Abstract: A waveform converting unit gives a change to a clock signal as a periodic voltage fluctuation that drives a pulse carver unit carrying out shaping into an RZ waveform. The pulse carver unit receives a bias voltage applied thereto from a bias voltage applying unit, is driven by the clock signal that is given a change by the waveform converting unit and that is amplified by an amplifying unit, and outputs an RZ pulse whose duty has been changed.

Abstract: A signal receiver, such as an RF-matched filter receiver, includes an optical source (e.g. a mode-locked laser) providing an optical signal, and a first optical modulator to modulate the optical signal with a received RF signal and provide a modulated optical signal. A second optical modulator modulates the modulated optical signal with a reference signal and provides a twice modulated optical signal. The modulators may be Mach-Zehnder Modulators (MZM) and/or Indium Phosphide (InP) modulators. An optical detector receives the twice modulated optical signal and provides a detected signal, and a processing unit receives the detected signal and extracts or measures cross-correlation between the received RF signal and the reference signal.

Abstract: A method for data transfer in an optical network, including: amplitude modulating, by a central office, an optical carrier by a downstream data with a first rate to generate a downstream optical signal carrying the downstream data; sending the downstream optical signal to a user terminal; obtaining, by the user terminal, the downstream data from the downstream optical signal; amplitude modulating, by the user terminal, the downstream optical signal by an upstream data with a second rate to generate an upstream optical signal, wherein the ratio of the first rate to the second rate is greater than 1; sending the upstream optical signal to the central office; and receiving, by the central office, the upstream optical signal, and obtaining, by the central office, the upstream data from the upstream optical signal. Furthermore, the present invention discloses a system and device for data transfer in the optical network.

Abstract: A reduction in size and cost of an optical modulator is achieved with a simple configuration, while improving the modulation characteristics. An optical modulator modulates light branched by an optical coupler and then couples the light via the optical coupler. The optical coupler is formed in a substrate having electro-optic effects. An optical waveguide is formed in the substrate and, includes a turnback section and ends into which the light branched by the optical coupler is input. A signal electrode is provided in the substrate along the optical waveguide. A modulation signal to modulate the light passing through the optical waveguide is input to the signal electrode.

Abstract: Provided is an optical interconnection system that transmits and receives a three-level signal. The optical interconnection system includes a first and a second optical interconnection device that transmits and receives a two-level signal, and a synthesizer that outputs a three-level signal by synthesizing signals from the first and second optical interconnection devices. The optical interconnection system may transmit and receive a three-level signal while using an optical interconnection device that interconnects a two-level signal.

Abstract: Embodiments of the present invention provide a method and apparatus for producing a phase coded non-return-to-zero (PC-NRZ) optical signal. The method includes providing an input optical signal; providing first and second drive signals, the first drive signal having a first data pattern of first and second signal levels, the second drive signal having a second data pattern, the second data pattern having third and fourth signal levels that toggle at least when the first drive signal changes from the first signal level to the second signal level; and modulating amplitude of the input optical signal with the first drive signal and modulating phase of the input optical signal with the second drive signal to produce the PC-NRZ optical signal. A PC-NRZ optical transmitter and an optical transmission system applying the PC-NRZ optical transmitter are also provided.

Abstract: A method includes modulating a laser that is coupled to a fiber; modulating the laser with a member selected from the group consisting of low frequency thermal modulation or bias modulation to broaden a laser linewidth, increase an SBS threshold and reduce an IIN; and modulating the laser with a predistorting modulation selected from the group consisting of phase modulation or amplitude modulation, the predistorting modulation being of equal magnitude but opposite phase as that produced in at least one member selected from the group consisting of the laser or the fiber as a result of the low frequency thermal modulation or bias modulation.

Abstract: An optical transmitter which modulates the phases and intensities of double pulses and then transmits them, includes a branching section which branches each of the input double pulses to first and second paths, a first optical modulator placed in the first path, second and third optical modulators placed in series in the second path, and a combining section which combines the double pulses having traveled through the first path with the double pulses having traveled through the second path to output double pulses. A control section controls such that each of the first and second optical modulators performs any one of relative intensity modulation and relative phase modulation on the double pulses passing through, and the third optical modulator performs relative phase modulation on the double pulses passing through.

Abstract: The frequency chirp modulation response of a directly modulated laser is described using a small signal model that depends on slow chirp amplitude s and slow chirp time constant ?s. The small signal model can be used to derive an inverse response for designing slow chirp compensation means. Slow chirp compensation means include electrical compensation, optical compensation, or both. Slow chirp electrical compensation can be implemented with an LR filter or other RF circuit coupled to a direct modulation source (e.g., a laser driver) and the directly modulated laser. Slow chirp optical compensation can be implemented with an optical spectrum reshaper having a rounded top and relatively large slope (e.g., 1.5-3 dB/GHz). The inverse response can be designed to under-compensate, to produce a flat response, or to over-compensate.

Abstract: Demodulation apparatus for demodulating phase-modulated signals comprises a quadrature signal generator (QSG) for generating in-phase (I) and quadrature-phase (Q) signals in response to an unmodulated input signal. The QSG provides fast frequency tracking of the input signal and excludes any high-frequency content the input signal.

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.

Abstract: Methods and apparatuses are provided for transmitting labels in an optical packet network. Groups of K payload bits are encoded into blocks of N bits by using a code in which each of the groups of K payload bits is represented by a corresponding one of at least two distinct codewords of differing weights to form coded payload packet data, where K and N are integers and K<N. Composite packet data is produced by choosing among the at least two distinct codewords according to a value of chip data based, at least partly, on label data. An optical signal for transmission via the optical network is produced by applying the composite packet data to an optical transmitter.

Abstract: According to one embodiment, a microwave photonic band-stop (MPBS) filter uses an electrical input signal to drive an optical Mach-Zehnder modulator. A modulated optical carrier produced by the modulator is applied to an optical filter having at least two tunable spectral attenuation bands that are located substantially symmetrically on either side of the carrier frequency. The resulting filtered optical signal is applied to an optical-to-electrical (O/E) converter to produce an electrical output signal.

Abstract: A hybrid balanced code is formed from a low rate (narrow bandwidth) balanced code and a high rate (wide bandwidth) low density code. Data encoded using the hybrid balanced code is transmitted between a first communication network entity and a second communication network entity. The hybrid code enables a system having a hybrid transmitter to transmit either a low rate stream detectable by a low rate receiver or a hybrid stream, from which the low rate data may be detected by a low rate receiver while both the high rate data and the low rate data may be detected by a high rate receiver.

Abstract: A method for generating D-N-PSK optical signals is disclosed wherein a laser is modulated to generate optical signal pairs including phase modulated and fixed phase portions, the phase modulated portions having a frequency encoding one or more data symbols and the fixed phase portion having a carrier frequency and a phase corresponding to the immediately preceding phase modulated portion. The output of the laser is passed through an optical spectrum reshaper having a transmission function chosen to attenuate a plurality of the phase modulated portions relative to the fixed phase portions. The phase modulated portions may have N frequency levels located on either side of the carrier frequency. One of the N frequency levels may be equal to the carrier frequency.

Abstract: The present disclosure provides a multi-carrier optical transmitter, receiver, transceiver, and associated methods utilizing offset quadrature amplitude modulation thereby achieving significant increases in spectral efficiency, with negligible sensitivity penalties. In an exemplary embodiment, an optical transmitter includes circuitry configured to generate a plurality of optical subcarriers, a plurality of data signals for each of the plurality of subcarriers, and a plurality of modulator circuits for each of the plurality of subcarriers, wherein each of the plurality of modulator circuits includes circuitry configured to offset an in-phase component from a quadrature component of one of the plurality data signals by one-half baud period.

Abstract: A signal-transmitting system includes a digital-to-analog converter, an optical modulator, first and second electrodes, an optical phase shifter, and an optical coupler. The digital-to-analog converter converts digital data into an electrical analog signal. The optical modulator includes a first optical waveguide configured to transmit a first optical carrier, a second optical waveguide configured to transmit a second optical carrier, a first electrode positioned on the first optical waveguide, and a second electrode positioned on the second optical waveguide. The first and second electrical couplers are configured to couple respective electrical analog signals and electrical carriers to electrodes to generate modulation waves. The modulation waves are different in phase. The optical phase shifter is configured to shift the second modulation wave by a predetermined phase, and the optical coupler is configured to couple the first and second modulation waves to generate an optical output signal.

Abstract: Frequency-locked optical comb sources are provided that utilize recirculating frequency shifting based on frequency conversion in a modulator, together with a filter. The filter may be a wavelength notch filter and include a plurality of notches. An example apparatus includes a coupler, an I/Q modulator, and a filter. A first input of the coupler receives a first input optical carrier having a first frequency, and a second input of the coupler re receives a set of frequency-shifted carriers from the filter. The input optical carrier may have a plurality of frequencies. The I/Q modulator shifts the frequency of a first output of the coupler. The filter filters modulated output from the I/Q modulator thereby limiting the frequency-shifted carriers to be within an optical bandwidth. A second output of the coupler provides a plurality of frequency-locked carriers containing the first input optical carrier and the set of frequency-shifted carriers.

Abstract: An optical DQPSK modulator comprises a pair of phase modulators. Each of the pair of the phase modulators is provided with first and second driving signals. The first and second driving signals are amplified by first and second amplifiers, respectively. An RZ intensity modulator generates an optical RZ-DQPSK signal from an optical DQPSK signal output from the optical DQPSK modulator. A photodetector generates a monitor signal from the optical RZ-DQPSK signal. A gain adjuster unit adjusts the gains of the first and second amplifiers so as to minimize the power of the monitor signal.

Abstract: An optical system and method includes a source-free optical network unit coupled to an optical fiber for receiving an original carrier signal with downstream data over the optical fiber. The optical network unit includes a modulator configured to remodulate the original carrier signal with upstream data to produce an upstream data signal for transmission back down the optical fiber in a direction opposite to a direction in which that original carrier signal was received.

Abstract: An optical transmitter is disclosed including a widely tunable laser coupled to a periodic optical spectrum reshaper (OSR) to convert frequency modulated pulses from the laser into amplitude modulated pulses. The laser is tuned to generate pulses corresponding to passbands of the OSR spanning a wide range of frequencies. The laser includes a gain section having an optical path length substantially shorter than the total optical path length of the laser. The laser may be a Y-branch laser having reverse-biased sampled gratings or ring resonator filters tuned by stripe heaters. The laser may also include a reflective external cavity section tunable by modulating the temperature of ring resonators or etalons. The OSR may be integrally formed with the external cavity of the ECL laser.

Abstract: The invention relates to a switchable infrared filter, consisting of a diamond carrier material (1), whereon a filter material (6), which is made of a thermochromic material, is disposed on one side and which can be connected to a heating device (2, 3).

Abstract: An optical transmitter is disclosed for transmitting a signal along a dispersive medium to a receiver. The optical transmitter generates adiabatically chirped profile having an initial pulse width and frequency excursion chosen such that high frequency data sequences include one bits that interfere destructively at a middle point of an intervening zero bit upon arrival at the receiver.

Abstract: An integrated optical transceiver includes an optical receiver that produces a first electrical signal at a reception electrical interface in response to a first optical signal, an optical transmitter that emits a second optical signal in response to a second electrical signal received at a transmission electrical interface, a first optical branching device that receives the first optical signal at an reception optical interface and to direct at least a portion of the first optical signal to the optical receiver, and a second optical branching device that directs the second optical signal to an transmission optical interface. The first optical branching device directs at least a portion of the first optical signal to the second optical branching device. The second optical branching device directs the portion of the first optical signal received from the first optical branching device to the transmission optical interface.

Abstract: An optical transmitter is disclosed wherein a directly modulated laser outputs a frequency modulated signal through a semiconductor optical amplifier. Both the optical transmitter and semiconductor amplifier are modulated according to an output of a digital data source. An optical filter is positioned to receive an output of the semiconductor optical amplifier and has a frequency dependent transmission function effective to convert the amplified signal into a filtered signal having enhanced amplitude modulation. In some embodiments, the semiconductor optical amplifier is coupled to the digital data source by means of a compensation circuit configured to high-pass filter the output of the digital signal source. In other embodiments, the semiconductor optical amplifier is coupled to the digital data source by means of a compensation circuit configured to produce an output including a first-order time derivative of the output of the digital signal source.

Abstract: A system operable to modulate a signal according to phase-shift keying (PSK) modulation includes one or more phase modulators that comprise one or more fractional phase modulators. A fractional phase modulator includes a splitter that splits a communication signal to yield a first communication signal with first amplitude and a second communication signal with second amplitude, where the ratio of the first and second amplitudes correspond to a phase shift. A phase shifter phase shifts the first or second communication signal. A first modulator modulates the first communication signal at a constant phase. A second modulator modulates the second communication signal at phases corresponding to the phase shift to encode data. A coupler couples the first communication signal and the second communication signal.

Abstract: System and method for m-ary phase shifting keying modulation. According to an embodiment, the present invention provides a method for performing m-ary phase-keying shift modulation. The method includes providing at least a first signal and a second signal by a signal source. The first signal and the second signal are characterized by a first signal strength level. The method also includes attenuating the second signal to provide a third signal. The second signal are characterized by a second signal strength level which is at approximate 50% of the first signal strength level. The method additionally includes coupling the first signal to a first bias voltage to provide a fourth signal. Furthermore, the method includes coupling the third signal to a second bias voltage to provide a fifth signal. The method also includes a step for providing a sixth signal by combing the fourth signal and the fifth signal.

Abstract: According to the invention, a very narrow-band transfer signal (LS) is generated by serially connecting a frequency modulator (2) and an amplitude modulator (4). The frequency modulator (2) is operated at a modulation index which at least largely suppresses the carrier signal (TS) while the amplitude modulator (4) suppresses the broadband portion of the spectrum by fading out the transfer signal (LS) during frequency-shift keying.

Abstract: The invention relates to a compensator of attenuation drift in an optical multi-wavelength switch (MWS) which uses input signal amplitude dither and external VOA dither cancellation to determine relative position of MEMS micro mirror hence indirectly determining attenuation level.

Abstract: An optical transmitter is discloses having a gain section and a phase section. The phase section is modulated to generate a frequency modulated signal encoding data. The frequency modulated signal is transmitted through an optical spectrum reshaper operable to convert it into a frequency and amplitude modulated signal. In some embodiments, a driving circuit is coupled to the phase and gain sections is configured to simultaneously modulate both the phase and gain sections such that the first signal is both frequency and amplitude modulated.

Abstract: A data modulator unit generates a DQPSK optical signal in accordance with a data signal. A phase shift unit provides a phase difference of ?/2 between a pair of arms. A photodetector converts an output signal of the data modulator unit into an electrical signal. A filter is a low-pass filter with a cut-off frequency lower than a symbol frequency, and filters an output signal of the photodetector. A monitor unit detects power of an output signal of the filter. A phase difference control unit adjusts the amount of phase shift in the phase shift unit so as to minimize power of an output signal of the filter.

Abstract: An optical transmitter includes an optical modulator including a phase modulator, and a delay interferometer to delay and interfere a part of an optical output of the optical modulator, and a controller to control an amplitude of a driving DPSK modulation signal to be supplied to the optical modulator based on a result derived from a level of an output signal of the delay interferometer.

Abstract: Methods and apparatus are provided for transmitting alternate-polarization phase-shift-keyed data. The output of a laser is modulated to optically encode electronic data using phase shift keying (PSK) to generate an optical signal. An alternate polarization PSK (APol-PSK) signal is generated by alternating the polarization of the optical signal using a modulator such that successive optical bits have substantially orthogonal polarizations.

Abstract: The present invention is a miniaturized differential M phase-shift modulator (M=2n: n is 2 or more) in which a plurality of Mach-Zehnder type light modulators each adapted to output a DPSK-modulated signal light by applying a driving voltage signal are arranged in parallel and that comprises a multiplexing waveguide adapted to output a DMPSK-modulated light by multiplexing outputs of the plurality of the Mach-Zehnder type light modulators, wherein a phase-shift voltage to produce a phase shift difference of substantially 2?/M for a plurality of the signal lights multiplexed by the multiplexing waveguide is applied to the plurality of the Mach-Zehnder type light modulators together with the driving voltage signal.

Abstract: An optical differentially phase shift keyed or DPSK binary signal which in the event of phase changes exhibits amplitude reductions and is phase-demodulated is provided. The received optical DPSK binary signal is additionally amplitude-demodulated and resulting phase and amplitude information is evaluated.

Abstract: An optical transmitter comprising: an optical source modulated with an input digital data signal so as to generate a first, frequency-modulated digital signal; and an amplitude modulator, modulated with the logical inverse of the input digital data signal, for receiving the first, frequency-modulated signal and generating a second, amplitude-modulated and frequency-modulated digital signal; wherein the optical source and the amplitude modulator are each configured so as to produce positive transient chirp.

Abstract: An optical transmission system for transmitting an optical pulse in a dielectric waveguide, the system including a filter for altering a shape of the optical pulse in both amplitude and phase with respect to time so as to substantially suppress the generation of third-order nonlinearities and increase a power level of the optical pulse, the filter further providing a secure encrypted optical waveform that may be decrypted by a matching optical filter, the system allowing for energy sharing of the pulses to substantially increase system bandwidth.

Abstract: A WDM optical transmission system of the invention: detects an optical waveform of an intensity-modulated optical signal adjacent to a phase-modulated optical signal in a wavelength range; calculates a phase modulation drive waveform for canceling XPM of the phase-modulated optical signal affected by the adjacent intensity-modulated optical signal in the optical transmission path, based on the detected result; and additionally phase-modulates the phase-modulated optical signal synchronously with the adjacent intensity-modulated optical signal, according to the drive waveform, to thereby compensate the XPM. As a result, excellent transmission characteristics can be realized.

Abstract: An optical transmission apparatus for suppressing deterioration of transmission quality due to XPM in a wavelength division multiplexing optical communication system in which an intensity modulation optical signal and a phase modulation optical signal exist in a mixed form. The apparatus has an intensity inversion signal light output section which outputs light having an intensity pattern obtained by inverting intensity changes of the intensity modulation optical signal near a wavelength of the intensity modulation optical signal in arrangement on wavelength axis of optical wavelengths that can be multiplexed as a wavelength division multiplexed signal as intensity inversion signal light, and a wavelength division multiplexed optical signal output unit which wavelength-division-multiplexes the intensity modulation optical signal, the phase modulation optical signal and light from the intensity inversion signal light output section and outputs a wavelength division multiplexed optical signal.

Abstract: In an optical transmitter comprising a directly modulated laser and a wavelength filter provided on a post-stage of the directly modulated laser, the wavelength filter has a modulated light input port for inputting modulated light output from the directly modulated laser, a filter transmitted light output port for outputting light having a wavelength included in a filter transmission band among the modulated light as filter transmitted light, and a filter cutoff light output port provided separately from the modulated light input port and the filter transmitted light output port and outputting light having a wavelength included in a filter cutoff band among the modulated light as filter cutoff light, and the peak of the filter transmission band is set on a shorter-wave side from the peak of the spectrum of modulated light output from the directly modulated laser.

Abstract: An optical phase difference control system is provided for controlling a phase difference of a single optical time-division multiplexed signal obtained by multiplexing a plurality of modulated optical signals encoded. The control system includes an interferometer and a low-frequency extractor. The interferometer is used for receiving part of the optical time-division multiplexed signal to split it into first and second signals, giving, between the first and second signals, a phase difference equivalent to one bit of the optical time-division multiplexed signal, and thereafter multiplexing the first and second signals. The low-frequency extractor is used for adding together signals, output from the interferometer, which have the similar intensity every two successive bits, and extracting a low-frequency waveform signal as a signal for controlling the phase difference of the single optical time-division multiplexed signal.

Abstract: An integrated optical source includes a Directly Modulated Laser (DML) and a filter which is positioned with the DML on a common substrate. The filter is configured to receive an input signal in the form of a modulated chirped optical signal. The filter is further configured to provide an output optical signal in the form of an amplitude and/or phase modulated optical signal, optimized for long-distance transmission in optical fiber.

Abstract: The invention is directed to code labeling in an optical network. The network includes a transmitting station operable to transmit an optical signal. The network also includes an encoder coupled to the transmitting station operable to label the optical signal composed of a group of codes. A receiving station operable to receive the labeled group of optical codes is also provided. The receiving station is operable to read the optical signal if the label of the received group of codes corresponds to the group of codes assigned to the receiving station.

Abstract: A quadrature amplitude modulation (QAM) signal generator, which can obtain optical signals such as QAM signals without handling multilevel electrical signals, can be produced by using a plurality of parallel Mach-Zehnder modulators (MZMs), such as quadruplex parallel MZMs (QPMZM). The quadrature amplitude modulation (QAM) signal generator includes a first waveguide, a first quadrature phase-shift-keying (QPSK) signal generator provided on the first waveguide, a second waveguide connected with the first waveguide at a wave-combining point, and a second quadrature phase-shift-keying (QPSK) signal generator provided on the second waveguide.

Abstract: An integrated optical source includes a Directly Modulated Laser (DML) and a filter which is positioned with the DML on a common substrate. The filter is configured to receive an input signal in the form of a modulated chirped optical signal. The filter is further configured to provide an output optical signal in the form of an amplitude and/or phase modulated optical signal, optimized for long-distance transmission in optical fiber.

Abstract: An optical modulator is provided which includes: an optical splitting part that splits an input light wave into two light waves; two optical waveguides that propagate the two light waves into which the input light wave is split, respectively; a first SSB modulating part that is provided in one of the two optical waveguides and modulates a light wave, which propagates into the first SSB modulating part, with a carrier frequency so that the light wave is converted into a different light wave having a single side band; a second SSB modulating part that is provided in the other of the two optical waveguides and modulates a light wave, which propagates into the second SSB modulating part, with a data signal in order to generate a signal light wave having a different single side band; and an optical combining part that combines the light wave modulated by the first SSB modulating part with the signal light wave generated by the second SSB modulating part.

Abstract: To compensate a waveform distortion by using a nature that a spectral shape is perfectly retained even if all the linear distortions occur on a time-axis. An optical pulse transmitted from an optical pulse transmitter (1) via an optical fiber transmission line (2) is transmitted. An optical Fourier transformer (3) receives an optical pulse, and optically Fourier-transforms an optical pulse on a time-axis onto a frequency-axis to reproduce the frequency spectrum of an optical pulse on a time-axis be effecting switching between frequency and time, thereby compensating a waveform distortion by a linear effect on the optical fiber transmission line (2). A photodetector (4) receives an optical pulse from the optical Fourier transformer (3) and transforms this into an electrical signal to thereby obtain a pulse waveform before a transmission over the optical fiber transmission line (2).

Abstract: An optical SSB-SC modulation section 13 subjects an optical signal fa outputted from an optical source 11 to an optical SSB-SC modulation based on the amplitude of an external electric signal fc to thereby output an optical intensity-modulated signal. An optical phase modulation section 14 subjects the optical signal fa to an optical phase modulation based on the amplitude levels of the first to nth external electric signals having frequencies f1 to fn to thereby output the resultant signal as an optical phase-modulated signal. An optical combining section 15 combines together the optical intensity-modulated signal and the optical phase-modulated signal. An optical detecting section 16 performs an optical homodyne detection through a squared detection of the optical intensity-modulated signal and the optical phase-modulated signal combined together to thereby produce a wideband modulated signal, being the difference beat signal between the two optical signals.

Abstract: A system and method for generating an optical return-to-zero signal. The system includes an electro-optical conversion system. The electro-optical conversion system is configured to receive an input electrical non-return-to-zero signal, process information associated with the input electrical non-return-to-zero signal, and generate a first electrical signal and a second electrical signal based on at least information associated with the input electrical non-return-to-zero signal. Additionally, the electro-optical conversion system is configured to delay a second electrical signal with respect to the first electrical signal by a predetermined period of time, process information associated with the first electrical signal and the delayed second electrical signal, and generate an output optical return-to-zero signal based on at least information associated with the first electrical signal and the delayed second electrical signal.

Abstract: The present invention is directed toward a method for setting a driving voltage of a differential quadrature phase-shift modulator, this method making signal quality superior in response to an individual difference in extinction ratio due to variations in manufacture of a device. To this end, signal quality of differential quadrature phase-shift modulated light output from a differential quadrature phase-shift modulator is acquired. An average amplitude of a first or second driving voltage signal is adjusted according to the signal quality of the thus-acquired differential quadrature phase-shift modulated light.