: A control device of modulating signal generates high-side signal and low-side signal. The high-side signal takes level in accordance with level of AC component of a monitor signal obtained by photoelectric conversion of modulated light, when the polarity of the AC component is positive, or its magnitude is zero. The high-side signal further takes constant level when the polarity of the AC component is negative. The low-side signal takes constant level when the polarity of the AC component is positive. The low-side signal further takes level in accordance with level of the AC component when the polarity of the AC component is negative, or its magnitude is zero. Then, the control device adjusts level of the modulating signal based on a greatest value of absolute values of levels taken by the high-side signal and a greatest value of absolute values of levels taken by the low-side signal.

Abstract: An emitter configured to output a sequence of periodic light pulses with different polarisations, the emitter comprising: a beam splitter configured to divide the pulses of a first sequence of pulses, such that each pulse is split between a first path and a second path, the first sequence of pulses having a varying phase and a first polarisation; a polarisation rotator configured to rotate the polarisation state of pulses in one of the first path or the second path with respect to the polarisation state of pulses in the other path; a time delay component configured to provide a time delay such that the first sequence of pulses in the first arm are delayed by one period with respect to the first sequence of pulses in the second arm; an optical combination component configured to combine the delayed first sequence of pulses from the first path with the first sequence of pulses from the second path to produce an output sequence of pulses where each pulse in the output sequence is a combination of a pulse from

Abstract: A multi-level optical signal is sampled to generate an eye diagram. The signal can be adjusted when eyes in the eye diagram have different heights. More specifically, a first value is determined, and the height of a first eye is adjusted using the first value. The first value is multiplied by a stored factor to produce a second value, and the height of a second eye is adjusted using the second value, and so on for other eyes. As a result, eye heights are the same. Similarly, optical power levels of the signal can be adjusted when the levels are not equally spaced. As a result, the optical power levels are equally spaced.

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 optical communication system includes a primary transceiver, a component, and secondary transceivers. The primary transceiver is operable to supply first optical subcarriers to an optical communication path, the first optical subcarriers being amplitude modulated at a first frequency to carry first control information and amplitude modulated at a second frequency to carry second control information. The component is operable to be coupled to the optical communication path and includes circuitry operable to detect the first control information. The secondary transceivers are coupled to a terminal end of the optical communication path. At least one of the secondary transceivers is operable to detect the second control information and block the first control information.

Abstract: An optical transmitter includes: a modulator, square law detector, and a processor. The modulator generates an optical signal indicating transmission data. The square law detector detects an intensity of the optical signal using a photodetector and output first intensity data indicating the detected intensity. The processor calculates, based on the transmission data, an electric field of the optical signal generated by the modulator by using parameters pertaining to a state of the modulator. The processor calculates second intensity data indicating the intensity of the optical signal based on the calculated electric field. The processor updates the parameters so as to reduce a difference between the first intensity data and the second intensity data. The processor controls the state of the modulator based on the parameters.

Abstract: A method of controlling power in a transmission system may include determining a first transmit power of a first transmit path, determining a second transmit power of a second transmit path, and controlling the first transmit path and the second transmit path based on a combination of the first transmit power and the second transmit power. The combination of the first transmit power and the second transmit power may include a sum of the first transmit power and the second transmit power. Controlling the first transmit path and the second transmit path may include determining a first effective power target for the first transmit path based on the first transmit power and the second transmit power, and determining a second effective power target for the second transmit path based on the first transmit power and the second transmit power.

Abstract: An optical transmission system transmits a Radio Frequency (RF) signal by a frequency division multiplexing method. The optical transmission system includes a Transmitter Optical SubAssembly (TOSA), an optical fiber, and a Receiver Optical SubAssembly (ROSA). The TOSA includes a surface emitting laser diode configured to be capable of emitting light at output of 0.8 mW or more. In the optical transmission system including the surface emitting laser diode, a noise index obtained by a measurement method including a predetermined step is 10.0 dB?V or less.

Abstract: An optical module includes an optical device that outputs an optical signal corresponding to a control voltage, a voltage controller that applies the control voltage on which a dither signal is superimposed to the optical device, a monitor unit that monitors the optical signal output from the optical device, and outputs a monitor signal, a multiplier that multiplies the monitor signal by a reference signal corresponding to the dither signal, a filter unit that extracts a direct-current component included in a multiplication result, and a controller that causes the voltage controller to change the control voltage in accordance with the direct-current component. The controller changes the frequency of the dither signal or the reference signal such that the frequency of the reference signal is twice as large as that of the dither signal, when the direct-current component satisfies a predetermined condition.

Abstract: A communication device is provided. The communication device includes a measurement device and a controller. The measurement device is configured to measure operation parameters and noise parameters corresponding to Wi-Fi channels used by the communication device. In response to the controller determining that a wireless transmitter/receiver unit (WTRU) is to connect to the communication device, the controller calculates a signal-to-noise ratio and a user ratio corresponding to each Wi-Fi channel according to the operation parameters and noise parameters, and calculates a congestion traffic value corresponding to each Wi-Fi channel according to the signal-to-noise ratio and the user ratio of each Wi-Fi channel. The controller selects a first Wi-Fi channel having the smallest congestion traffic value from among the plurality of Wi-Fi channels to communicate with the WTRU.

Abstract: An optical transmission apparatus (100) includes an optical transmitter (200) including an optical modulator (220) and an observation optical modulator (230) that attenuate optical power of input continuous wave light by an electro-absorption effect and output the continuous wave light. The optical modulator (220) performs pulse amplitude modulation on the continuous wave light and outputs the optical signal.

Abstract: A modified Sagnac loop phase-modulated microwave photonic link with a pulsed optical source is disclosed. Unlike a conventional Sagnac loop, the optical phase offset of the loop can be adjusted to quadrature by applying a synchronized modulation signal to an in-loop phase shifting phase modulator. Thereby, it exemplifies the fundamental RF response.

Abstract: A dual-mode optical transceiver is disclosed. The dual-mode optical transceiver includes a receiver section configured to receive both coherently modulated and intensity modulated optical signals and to be optically switched between a first receiver mode for direct detection and a second receiver mode for coherent detection, and a transmitter section including a nested Mach-Zehnder Modulator or a polarization multiplexed quad Mach-Zehnder Modulator configured to be operated in a first transmission mode to output an intensity modulated optical signal and a second transmission mode to output a coherently modulated optical signal. In some implementations, the dual-mode optical receiver includes an optical switch configured to selectively direct a received optical signal down a direct detection optical circuit or a coherent detection optical circuit based on a control signal applied to the optical switch.

Abstract: An electro-absorption bias circuit may include a temperature sensor. The electro-absorption bias circuit may include a controller to provide a temperature-dependent control signal based on data received from the temperature sensor. The electro-absorption bias circuit may include a power supply to provide an output voltage based on the temperature-dependent control signal from the controller. The electro-absorption bias circuit may include an electro-absorption driving circuit to output a bias voltage applied to the output voltage provided by the power supply.

Abstract: A timing adjuster shifts a timing between a first data-stream group and a second data-stream group in accordance with a timing setting. A data generator in first test mode generates a first test-data stream repeating 2N-bit marks and 2N-bit spaces as each of a first data stream and a third data stream, and generates a second test-data stream that is N-bit shifted from the first test-data stream, where N denotes a natural number. A first phase-difference setting and a second phase-difference setting are rendered zero. The timing adjuster adjusts the timing setting so as to maximize a detected value from a peak detection circuit.

Abstract: In one example in accordance with the present disclosure, a subsystem is provided. The subsystem includes a signal driver/receiver capable of sending and receiving data and signals over a passive cable. The subsystem includes a connection discovery engine to access a low-level enable or disable control of the signal driver/receiver and a low-level loss-of-signal (LOS) control of the signal driver/receiver. The connection discovery engine modulates the enable or disable control to send a local unique ID of the signal driver/receiver over the passive cable. The connection discovery engine monitors timings of transitions on the LOS control to receive, over the passive cable, a remote unique ID of a signal driver/receiver in a second subsystem connected by the passive cable.

Abstract: There is provided an optical transmitter including a memory, a processor coupled to the memory and the processor to generate an electric signal, an optical generator to generate light, an optical modulator to modulate the light with the electric signal to create an optical signal, a first voltage electrode to apply a first voltage to the optical signal, a second voltage electrode to apply a second voltage to the optical signal to which the first voltage is applied, and a detector to detect an optical power of the optical signal to which the second voltage is applied, wherein the processor stops generating the electric signal, controls the first voltage electrode to change the first voltage after the stop of generating the electric signal, and controls the second voltage electrode to change the second voltage according to the detected optical power after the change of the first voltage.

Abstract: An optical transmitter includes: an amplitude control circuit, an E/O (Electrical-to-Optical) circuit, a detector and an optical power control circuit. The amplitude control circuit controls an amplitude of an input electric signal to generate a constant amplitude electric signal. The E/O circuit generates a modulated optical signal from the constant amplitude electric signal by a direct modulation. The detector detects an amplitude modulation component of the input electric signal. The optical power control circuit controls a power of the modulated optical signal based on the amplitude modulation component detected by the detector.

Abstract: Systems and methods for relaying upstream signals received from a plurality of subscribers to a remote head end. Preferably, the systems and methods use a switch that selectively opens when upstream RF signals are not present and closes when upstream RF signals are present, in a manner that reduces noise.

Abstract: The present invention provides an optical source comprising a laser, a first optical power splitter, phase changing equipment, polarisation state setting equipment, a polarisation beam coupler and an output. The laser is configured to generate an optical signal. The first optical power splitter is configured to split the optical signal into a first optical signal and a second optical signal. The phase changing equipment is configured to change the phase of at least one of the first optical signal and the second optical signal such that the first optical signal has a first phase and the second optical signal has a second phase different from the first phase by a preselected phase difference.

Abstract: An optical communications apparatus comprising a host (100) and an optical module (200) comprising a Mach-Zehnder modulator (202), MZM, wherein the optical module is removably connected to the host via a connection path, the optical communications apparatus comprising: a signal generator (101) at the host, configured to generate a plurality of calibration signals at a plurality of frequencies; a host interface (102) configured to transmit the calibration signals to the optical module via the connection path; a module interface (201) configured to receive the transmitted calibration signals; wherein the MZM is configured to use the calibration signals to modulate a laser light source (206) and biased to a point at which average output power is proportional to the output modulated signal; an optical detector configured to measure an average magnitude of an output of the MZM when each of the calibration signals is used to modulate the laser light source; one of a host calibration unit (103) and a module calibrat

Abstract: A radio frequency over glass (RFoG) system may be modified to extend a downstream band. A transimpedance amplifier with a downstream path may be used in the RFoG system in combination with an upstream path having greater than 200 MHz radio frequency (RF) bandwidth to provide the greater than 1.2 GHz downstream bandwidth overlapping with the greater than 200 MHz upstream bandwidth. The RFoG system may include a gateway facilitating an optical network unit and modem connection, the gateway having an express upstream port and an express downstream radio frequency (RF) port. The gateway may be configured for processing legacy RFoG signals in an upstream and a downstream direction and for at least one of generating or processing, via the express ports on the modem, RFoG signals in an extended spectrum beyond 42 MHz in the upstream direction and beyond 1000 MHz in the downstream direction.

Abstract: A PAM4 driver with at least 56 Gbps speed for driving a Mach-Zehnder modulator. The PAM4 driver is configured as 2-bit CMOS digital-to-analog convertor including a drive control module for receiving a pair of incoming differential digital data and generating a first processed reference signal and a second processed reference signal. The PAM4 driver further includes a mirrored buffer circuit to produce two sets of four voltage levels. Furthermore, the PAM4 driver includes a decoder module controlled by a switch bias control module configured to decode each of the two sets of four voltage levels for generating a first output signal and a complementary second out signal with 4 independently adjustable analog levels for driving the Mach-Zehnder modulator with close ended termination resistor.

Abstract: A satellite in low-Earth orbit (LEO) or medium-Earth orbit (MEO) with a modern image sensor and/or other remote sensing device can collect data at rates of 10 Mbps or higher. At these collection rates, the satellite can accumulate more data between its passes over a given ground station than it can transmit to the ground station in a single pass using radio-frequency (RF) communications. Put differently, the sensors fill the spacecraft's memory faster than the spacecraft can empty it. Fortunately, free-space optical communications signals can carry far more data than RF communications signals. In particular, a spacecraft can transmit over 1 Tb of data in a single pass using burst wavelength-division multiplexed (WDM) optical signals. Each burst may last seconds to minutes, and can include tens to hundreds of WDM channels, each of which is modulated at 10 Gbps or more.

Abstract: A PAM4 driver with at least 56 Gbps speed for driving a Mach-Zehnder modulator. The PAM4 driver is configured as 2-bit CMOS digital-to-analog convertor including a drive control module for receiving a pair of incoming differential digital data and generating a first processed reference signal and a second processed reference signal. The PAM4 driver further includes a mirrored buffer circuit to produce two sets of four voltage levels. Furthermore, the PAM4 driver includes a decoder module controlled by a switch bias control module configured to decode each of the two sets of four voltage levels for generating a first output signal and a complementary second out signal with 4 independently adjustable analog levels for driving the Mach-Zehnder modulator with close ended termination resistor.

Abstract: In one embodiment, a method includes receiving an optical input signal to be modulated by an IQ modulator. The method includes applying data to first and second modulators during a first operation, and applying a first pattern of data to the first modulator and a second pattern of data to the second modulator during a second operation. The second operation results in an optical output signal of the IQ modulator having a low power output and a high power output. The first and second patterns are defined to provide respective desired average powers for a predefined time period based on the low and high power outputs. In another embodiment, a method includes indentifying a transmitter in an optical system by low bit rate signaling. Low bit rate signaling includes receiving an optical input signal from an optical source and transmitting identification data of the transmitter.

Abstract: A communication system includes: a first communication device carried by a user and including a first intra-body communication unit configured to carry out data communication with the second communication device via the user's body, and a charge control unit configured to control a charge amount on the body surface; and a second communication device including a capacitive touch panel, an intra-body communication antenna, a second intra-body communication unit configured to carry out data communication with the first communication device via the body, and an intra-body communication control unit configured to perform control to increase signal strength of a signal received at the second intra-body communication unit when a measured value of the signal strength is lower than a predetermined threshold under a condition that user's touch operation on the touch panel is started.

Abstract: Phase shift keying optical modulation apparatus comprising optical phase shifting apparatus and an optical modulator. The optical phase shifting apparatus is arranged to receive an optical carrier signal and is arranged to selectively apply a preselected optical phase shift to the optical carrier signal in dependence on a symbol of a 2N-level phase shift keying modulation format to be encoded onto the optical signal. The optical modulator is arranged to receive the optical carrier signal from the optical phase shifting apparatus and is arranged to apply a phase modulation to the optical carrier signal in dependence on the symbol, to thereby encode the symbol onto the optical carrier signal. The phase modulation is a phase-modulation of an N-level phase shift keying modulation format.

Abstract: The disclosure relates to a method for optical frequency-locked multi-carrier generation based on one directly-modulated laser (DML) and one phase modulator (PM) in cascade driven by sinusoidal waveform (at the same or different frequency). When the DML and PM is driven by the same frequency RF signal at 12.5 GHz, adopting this method, 16 optical subcarriers with 12.5-GHz frequency spacing are generated with power difference less than 3 dB. When the DML and PM is driven by the different frequency with DML at 12.5 Ghz and PM at 25 GHz, over 24 optical subcarriers are generated with 12.5-GHz frequency spacing and amplitude fluctuation less than 3 dB. The number of the generated optical subcarriers can be further increased when the driving power for the DML is increased.

Abstract: An expurgated pulse position modulation (EPPM) technique can be used to encode information for wireless transmission. Such an EPPM technique can be compatible with a simple receiver architecture, such as including a shift register and pulse position modulation (PPM) decoder. A multi-level EPPM (MEPPM) approach can increase the available symbols in the modulation constellation and can be used to accommodate multiple users or devices concurrently. Interleaving techniques can be used such as to reduce inter-symbol interference. An optical transmitter and an optical receiver can be used, such as including using energy in a visible range of frequencies. In an example, an optical source such as including one or more light emitting diodes can provide visible light for illumination, and the EPPM technique can include using codewords specified to provide a desired dimming level when such codewords are used to intensity modulate the optical source, without perceptible flicker.

Abstract: An optical transceiver comprising an optical signal input, a first modulation section coupled to the optical signal input, a second modulation segment coupled to the optical signal input and positioned in serial with the first modulation section, wherein the first modulation section comprises a first digital electrical signal input, a first digital driver coupled to the first digital electrical signal input, and a first modulator coupled to the first digital driver, and wherein the second modulation section comprises a second digital electrical signal input, a second digital driver coupled to the second digital electrical signal input, and a second modulator coupled to the second digital driver, and an optical signal output coupled to the first modulation section and the second modulation section.

Abstract: A modulator device for converting digital data into modulation of an optical signal includes an electronic input for receiving an input data word of N bits and an electrically controllable modulator for modulating the intensity of an optical signal, the modulator including M actuating electrodes where M?N. An electrode actuating device, most preferably a digital-to-digital converter, operates actuating electrodes so that at least one electrode is actuated as a function of values of more than one bit of the input data word. According to an alternative, or supplementary, aspect of the invention, the set of electrodes includes at least one electrode having an effective area which is not interrelated to others of the set by factors of two. In one preferred implementation, a Mach-Zehnder modulator also provides phase modulation to give QAM functionality. Another implementation employs a semiconductor laser.

Abstract: A 2n-QAM (e.g. 16-QAM) optical modulator comprising cascaded I-Q modulators. The first I-Q modulator applies 2n-2 (e.g. 4) QAM to an optical signal, having a constellation diagram with the 2n-2 (e.g., 4) constellation points located in quadrant I. The second I-Q modulator subsequently applies a quaternary phase-shift keying (QPSK) modulation scheme to the optical signal, thereby rotating the constellation points of the 2n-2-QAM modulation scheme to quadrants II, III and IV, to produce a 2n-QAM modulation constellation diagram. The rotation causes the 2n-QAM modulator to inherently apply four quadrant differential encoding to the optical signal. A method of 2n-QAM optical modulation is also provided and optical signal transmission apparatus comprising the 2n-QAM optical modulator.

Abstract: A method for optically transmitting data between a transmitter and a receiver is disclosed, in which a color coding method based on a plurality of elemental colors is provided for the coding and transmission of the data, which color coding method involves a respective elemental color being sent by a respective transmitter-end optical radiation source and being received at the receiver end by a respective optical radiation receiver. The method provides for a control loop to be formed between the transmitter and the receiver, wherein the transmitter sends calibration messages to the receiver, and wherein a piece of compensation information is ascertained by comparing at least one channel property of at least one received calibration message with a corresponding channel property of at least one previously sent calibration message, and wherein the transmitter takes the compensation information as a basis for adjusting at least one transmission parameter.

Abstract: An optical transmitter includes: a modulator driver to generate a drive signal from an input signal; a modulator to generate a modulated optical signal according to the drive signal; an amplitude detector to detect an input amplitude representative of an amplitude of the input signal; and a controller to generate a waveform control signal according to the input amplitude detected by the amplitude detector. The modulator driver controls a waveform of the drive signal according to the waveform control signal.

Abstract: An optical access network with centralized digital optical line termination OLT including an optical line termination unit having a digital transmitter and a coherent receiver for downstream signal transmitting and upstream signal receiving, and at least one optical network unit ONU with transceiver functions for communicating with the OLT over an optical path, the ONU including intensity modulation and single photodiode detection, wherein the digital transmitter includes digital signal processing DSP, digital-to-analog conversion DAC and analog-to-digital conversion ADC functions that can be shared by all multiple ones of the ONU in the network, the DSP reducing or removing dispersion and non-linearity effects in the network and the coherent receiver enabling performance of the downstream stream signal transmitting to match that of the upstream signal receiving in the OLT.

Abstract: An optical communication method includes converting an optical pulse amplitude modulation (PAM) signal to a square QAM signal using an optical delay interferometer (DI) to perform all-optical PAM to QAM conversion in the DI; performing optical de-correlation of I and Q tributaries of the QAM signal to avoid frequency dependent attenuation in RF cabling which impacts signal quality; and finding optimal phase control mechanism of the DI by monitoring and equalizing down-converted I and Q electrical signal amplitudes, using coherent detection; and emulating a square quadrature amplitude modulation (QAM) optical signal with duplicated data copies.