Abstract: Aspects of the invention provide transmitters and receivers for managing multiple optical signals. High order modulation, such as phase and/or amplitude modulation, is used to achieve multiple bits per symbol by transporting multiple asynchronous data streams in an optical transport system. One or more supplemental multiplexing techniques such as time division multiplexing, polarization multiplexing and sub-carrier multiplexing may be used in conjunction with the high order modulation processing. This may be done in various combinations to realize a highly spectrally efficient multi-data stream transport mechanism. The system receives a number of asynchronous signals which are unframed and synchronized, and then reframed and tagged prior to the high order modulation. Differential encoding may also be performed. Upon reception of the multiplexed optical signal, the receiver circuitry may employ either direct detection without a local oscillator or coherent detection with a local oscillator.

Abstract: A system for transporting a plurality of digital signals (i.e. “n” digital signals) over an optical fiber includes a plurality of modems for modulating each digital signal on a respective analog signal. Each resulting RF signal is processed by a corresponding up-convertor, which includes a mixer and local oscillator, to produce a frequency band which can be a double sideband or single sideband of the modulated signal. The resulting frequency bands output by the up-convertors are non-overlapping and are spaced apart within a single sub-octave. An RF combiner combines the frequency bands and the combined RF signal is converted into an optical signal by an optical transmitter that outputs to an optical fiber. An optical receiver converts the optical signal from the fiber to an RF signal that is directed to an RF splitter. Signal fractions from the splitter are filtered, down-converted and demodulated to recover the initial digital signals.

Abstract: An adjustable delayer for adjustably delaying an input signal based on a delay adjustment input information describing a desired delay includes a plurality of series-connected tunable delay circuits, wherein a first of the tunable delay circuits is configured to receive the input signal. The adjustable delayer also includes a closed-loop control circuit configured to provide a first delay tuning information to tune a combined delay of the plurality of tunable delay circuits to fulfill a predetermined condition. The adjustable delayer also includes a combiner to combine the first delay tuning information with a second delay tuning information, that is based on the delay adjustment input information, to obtain a combined delay tuning information. The adjustable delayer is configured to tune a delay of one or more of the tunable delay circuits based on the combined delay tuning information.

Abstract: In various embodiments, a monolithic integrated transmitter, comprising an on-chip laser source and a modulator structure capable of generating advanced modulation format signals based on amplitude and phase modulation are described.

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 system, e.g. for optical communication, includes an I-Q modulator and a transmission signal processor. The I-Q modulator is configured to modulate a first light source in response to first I and Q modulation signals. The transmission signal processor is configured to receive a data stream including data corresponding to a first data subchannel. The processor maps the data subchannel to an optical transmission subchannel and outputs the first I and Q modulation signals. The I and Q modulation signals modulate the light source to produce an optical transmission signal that includes wavelength components corresponding to the optical transmission subchannel.

Abstract: A method of converting an optical communications signal having a differentially encoded multilevel modulation format into communications traffic bits, the multilevel modulation format having a plurality of constellation points, the method comprising: receiving a consecutive pair of symbol signals of said optical communications signal, the pair of symbol signals being arranged to differentially encode a plurality of communications traffic bits; and generating a plurality of optical binary signals in dependence on the symbol signals, each optical binary signal having a respective binary signal level, wherein the optical binary signals form optical versions of the encoded communications traffic bits.

Abstract: A system for generating a frequency modulated linear laser waveform includes a single frequency laser generator to produce a laser output signal. An electro-optical modulator modulates the frequency of the laser output signal to define a linear triangular waveform. An optical circulator passes the linear triangular waveform to a band-pass optical filter to filter out harmonic frequencies created in the waveform during modulation of the laser output signal, to define a pure filtered modulated waveform having a very narrow bandwidth. The optical circulator receives the pure filtered modulated laser waveform and transmits the modulated laser waveform to a target.

Abstract: In one embodiment, the optical transport system has an optical transmitter, an optical receiver, and one or more phase-sensitive amplifiers (PSAs) disposed within an optical link that connects the optical transmitter and receiver. The optical transmitter employs a first nonlinear optical process to generate a two-carrier signal in a manner that makes this signal suitable for phase-sensitive amplification. The PSAs employ a second nonlinear optical process to optically amplify the two-carrier signal in a phase-sensitive manner to counteract the attenuation imposed onto the two-carrier signal by lossy components of the optical link. The optical receiver employs a third nonlinear optical process in a manner that enables the receiver to beneficially use redundancies in the two-carrier signal, e.g., for an SNR gain.

Abstract: A subscriber-side optical network unit (ONU) includes a control LSI for outputting a data signal and a pre-bias signal at fixed intervals, an optical transmitter-receiver for producing optical output in response to these signals, and a light-emission error preventing circuit for preventing light-emission error. First and second light-emission error detecting circuits output an abnormality detection alarm signal when no rising edge occurs in the data signal and pre-bias signal for a prescribed period of time. An OR element, when receiving the abnormality detection alarm signal from at least one of the first and second light-emission error detecting circuits, supplies the optical transmitter-receiver with a shutdown signal and halts the optical output.

Abstract: An optical network includes a multidimensional coder and modulator for handling multiple-in-multiple-out MIMO spatial lightpath properties and content of any specific supercarrier, a spatial mode multiplexer responsive to orthogonal frequency division multiplexing OFDM transmissions and the multidimensional coder, a spatial-spectral routing node coupled over a fiber link to the spatial mode multiplexer for performing switching granularity by a spatial mode reconnection, a multidimensional decoder and demodulator; and a spatial mode demultiplexer coupled over a fiber link to the spatial-spectral routing node and responsive to the multidimensional decoder and demodulator.

Abstract: A method and apparatus for loading, detecting, and monitoring channel-associated signals are provided. Channel-associated signals are identified with spread spectrum codes in the electrical domain, and after being modulated to an optical service signal at respective loading points separately, the channel-associated identification signals are transmitted in the optical channel along with the optical signal. At any downstream detecting point, passing optical signals can be converted through photoelectric conversion, and the channel-associated identification signals are de-spread. By detecting the channel-associated signals, it is possible to learn about whether the upstream loading point work normally, whether the optical channel operates normally, etc., and thereby to find possible failures, solve problems, and monitor quality parameters of optical signals in real time, and improve reliability of the optical signal transmission.

Abstract: An LED light and communication system is in communication with a broadband over power line communications system. The LED light and communication system includes at least one optical transceiver. The optical transceiver includes a light support having a plurality of light emitting diodes and at least one photodetector attached thereto, and a processor. The processor is in communication with the light emitting diodes and the at least one photodetector. The processor is constructed and arranged to generate a communication signal.

Abstract: The invention relates to an apparatus and a method for modulation of an optical signal with a data signal, said apparatus (6) comprising a configurable digital encoding unit (8) encoding data of said data signal to provide an encoded modulation control signal (EMCS), and a signal modulation unit (9) modulating said optical signal with respect to its signal phase and/or signal amplitude in orthogonal polarization directions in response to said encoded modulation control signal (EMCS) to generate a multi-dimensional optical signal vector.

Abstract: A technique in which an outgoing signal is encoded to have multiple signal levels to modulate a light source, in which respective signal levels are indicative of different signal states of more than one bit. The multi-level signal is transmitted on a passive optical network (PON) having passive splitters to split the modulated light to transmit the light having multiple signal levels to a plurality of destinations via the PON.

Abstract: An inventive method for multi-symbol polarization switching for differential detection optical systems includes modulating a laser source by a DQPSK modulator, driving the DQPSK modulator with a data block configured for generating multi-symbol polarization-switched DQPSK differential-encoded signals, and polarizing the multi-symbol polarization-switched DQPSK signals with a polarizing modulator whose modulation speed is based on how often polarization states vary, wherein the data block provides a bits manipulation to provide the multi-symbol polarization switching thereby enabling differential detection for recovering correct original data by a receiver.

Abstract: A method for generating a 400 Gb/s single channel optical signal from multiple modulated subchannels includes carving respective modulated subchannels into return-to-zero RZ modulated subchannels having non-overlapping peaks with intensity modulators having a duty cycle less than 50%, and combining the subchannels into a single channel signal aggregating the bit rate of each of the subchannels. The subchannels are combined with a flat top optical component for increased subsequent receiver sensitivity.

Abstract: Data for transmission by an optical transmitter that is driven by a signal driver is encoded, where the encoding is according to a criterion that specifies a reduction of an aggregate electrical current of the signal driver.

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: An apparatus comprises a coherent optical transmitter. The coherent optical transmitter comprises a first modulator for generating a first polarization, a second modulator for generating a second polarization, and a symbol interleaver configured to receive a first symbol stream intended to be transmitted on a first polarization and a second symbol stream intended to be transmitted on a second polarization, to direct one portion of symbols of the first symbol stream to the first modulator for modulation onto the first polarization and another portion of the symbols of the first symbol stream to the second modulator for modulation onto the second polarization, and to direct one portion of symbols of the second symbol stream to the first modulator for modulation onto the first polarization and another portion of the symbols of the second symbol stream to the second modulator for modulation onto the second polarization.

Abstract: A system is configured to receive a block of symbols, associated with a phase-modulated signal that includes data symbols that correspond to a payload associated with the signal, and control symbols; process the control symbols to identify an amount of phase noise associated with the control symbols; reset a phase, associated with each of the data symbols, based on the amount of phase noise and a reference phase; interleave the respective data samples, of each of the data symbols with other data samples, where the interleaved respective data samples cause errors, associated with the respective data samples, to be spread out among the other data samples and reduces an error rate relative to a prior data rate that existed before the interleaving; and perform forward error correction on the interleaved respective data samples.

Abstract: Light output from a seed light source generation unit that outputs continuous light having a single frequency or a plurality of frequencies is input by a multi-wavelength light source to an optical circulation unit, and light having a plurality of frequencies that is frequency-synchronized with seed light output from the seed light source generation unit is generated. The optical circulation unit is provided with an optical frequency shifter to shift light frequencies, and includes a circulation circuit to return output from the optical frequency shifter to the input side. On a circulation path, an optical spectral shaper capable of adjusting an optical amount of attenuation for each frequency unit is provided so that optical amount of attenuations are adjusted, and thereby the number and the like of optical frequencies output from the optical circulation unit are changed.

Abstract: Disclosed is an apparatus and a method for transmitting data by using visible light. The transmission apparatus includes: a Serial-to-Parallel (S/P) converter for performing a Serial-to-Parallel conversion on transmission data, and generating multiple parallel data; a modulation means for modulating the multiple parallel data generated by the S/P converter, and generating multiple modulation signals; an Inverse Fast Fourier Transform (IFFT) means for performing an IFFT on the multiple modulation signals so that the multiple modulation signals are orthogonal to one another, and generating an IFFT signal; and a light-emitting means for causing a light source to emit light based on the IFFT signal generated by the IFFT means.

Abstract: Return To Zero (RZ) shaping is performed for a first I/Q modulator whose output corresponds to a first polarization component using a first two digital-to-analog convertors (DACs), each of which is sampled at approximately twice a modulation symbol rate or more and has an output with a first interleaving order that interleaves one of a first pair of intended drive signal patterns and zeros. RZ shaping is also performed for a second I/Q modulator whose output corresponds to a second polarization component using a second two DACs, each sampled at approximately twice the modulation symbol rate or more and having a second interleaving order that interleaves zeros and one of a second pair of intended drive signal patterns, the second interleaving order opposite the first interleaving order. The first polarization and the second polarization may be combined, thereby forming an Interleaved Return To Zero (IRZ) Polarization Division Multiplexed (PDM) signal.

Abstract: A method of making an optical modulator by determining the material composition of the quantum well region in the waveguide portion of the modulator so that the modulator is transparent at a gain peak wavelength that is greater than the predetermined wavelength by a predetermined amount, and fabricating the modulator with the determined material composition.

Abstract: A Pseudo-Return-to-Zero modulator is provided with a narrow pulse clock generator, a modulator driver, and an optical modulator. The narrow pulse clock generator generates a narrow pulse clock of order n, where one of levels occupies half a symbol period and the other level occupies (n?1) plus half a symbol period, n being equal to or more than two. The modulator driver generates an electrical signal in response to binary data and the narrow pulse clock. The optical modulator modulates an optical carrier in response to the electrical signal so that the modulated optical carrier is in a PRZ(n) format.

Abstract: The method includes: receiving a first Non Return to Zero (NRZ) data signal and a synchronous clock signal, and performing Return to Zero (RZ) processing to generate a first complementary RZ data signal pair; receiving a second NRZ data signal and a synchronous clock signal, and performing RZ processing to generate a second complementary RZ data signal pair; and modulating the first complementary RZ data signal pair and the second complementary RZ data signal pair on light to generate an RZ-Differential Quadrature Phase Shift Keying (RZ-DQPSK) optical signal. Through the method and device, RZ processing are performed on the NRZ data signals to generate the complementary RZ data signal pairs, and the complementary RZ data signal pairs are modulated on the light, thereby reducing the cost and the insertion loss of the entire device, lowering the requirements for input optical power and reducing the complexity of loop circuit control.

Abstract: Consistent with the present disclosure, data, in digital form, is received by a transmit nodes of an optical communication, and converted to analog signal by a digital-to-analog converter (DAC) to drive a modulator. The modulator, in turn, modulates light at one of a plurality of wavelengths in accordance with the received data. The modulated light is then transmitted over an optical communication path to a receive node. At the receive node, the modulated optical signal, as well as other modulated optical signals are supplied to a photodetector circuit, which receives additional light at one of the optical signal wavelengths from a local oscillator laser. An analog-to-digital converter (ADC) is provided in the receive node to convert the electrical signals output from the photodetector into digital form. The output from the ADC is then filtered in the electrical domain, such that optical demultiplexing of individual channels is unnecessary.

Abstract: An adaptive signal processing method to achieve an increase in capacity of data transfer systems, in which control data is returned via a backward channel. The method provides signal processing using an electrical sub-carrier sub-division according to frequency, the electrical sub-carrier with the lowest carrier frequency being permanently used as the backward channel (RC) for transferring control information relating to the current transfer quality of each sub-carrier. An electrical modulation on N parallel sub-carriers takes place in the transmitter (Tx) and then an optical intensity modulation is carried out for a serial data transfer in the optical channel (IRWC). The discrete division of the information to be transferred to the sub-carriers in a real-time operation can take place by the implementation of specific bit-loading algorithms.

Abstract: For providing circuit arrangement and method for transmitting signals from a data source to a data sink, the signals being TMDS encoded, the driver circuit is supplied by a connection interface, connected upstream, assigned to data source, with supply voltage, electrical TMDS encoded signals are electro-optically converted by an LED connected downstream of the driver circuit and coupled into an optical fiber as light supplied with TMDS encoded signals, the direct current portion supplied from TMDS transmitter to connection interface, to data source, is converted by driver circuit to a modulated signal current for controlling LED.

Abstract: Methods and apparatus for line coding in a communications network are described. According to one embodiment of the invention, downstream communications traffic bits are received and mapped into downstream bit positions of a transmission structure. A pre-selected bit in each upstream bit positions of the transmission structure is provided to form a downstream transmission structure. A downstream optical signal carrying the downstream transmission structure is generated for transmission. Upstream communications traffic bits are also received and mapped into the upstream bit positions of the transmission structure to form an upstream transmission structure. An upstream optical signal carrying the upstream transmission structure is generated for transmission.

Abstract: An optical modulator includes a light input/output unit receiving an incident optical signal which has not been modulated, splitting the incident optical signal into a first optical signal and a second optical signal, and transmitting the first and second optical signals to a first path and a second path, respectively, of an optical waveguide. A phase shifter is positioned in at least one of the first and second paths and modulates a phase of at least one of the first and second optical signals, which have been received through the first and second paths, respectively, in response to an electrical signal. A phase-modulated signal is output. A reflective grating coupler reflects signals respectively received through the first and second paths back along the first and second paths respectively.

Abstract: A modulation method, especially an optical modulation method, using the principle of discrete IQ modulation. The modulation method includes generating a carrier signal (Sc) and splitting the carrier signal at a splitting position in an I branch signal and a Q branch signal; modulating the amplitude of the I branch signal according to a first modulation signal and modulating the amplitude of the Q branch signal according to a second modulation signal, each of the first and second modulation signals being arranged to adopt a given number of values according to a given number of constellation points of a given modulation scheme; phase shifting the signal in the Q branch versus the signal in the I branch; and combining the signals in the I branch and Q branch at a combining position. The combined modulated signal (Stx,mod) is arranged to be transmitted over a transmission path.

Abstract: A system includes an optical power meter operable to generate an optical power signal corresponding to the optical power of a received output signal generated by an optical IQ-modulator. The system further includes a processor operable to receive the optical power signal and determine, based on a minimization algorithm and the received optical power signal, a first bias voltage to be applied to a first sub-modulator of the optical IQ-modulator and a second bias voltage to be applied to a second sub-modulator of the optical IQ-modulator. The system may also include a peak power meter operable to generate a peak power signal corresponding to the peak power of the received output signal generated by the optical IQ-modulator, wherein the processor is further operable to determine, based on a minimization algorithm and the received peak power signal, a third bias voltage to be applied to a phase shift component of the optical IQ-modulator.

Abstract: Since it is difficult to emit a control a IQ modulator emitting modulated lightwave according to QAM format without signal degradation of said emitted signal due to low frequency dither used for the control of said modulator, a method for controlling an optical transmitter according to an exemplary aspect of the invention includes: generating a multilevel electrical signal by means of combining two or more binary electrical signals, where said multilevel signal is used to drive the modulator of adding a low frequency dither signal on several of the binary electrical signals, wherein the phase of the added dither signal depends on the value of the binary signal to which it is added; tapping a portion of light after the modulator and generating a monitor signal from the tapped light; controlling the modulator according to the monitor signal.

Abstract: An optical modulator module includes an optical modulator including an optical waveguide which conducts an inputted optical signal, and m modulator regions on the optical waveguide; and m discrete driving circuits serially connected to one another. The discrete driving circuits include a driving circuit which outputs a signal obtained from a digital input signal with a synchronization signal to one of the modulator regions, and a phase shifting circuit which outputs a signal resulting from giving a delay to a signal branched from the synchronization signal. A discrete driving circuit receives the signal outputted from the phase shifting circuit. Each of the modulator regions includes modulation electrodes, an electric field caused by a modulation electric signal applied to each of the modulation electrodes penetrates by a penetration length d, and every two adjacent modulation electrodes has a distance Lgap given by Lgap=2d.

Abstract: An optical transmitter includes: a selection circuit; a signal processing circuit; an optical modulator; and a control circuit. The selection circuit selects signal components on the sides of the maximum and minimum values in a multivalued electrical signal for modulation of a transmitting signal. The signal processing circuit generates a multivalued electrical signal into which the transmitting signal is converted by a combination of a superimposed signal that a low-frequency wave is superimposed on the signal components and a signal having a plurality of intermediate amplitude values on which the low-frequency wave is not superimposed. The optical modulator modulates a carrier light on the basis of the multivalued electrical signal. The control circuit controls the reference amplitude value or amplitude of the multivalued electrical signal on the basis of the low-frequency components contained in a modulated optical signal.

Abstract: Lamps having light emitting diodes configured for data transmission require the high-frequency circuit of higher power. In order to simplify the required electronics, the light emitting diodes are divided into groups and the groups are modulated differently. Due to the multilevel modulation, the symbol rate can be reduced with the data rate remaining the same, thus reducing the switching rate and the circuitry complexity.

Abstract: Data security of a multi-dimensional code system is increased. An optical device is provided with a single input port; a splitter splitting an input light from the input port into a plurality of lights; a plurality of phase shifters each shifting one of the lights split by the splitter; a multi-port encoder/decoder inputting the lights whose phases are shifted by the phase shifters and generating spectral encoded codes; and a plurality of output ports outputting the spectral encoded codes generated by the multi-port encoder/decoder.

Abstract: An optical transmission and reception system in which a plurality of tributary signals are converted into multilevel modulated light for transmission and reception. An apparatus for transmitting multilevel modulated light includes: FECs which perform error correction processing including addition of a tributary identifier; and a GEAR BOX which performs rate conversion on the processed signals.

Abstract: A de-emphasis format signal generator can be configured to combine first and second electrical non-de-emphasis formatted signals provided to first and second optical modulators, coupled in parallel with one another, to provide a combined optical signal having a de-emphasis format. Accordingly, three aspects of a de-emphasis formatted signal, including a de-emphasis delay aspect, a de-emphasis attenuation aspect, and a de-emphasis combining aspect, can provided separately and in different domains (such as in the electrical domain and in the optical domain) which can be combined with one another to provide an output de-emphasis formatted optical signal.

Abstract: In general, optical communication systems and methods may generate higher-level nmQAM from nQAM signals using one or more delay line interferometers (DLIs) arranged in various configurations. The nQAM signals may be generated by a lower-level modulator, such as a BPSK modulator, QPSK modulator or lower-level QAM modulator, with binary driving signals. Different parameters of the DLIs, such as free spectral range (FSR), phase shift, and amplitude imbalance, may be selected to accomplish the desired higher-level nmQAM depending upon the nQAM signal.

Abstract: A laser system includes an array of lasers that emit light at a number of different, fixed wavelengths. A group of optical transport systems connect to the laser system. Each of the optical transport systems is configured to modulate data signals onto the light from the laser system to create optical signals and transmit the optical signals on one or more optical fibers.

Abstract: In a first embodiment of the present invention, a method is provided comprising: receiving a selection of a desired brightness level of a light source; receiving a piece of data to be transmitted via visible light communication using the light source; selecting a duty cycle, described by an encoding scheme, based on the desired brightness level; encoding the data using the encoding scheme, wherein the encoding includes identifying a code corresponding to both the piece of data and the selected duty cycle; and transmitting the identified code via visible light communication using the light source.

Abstract: Structures and methods of generating 8-QAM signals through the effect of a cascaded I/Q modulator and Mach-Zhender modulator. The 8-QAM signals are generated by applying one binary sequence to the dual-drive Mach-Zehnder modulator (MZM) and two binary sequences to the I/Q modulator. Operationally, the I/Q modulator generates QPSK constellation(s), while the dual drive MZM either maintains the QPSK constellation at an out ring, or attenuates its amplitude to the inner ring and rotates its phase by ?/4 phase depending on the binary data it was driven by.

Abstract: Methods and systems for a photonically enabled complementary metal-oxide semiconductor (CMOS) chip are disclosed and may comprise in an integrated circuit comprising a driver: amplifying a received signal in a plurality of partial voltage domains, and generating the partial voltage domains in a domain splitter in the driver. A voltage domain boundary value between two partial voltage domains may be controlled utilizing a differential amplifier that samples an output voltage of a cascade amplifier that is an input to the driver and controls a current supplying said cascade amplifier. A series of diodes may be driven in differential mode via the amplified signals. An optical signal may be modulated via the diodes, which may be integrated in a Mach-Zehnder modulator or a ring modulator. The diodes may be connected in a distributed configuration. The amplified signals may be communicated to the diodes via transmission lines, which may be even-mode coupled.

Abstract: An optical transmitter includes: an optical modulator including a first modulation unit and a second modulation unit respectively configured to propagate a first optical signal and a second optical signal that are obtained by splitting input light; a signal generator configured to generate a first drive signal and a second drive signal that are respectively supplied to the first modulation unit and the second modulation unit; a phase controller configured to control a phase difference between the first optical signal and the second optical signal in the optical modulator; and a phase difference detector configured to detect the phase difference between the first optical signal and the second optical signal controlled by the phase controller. The signal generator generates the first drive signal and the second drive signal based on the phase difference detected by the phase difference detector.

Abstract: [PROBLEM] Providing an optical source that outputs optical frequency modulated light having a constant output optical intensity. [MEANS FOR SOLVING THE PROBLEM] Provided is a light source apparatus that outputs an optical signal having an optical frequency corresponding to a frequency control signal, the light source apparatus including a laser light source section that outputs laser light having an optical frequency corresponding to the frequency control signal; and an optical intensity adjusting section that compensates for intensity change of the laser light to output laser light in which the intensity change caused by a change in the optical frequency is restricted.

Abstract: Communication apparatus and techniques, such as for optical communication, can include providing a reference frequency derived from an atomic energy level transition or a molecular energy level transition, generating at least two specified optical carrier signals at least in part using the reference frequency, coherently modulating the specified optical carrier signals using respective baseband information signals to provide respective coherently-modulated optical subcarriers. A combined optical information signal comprising the optical subcarriers can be transmitted to a receiver, such as via a fiber optic cable. In an example, a received optical information signal can be optically Fourier transformed to provide respective coherent outputs, which can be coherently downconverted.

Abstract: A method of phase modulating optical radiation by the steps of phase modulating the optical radiation by using a modulator having an extinction ratio in order to provide a multilevel phase shift key signal, and applying to each optical pulse a phase-shift having an absolute value depending on the extinction ratio and a sign depending, for each of the optical pulses, on the respective optical phase value. An apparatus implementing the method is also disclosed.