Abstract: Methods for performing time-domain equalization of an information signal represented by an optical signal are provided. A representative method includes: receiving the optical signal; optically splitting the optical signal into beams; optically delaying at least one of the beams; detecting a plurality of the beams to generate respective electrical signal components; and combining a plurality of the electrical signal components to generate an electrical output signal representing the information signal. Systems and other methods also are provided.

Abstract: A wavelength multiplex transmission system is provided to reduce crosstalk among wavelengths and reduce deterioration of signals. At a transmission apparatus, one input signal is differentially divided into two; each of the two is converted to an optical signal; and then they are wavelength-multiplexed and transmitted. When crosstalk is arisen in the wavelength multiplex transmission system, the crosstalk is superposed on the two optical signals. The crosstalk is equally superposed on each of the signals with inverted polarities. Accordingly, converting the optical signals to electrical signals and then differentially combining them at a receiving apparatus, their signal components are accumulated, while their crosstalk components are cancelled out. Thereby, in the wavelength multiplex transmission system, deterioration of optical signals due to crosstalk can be reduced.

Abstract: Tunable PMD emulators and compensators for producing different PMD profiles with an adjustable average DGD value.

Abstract: Techniques and systems for monitoring of optical signals are described. Each of a plurality of optical signals is supplied to an optical port. A port signal is generated based on each of the optical signals and each of the port signals is subjected to a time delay to create a time delayed signal, with a different time delay being present in each of the time delayed signals. The time delayed signals are multiplexed to create a multiplexed signal comprising a plurality of multiplexed signal components, each component corresponding to one of the time delayed signals and exhibiting a time delay characterizing the corresponding time delayed signal. A desired one or ones of the multiplexed signal components are selected by analysis or display by specifying a time delay present in the time delayed signal represented by the desired component, and selecting a signal component exhibiting the specified time delay.

Abstract: A method of producing narrow optical pulses includes receiving first and second optical pulses having first and second widths, respectively, the second optical pulse having a delay relative to the first optical pulse, and selectively interfering the first and second optical pulses to produce a third optical pulse having a third width narrower than both said first and second widths.

Abstract: In accordance with the invention, a variable optical delay line with a large continuous tuning range comprises an incremental variable delay line to provide delay selected from a sequence of incrementally differing delays and a continuous variable delay line to provide a continuously variable delay over a range encompassing a delay increment in the first variable delay line. In a preferred embodiment, the first variable delay line comprises an array of delay paths where each path is curved differently from the others to provide an incrementally different delay. The second variable delay line is a tunable delay path continuously tunable over the delay increment of the first.

Abstract: A scaleable high-capacity network comprises several non-uniform composite-star networks interconnected by a number of lateral uniform composite-star networks, thus forming an irregular two-dimensional network. Each non-uniform composite star network comprises electronic edge nodes, possibly of significantly different capacities, interconnected by optical core nodes. The optical core nodes are not connected to each other, and each may be configured differently and have a different reach index, where the reach index of a core node is the number of edge nodes to which the core node directly connects. The selection of a route through a core node within a non-uniform composite-star network is based on a composite index determined according to the reach index of the core node and the propagation delay along the route.

Abstract: The invention is also related to devices for a synchronization of data in an optical WDM transmission system, consisting of the following parts: A wavelength demultiplexer (1) for demultiplexing the incoming data stream in the synchronizer, delay lines (2) for the individual wavelength channels, a multiplexer (10), a modulator (3) modulated by a high frequency clock signal (5) and at least one photodetector (4) tapped to output line (B) where the photodetector (4) is connected to an electronic control circuit (6) which is connected to the findividual delay lines (2) for an automatic delay control.

Abstract: Devices and techniques for achieving signal filtering in RF or microwave frequencies by optical filtering via two optical resonators in two separate optical paths. One optical resonator is tunable to tune the filtering in RF or microwave frequencies. Tunable opto-electronic oscillators may be constructed based on described filters.

Abstract: This invention provides a technique for realizing low-cost optical signal waveform monitoring with improved realtimeness to be applied to signal quality monitoring in an actual optical transmission system, and a technique for stably controlling an optical transmitter/receiver and various compensators by means of this waveform monitoring. Opening/closing of a optical gate is controlled by means of a clock signal synchronized with an optical signal input from a photocoupler and having a period equal to the bit interval of data or N (N: a positive integer) times longer than the bit interval to allow each pulse of the optical signal for one bit of data to pass through the optical gate for only part of the time width of the gate. A photoelectric conversion element to which the optical signal transmitted through the optical gate for only part of the time width obtains an average light intensity of the input optical signal. Information on this average light intensity is output to a monitoring output section.

Abstract: A polarization mode dispersion (PMD) feedforward compensator compensates first and second order PMD. An optical signal is provided to a PMD detector that senses first and second order PMD in the optical signal and produces control signals for the PMD compensator. The PMD compensator comprises, in series, a first polarization controller, an adjustable delay, a second polarization controller, a first fixed delay, a third polarization controller and a second fixed delay.

Abstract: The dynamic gain equalizer for flattening a gain profile of an optical amplifier includes: an optical waveguide circuit having multistage optical couplers, demultiplexing and multiplexing, each formed by connecting optical couplers arranged at a plurality of stages; and optical connecting circuits including optical phase shifters each capable of changing a phase of propagating light and optical delay lines each for adding a predetermined delay time to the propagating light, said dynamic gain equalizer in which at least one of the optical couplers in the two multistage optical couplers are provided with variable optical amplitude means, respectively, and each of the multistage optical couplers are formed asymmetrically with respect to an extension of a line which connects a center arranged position of optical outputting ends of the demultiplexing multistage optical coupler with a center arranged position of optical inputting ends of the multiplexing multistage optical coupler.

Abstract: An optically modulated signal is generated for use in transporting data by generating a so-called sub-carrier modulated optical signal and, then, vector modulating the sub-carrier modulated optical signal to yield the desired modulated optical signal for transmission. The vector modulation includes a phase component and an amplitude component. In one specific embodiment of the invention, an apparatus for use in generating a modulated optical signal includes a generator to generate a sub-carrier modulated optical signal including an optical carrier and at least one sub-carrier and an analog vector modulator coupled to receive both the sub-carrier modulated optical signal from the generator and a data signal. The analog vector modulator generates an output optical signal by phase modulating and/or amplitude modulating the sub-carrier of the received optical signal in response to the data signal.

Abstract: A wavelength-division multiplexed optical transmission system to keep the correlation of data patterns among wavelength channels to the low level, preventing large XPM and XGM from occurring when the correlation is strong, and assuring a stable transmitting quality.

Abstract: An operation unit of a PMD compensation module includes a PBS (polarization beam splitter), a compensating part and a combiner. The PBS separates an optical input into a first polarized signal and a second polarized signal. The compensating part includes a fixed prism and a movable prism. The first polarized signal outputted from the PBS travels through the fixed prism and the movable prism in series. The light path of the first polarized signal in the movable prism is elongated or shortened according to a position of the movable prism. A continuously variable delay can thus be applied between the first and second polarized signals. The combiner recombines the first polarized signal received from the compensating part and the second polarized signal received from the PBS into an optical output signal.

Abstract: A method and apparatus for transmitting information using the phenomenon of quantum entanglement. Two streams of quantum-entangled particles are emitted from a source. Performing a measurement on one of the streams results in the observable destruction of interference on the other stream. Information is transmitted by modulating the performance of the measurement on the first stream, and received by observing the presence or absence of interference in the second stream.

Abstract: An optical time-division multiplex signal processing apparatus includes an optical dispersion part providing optical dispersion to an optical time-division multiplex signal and an optical clock signal, an optical detector coupled optically to the optical dispersion part for detecting a beat signal formed between the optical time-division multiplex signal and the clock signal in a superposed state, and a filter connected to an output terminal of the optical detector for filtering out an electric signal of a desired frequency band from an output electric signal of said optical detector.

Abstract: An optical communication equipment comprises shared optical sources 88a–88d to be shared by communication nodes 100a–100d, the wavelengths of optical signals 76a–76d are converted into desired wavelengths ?a–?d according to the addressed information of the corresponding optical label signals 77a–77d by using the shared optical sources 88a–88d, and routed to the addressed communication nodes without being converted into electrical signals by using the wavelength routing function of the cyclic-wavelength arrayed-waveguide grating (AWG) 120. The load of each communication node can be reduced by incorporating the multi-wavelength optical sources, which can be shared among individual communication nodes, into the router 80.

Abstract: A delayed optical signal is generated from an inputted optical signal by cyclically transmitting the inputted optical signal between at least two ends of an optical medium and outputting the inputted optical signal from one of the ends of the optical medium after at least one transmission cycle via the optical medium. Each transmission of the inputted optical signal in a direction via the optical medium is carried out over a wavelength resource that is different from a wavelength resource used in a preceding transmission of the inputted optical signal in a direction via the optical medium. Interference among repeated transmissions of the inputted optical signal via the optical medium is therefore minimized or even avoided. Related apparatus and method are also described.

Abstract: A card for transmitting data over at least one optical fiber includes a transmitter having at least one light source and a phase modulator for phase modulating light from the source so as to create phase-modulated optical signals in the light as a function of an input electronic data stream; and a receiver having an interferometer for reading received optical signals.

Abstract: A multiplexing/demultiplexing system has a multiplexor that includes a first plurality of optical switches having a plurality of outputs and a first plurality of optical delay elements coupled to the optical switches. A source of optical light is coupled to the delay elements, and an optical combiner is coupled to the plurality of outputs and a source of framing pulses. A demultiplexor includes a first and second splitter, and a threshold detector coupled to the first splitter. The demultiplexor further includes a second plurality of optical delay elements coupled to the threshold detector, and a second plurality of optical switches coupled to the second splitter and the second plurality of delay elements.

Abstract: A waveform synthesizer comprising for synthesizing RF lightwave waveforms in the optical domain. These waveforms are constructed by generating their constituent Fourier frequency components or tones and then adjusting the amplitudes of those frequency components or tones. The apparatus includes: a RF-lightwave frequency-comb generator; and a multi-tone, frequency selective amplitude modulator coupled to the RF-lightwave frequency-comb generator for generating a continuous-wave comb comprising a set of RF tones amplitude modulated onto a lightwave carrier.

Abstract: Optical transmitter/receivers for use in a DWDM systems are provided. Transmission of data signals in a quadrature-return-to-zero (QRZ) format achieves a data transmission rate equal to eight times a base data rate, i.e., 80 Gbps over a 100 GHz channel if the base data rate is 10 Gbps, with high non-linear performance by setting the polarization state of the data bands such that non-linear effects induced by PMD are reduced. Additionally, a transmitter achieves a transmission data rate equal to 16 times the base data rate by sharpening the QRZ pulses and interleaving pulse-sharpened QRZ data signals in the time domain, further doubling the data rate. Using counterpropagation in the transmitter, carrier signals and data signals traverse the same length of fiber, reducing fringing effects in the transmitter. Related techniques enhance reception and detection of data at high data rates. A local pulse-sharpened carrier is mixed with a QRZ data signal at a detector reducing amplification noise by a factor of two.

Abstract: A bit-rate independent optical receiver and a method thereof. In the bit-rate independent optical receiver, an optoelectric converter converts an input optical signal to an original electrical signal, a bit rate identifying unit forms a resultant signal by performing an exclusive-OR (XOR) logic operation on the original electrical signal received from the optoelectric converter and a second signal corresponding to the original electrical signal delayed by a predetermined quantity of time, and detects a bit rate from the resultant signal, a reference clock generator generates a reference clock signal according to the detected bit rate, and a clock and data recovery circuit recovers a clock signal and data from the input signal according to the reference clock signal.

Abstract: The optical sampling system performs by detecting the interference effect which is a linear correlation between the signal lights and the optical pulses, so that both the signal lights and the optical pulses can have relatively low intensities, and the reception sensitivity is high. Also, the pulse width of the optical pulses and the amount of delay given to the optical pulses are the only factors that limit the time resolution, so that it is possible to provide the optical sampling system with excellent time resolution and power consumption properties, and it is possible for the optical sampling system to monitor not only the intensity of the signal lights but also the frequency modulation component as well.

Abstract: Provided are a polarization mode dispersion (PMD) compensator and method for automatically and rapidly compensating PMD occurring in an optical transmission fiber in a high-speed optical transmission system. The polarization mode dispersion compensator includes a separator and a differential time delay remover. The separator aligns orthogonal first and second polarization components of a received optical signal with respect to two orthogonal axes of a polarization beam splitter using optical signal information output via a second path of a first path and the second path of the two outputs of the polarization beam splitter, splits the first and second polarization components, and transmits the first polarization component via the first path and the second polarization component via the second path. The differential time delay remover receives the first and second polarization components that have been split to remove a differential time delay between the first and second polarization components.

Abstract: For suppressing intra-channel four wave mixing in a time division multiplexing (TDM) system, where N synchronous data streams, each having a reduced data pulse width within a bit slot timing interval, from parallel to serial form, are converted for optically bit interleaving the N synchronous data streams into the optical communication link at a nominal bit slot delay between sequential N synchronous data streams related to the bit slot timing interval to provide a serial data sequence of short optical pulses having an equal bit slot delay between sequential pulses, a sequential bit slot delay is varied between two of the short optical pulses to provide an unequal bit slot delay between sequential pulses within the serial data sequence of short optical pulses for suppression of undesired intra-channel four-wave mixing pulses among the pulses and thereby, improvement of transmission performance.

Abstract: A system for all-optical signal regeneration is provided, which makes it possible to exhibit desired intensity noise suppressing function with respect to pulsed input signal light without increasing the injection current of semiconductor optical amplifiers even if the magnitude of nonlinear phase shift of the input signal light is less than ?. The output light of the first delay interference unit is subjected to phase shift in the first nonlinear semiconductor waveguide and then, applied to the second delay interference unit along with the clock light. In the second delay interference unit, the first interfered light is generated from the output light while the second interfered light is generated from the clock light having an opposite logic to the input light. The second interfered light is subjected to phase shift by the first interfered light in the second nonlinear semiconductor waveguide and then, applied to the third delay interference unit.

Abstract: Methods and apparatus for coherent PMD generation are provided. A PMD generator can include at least four birefringent stages in optical series, thereby forming at least three pairs of adjacent stages. Each of the stages includes a harmonic differential group delay element and a phase-compensating element. The generator can be made colorless (i.e., made to have the same PMD at each WDM channel) and can be operated such that DGD and second order PMD can be independently generated and controlled. These PMD generators can be used in PMD compensators and PMD emulators.

Abstract: A method and apparatus for providing optical 3R regeneration involving: 1) generating an encoded optical clock signal from at least an optical signal; 2) introducing the encoded clock signal into a delay interference section of a regenerator such that an amplitude modulated clock signal is produced; andoutputting the amplitude modulated clock signal wherein the output amplitude modulated clock signal preserves information present within the input optical signal.

Abstract: According to the cross phase modulation suppressing device of the present invention, the wavelength multiplexing optical signal from an optical fiber having polarization orthogonality between the adjacent channels is split for every channel and the split optical signals are led to delaying optical waveguides of different lengths by the AWG (Arrayed Waveguide Grating) connected to a second port of an optical circulator, and the split optical signals with each delay added are reflected by the Farraday mirrors in polarization states orthogonal to each other and again led to the delaying optical waveguides. The reflected lights are combined by the AWG and supplied to a third port of the optical circulator as the wavelength multiplexing optical signal with orthogonality of polarization states kept between the adjacent channels.

Abstract: The present invention is directed to an integrated system for performing dispersion compensation on wavelength channels in WDM or DWDM transmissions. The system includes a tunable integrated dispersion compensation module that performs chromatic dispersion compensation and polarization mode dispersion compensation on each of the wavelength channels in the transmission. Feedback is used to adjust the tunable integrated dispersion compensation module until receiver performance is optimized.

Abstract: An electromagnetic matched filter based multiple access communications system having a source of modulated pulses from a digital data stream; an initial filter which shapes the incoming modulated pulse into a desired pulse for transmission across the communication medium; a second filter, identical to the initial filter, which is matched to the pulse which exit the communication medium, a detector which converts the modulated pulse stream into the original digital data stream, and signals which are designed with specific mathematical properties which make the system efficient and minimizes crosstalk between channels. The signals decay rapidly from the central lobe at a higher than 1/x rate and the zero points of the autocorrelation function having high order multiplicities. The type of system allows multiplexing of multiple data streams with much greater flexibility, robustness, and density.

Abstract: Methods and apparatus for coherent PMD generation are provided. A PMD generator can include at least four birefringent stages in optical series, thereby forming at least three pairs of adjacent stages. Each of the stages includes a harmonic differential group delay element and a phase-compensating element. The generator can be made colorless (i.e., made to have the same PMD at each WDM channel) and can be operated such that DGD and second order PMD can be independently generated and controlled. These PMD generators can be used in PMD compensators and PMD emulators.

Abstract: Methods and apparatus for coherent polarization mode dispersion generation are provided. A generator can include at least four birefringent stages. The birefringent stages are in optical series, and each includes a differential group delay (“DGD”) element. The intermediate stages' DGD elements are harmonic. Also, these intermediate stages each include a phase-shifting element. The generator can also include a polarization mode-mixing apparatus and a variable phase-shifting apparatus. The mode-mixing apparatus is capable of inducing polarization mode-mixing between at least one pair of adjacent stages to generate DGD and second order PMD independently at at least one optical frequency. The variable phase-shifting apparatus can include a phase-shifting controller coupled to each of said phase-shifting elements. A graphical user interface for PMD emulation, a PMD compensator for reducing PMD impairment, and calibration methods are also provided.

Abstract: A photonic arbitrary waveform modem utilizes a bipolar coding scheme. The bipolar coding scheme includes an arbitrary waveform modem which includes a plurality of tapped delay lines and is implemented by partitioning each optical frequency chip into positive and negative segments. Signals are decoded by effectively multiplying the transmit and receive code vectors and individually summing the positive and negative tap weights. The positive and negative tap weights are differenced to recreate the transmitted signal. The bipolar coding scheme allows for the use of truly orthogonal codes which decreases the interference and reduces the probability of detection.

Abstract: A spread spectrum waveform generator has a photonic oscillator and an optical heterodyne synthesizer. The photonic oscillator is a multi-tone optical comb generator for generating a series of RF comb lines on an optical carrier. The optical heterodyne synthesizer includes first and second phase-locked lasers, where the first laser feeds the multi-tone optical comb generator and the second laser is a single tone laser whose output light provides a frequency translation reference. At least one photodetector is provided for heterodyning the frequency translation reference with the optical output of the photonic oscillator to generate a spread spectrum waveform. A receiver pre-processor may be provided to operate on the spread spectrum waveform.

Abstract: A micro-optical delay element for a time-division multiplexing scheme is disclosed wherein two light beams are provided to a beam splitter/combiner (BS/C) in the absence of optical fibre. At least one beam exiting a modulator is collimated and reaches the (BS/C) unguided as a substantially collimated beam.

Abstract: A scaleable high-capacity network comprises several non-uniform composite-star networks interconnected by a number of lateral uniform composite-star networks, thus forming an irregular two-dimensional network. Each non-uniform composite star network comprises electronic edge nodes, possibly of significantly different capacities, interconnected by optical core nodes. The optical core nodes are not connected to each other, and each may be configured differently and have a different reach index, where the reach index of a core node is the number of edge nodes to which the core node directly connects. The selection of a route through a core node within a non-uniform composite-star network is based on a composite index determined according to the reach index of the core node and the propagation delay along the route.

Abstract: For suppressing intra-channel four wave mixing in a time division multiplexing (TDM) system, where N synchronous data streams, each having a reduced data pulse width within a bit slot timing interval, from parallel to serial form, are converted for optically bit interleaving the N synchronous data streams into the optical communication link at a nominal bit slot delay between sequential N synchronous data streams related to the bit slot timing interval to provide a serial data sequence of short optical pulses having an equal bit slot delay between sequential pulses, a sequential bit slot delay is varied between two of the short optical pulses to provide an unequal bit slot delay between sequential pulses within the serial data sequence of short optical pulses for suppression of undesired intra-channel four-wave mixing pulses among the pulses and thereby, improvement of transmission performance.

Abstract: The present invention provides an all optical system for generating high rate modulated signals including: a generator for generating a first periodic signal at a first rate; an optical chopping device arranged to receive the first periodic signal for producing a second periodic signal having pulses that are narrower than the pulses of the first signal; a splitting device for receiving and splitting the second periodic signal into multiple images of the second periodic signal propagating along multiple optical paths, the multiple optical paths including optical modulators for modulating the images of the second periodic signal at a first rate to produce modulated signals; an interleaving device for receiving and interleaving the modulated signals to produce a stream of modulated signal having a second ratewhich is higher than the first rate.

Abstract: An improved method and apparatus for optical and radio frequency implementation of a fast frequency hopping spread spectrum communication for code division multiple access systems is disclosed. The method avoids the frequency hopping synthesizer requirements in the transmitter as well as in the receiver. In a system where a pool of CDMA users share a channel characterized by a number of F available frequencies (or frequency bands), each user is assigned a subset of M (M less than or equal to F) frequencies from the F available frequencies, selected and ordered in time as prescribed by his own code (or address). In the transmitter, the information bit sequence modulates a broadband source so that the energy assigned to a data bit is concentrated on just a short interval of the bit period which is less than or equal to the so-called chip interval.

Abstract: An optical communication system and method are disclosed. Optical communication may be implemented with less complicated and costly components yet use RZ-like signal formats. The method may also be adapted to provide communication with beneficial phase relationships among optical pulses. An originating signal has a plurality of pulses, each pulse defined by a leading edge and a falling edge. A plurality of first optical pulses are created and transmitted on an optical communication medium in which each first optical pulse corresponds to a leading edge of a corresponding pulse of the originating signal. A plurality of second optical pulses are created and transmitted on an optical communication medium in which each second optical pulse corresponds to a falling edge of a corresponding pulse of the originating signal.

Abstract: Coherent optical equalization is applied in the optical domain to an input optical signal that includes a wanted optical signal and an unwanted optical signal temporally delayed relative to the wanted optical signal. A first optical signal that includes at least the wanted optical signal is split into first beams that include a first beam subject to delay. The first beam subject to delay is delayed to provide a delayed first beam. Beams that include the delayed first beam are coherently summed to produce a second optical signal in which the unwanted optical signal has a reduced intensity compared with in the input optical signal. In the coherent summing, the instance of the wanted optical signal in the delayed first beam cancels the unwanted optical signal in another of the beams that are coherently summed.

Abstract: An optical pulse pattern generator can generate optical pulse signals with various periods and patterns. It supplies an optical pulse from an optical pulse source to a variable optical delay line circuit including cascade-connected characteristic-variable asymmetrical Mach-Zehnder interferometers via an optical combiner and splitter. The optical pulse is fed back to the optical combiner and splitter from the final stages of the cascade-connected characteristic-variable a symmetrical Mach-Zehnder interferometers via an optical exclusive OR circuit and optical amplifier. Making directional couplers with variable coupling ratio, and directional couplers with variable coupling ratio in operation can cause the final stage of the cascade-connected characteristic-variable asymmetrical Mach-Zehnder interferometer to produce a random pulse train.

Abstract: A multi-wavelength light source apparatus includes a tunable light source, optical intensity modulator, optical coupler, annular optical delay circuit, and optical gate device. The tunable light source successively changes and outputs a plurality of output lights different in wavelength from one another. The optical intensity modulator outputs a modulated signal light obtained by modulating an amplitude of the output light outputted from the tunable light source over a predetermined time. The optical coupler is optically connected to the optical intensity modulator, and receives the light outputted from the optical intensity modulator. The annular optical delay circuit is optically connected to the optical coupler, and delays a part of the output light outputted from the optical intensity modulator over a time longer than the predetermined time.

Abstract: A method and apparatus for optical return-to-zero (RZ) modulation based on a single Mach-Zehnder modulator driven by non-return-to-zero (NRZ) electrical signals. The method and apparatus allow for continuously electrically tunable duty cycles and lead to chirped-RZ formats. A “push-pull” embodiment involves driving one control arm of the Mach-Zehnder with a differentially encoded version of an NRZ data stream and driving the other control arm with an inverted and time-delayed copy of the same differentially encoded data stream. A “push-push” embodiment involves driving one control arm of the Mach-Zehnder with a differentially encoded version of an NRZ data stream and driving the other control arm with a time-delayed but non-inverted copy of the same differentially encoded data stream. In one or more embodiments, the duty cycle of the RZ modulation is controlled via the selection of the time delay between the electrical signals that drive the two arms of the Mach-Zehnder.

Abstract: An optical communication equipment comprises shared optical sources 88a-88d to be shared by communication nodes 100a-100d, the wavelengths of optical signals 76a-76d are converted into desired wavelengths &lgr;a-&lgr;d according to the addressed information of the corresponding optical label signals 77a-77d by using the shared optical sources 88a-88d and routed to the addressed communication nodes without being converted into electrical signals by using the wavelength routing function of the cyclic-wavelength arrayed-waveguide grating (AWG) 120. The load of each communication node can be reduced by incorporating the multi-wavelength optical sources, which can be shared among individual communication nodes, into the router 80.

Abstract: An optical TDM multiplexing apparatus to multiplex a plurality of input signals in the optical stage in the time domain according to the invention comprise a plurality of signal light sources to generate optical signals each having a wavelength different from the others to carry each of the plurality of the input signals, a timing adjuster to adjust timings between the respective optical signals so that each optical signal output from the plurality of the signal light sources is disposed on a time slot different from the others in the time domain, an optical multiplexer to multiplex each optical signal output from the timing adjuster in the wavelength domain and a wavelength converter to convert each wavelength of the output light from the optical multiplexer into a predetermined wavelength.

Abstract: In an optical transmission system, a multiplexer frequency-division-multiplexes a plurality of signals, and outputs the resultant signal to an FM modulator. The FM modulator converts the frequency-division-multiplexed signal into an FM modulated signal through frequency modulation using the frequency-division-multiplexed signal as an original signal. A frequency-divider converts the FM modulated signal into a frequency-divided FM modulated signal whose frequency is ½n (n is an integer of not less than 1) the frequency of the FM modulated signal. An optical modulator has a predetermined input-voltage vs. output-optical-power characteristic, and is biased at the minimum point (voltage) about the output optical power. The optical modulator modulates an unmodulated light fed from a light source with the applied frequency-divided FM modulated signal to produce an optical signal whose optical carrier component is suppressed, and sends the optical signal to an optical transmission line.