Abstract: An optical transceiver is controlled through the use of a monitor optical signal generator and monitor optical signal detector mounted in close physical proximity to the optical signal generator and detector of the transceiver in a housing having a reflective surface. The monitor optical signal generator transmits a reference optical signal that is reflected and directed to the monitor optical signal detector by the reflective surface of the housing. Changes in the reference optical signal detected at the monitor optical signal detector are used for controlling the optical signal generator of the transceiver.

Abstract: A method and system for generating both return-to-zero (RZ) and carrier suppressed return-to-zero (CSRZ) shaped signals using only a single optical modulator. The system includes: a switch for receiving a data signal and a clock signal as inputs, and outputting a voltage signal; a unit for controllably adjusting the phase of said clock signal before input to the switch; an optical modulator for receiving a continuous wave light (CW) signal and the voltage signal as inputs, and outputting one of an RZ and a CSRZ signal. To generate a CSRZ signal, the optical modulator is biased at a transmission minimum level signal. To generate an RZ signal, the optical modulator is biased at a transmission maximum level and the clock signal is phase shifted. Also disclosed is an optical communication transceiver including a plurality of optical modulator circuits generating both RZ and CSRZ signals.

Abstract: Using a switching signal from a coarse/fine switching and operation mode switching circuit, the width of change of a counter control value during power up is increased, and the width of change is reduced once a steady state is reached. In the steady state, the frequency of updating is limited by a control signal from an update permit control circuit. In the steady state, the frequency band of a current source in an LD driving circuit is reduced in width.

Abstract: An optical transmitter includes a laser driver capable of receiving data and applying the data to drive a laser diode over a transmission line having first and second ends. The first end of the transmission line is coupled to an output of the laser driver. A first terminal of an amplifier is coupled to the second end of the transmission line. A second terminal of the amplifier is coupled to the laser diode. The signal amplitude applied at the first terminal controls optical output amplitude of the laser diode.

Abstract: The object of the present invention is to provide a WDM optical communication system and a WDM communication method wherein deviation of transmission characteristics of optical signals of respective wavelengths is reliably controlled, based on reception information such as the OSNR, BER and the like measured at the receiving end, thereby enabling optimal transmission conditions to be realized. For this purpose, the present WDM optical communication system transmits WDM signal light of wavelengths ?1˜?n, which has been generated by the transmitting end of one terminal station, to the receiving end of the other terminal station through an optical transmission path. At the receiving end, the OSNR and BER of the optical signals of wavelengths ?1˜?n are measured, and the result is superimposed on overhead information transmitted along the opposing line of the optical transmission path as reception information.

Abstract: A cosite interference rejection system allows cancellation of large interfering signals with an optical cancellation subsystem. The rejection system includes an interference subsystem coupled to a transmit system, where the interference subsystem weights a sampled transmit signal based on a feedback signal such that the weighted signal is out of phase with the sampled transmit signal. The optical cancellation subsystem is coupled to the interference subsystem and a receive antenna. The optical cancellation subsystem converts an optical signal into a desired receive signal based on an interfering coupled signal and the weighted signal. The weighted signal is therefore used to drive the optical cancellation subsystem. The rejection system further includes a feedback loop for providing the feedback signal to the interference subsystem based on the desired receive signal.

Abstract: An on-chip parallel data generator, including a Built In Self Test (BIST) generator, is integrated into a laser driver array of a parallel optical communication transmitter so that all optical outputs switch simultaneously. The BIST generator requires only one clock input which clocks the BIST generator for all channels. The optical outputs respond to either the on-chip BIST generator or the electrical inputs if a valid signal is present on the inputs.

Abstract: An optical transmitter for use in an optical transmitting system based on PDS (Passive Double Star) technology, does not erroneously output an optical signal when the optical transmitter is powered on/off. The optical transmitter has a current source 1 for outputting a drive current having a magnitude corresponding to an input control signal, a Laser diode (LD) for generating an optical output signal based on the received drive current, a modulator 9 for controlling the supply and cutoff of the drive current to the Laser diode (LD), a source voltage detector 3 for monitoring a source voltage to detect whether the source voltage is lower than a predetermined voltage, and a switch circuit 4 for outputting a control signal to the current source 1 to stop the supply of the drive current when the source voltage is determined to be lower than the predetermined voltage.

Abstract: In a WDM optical communication system, at least one optical tunable filter is placed along an optical fiber provided as an optical transmission path between a transmitting station and a receiving station. The optical tunable filter has a controllable transmission factor versus wavelength characteristic. In the receiving station, the transmission characteristics (for example, optical signal to noise ratios and Q factors) for optical signals of different wavelengths propagated over the optical fiber are measured. The measurements are sent to the transmitting station. The transmitting station then properly controls both the amounts of pre-emphasis in the transmitting station and the wavelength characteristic of the optical filter on the basis of the measurements to thereby equalize the transmission characteristics for the optical signals.

Abstract: The optical transmitter comprises a light source which inputs continuous optical signal and a driving circuit which inputs driving signal to an optical modulator of Mach-Zehnder type. A photo coupler separates a part of the output of the optical modulator. A photo diode converts this part into electric signal. A band-pass filter and a pre-amplifier extract a frequency component of the driving signal contained in the electric signal. A mixer conducts synchronous detection between the driving signal and the extracted frequency component. Finally, a bias voltage control circuit controls a bias voltage based on a result of the phase comparison.

Abstract: Apparatus and methods for linearizing an optical transmitter are described. A linearized optical transmitter according to the present invention includes a modulator bias voltage supply that biases an optical modulator. The optical modulator modulates an optical signal with a payload modulation signal. A feedback circuit receives electrical distortion signals generated by the modulator and generates a control signal in response to at least one of the electrical distortion signals. The control signal changes the bias voltage generated by the modulator bias voltage supply so as to reduce the at least one electrical distortion signal.

Abstract: A parallel optical module is constructed to include a plurality of photodetectors (MD1, MD2) which detect output lights of a plurality of arbitrary channels of a laser light source (3) having a plurality of channels, a plurality of detection and control loops which detect and control intensities of output lights of the laser light source based on detection signals from the plurality of photodetectors, and a control circuit (1) which stops output of the laser light source when an intensity of output light detected by at least one of the plurality of detection and control loops does not satisfy a predetermined standard.

Abstract: Disclosed is a technique for compensating for optical passband shift of an optical component (for example an optical demultiplexer). A broadband source coupled to a dispersive element generates a chirped pulsed optical signal. Data is modulated onto particular wavelengths of the chirped pulsed optical signal by appropriately synchronizing a data modulator. The modulated signal is transmitted to the downstream optical demultiplexer, which may be subject to passband shift due to, for example, changes in environmental conditions. A feedback signal from an output port of the demultiplexer is provided to the transmitter and is used to phase shift the modulator. The phase shift results in effectively adjusting the wavelength onto which the data is modulated to substantially correspond to the passband centers of the demultiplexer.

Abstract: An optical communication system suitable for a coherent optical satellite communication is configured to include an optical transmission device having a laser signal generator, a first reference laser signal generator having a first local oscillating laser signal generator and an automatic frequency controller, an optical receiving device, and a second reference optical signal generator having a second local oscillating laser signal generator. The first reference local oscillating laser signal generator and the automatic frequency controller are used to generate a fixed beat reference optical signal, and thus the optical receiving device is capable of locking the transmitted laser signal according to the fixed beat reference laser signal in a way of heterodyne receiving so as to demodulate the transmitted signal frequency accurately and resolve the problem of laser frequency drifting.

Abstract: An optical transmission circuit includes: a semiconductor laser; a drive circuit for supplying drive current to the semiconductor laser; a duty changing circuit for changing a duty value of an input data; a converting circuit for supplying a duty control signal to the duty changing circuit in order to adjust the duty value of the input data; and an adjusting circuit for supplying an optical power control signal to the converting circuit and the drive circuit. The adjusting circuit performs an initial setting of an optical power of the semiconductor laser, and the converting circuit performs the initial setting of the duty value so as to have a characteristic opposite to the optical power. According to the above structure, it is possible to realize the duty adjustment and the optical power adjustment by using only one adjusting circuit so that it is possible to achieve a simplified, miniatuarized, and low cost optical transmission circuit.

Abstract: An active assembly apparatus of planar lightguide circuit is described. The active assembly apparatus has an optical signal generating and receiving device, a feedback control device, and at least one displacement device made of piezoelectric substrate. The optical signal generating and receiving device connects to a transmitting core in a planar lightguide circuit to transmit optical signals to the transmitting core for judging an optical receiving element position and receive optical signals from the transmitting con for judging an optical emitting element position. The feedback control device determines whether the optical receiving element and the optical emitting element are at their respective best positions and, if not, controls the displacement devices to move the optical receiving element and the optical emitting element to their respective best position.

Abstract: Because the phase comparison of the light signal data row and the light clock signal, and the coding of the light signal by the light signal, are simultaneously conducted, the influence of the phase variation in the signal path is not affected in principle, and the optimum phase condition is automatically established/maintained, and thereby, the present invention operates as an all-light type light receiver by which the light data and light clock are reproduced. Further, because the electric signal used herein exists in the range from the DC to the frequency of the difference between the light signal data row and the light clock signal, problems peculiar to the high speed electric signal can be avoided.

Abstract: An optical transmission system for an optical communications system that has an optical source, an optical modulator for modulating an optical output of the optical source, and an optical filter arranged to substantially remove one of the upper and lower sidebands of the modulated optical output of the optical source. The optical transmission system further includes a control means to control at least one of the optical source and the optical filter to ensure that substantially only half of the power of the modulated optical output of the optical source is transmitted by the filter, thereby reducing the bandwidth of the optical signals transmitted by the system.

Abstract: A wavelength stabilization control device for controlling a light-wave output by a tunable component in an optical communication system, including a beam splitting component, a first photo-detecting component, a second photo-detecting component, a Fabry-Perot Etalon and an optical filtering component. The beam splitting component splits the light-wave into a first light-wave and a second light-wave. The first photo-detecting component receives the first light-wave and transforms the first light-wave into a first electric signal. The second photo-detecting component receives the second light-wave and transforms the second light-wave into a second electric signal. The Fabry-Perot Etalon is provided between the beam splitting component and the second photo-detecting component for separating a light-wave including a specific wavelength from the second light-wave.

Abstract: A high efficiency light emitting diode (LED) driver circuit utilizes a capacitor to regulate the LED driving current. The voltage across the capacitor is monitored to maintain a preselected low threshold voltage on the capacitor, which determines the LED optical emission intensity. The capacitor provides the LED driver current by discharging through the LED during transmission intervals, and the power supply for the device is used only to maintain the capacitor charge level. The LED driver circuit accordingly operates at high efficiency with low power consumption. The LED driver current can be regulated by changing the low and high threshold voltages of the capacitor pump controller, thereby to control the optical intensity of the LED.

Abstract: The present invention alms at providing a low cost optical transmitter capable of controlling, with a high precision, fluctuations in optical output characteristic of a semiconductor light emitting device such as due to a temperature change.

Abstract: A device for interactively transmitting optical signals in a first wavelength and receiving optical signals in a second wavelength both through a one-core optical fiber, includes a first photodiode that converts a received optical signal into a first electric signal, a second photodiode that converts an optical signal into a second electric signal, a first amplifier connected between the second light-electricity signal converter and the coherent light remover, a second amplifier connected to the second light-electricity signal converter, and a differential amplifier that subtracts the second electric signal from the first electric signal.

Abstract: A dispersion compensation controlling apparatus used in a very high-speed optical communication system adopting optical time division multiplexing system comprises a first specific frequency component detecting unit (2a) detecting a first specific frequency component in a baseband spectrum in a transmission optical signal inputted to a receiving side over a transmission fiber as a transmission line (6a), a first intensity detecting unit (3a) detecting information on an intensity of the first specific frequency component detected by the first specific frequency component detecting unit (2a), and a polarization-mode dispersion controlling unit (220a) controlling a polarization-mode dispersion quantity of the transmission line (6a) such that the intensity of the first specific frequency component detected by the first intensity detecting unit (3a) becomes the maximum, thereby easily detecting and compensating polarization-mode dispersion generated in a high-speed optical signal.

Abstract: Disclosed is an optical frequency controlling device for ultra-dense wavelength-division-multiplexed optical channels in which center frequencies of optical channels are aligned.

Abstract: An agile network is provided with a layered control system for maintaining a network-wide target performance parameter (e.g. power) along all end-to-end connections. A connection is controlled at the physical layer using optical control loops that have a concatenated response based on a set of loop time constants. The network is separated into gain based span loops and power based switch loops; each link has a gain profile, and requires a per-wavelength power target as the output power target for the switch loop at the start of the link. Use of achievable gain for the span loops allow to optimize the performance of the link. Use of individual achievable power targets allows each switch loop to autonomously ramp on and off channels without causing interference with existing and other ramping channels. A loop control uses a model-based rules block, to distribute control signals to an optical section encompassing a plurality of optical components.

Abstract: Plural subcarrier-multiplexed AM signals 30 are input and narrow-band-FM-modulated by a voltage controlled oscillator 4 including the fundamental carrier wave and higher-order harmonics as the output, and the FM carrier wave component of the higher-order harmonics of the fundamental carrier wave is selectively taken out by a band-rejection filter 5, shifted to the lower frequency side by a frequency converter 7, converted into an optical signal by an electric/optic converter 3 and transmitted.

Abstract: The invention provides a method and system for selectively canceling a specified frequency band in the payload of an optical communication system. This selected frequency band is to be used for launching pilot tones for power measurement and identification. The method controls the intensity of the optical payload signal through an intensity modulator that is included in the optical communication system. The frequency band in payload to be cancelled is removed where as the other frequency components of the payload are passed without attenuation. An embodiment that uses a feed-forward unit, a feedback unit and a control unit for generating a cancellation signal for the intensity modulator is described. An advantage of the method is that it removes a continuum of payload tones in the specified frequency band to be cancelled.

Abstract: The present invention is a device to increase the bit rate and distance at which data can be transmitted by optical fiber. The device compensates the polarization dispersion of the line by processing a received optical signal with the use of a polarization controller, the generation of a differential group delay between two orthogonal polarization modes and a control unit for the polarization controller. The data that is sent is redundant to enable detection of errors affecting the data received and the control unit is adapted to minimize the error rate calculated in real time by using the redundant data. The application of the device is to long-haul optical transmission, in particular over stranded fibers.

Abstract: With the use of a wavelength multiplex light source capable of being adapted to a wavelength standard channel by an easy method, wavelength multiplex optical communication equipment is realized at a low cost and with excellent repeatability in performance. In a preferred implementation, a part of output light of a tunable light source 101 is guided to a wavelength stabilizer device where the difference thereof from a predetermined wavelength is detected with the use of photodetectors and a processor and fed back to the light source via controllers. Specifically, a controller 108 supplies a widely-variable output to an upper electrode of a heater-integrated tunable laser, which is formed by mounting a thin film heater just above the upper electrode of a distributed feedback (DFB) semiconductor laser that excels in wavelength controllability. The controller and compensates for the variance of the wavelength of the output light from the predetermined frequency using the output of the processor.

Abstract: A correcting method of an optical signal transmission system that applies an optical signal generated by light-emitting action to an input end of an optical fiber and converts an optical signal arising at an output end of said optical fiber to an electrical signal by photo-electric conversion including: transmitting said optical signal by inputting said optical signal to said optical fiber and generating said electrical signal; and adjusting at least one of an electric current related to said light-emitting action and an electric current related to said photo-electric conversion according to an electric current of said electric signal.

Abstract: A method and apparatus for applying an electrical signal as a first of two inputs to a logic element, manipulating the output of the logic element such that the logic element produces a resulting electrical signal that logically transitions only when the input signal has associated with it a predetermined logic state, shaping the resulting electrical signal according to a desired RZ optical signal, amplifying the shaped electrical signal such that a maximum and a minimum signal level of the shaped electrical signal correspond to the adjacent optical power transfer zeroes of an optical modulator, and applying the amplified electrical signal as a driver input to the optical modulator.

Abstract: An optical transmitter is capable of constantly operating at an optimal operating point, even when a polarization angle varies, which is realized by an operation processing device controlling such that a predetermined range of an input-and-output characteristic of a modulator is scanned in order to obtain a bias voltage point that gives an optimal operation range, and an operation point controlling circuit controlling the operation range by a feedback control with the detected bias voltage point as a starting point.

Abstract: An apparatus and method is disclosed for protecting access to a shared medium in an optical communications system which has plural remote terminals coupled to a central terminal over the shared medium. According to one aspect, if an optical transmitter for an individual remote terminal is active for a first prescribed time interval when it has not been enabled for such transmission, the optical transmitter is disabled. According to another aspect, the continuous time that an individual terminal is enabled to transmit onto the shared medium is monitored. If the enabled transmission for the individual terminal exceeds a second prescribed time interval, the optical transmitter for the individual terminal is disabled.

Abstract: In an optical amplifier according to the present invention, a change signal from a change signal source is fed into a light source or a drive circuit. The wavelength of light outputted from the light source is changed based on the change signal. The wavelength-changed output light from the light source is outputted as pumping light from a pumping light generator to be supplied backwardly via an optical multiplexer/demultiplexer into an optical fiber. Signal light is Raman-amplified in the optical fiber with the supply of the pumping light.

Abstract: The present invention relates to an optical communication apparatus for detecting the intensity of light in an optical modulator or the intensity of a modulation signal and for controlling the operating point of the optical modulator based on the result of detection. In the optical communication apparatus having such a configuration, the operating point of the optical modulator can be kept stable even when the input light or the modulation signal is temporarily non-existent in the optical communication apparatus.

Abstract: The invention provides an optical communication system, an optical transmitting apparatus, an optical receiving apparatus, an optical communication method, and a storage medium, in which a large-capacity transmission can be performed at high speed and multiplexing efficiency can be improved. The optical communication system includes an optical transmitting apparatus and an optical receiving apparatus connected via a transmitting medium having anomalous dispersion characteristics. In this system, the optical transmitting apparatus converts a plurality of information signals output from a plurality of signal sources into light signals having amplitudes different according to the respective information signals to output the light signals LP, by providing an individual specified optical intensity capable of performing an optical soliton transmission.

Abstract: In an optical transmitter, continuous wave light from a laser passes through a data modulator (DM) for non-return-to-zero (NRZ) encoding of a data stream and through a pulse modulator to add return-to-zero encoding to the modulated optical signal. A modulator controller monitors the output optical signal power, optimizes the bias setting for the DM and the PM, and optimizes the phase relationship between the pulse and data components of the modulated optical signal. For each optimization, a low amplitude and low frequency dither signal is injected at appropriate points in the modulator. A single photo detector and electrical receiver are used in a multiplexed fashion to monitor the optical output signal and derive separate feedback signals. Remaining control circuitry forces a null in a respective residual dither component in the optical output signal to maintain the desired bias level or phase alignment.

Abstract: A dynamic range extender for optical transmitters comprises a bipolar distortion compensator for increasing drive signal gain as the absolute level of an input signal increases beyond a selected input voltage threshold, a signal coupler for dividing the input signal into complementary signals, a unipolar distortion compensator for increasing drive signal gain of each complementary signal beyond a selected forward current threshold, a signal clipper for pre-clipping each complementary signal below a selected clipping threshold, and complementary driver outputs to drive each of a pair of laser diodes in a complementary push-pull arrangement. The pre-clipping prevents the laser diodes from being driven below their threshold current level, and the distortion compensation suppresses second and third order harmonic distortion when the complementary signals generated by the laser diodes are combined by differential photodiodes.

Abstract: The transmission device comprises a transmission unit (1) having a plurality of useful lasers (3b to 3m), which are arranged in a row (2) and emit useful radiation vertically with respect to the covering area (1b) of the transmission unit. In order to regulate the useful radiation power, a monitor receiver (20a) is arranged on a mounting plane (26a) which is laterally adjacent to the transmission unit (1) and lies above the covering area (1b). The monitor receiver projects above an assigned monitoring laser (3a) like a cantilever support in such a way that its radiation-sensitive area (23a) is opposite the optically active zone (4a) of the monitoring laser (3a).

Abstract: A linear laser diode driver circuit is provided in which a solid state laser diode and its back-facet photodiode are configured into the feedback loop of a high-speed operational amplifier. In this configuration, the light output from the laser diode is directly proportional to the input voltage to the operational amplifier and is independent of the laser diode's temperature characteristics.

Abstract: A laser transmitter comprising a laser diode (1) and a monitoring photodiode (2) adapted to receive a small part (LS1) of a light signal (LS) of the laser diode and to derive therefrom an output current (SC). The transmitter further comprises regulation means (4) adapted for receiving the output current and for sending a signal (CS) to a current driver (5) in order to regulate the input current (IC) of the laser diode (1) as a function of this output current (SC). The transmitter also comprises a register (6) adapted to store data to be used by the regulation means (4) or to be read by a serial interface, and pattern detection means (7) adapted to scan all the traffic and thus all the packets of the upstream flow to the laser diode (1) to check whether pre-determined bit-patterns are present.