Abstract: An optical receiver includes a two-stage constant modulus algorithm (CMA) equalizer. The first stage is a modified version of a CMA equalizer and the second stage is a conventional CMA equalizer. The first stage may be made up of four sub-equalizers, of which only two of the sub-equalizers are independent, i.e., uncorrelated to each other. This first stage equalizer compensates for polarization-mode dispersion (PMD). The second stage equalizer is a conventional CMA equalizer made up of four sub-equalizers that are adjusted independently. This second stage equalizer may compensate for polarization-dependent loss (PDL). The receiver includes a first processor that determines PMD information based on a plurality of transfer function parameters of the modified CMA equalization of the first stage equalizer and the modified-equalized output and a second processor that determines PDL based on a plurality of transfer function parameters of the CMA equalization of the second stage equalizer.

Abstract: A method for monitoring a passive optical network (1), PON, having a tree-like structure with a main line (3) and at least two branches (6.1 to 6.3), comprising: transmitting a wake-up signal (10) from the main line (3) to at least two monitoring units (DPM1 to DPM3) arranged in the at least two branches (6.1 to 6.3), in each of the monitoring units (DPM1 to DPM3), detecting the wake-up signal (10) and transmitting a response signal (A, B, C) back to the main line (3), each of the monitoring units (DPM1 to DPM3) generating a pre-defined time delay (?tA to ?tC) between the detection of the wake-up signal (10) and the start of the transmission of the response signal (A, B, C), and receiving the response signals (A, B, C) at the main line (3), the receiving times (R1 to R3) of the response signals (A, B, C) being different from each other, the difference between the receiving times (R1 to R3) being adjusted by the pre-defined time delays (?tA to ?tC) of the monitoring units (DPM1 to DPM3).

Abstract: An apparatus for simulating radio frequency (RF) signal propagation characteristics in a wireless communication network is disclosed. The apparatus includes a first RF terminal and a second RF terminal. A first optical modulator is in electrical communication with the first RF terminal. An optical delay line is in optical communication with the first optical modulator. A first optical demodulator is in optical communication with the optical delay line and in electrical communication with the first RF terminal. A second optical demodulator is in optical communication with the optical delay line and in electrical communication with the second RF terminal. A second optical modulator is in electrical communication with the second RF terminal and in optical communication with the optical delay line.

Abstract: A phase shift keyed demodulator includes first and second beam splitters, a first optical path, a second optical path, and a wavelength tuner. The first beam splitter splits an input signal into first and second output signals. The second beam splitter splits each first and second output signal into a transmitted signal and a reflected signal. The first optical path includes an optical path of each transmitted signal from a beam splitting surface to a reflector and back to the beam splitting surface. The second optical path includes an optical path of each reflected signal from the beam splitting surface to a mirror surface and back to the beam splitting surface. A path difference introduces a delay between the transmitted signal and the reflected signal. The wavelength tuner tunes the demodulator to a predetermined central wavelength and introduces a phase shift between first and second transmitted signals.

Abstract: An optoelectronic timing system includes an optical timing compensation system in which optical pulses developed by a semiconductor laser are advanced or retarded based upon an expected arrival time. The pulses are directed into a number of time-quantifiable optical paths. Time quantification for a pulse is based upon the time required for a pulse to travel a particular length at the speed of light. Pulses are directed into an advancing path or a retarding path by optical switches which compare an expected arrival time of a new pulse to an expected arrival time based on a previous pulse. The optical compensation system is incorporated into a precision timing device in which multiple optical paths, having decreasing lengths in a defined pattern, are arranged in serial fashion so as to have each subsequent path of the series represent a travel time one order of magnitude different than a travel time of an adjacent path.

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: The present invention converts each of the optical differential signals from DPSK demodulator from an optical signal into an electrical signal by using optical-electrical signal converters. Thereafter, each electrical signal is subjected to amplification adjustment at an appropriate amplification factor by variable amplifier, and an appropriate delay amount is added to each electrical signal by variable delay line, and thereafter data discrimination is performed by discriminator. Since two differential signals after DPSK demodulation are subjected to amplitude and delay adjustments, the need for optical parts is obviated enabling the use of electric circuits which can be integrated. Thus, the cost of the optical reception device will be reduced. Moreover, the since electric signals whose phases and amplitudes are equalized are inputted to discriminator, erroneous determination of data at discriminator will be reduced.

Abstract: A light transmission system has a light transmission module having a light transmission path that transmits a data signal as an optical signal, wherein the light transmission module converts the optical signal transmitted through the light transmission path to an electrical signal and outputs the converted optical signal as a binarization signal, an electrical transmission path that outputs a clock signal as a binarization signal, a reception processing unit that performs a reception process on each of the data signal and the clock signal, and a first delay unit that delays a rise start time of the clock signal with respect to a rise start time of the data signal for the binarization signal. A delay amount of the clock signal by the first delay unit is a time less than or equal to a maximum value of a data dependency jitter (DDJ).

Abstract: An OADM in a wavelength division multiplexing transmission system includes a wavelength selection switch that selects a predetermined wavelength from a multiple optical signal obtained by multiplexing a phase modulated signal and an intensity modulated signal and outputs the selected wavelength signal to a predetermined output port. The wavelength selection switch has a different delay for each wavelength of the multiple optical signal. For example, the wavelength selection switch includes a mirror array. Optical paths from the surfaces of mirrors arranged on the mirror array to the diffraction grating are different in the case of adjacent mirrors.

Abstract: A tunable dispersion compensator (TDC) is tuned from a first dispersion setpoint to a second dispersion setpoint while maintaining continuity of the dispersion. The dispersion tuning follows a pre-determined trajectory in the time domain, so that continuity of the optical dispersion across the channel optical bandwidth is maintained while minimizing all other TDC-induced optical impairments during a tuning period.

Abstract: The invention relates to a communications node (10) for routing an optical signal 5 comprising at least one data packet, the node (10) having an input optic fiber (12) and an output optic fiber (14) in communication with each other, the input optic fiber (12) in communication with an optical splitter (20) which is arranged to split an incoming optical signal into at least two substantially identical optical signals, the optical splitter (20) further arranged to pass one of the optical signals to an optical correlator (22) and the other of the optical signals to an input optical switch (24), the optical correlator (22) being arranged to compare an address of the packet with a reference address (40) and to generate a trigger if the reference address (40) matches the address of the packet, the input optical switch (24) being arranged to route the data packet to an optical to electrical converter (28) in response to the trigger.

Abstract: A dispersion compensation device includes: an optical branching unit to branch an optical signal to be received; a first dispersion compensator to perform dispersion compensation on one part of the optical signal branched by the optical branching unit with a variable compensation amount; a second dispersion compensator to perform dispersion compensation on another part of the optical signal branched by the optical branching unit; a monitoring unit to monitor the communication quality of an output optical signal of the second dispersion compensator; and a controlling unit to determine the direction of variation in chromatic dispersion of the optical signal based on the direction of variation in communication quality monitored by the monitoring unit and control the compensation amount of the first dispersion compensator based on the result of the determination.

Abstract: A frequency up-conversion system includes an optical splitter, an optical modulator, an optical phase-shifter, and an optical coupler. In one embodiment of the present disclosure, the optical splitter is configured to split an optical wave into a first optical wave and a second optical wave, the optical modulator is configured to modulate the first optical wave to form a modulation wave, the optical phase-shifter is configured to shift the phase of the second optical wave by a predetermined phase to form a shifting wave, and the optical coupler is configured to couple the modulation wave and the shifting wave. In one embodiment of the present disclosure, the optical modulator and the optical phase-shifter are connected in a parallel manner.

Abstract: The present disclosure relates to coherent optical receiver systems and methods for determining and correcting for optical angle and magnitude imbalance and for delay imbalance between quadrature paths. The present invention iteratively determines and corrects imbalance error and differential delay entirely in the digital domain (after an analog to digital conversion) in the presence of all the other impairments (polarization mode dispersion, chromatic dispersion, polarization gain imbalance, and polarization delay imbalance) using only the corrupted received signal during normal operation, i.e. without the use of training data. The present invention provides an effective adaptive scheme to drive impairments to zero, without using of any calibration of training, and may be applied during normal operation of the receiver via electrical circuitry or the like.

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: A timing signal distribution system includes an optical frequency stabilized laser signal amplitude modulated at an rf frequency. A transmitter box transmits a first portion of the laser signal and receive a modified optical signal, and outputs a second portion of the laser signal and a portion of the modified optical signal. A first optical fiber carries the first laser signal portion and the modified optical signal, and a second optical fiber carries the second portion of the laser signal and the returned modified optical signal. A receiver box receives the first laser signal portion, shifts the frequency of the first laser signal portion outputs the modified optical signal, and outputs an electrical signal on the basis of the laser signal. A detector at the end of the second optical fiber outputs a signal based on the modified optical signal. An optical delay sensing circuit outputs a data signal based on the detected modified optical signal.

Abstract: In communications where synchronization of optical signals containing data is required, a multi-channel optical arrayed time buffer may be used. The time buffer includes multiple delay paths comprising delay elements, some of which can be shared to dispense different delays. In an embodiment, an arrayed waveguide grating (AWG) is illustratively used to route an optical signal to a first delay path, which is returnable to the AWG through the first delay path to be rerouted to a second delay path. The total delay affordable to the optical signal is a function of at least a first delay afforded by a delay element in the first delay path, and a second delay afforded by a delay element in the second delay path. In addition, without returning to the AWG, another optical signal may be routed through the second delay path alone to be afforded the second delay only.

Abstract: The present invention provides a method of generating time-division multiplexed encoded transmission signals, including encoding optical pulse signals for each of a plural multiplexed channels and generating a transmission signal for each channel, performing time division multiplexing on first and second transmission signals and generating a 2-channel multiplexed signal modulating the multiplexed signal with a modulation signal having a frequency of (F??f) Hz, detecting a strength of a ?f Hz frequency component of the multiplexed signal changing a time delay amount of the second transmission signal with respect to the first transmission signal, and determining a time delay amount at which a strength of the ?f Hz frequency component is minimized and adjusting the transmission signals of the individual channels such that they are arranged at equidistant intervals on a time axis.

Abstract: An optical network transmitter comprising a fractional-bit delay module, an optical modulator coupled to the fractional-bit delay module, and a band-limiting optical filter coupled to the optical modulator. Also disclosed is a transmission system comprising a source configured to generate two complementary binary data streams, a fractional-bit delay module in communication with the source and configured to delay one of the complementary binary data streams, a modulation module in communication with the source and the fractional-bit delay module and configured to convert the undelayed complementary binary data streams and the delayed complementary binary data streams into a fractional-bit delayed optical duobinary signal, and a band-limiting node in communication with the modulation module and configured to filter and transmit the optical duobinary signal.

Abstract: In an optical transmission system including a transmitter Tx and a receiver Rx connected via a fiber link F, where the receiver Rx is adapted to utilize Forward Error Correction (FEC) on received signals, a polarization scrambler is provided at the transmitter Tx to scramble the polarization state of a transmitted signal, a polarization delay line is provided at the receiver Rx for controlling the polarization mode dispersion induced distortion of a received signal, a feedback unit is provided at the receiver Rx for providing a feedback signal based on at least part of the received signal, and at least one polarization controller interconnects the fiber link F and the polarization delay line. The polarization controller is operable based on the feedback signal to mitigate the polarization mode dispersion of the signal.

Abstract: A demodulator comprises an input splitter, optical device sets, and couplers. The input splitter splits an input signal comprising symbols to yield a number of signals. A first optical device set directs a signal of along a first path. A second optical device set directs another signal along a second path to yield a delayed signal. At least a portion of the second path is in free space. A path length difference between the first path and the second path introduces a delay between the first signal and the second signal. A coupler receives a portion of the signal and a portion of the delayed signal to generate interference, where the interference indicates a phase shift between a phase corresponding to a symbol and a successive phase corresponding to a successive symbol.

Abstract: It is an object of the present invention to provide an FSK demodulator which can be used in the optical information and telecommunications and the like, and which can appropriately demodulate an FSK signal by compensating a delay of an optical FSK modulated signal due to dispersion and the like of an optical fiber. The above-mentioned problem is solved by a frequency shift keying (FSK) demodulator (1) composed of a branching filter (2) for branching an optical signal according to wavelengths thereof; a delay adjusting apparatus (3) for adjusting a delay time of two lights branched by the branching filter; a first photodetector (4) for detecting one optical signal branched by the branching filter; a second photodetector (5) for detecting a remaining optical signal branched by the branching filter; and a means (6) for calculating a difference between an output signal of the first photodetector and an output signal of the second photodetector.

Abstract: The system includes: a two-light wave generator for generating light beams having wavelengths ?1 and ?2 that are spaced apart by a frequency of a signal M1 from a laser; a photodetector for detecting a signal M2 from the light beams transmitted through an optical fiber; an optical modulator for frequency-shifting the light beams by a frequency of a signal M3; a Faraday reflector for reflecting the light beams; an optical coupler for mixing the light beams that have been returned to a polarization beam splitter, with the generated light beams; a photodetector for converting the light beams into microwave signals; an image rejection mixer for frequency-converting the signals obtained through the conversion by using the signal M1 to output a two side bands; and a phase difference detector for detecting a phase difference between the side bands, and controlling a phase shifter so that the phase difference becomes 0.

Abstract: Systems and methods are described that derive a relationship between an optical transmitter's extinction ratio (Er) and its interferogram wing-to-peak ratio (Iwp). The change in an optical transmitter's Iwp correlates with a change in measured Er. As the Er of a telecom signal changes, the power of the modulated signal's interferogram wings change. After a relationship between Iwp and measured Er has been derived for an optical transmitter, the relationship may be used after deployment to determine an Er by measuring an Iwp.

Abstract: Signals can be superimposed on optical phase even when low-coherency light is used, and a bit rate and a signal coding format similar to those used in ordinary optical communications can be used. A transmitter includes an asymmetric interferometer or an antisqueezed light generator to convert a train of single pulses into a train of dual pulses. A receiver also includes an asymmetric interferometer that provides the same delay time as that between the dual pulses. The receiver allows pulses originating in the same light source to interfere, so that signals can be superimposed on the phase even when a low-coherency light source is used. The delay time (optical path length difference) provided in the asymmetric interferometer is set to be longer than half the period of the pulses outputted from the optical pulse source.

Abstract: A method and apparatus for implementing an RF photonic transversal filter that utilizes tap apodization and wavelength reuse to obtain a high side lobe suppression together with narrow and configurable passbands. Several taps are obtained from one wavelength by using dispersive optical delay lines such as chirped fiber gratings that introduce a delay between successive wavelengths. A selected subset of the input wavelengths is utilized to generate multiple taps per wavelength. Some of the taps are apodized to generate various filter transfer functions that yield a high side lobe suppression ratio.

Abstract: The present invention inputs a signal synthesized an optical pulse with a variable-wavelength laser beam different in wavelength from it to a delay unit (S1). The delay unit branches the signal to two optical signals, produces an optical path difference between them to afford a delay, synthesizes them again to generate a multiplexed optical signal, and minutely varies the optical path length of one of them (S2). The present invention measures output variance of the delay unit on a variable-wavelength laser beam resulting from the minute variance (S3), and controls the optical path difference so as to minimize output variance at a position where the output is a maximum or minimum, or is a specific value other than them (S4). This stabilizes a phase difference between adjacent pulses of the multiplexed optical signal outputted from the delay unit (5) with a simple construction in optical time division multiplexing technology.

Abstract: Fully optical device for breaking down the dynamic range of an optical signal and system for measuring the signal, using this device. This device comprises fully optical means to break down this dynamic range.

Abstract: In an optical receiving apparatus for receiving an optical DQPSK signal, a phase difference between both arms of an optical interferometer is controlled to an optimum value. The optical DQPSK signal is incident on two optical interferometers in each which a delay-time difference between two arms is set to be equal to a 1-symbol time of the optical DQPSK signal and which are orthogonal to each other. The optical receiving apparatus converts the optical DQPSK signal into an intensity signal and receives it. A differential amplifier obtains a difference signal between outputs of a pre-amplifier and a discriminator connected thereto. The difference signal includes, as an amplitude, a phase shift in a phase section. A control circuit adjusts the phase of the phase section in the optical interferometers to reduce this difference signal, and changes the phase difference between the two arms to a desired phase difference.

Abstract: According to one embodiment, a multiplex delay unit comprises an optical all-pass filter (OAPF) adapted to apply continuously tunable group delay to a wavelength division multiplexing (WDM) signal so that all of its WDM components are delayed by substantially the same delay time. The OAPF has a free spectral range (FSR) that matches spectral separation between carrier wavelengths of the WDM signal. Advantageously, an optical multiplex synchronizer suitable for feeding a synchronous optical switch fabric can be implemented as an integrated waveguide circuit using a plurality of such multiplex delay units.

Abstract: An optoelectronic timing system includes an adaptive frequency generator system in which optical pulses are developed by a semiconductor laser. The pulses are directed into a number of time-quantifiable optical paths. Time quantification for a pulse is based upon the time required for a pulse to travel a particular length at the speed of light. Pulses are recombined at a nodal point and exhibit a numerical relationship with the periodicity of the issued pulse train equal to the numerical relationship between the lengths of the number of optical waveguides. A pulse detector and a regenerator are coupled to the semiconductor laser. A regeneration waveguide having a length equal to the longest of the optical paths is coupled to receive pulses from the laser.

Abstract: An optical transmitter apparatus for use in an optical communications network has a polarization dithering unit, an optical transmitter unit, and a transmission fiber. The polarization dithering unit is connected in series between an output of the optical transmitter unit and the transmission fiber.

Abstract: A pulse modifier, and associated lithographic apparatus and a method for manufacturing a device, is disclosed. The pulse modifier is configured to receive an input pulse of radiation and further configured to emit a plurality of corresponding output pulse portions of radiation, wherein the respective pulse portions are respectively mirrored about an axis transverse to the optical axis and mirrored about a point of the optical axis of the pulse portions.

Abstract: A highly precise clock synchronization apparatus in a real-time locating system (RTLS), includes an optical transmitting/receiving unit for receiving a clock information frame from a clock synchronization server, converting the received clock information frame in series-parallel, and transmitting/receiving the clock information data and the clock information; an offset estimation unit for detecting a preamble signal and a clock information signal from the series-parallel converted clock information frame, calculating a phase difference value by comparing the detected preamble signal with the detected clock information signal, and outputting an offset value based on the calculated phase difference value; and a clock synchronization unit for updating a local clock value to a time of the clock synchronization server based on the offset value and the clock information frame.

Abstract: A method and system for improving the performance of a differential-phase modulated optical communication system is disclosed. The system comprises a demodulator having a tunable element to adjust the free-spectral range (FSR) thereof, and a tunable phase shifter to adjust a frequency of a signal passing therethrough.

Abstract: A filter conducts the round trip by using the return optical signal that has been shifted in frequency, and measures the transmission optical signal and the return signal in phase by the principle of the Michelson interferometer at the same time, independently, and splits the two optical signals. A polarization state in which transmission and reception optical signals within an optical phase shifter which enters one route of the two optical signals are made orthogonal to each other is provided, to thereby distinguish the transmission and reception signals of the round trip from each other. The light is allowed to pass the shifter in incoming and returning to remove the polarization rotation of the shifter by using the reversibility of the light. Then, the phases of the transmission signal and the return signal are measured and synchronized with each other to conduct the transmission phase compensation.

Abstract: One embodiment of the invention provides an optical signal synchronizer having a plurality of optical channel synchronizers. Each optical channel synchronizer receives a respective input wavelength division multiplexing (WDM) signal and processes it to produce a corresponding output WDM signal, in which optical data packets corresponding to different carrier wavelengths are synchronized to each other regardless of the presence or absence of such synchronization in the input WDM signal. The optical signal synchronizer further has an optical multiplex synchronizer that receives the output WDM signals from the optical channel synchronizers and synchronizes them to each other and to an external reference clock without demultiplexing any of them into individual WDM components.

Abstract: Methods, apparatuses, and systems are presented for performing adaptive equalization involving receiving a signal originating from a channel associated with inter-symbol interference, filtering the signal using a filter having a plurality of adjustable tap weights to produce a filtered signal, and adaptively updating each of the plurality of adjustable tap weights to a new value to reduce effects of inter-symbol interference, wherein each of the plurality of adjustable tap weights is adaptively updated to take into account a constraint relating to a measure of error in the filtered signal and a constraint relating to group delay associated with the filter. Each of the plurality of adjustable tap weights may be adaptively updated to drive group delay associated with the filter toward a target group delay.

Abstract: The present disclosure relates to systems and methods for geographically-diverse redundant servers and the like interconnected via wavelength division multiplexed (WDM) systems with managed path differential delay of the WDM systems. The present disclosure provides transport systems and methods incorporating absolute time references, such as global positioning system (GPS) time references and/or the like, and selective buildout delays, such as first-in, first-out (FIFO) buildout delays and/or the like. In one exemplary embodiment, the transport systems and methods of the present invention are used in conjunction with the International Business Machine Corporation (IBM) Geographically-Dispersed Parallel Sysplex (GDPS) integrated, automated application and data availability solution to meet and/or exceed the associated 10 microseconds transmit/receive path differential delay requirement. Other comparable uses are also contemplated herein, as will be obvious to those of ordinary skill in the art.

Abstract: A method for receiving an optical signal is included where an ingress signal is split into a first portion and a second portion. A relative delay is induced between the first portion and the second portion, which are optically interfered to generate at least one interfered signal. Quality criteria of a monitored signal at least based on the at least one interfered signal is monitored so that a relative delay based in the quality criteria may be adjusted.

Abstract: An optoelectronic device implements a serializer array circuit or multi-channel CDR circuit to reduce the cost and size of the circuit. An efficient serializer array circuit includes a plurality of serializer blocks sharing the functionality of a single CMU to clock a plurality of serial signals out of the final stages of the serializer blocks. An efficient multi-channel CDR circuit includes a single CDR for acquiring the clock for one of a plurality of data signals and a plurality of DLLs using the recovered clock to acquire the data for the plurality of data signals. Alternately, an efficient multi-channel CDR circuit includes a single frequency acquisition loop and a plurality of data acquisition loops.

Abstract: A signal regeneration device which makes an extracted clock signal highly accurate while maintaining superior receiving sensitivity. To this end, a device of the present invention is configured to have a branch section for branching an input electrical signal which has been demodulated from a differential phase-shift modulated state; a first filter for equalizing a waveform of one of the demodulated electrical signals branched by the branch section; a clock recovery section for recovering a clock signal from the demodulated electrical signal whose waveform has been equalized by the first filter; and a data regeneration section for regenerating a data signal from a remaining one of the demodulated electrical signals branched by the branch section and from a clock signal recovered by the clock recovery section.

Abstract: Asynchronous optical data is aligned with synchronous convergence points in an optical packet switching system. The convergence points can be any place where data enters an optical packet switching element, buffer stage, switch fabric, etc. The arrival time for data approaching the convergence point is compared with a reference signal associated with the upcoming convergence point. The comparison is used to identify the amount of time-shift required to align the approaching data with the reference signal. Control information is derived according to the comparison and used to control an optical data aligner that synchronizes the data with the convergence point.

Abstract: A secure optical communication scheme uses differential delay D in an unbalanced Mach-Zehender interferometer to provide two copies of the optical source signal at a remote phase modulator separated in time by D. As D is much bigger than the coherence time source, the two copies of the signal are effectively uncorrelated. Both signals are phase-modulated by the remote sender's data and returned to the unbalanced interferometer. The phase modulator will be converted into amplitude modulation by the action of the interferometer.

Abstract: A signal detector system (10) comprises a single signal detector (11) having a limited on-time during which any received electromagnetic signal can be assessed. The signal detector (11) receives electromagnetic signals from a single direction in space (D) through a single optical fibre (12), a signal splitter 13 which splits the collected signal between three optical paths (20, 30 and 40), and a signal combiner (14) which combines the portions of the signal transmitted by the three optical paths (20, 30 and 40) and transmits the combined signal to a signal detector input (15). Each of the optical paths (20, 30 and 40) includes a respective optical delay (21, 31 and 41) designed to delay transmission of any received signal towards the signal detector (11). In this manner the signal detector (11) will receive any signals that arrived at the optical fibre (12) during three separate periods of time.

Abstract: A first interferometer comprises a first delay element and a first phase shift element, and a second interferometer comprises a second delay element and a second phase shift element. The amounts of phase shift in the first and second phase shift element are zero and ?/2, respectively. A first photo detector comprises first and second photodiodes connected in parallel, and a second photo detector comprises third and fourth photodiodes connected in series. The first photodiode is provided with a first optical output of the first interferometer, the second photodiode is provided with a first optical output of the second interferometer, the third photodiode is provided with a second optical output of the first interferometer, and the fourth photodiode is provided with a second optical output of the second interferometer. A signal process circuit recovers transmitted data based on output signals of the first and second photo detectors.

Abstract: Disclosed is a method for manufacturing a multimode optical fiber for high data rate LAN using MCVD, which includes a deposition process for forming a clad layer and a core layer, doped with an additive for controlling a refractive index, on an inner wall of a quartz tube by injecting a deposition gas into the quartz tube and applying heat to outside of the quartz tube; and a collapse process, which is repeatedly conducted N times, for filling up a gap in the quartz tube by applying heat of a temperature over a deposition temperature to the quartz tube after the core layer is completely deposited. In the method, together with an N?1th collapse process, an etching process of injecting a reaction gas for etching into the quartz tube is conducted in order to eliminate a portion of which refractive index is transformed due to evaporation of the additive.

Abstract: The present invention is an optical multiplex communication system in which an optical wavelength division channel and an optical code division channel can coexist, wherein a WDM channel section 86 has a wavelength demultiplexer 36 and WDM channels W1 to W4. An optical pulse string 83-3 is demultiplexed by the wavelength demultiplexer 36, and for channel W1, an optical pulse 37 with wavelength ?1 is input to an intensity modulator 114 and converted into an optical pulse signal of channel W1, and is output as a wavelength division optical pulse signal 115, where transmission information of channel W1 is reflected.

Abstract: An optical transmitter generates a transmission signal having a frame as a unit, the frame including a single optical pilot signal with a constant optical phase and a plurality of phase-modulated optical data signals, and outputs the transmission signal into a transmission line. In a receiver, a splitter splits the optical signal input from the transmission line. On a second arm of a Mach-Zehnder interferometer, an optical gate transmits the optical pilot signal and a duplicator duplicates the optical pilot signal output from the optical gate at predetermined time intervals. A balanced optical receiver converts the interfered optical signal output from the interferometer into an electrical signal. A gate and a discriminator extract the data from the electrical signal output from the receiver.

Abstract: A calculation processing unit controls temperature of a Peltier device based on a slope of a waveform obtained by subtracting a waveform of a B-arm monitoring signal from a waveform of an A-arm monitoring signal and a value obtained by subtracting a value B of the B-arm monitoring signal from a value A of the A-arm monitoring signal. Similarly, the calculation processing unit controls a phase of the A-arm and a phase of the B-arm. An A-arm side micro-controller controls temperature of an A-arm side heater 22 based on the value of the A-arm monitoring signal, and controls the phase of the A-arm. A B-arm side micro-controller controls temperature of a B-arm side heater based on the value B of the B-arm monitoring signal, and controls the phase of the B-arm.