Abstract: A transmission device including: a signal power detection circuit that detects signal power of a wavelength-division-multiplexed optical signal to be transmitted to a transmission line into which pumping light is inputted from a Raman amplifier; a variable optical attenuator that attenuates the wavelength-division-multiplexed optical signal; and a control circuit that reduces an attenuation amount of the variable optical attenuator depending on an increase in the signal power.

Abstract: A laser diode drive system for generating a drive current for a laser diode is described. The laser diode drive system comprises a first laser diode driver connected to the laser diode by a first cable to provide a drive current source for the laser diode. A second laser diode driver is then connected to the laser diode by a second cable to provide a low current sink for the laser diode. A feedback control loop is employed to provide a feedback signal for the second laser diode driver from to sample of an output field of the laser diode. The laser diode drive system exhibits low power consumption while being capable of creating sufficient feedback bandwidth to reduce the excess optical noise by at least an order of magnitude at 1 MHz compared with laser diode drive systems comprising just a first laser diode driver.

Abstract: Modules for optical time-domain reflectometry (OTDR) are connected via at least one fiber link of a fiber optic communication network. The modules can perform OTDR operations on the at least one fiber link. In addition, the modules can establish an inter-node communication channel between each other on the at least one fiber link. The channel allows the OTDR modules to synchronize their OTDR operations and to exchange information, such as OTDR traces, between each other.

Abstract: A system, a non-transitory computer readable media and a method for intra data center optical communication, the method may include (a) receiving an optical input signal by a coherent optical receiver of a second unit of a data center; wherein each input optical signal represents a transmitted optical signal that was transmitted by a coherent transmitter of a first unit of the data center; wherein the transmitted optical signal is generated by modulating a transmitter laser signal that is outputted from a laser of the coherent transmitter; (b) generating, by a controllable laser of the coherent optical receiver, a reference signal; wherein a frequency of the reference signal is controlled by a processor of the coherent optical receiver; and (c) recovering data embedded in the optical input signal; wherein the recovering of the data comprises optically processing the reference signal and the optical input signal.

Abstract: An optical transmission characteristic measurement method includes starting transmission of an optical signal from a transmitting node to a receiving node; receiving a bit error rate value measured by the receiving node and relates to the optical signal; determining whether the bit error rate value is higher than a given threshold; adjusting input power of the optical signal to lower until it is determined that the bit error rate value is higher than the given threshold when it is determined that the bit error rate value is not higher than the given threshold; estimating an optical signal to noise ratio from the bit error rate value when it is determined that the bit error rate value is higher than the given threshold; and calculating an optical signal to noise ratio based on the estimated optical signal to noise ratio and an amount of lowering of the input power.

Abstract: A method includes receiving an optical signal through an optical link and determining a receiving power for the optical link. The method further includes comparing the receiving power for the optical link to a first receiving power threshold and transitioning a clock and data recovery circuit form a normal mode to a holdover mode when the receiving power is less than the first receiving power threshold. The clock and data recovery circuit, when operating in the holdover mode, configured to hold a recovered clock to a known-good clock frequency. When the receiving power for the optical link is greater than a second receiving power threshold, the method initiates a transition of the clock and data recovery circuit from the holdover mode to the normal mode and reacquires synchronization between the recovered clock and a current rate of the incoming data stream using the known-good clock frequency.

Abstract: An apparatus comprises: a first input tap; a first optical modulator coupled to the first input tap; a first output tap coupled to the first optical modulator so that the first optical modulator is positioned between the first input tap and the first output tap; and a controller indirectly coupled to the first input tap and the first output tap.

Abstract: An optical transmitter includes an optical modulator configured to modulate input light and output a light signal, a drive unit configured to output a modulation data signal to the optical modulator, and a bias controller configured to perform feedback control of bias voltage applied to the optical modulator. During a modulation OFF operation of the optical modulator, the bias controller switches a control target point from a first control target point to a second control target point and executes the feedback control.

Abstract: An optical transmitter has an array of laser diodes, which output optical signals from a forward end, and controls the power of the optical signals. The optical transmitter has photodiodes detecting the optical power of optical signals from a reverse end and a LD-DRV unit that supplies to the laser diodes, bias current amplitude modulated to a predetermined frequency that differs from that of the drive signal of the laser diodes. The optical transmitter has a frequency analyzing unit that separates a signal detected by a photodiode, into an optical signal component from a target laser diode and crosstalk optical signal components received from other laser diodes; and a control unit that computes for each detected signal, a ratio of the crosstalk optical signal components to the optical signal component, and performs based on the ratio, a computation to remove the crosstalk optical signal components from the detected signal.

Abstract: Methods and apparatus for controlling a bias voltage supplied to an optical modulator, the modulator comprising a biasable component, the biasable component being configurable to be biased by application of the bias voltage (20) such that the modulator operates at quadrature, the method comprising: providing a target for the output power of the modulator, the target for the output power of the modulator being an output power corresponding to the modulator operating at quadrature; applying, to the biasable component, a bias voltage (20) having an initial value of 0V; and, thereafter, varying the bias voltage (20) until the value of the bias voltage (20) is the value that is closest to the initial value and that biases the biasable component so that the output power of the modulator is within a pre-defined range of the target output power.

Abstract: A laser safety control system is configured with a power source module directly coupled to an AC source and including a galvanically isolated DC/DC converter with at least one output capacitor, and a safety mechanism. The safety mechanism has first and second safety channels which operate independently from one another so as to switch the normal operating regime of the power source module to the safe regime. In the normal operating regime, its DC output has a high voltage, whereas in the safe regime the DC output has a low voltage lower than the high voltage. The safety channels each include a shutdown circuit operative to switch the DC/DC converter off and a discharging circuit operative to discharge the output capacitor. The switching off DC/DC converter and discharging of the output capacitor define the safe regime of the power source module.

Abstract: An optical transmitter includes a light source configured to generate direct current light; a multi-value modulator configured to modulate the direct current light; an optical switch configured to block output light of the multi-value modulator; a driving circuit configured to output a driving signal for driving the multi-value modulator; a bias control circuit configured to control a bias voltage applied to the multi-value modulator, according to an optical output power of the multi-value modulator; and a control circuit configured to control operations of the optical switch, the driving circuit and the bias control circuit, wherein the control circuit decreases an amplitude of the driving signal output from the driving circuit while synchronizing with the blocking of the output light of the multi-value modulator by the optical switch.

Abstract: Disclosed is an optical transceiver 1 including a phase locked loop circuit 3a configured to receive a reference clock CL1 and remove a jitter component of the reference clock CL1; a second phase locked loop circuit 3b configured to receive an output of the first phase locked loop circuit, generate a multiplied clock CL3 synchronized with the output, and when the frequency of the output deviates from a predetermined range and is in an abnormal state, output an alarm signal ALM1; and an optical transmitter module 5 configured to output an optical output signal modulated based on the multiplied clock CL3 and electrical signals D1, D2, D3, and D4 from the outside.

Abstract: An optical transmitter may include an optical source to provide a first optical signal having a varying frequency; an optical circuit to receive a portion of the first optical signal and provide a second optical signal corresponding to a change in frequency of the first optical signal; a photodetector to receive the first optical signal and provide an electrical signal that is indicative of the change in frequency of the first optical signal; an integrator to receive the electrical signal and provide an inverted electrical signal; and a controller to process the inverted electrical signal and provide a current, associated with the inverted electrical signal, to the optical source. The optical source may reduce the phase noise associated with the first optical signal based on the current.

Abstract: A method to control an optical receiver implemented with a semiconductor optical amplifier (SOA) is disclosed. The SOA has a p-n junction operable in a PD mode when it is supplied with a zero or reverse bias. The SOA detects the magnitude of the incoming light and the driving current supplied thereto is adjusted based on thus detected magnitude of the incoming light such that the outgoing light provided to the PD has a magnitude within a preset range.

Abstract: Methods and apparatus for accurately determining wavelength by compensating a time delay using a bidirectional wavelength scan are provided.

Abstract: A communication system including: a transmission apparatus configured to modulate a first light by using a first signal to be transferred and a second signal having a frequency different from a frequency of the first signal so as to generate a first optical signal, modulate a second light by using a third signal to be transferred and a fourth signal having a frequency different from a frequency of the third signal so as to generate a second optical signal, polarization-multiplex the first optical signal and the second optical signal, and transmit a polarization-multiplexed optical signal in which the first optical signal and the second optical signal are polarization-multiplexed, each of the first light and the second light being polarized; and a measuring apparatus configured to measure powers of the second signal and the fourth signal which are included in the polarization-multiplexed optical signal transmitted from the transmission apparatus.

Abstract: An optical signal transmitter of the present invention includes: two phase modulating portions; a phase shifter which displaces carrier phases of two output lights from the phase modulating portions by ?/2; a multiplexing portion which multiplexes two signal lights, carrier phases of the two signal lights being made orthogonal to each other by the phase shifter; a drive signal electrode portion which supplies a differential data signal to each of four paths of interference optical waveguides, each of the two phase modulating portions having the interference optical waveguides, the differential data signal having an amplitude which is equal to a half-wave voltage V? of the two phase modulating portions; a drive amplifier which amplifies the differential data signal to be supplied to each of the four paths of the interference optical waveguides; a data bias electrode portion which supplies a total of four data bias voltages to two arms, each of the two phase modulating portions having the two arms; an orthogona

Abstract: After a startup of an optical transmitter, a control is started in such a way that a modulation amplitude of a driving signal of a phase modulator is set as 0, and that an operational point of a bias voltage is set as the lowest point of light transmission characteristics of the phase modulator. When the operational point of the bias voltage reaches the lowest point, the modulation amplitude of the driving signal is gradually increased from 0 to 2V?.

Abstract: An optical transmitter includes an optical modulator having first and second waveguides to modulate carrier light at each of the waveguides using a driving signal with 2*n intensity levels (n is an integer 1 or greater); and a phase shifter to cause a phase difference between a first optical signal and a second optical signal output from the first waveguide and the second waveguide, respectively. A photodetector converts a portion of a multilevel optical modulation signal acquired by combining the first optical signal and the second optical signals into an electrical signal. A monitor detects a change in an alternating current component in the detected modulation signal. A controller controls at least one of a first bias voltage and a second bias voltage being supplied to the first waveguide and the second waveguide, respectively, so as to increase the power value of the alternating current component.

Abstract: An optical transmission device includes an extractor that extracts respective optical signals from optical signals multiplexed from a plurality of optical signals of different wavelengths, a detector that detects wavelengths of the extracted respective optical signals, a storage that stores the wavelengths of the detected respective optical signals, and a processor that is operative to derive trends in wavelength variation of the respective optical signals based on the detected respective optical signals and the respective optical signals stored in the storage, and determines that either one or both of the extractor and the detector cause the wavelengths to be varied when the trends in wavelength variation of two or more wavelengths are the same.

Abstract: The embodiments herein provide a device and a method for extending the bandwidth of short wavelength and long wavelength fiber optic lengths. The embodiments herein provide for an optical transmitter package device comprising: a laser diode; and a semiconductor optical amplifier connected directly after and in close proximity to the laser diode, wherein the semiconductor optical amplifier is adapted to operate in a frequency domain such that the semiconductor optical amplifier filters and reshapes optical wavelengths from the laser diode, and wherein the semiconductor optical amplifier is biased below an amplification threshold for the semiconductor optical amplifier. The device may also comprises a feedback circuit which comprises an optical splitter, wherein the feedback circuit samples reshaped optical output from the semiconductor optical amplifier and dynamically adjusts one or both of the semiconductor optical amplifier and the laser diode.

Abstract: A WDM device having a controller that individually controls the operating parameters of tunable lasers and the temperatures of an optical multiplexer and etalon. The device employs a spectral analyzer to measure the spectral composition of the optical output signal produced by the device. Based on the analyses of the measured spectral composition, the controller sets the temperatures of the tunable lasers, optical multiplexer, and optical etalon to values that cause: (i) middle frequencies of transmission bands of the optical multiplexer to be spectrally aligned with the corresponding frequencies of the specified frequency grid, (ii) each laser line to be properly positioned within the corresponding transmission band, and (iii) transmission resonances of the optical etalon to be properly positioned with respect to the laser lines.

Abstract: An optical system has an optical emitter that transmits an optical signal through an optical fiber. An optical detector detects light from the fiber and provides an analog signal indicative of such light. A crosstalk cancellation element is configured to receive an electrical signal from the optical emitter and to adjust such signal in order to form a cancellation signal that models the optical and/or electrical crosstalk affecting the analog signal. The cancellation signal is subtracted from the analog signal thereby removing optical and/or electrical crosstalk from the analog signal.

Abstract: A method of superimposing N optical transmission modes for collective transmission along a multimode optical fiber is provided where each of the N optical signals comprises N distinct superimposed transmission modes (M1, M2, . . . ) and a portion of each of the N propagating optical signals is sampled at a receiving end of the data transmission network. N2?1 distinct measurement conditions are derived from a transmission matrix T and a special unitary matrix group SU(N) corresponding to the superimposed transmission modes (M1, M2, . . . ) at the receiving end of the data transmission network and N2?1 measurements are extracted from the sampled signals. The extracted N2?1 measurements are used to solve a matrix equation corresponding to the generated SU(N) matrices and the output matrix transposed and used to generating principal state launch conditions from the eigenvectors of the transposed output matrix to form a principal state in each of the N optical signals.

Abstract: A method of operating an optical amplifier includes determining a gain of the optical amplifier and providing a modulator drive signal to an optical signal source. The modulator drive signal is a function of the gain of the optical amplifier. The method also includes producing an input optical signal using the optical signal source. The input optical signal includes a first plurality of pulses, each of the first plurality of pulses having an amplitude related to the modulator drive signal. The method further includes coupling the input optical signal to the optical amplifier and amplifying the input optical signal using the optical amplifier to produce an output optical signal including a second plurality of pulses.

Abstract: An optical modulator device directly-coupled to a driver circuit device. The optical modulator device can include a transmission line electrically coupled to an internal VDD, a first electrode electrically coupled to the transmission line, a second electrode electrically coupled to the first electrode and the transmission line. A wave guide can be operably coupled to the first and second electrodes, and a driver circuit device can be directly coupled to the transmission line and the first and second electrodes. This optical modulator and the driver circuit device can be configured without back termination.

Abstract: An apparatus comprising a plurality of optical transmitters and a wavelength locker shared by the plurality of optical transmitters. A periodic transmission filter used for wavelength locker operations is in a network communication path and shapes optical transmissions from the plurality of optical transmitters to a network. An apparatus comprising at least one processor configured to receive a pre-filter signal corresponding to part of an optical signal comprising a pilot tone and to receive a post-filter signal corresponding to a part of the optical signal that passes through a period transmission filter, wherein a filtered part of the optical signal is directed into a network. The processor is also configured to perform wavelength locking based on a quadrature detection technique that aligns an adiabatic logical one position of a modulated transmission signal with a spectral transmission peak of the period transmission filter.

Abstract: The disclosure relates to a tunable 50 GHz and 100 GHz channel spacing DWDM transceiver, and methods of making and using the same. The transceiver comprises an electro-absorption modulation laser (EML), a system board configured to compare a preset wavelength with an actual emission wavelength of the EML, a microcontroller and one or more associated registers configured to communicate with the system board, a temperature controlling circuit configured to stabilize the actual emission wavelength of the EML; and a wavelength meter connected to the output of the EML and having an output connected to the system board. The system board may be configured to provide a feedback loop from the EML to the microcontroller. The transceiver, suitable for 50 GHz channel spacing standards, can be made from existing standard transceivers and can switch between 50 GHz and 100 GHz channel spacing modes.

Abstract: A distortion compensation circuit compensates for distortion generated by one or more non-linear elements such as a laser device and/or an optical fiber and may include a primary signal path for carrying an input signal and a secondary signal paths for generating distortion. The distortion compensation circuit may also include a controllable phase inverters and a tunable filter. For example, the secondary signal path may include a distortion generator to produce distortion products from the input signal and a signal controlled phase inverter that inverts the phase of the distortion products and a tunable filter that adjusts the phase of the frequency dependent distortion. The phase inversion and tunable filter may be controlled in response to control signals generated based on one or more parameters such as, for example, laser power, input RF channel loading, temperature, and fiber length.

Abstract: The present invention provides a wavelength division multiplexing system and a method and device for its residual dispersion compensation, wherein the device for residual dispersion compensation of wavelength division multiplexing system comprises: a performance parameter detecting device for receiving and detecting performance parameter of receiving terminal optical signal and sending detecting result of the performance parameter to a central control device; the central control device for deciding a dispersion regulating mode of a tunable dispersion compensator according to the detecting result of the performance parameter and sending the dispersion regulating mode to a tunable dispersion compensator control device through control signaling; and the tunable dispersion compensator control device for receiving the control signaling sent by the central control device and adjusting dispersion compensation amount of the tunable dispersion compensator according to the control signaling in order to make residual di

Abstract: An optical network and method of protection switching between first and second transceivers where dispersion compensation is effected electrically in the transmitters. The method includes detecting, at the second transceiver, a signal failure of a signal transmitted from the first transceiver and, upon detecting the signal failure, signaling the first transceiver to change its compensation function. The signaling can be done by encoding overhead bits in a signal transmitted from the second to the first transceiver. Another method of protection switching includes both transceivers toggling alternate reception paths upon detecting a signal failure and changing their dispersion compensation function to that of their respective alternate path.

Abstract: An optical transmission apparatus includes an optical transmitter that outputs a signal light corresponding to a wavelength of a WDM light, a multiplexer that multiplexes lights input to the plurality of input ports, and that outputs a light generated through the multiplexing from the one or more output port, an optical amplifier that amplifies the light output from the multiplexer; and an amplified spontaneous emission (ASE) transmitter that inputs branching off part of the light output from the optical amplifier by a splitter and multiplexes, with the signal light, ASE in a wavelength band corresponding to an unused wavelength adjacent to the signal light included in the branched-off light.

Abstract: A phase shift unit provides a prescribed phase difference (?/2, for example) between a pair of optical signals transmitted via a pair of arms constituting a data modulation unit. A low-frequency signal f0 is superimposed on one of the optical signals. A signal of which phase is shifted by ?/2 from the low-frequency signal f0 is superimposed on the other optical signal. A pair of the optical signals is coupled, and a part of which is converted into an electrical signal by a photodiode. 2f0 component contained in the electrical signal is extracted. Bias voltage provided to the phase shift unit is controlled by feedback control so that the 2f0 component becomes the minimum.

Abstract: A method is provided to lower the overall power consumption of small form-factor pluggable (SFP) transceivers. The method includes receiving an indication to operate the SFP transceiver in a low power mode, and setting the SFP transceiver to a low power mode in response to the indication by at least switching off a thermal electric cooler (TEC) that controls a temperature of a laser diode of the SFP transceiver. The proposed method may be implemented whenever a reach is not more than a predetermined distance, for example, 65 kilometers. At such reduced distances, the TEC of the SFP transceiver can be switched off while still guaranteeing link functionality. The instant low power mode has the benefit of reducing the power consumption of the SFP transceiver so that, for example, host platforms with lower power delivery budgets can support the SFP transceiver for at least some applications.

Abstract: Apparatuses and methods for modulating an optical signal are disclosed. One embodiment is a method comprising: phase modulating a slave laser which is injection locked to a master laser to produce an arcsine phase modulated optical signal, and combining the arcsine phase modulated optical signal with an output optical signal from the master laser.

Abstract: A multi-mode optoelectronic oscillator (MM-OEO) includes an OEO cavity having an input for receiving an RF signal and an RF output. The OEO cavity includes a) a first laser having a first laser output, a second laser having a second laser output, b) a modulator having i) a first input coupled to the first laser output, ii) a second input coupled to the second laser output, iii) a third input, iv) a first modulator output, and v) a second modulator output, c) a semiconductor optical amplifier (SOA) having an input coupled to the first modulator output and having an SOA amplified output, d) a photodetector coupled to the SOA amplified output and having an output, and e) a coupler having an input coupled to the photodetector output and having a first output coupled to the third modulator input and a second output, whereby an amplified RF signal is produced at the OEO RF output.

Abstract: A clock signal from a single reference clock is frequency converted, and the frequency-converted signal is input to an equal-interval-optical-frequency-comb generator and a modulator of an optical modulator. By varying the electric frequency of the clock signal input to the equal-interval-optical-frequency-comb generator, frequency intervals of a frequency comb to be generated can be varied, while by selectively employing a particular optical frequency from among the continuous light beams of the generated frequency comb, a frequency comb having unequal intervals can be generated. It is also possible to vary the modulation rate by varying the clock frequency of a driving signal to be input to the optical modulator. By using a clock signal of a single reference clock, the frequency intervals of the frequency comb and the variation of the modulation rate synchronize with each other.

Abstract: A method is provide for optically transferring data between a transmitter and a receiver employs a color coding method based on a plurality of elementary colors for encoding and transferring the data. Each elementary color is transmitted by one optical radiation source each on the transmitter side, and is received on the receiver side by one optical radiation receiver each. A control loop is formed between the transmitter and the receiver, wherein calibration messages are sent by the transmitter to the receiver, and wherein compensation information is determined by means of comparing at least one channel property of at least one received calibration message to a corresponding channel property of at least one previously transmitted calibration message, and wherein an adjustment of at least one transmitting parameter is made in the transmitter on the basis of the compensation information.

Abstract: A communications link for carrying data between a transmitter and a receiver operates according to a communications protocol (such as PCI Express (PCIe)) specifying a reduced-power link operating state in which the transmitter generates a reduced-amplitude electrical output signal and the receiver is to operate in a power-save mode. The communications link includes an electro-optical link and a circuit coupling an output of the transmitter to an electrical input of the electro-optical link. The circuit is configured to detect initiation of the reduced-power operating state and to send messages to the receiver to maintain a normal amplitude of an optical signal on the electro-optical link.

Abstract: An infrared transmitter is obtained that transmits a signal by changing a luminance of an infrared emitting LED, the infrared transmitter including: a transmission signal generating unit; a biasing voltage generating unit that generates a biasing voltage according to a magnitude of a transmission signal; a signal/voltage mixing unit that mixes the transmission signal and the biasing voltage; and a voltage-current conversion unit that converts a voltage into a current, in which the LED is driven by the current obtained by the conversion in the voltage-current conversion unit, so that power consumption efficiency can be improved.

Abstract: An apparatus comprising at least one processor configured to receive a wavelength-division-multiplexed (WDM) signal from a remote node, wherein the WDM signal comprises a first channel carrying a first remotely generated signal, a second channel carrying a second remotely generated signal, and a third channel, adapt the WDM signal into a composite WDM signal by: dropping the first remotely generated signal from the first channel; adding a first locally generated signal to the first channel; and adding a second locally generated signal to the third channel, and provide wavelength locking to the first locally generated signal and the second locally generated signal without providing wavelength locking to the second remotely generated signal.

Abstract: A driver circuit configured to generate a drive signal for an optical source comprises an overshoot controller that provides an amount of overshoot for a given logic state of the drive signal as a function of a duration of at least one previous logic state of the drive signal. The drive signal may alternate between a first logic state associated with a first operating mode of the optical source and a second logic state associated with a second operating mode of the optical source. The overshoot controller may be configured to provide amounts of overshoot for respective instances of the first logic state that are proportional to the durations of their respective immediately preceding second logic states. The driver circuit may be implemented in a heat-assisted magnetic recording system in which the optical source alternates between on and off states associated with respective magnetic write and magnetic read modes.

Abstract: Provided is an optical module. The optical module includes: an optical bench having a first trench of a first depth and a second trench of a second depth that is less than the first depth; a lens in the first trench of the optical bench; at least one semiconductor chip in the second trench of the optical bench; and a flexible printed circuit board covering an upper surface of the optical bench except for the first and second trenches, wherein the optical bench is a metal optical bench or a silicon optical bench.

Abstract: An optical transmission apparatus includes an interleaver configured to filter an optical carrier, a multiplexer configured to combine lights output from the interleaver to generate a composite light, a monitor configured to monitor a light intensity of the composite light, and a control circuit configured to change a grid spacing in a filter characteristic of the interleaver in a direction in which an amount of change in a light intensity of the composite light increases, on the basis of a monitoring result measured while changing a center frequency in the filter characteristic of the interleaver and to change the center frequency in the filter characteristic in a direction in which a maximum value of the light intensity increases, on the basis of the monitoring result.

Abstract: Systems and methods are provided for a low frequency AC comparison circuit. The low frequency AC comparison circuit includes circuitry configured to receive a monitoring signal generated by an optical detector, the monitoring signal being proportional to an amount of light generated by an optical transmission device that transmits based on a data signal that is received by an optical driver. The comparison circuit is further configured to generate a modulation current control signal that is transmitted to the optical driver based on a comparison of a low frequency AC component of the monitoring signal and a correlated low frequency AC component of the data signal.

Abstract: An optical transmitter for converting an input data series into an optical multi-level signal and for outputting the same, includes an LUT in which data for executing optical multi-level modulation is stored and from which first modulation data and second modulation data are output based on the input data series. A DAC converts the first modulation data by D/A conversion to generate a first multi-level signal. A DAC converts the second modulation data by D/A conversion to generate a second multi-level signal. A dual-electrode MZ modulator includes a first phase modulator for modulating light from a light source in accordance with the first multi-level signal and a second phase modulator for modulating light from the light source in accordance with the second multi-level signal, and combines an optical signal from the first phase modulator and an optical signal from the second phase modulator to output the optical multi-level signal.

Abstract: A optical link for achieving electrical isolation between a controller and a memory device is disclosed. The optical link increases the noise immunity of electrical interconnections, and allows the memory device to be placed a greater distance from the processor than is conventional without power-consuming I/O buffers.

Abstract: An optical modulation apparatus includes a first modulator, a second modulator, a multiplexer, a calculator and an adjustor. The first modulator configured to modulate light emitted by a light source using a first input signal and output a first modulated signal. The second modulator configured to modulate the light using a second input signal and output a second modulated signal. The multiplexer configured to multiplex the first and second modulated signals and output a multiplexed signal. The calculator configured to calculate a power difference between a higher-side frequency component having a frequency higher than a center frequency of the multiplexed signal and a lower-side frequency component having a frequency lower than the center frequency. The adjustor configured to adjust delays of the first and second input signals based on the power.

Abstract: The present invention provides a control apparatus including: an output monitor which monitors polarization-multiplexed output light output from a polarization multiplexing light modulator which modulates light of two systems independent of each other, polarization-multiplexes light signals of the two systems subjected to the light modulation, and outputs the polarization-multiplexed light signals; and a control unit which controls a delay time difference at a stage where the light signals of the two systems forming the polarization multiplexing light modulator are polarization-multiplexed based on a monitor result of the output monitor. The control apparatus controls a delay time difference between polarization channels easily or surely.