Abstract: There is provided a WDM optical transmission system and transmission method that have excellent spectral efficiency. The WDM optical transmission system is provided with: an optical transmitting section having an optical transmitter that generates N wave (wherein N is an integer of 2 or greater) optical signals with an optical frequency spacing ?f [Hz] and modulated by a modulation bit rate B [bit/s] (wherein B/?f?1 [bit/s/Hz]) using a modulation device, and having a coupler that couples the optical signals; an optical receiving section provided with an optical DFT circuit of a sampling frequency ?f [Hz] that is equal to the optical frequency spacing; and a bit phase adjustor that makes bit phases of respective wavelength division multiplexed signals synchronous at an input of the optical DFT circuit.

Abstract: Binary information is subjected to RZ encoding and multi-level encoding, and the encoded signal is optically modulated.

Abstract: An optical network terminator for terminating and reducing the accumulated noise in optical networks, particularly ring based networks. The terminator eliminates problems of noise accumulation from amplifier spontaneous emission (ASE), thermal noise, etc., while providing bi-directional communications in the optical network. The optical network may have any topology including ring, star, mesh, point-to-point, etc. In the case of an optical ring, the ring is broken and an optical terminator is placed in line therewith. The optical network terminator includes a filer such as an optical demultiplexer/multiplexer or Fiber Bragg Grating (FBG) based filter. Each individual wavelength of light is filtered and a multi-wavelength optical output is generated whereby the noise accumulation is removed. Each channel is adapted to only pass a band-limited signal around the center frequency corresponding to the wavelengths supported by the particular optical ring network.

Abstract: A high-speed optical transmitter having an optical modulator and a driver circuit while maintaining optical modulator performance. The high-speed optical transmitter comprises the optical modulator which modulates and outputs an input light in accordance with an applied voltage, and a driver circuit which outputs the applied voltage into the optical modulator and has an emitter follower circuit at an output stage thereof.

Abstract: An iterative process is used to set the phase prechirp of a WDM optical transport system to a system's optimal level that maximizes the signal quality. A signal degradation factor takes into account linear and non-linear effects along the optical path and is used as a receive end feedback signal to control the phase prechirp level at the transmitter site. By using the FEC corrected errors rate as the feedback signal, optimization of signal quality is performed even when the system is running error free. By using an adaptive phase prechirp transmitter, signal degradation compensation can be also performed on a per wavelength basis to compensate for the residual dispersion slope and to allow optimization of individual channels independently of the net link dispersion value.

Abstract: A transmitter comprises an oscillator, a phase lock loop, a serializer, and an electrical-to-optical converter. The oscillator is enclosed in a metal shield. The metal shield is soldered to a ground ring of the printed circuit board. In one embodiment, the oscillator is voltage-controlled oscillator.

Abstract: A system that transmits amplitude modulated data in a wavelength-encoded format and then uses a wavelength-sensitive receiver to convert the received optical signal back to the original amplitude modulated data. This system enables transmission of optical signals that are less sensitive to attenuation and attenuation changes. This system is applicable to data in digital, multilevel, or analog formats.

Abstract: Systems, apparatuses, and methods for driving an optical source with a current source. The optical source driver has a primary control loop having a DC—DC converter and an operational amplifier, wherein the DC—DC converter has a power input, a power output connected to the input of the optical source, and a control input, and wherein the operational amplifier has a first input connected between the optical source and the current source, a second input, and an output connected to the control input of the DC—DC converter, for controlling the output of the DC—DC converter in response to a control signal at the second input.

Abstract: A detector outputs a detection signal indicating amplitude variation of an input frequency-multiplexed signal. An amplitude controller adjusts the amplitude of the frequency-multiplexed signal by referring to the detection signal. A modulator modulates the amplitude-adjusted frequency-multiplexed signal to produce a predetermined modulated signal. A second multiplexer multiplexes the modulated signal and the detection signal to produce a multiplexed signal. An optical transmitter converts the multiplexed signal into an optical signal, and then sends it out to an optical transmission path. An optical receiver converts the received optical signal into an electrical signal. A separator separates the modulated and detection signals from the electrical signal. A demodulator demodulates the modulated signal to output the frequency-multiplexed signal. An amplitude adjuster adjusts the amplitude of the frequency-multiplexed signal by referring to the detection signal to reproduce the original amplitude variation.

Abstract: An optical reception apparatus comprises an optical receiver to receive an optical signal from an optical transmission line, an error corrector to correct an error of the received signal and to transmit the error-corrected signal and error rate information before error correction, a judging apparatus to judge transmission quality of the optical transmission line according to the error rate information from the error corrector and a threshold value equal to an error rate lower than an error correction limit of the error corrector, and a selective breaker to transmit the signal whose error is corrected by the error corrector in normal state and to block transmission of the signal whose error is corrected by the error corrector when the judged result by the judging apparatus indicates deterioration of the transmission quality of the optical transmission line.

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) con trolling 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: A method and system for dispersion control of electromagnetic signals in communication networks by narrowing the widths of electromagnetic pulses such as modulated laser signals. Generally, in the preferred embodiment, the present invention utilizes a feedback loop based on dither frequency modulation which dynamically adjusts the alignment of the laser center frequency with the filter passband. In this way, there is an acceptable tradeoff between optical power and pulse width, so a higher power laser can be used to generate a narrower optical pulse. The narrower pulses then travel farther in the fiber link before reaching their dispersion limit. It is believed that, by using this invention, existing link distance could be doubled, while re-using existing installed singlemode fiber. The systems employing the feedback loop may be information carrying or control systems.

Abstract: A single-stage all-pass optical filter is disclosed that may be applied to generate a large tunable delay of an optical pulse train. The all-pass optical filter includes an input port for receiving an input optical pulse having a regular repetition rate; an output port; a splitter/combiner; and one feedback path. A plurality of frequency-dependent time delay periods are applied to the input optical pulse so that the filter is characterized by a time-delay spectrum having a plurality of delay peaks. The free-spectral range (FSR) of the filter, i.e., the spacing between the delay peaks, is matched to the regular repetition rate of the input optical pulse. This matching is accomplished by the FSR being equal to the repetition rate or offset from the repetition rate to a sufficiently small degree that each frequency of the pulse train will fall within the bandwidth of one of the plurality of delay peaks.

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: 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 apparatus and associated method for generating predistortion IMD in a predistortion circuit. The method comprising adjusting the bias voltage, adjusting the bias current; adjusting the gain of the amplifier; and adjusting the differential bias current flowing through each diode in an antiparallel diode pair. In one aspect, the bias voltage, the bias current, the gain of the amplifier, and the differential bias current can be iteratively adjusted to generate both even-order and odd-order predistortion IMD.

Abstract: Optical transmission systems of the present invention include at least one optical amplifier generally including an optical signal amplifying medium supplied with pump power in the form of optical energy in via an optical pump source. The pump source includes multiple optical sources, at least two of which provide optical energy in first and second wavelength ranges separated by a frequency difference. The amplifier includes a wavelength controller configured to adjust the wavelength range of at least one of the optical sources to vary the frequency difference in a manner sufficient to vary optical intensity noise produced when the optical energy from the multiple optical sources is combined.

Abstract: In order to obtain an optical transmitter module for converting an input electric signal to a light signal with fidelity and outputting it therefrom, a terminal resistor Rt and an optical modulator MD are connected in parallel within a package including a laser diode with a monolithically integrated optical modulator for obtaining the light signal according to the electric signal. One thereof is grounded and the other thereof is connected to a wire inductance (L1) and an impedance matching resistor Rd in series with this parallel connection. Further, a high frequency transmission line (micro-strip line) MSL for the transmission of the electric signal is connected to the other end of the impedance matching resistor Rd.

Abstract: A transmitter that performs stimulated Brillouin scattering suppression is provided. The transmitter includes a non-linear device having an optical input adapted to receive an optical signal, an amplitude modulation input adapted to receive an amplitude modulation signal, a phase modulation input and an output. The transmitter also includes a stimulated Brillouin scattering (SBS) oscillator/driver having first and second oscillators coupled to the phase modulation input of the non-linear device and an amplifier coupled to the output of the non-linear device. The transmitter further includes a laser coupled to the optical input of the non-linear device.

Abstract: An optical transmitter and methods of generating an optical signal having SBS suppression are described. An optical transmitter having SBS suppression according to the present invention includes a signal generator that generates a SBS suppression signal. A laser generates a line width broadened optical signal having AM noise. A signal processor generates a modified SBS suppression signal from the SBS suppression signal. A modulator modulates the line width broadened optical signal having the AM noise with a payload modulation signal and with the modified SBS suppression signal to generate a payload modulated optical signal having SBS suppression and reduced AM noise.

Abstract: Optical transmission being performed by frequency modulating frequency-division-multiplexed multi-channel signals as a single unit, distortion that is caused by a ripple-shaped group delay deviation in a transmitter 2, a receiver 4 and an optical link 3 is reduced by providing a level adjuster 2a for adjusting the level of frequency-division-multiplexed multi-channel signals input to the FM modulator 2b, and by increasing the input level of multi-channel signals to the FM modulator 2b by level adjusting means 2a to enlarge the bandwidth of FM signal, in the case where the number of channels is small.

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: An optical transmission system comprising an input for accepting a signal, a laser diode within an optical transmitter for signal modulation and/or for signal amplification, a nonlinear material for compensating signal distortions, a transmission fiber for signal transmission, and an optical receiver for receiving the signal. The optical transmission system may include a multiple of input signals, each input signal fed into one of a multiple of optical transmitters. Each of the multiple of optical transmitters is coupled to a nonlinear material. The output of each nonlinear material is coupled to an optical multiplexer for multiplexing the multiple of input signals into a multiplexed signal for transmission through a transmission fiber. The multiplexed signal is then de-multiplexed into a multiple of de-multiplexed signals, each de-multiplexed signal corresponding to each of the multiple of input signals, and each de-multiplexed signal is received by one of a multiple of receivers.

Abstract: An optical transmitter for compensating signal distortion, the optical transmitter includes an input for accepting a signal, a laser driver for amplifying and/or reshaping the signal, a distributed feedback laser diode coupled to the laser driver for signal modulation, a nonlinear material coupled to the distributed feedback laser diode for compensating signal distortions caused by the laser diode, and an output for sending the signal to the transmission link.

Abstract: To increase the bit rate at which and the distance over which data can be transmitted by optical fiber, polarization dispersion is compensated by means of a polarization controller, a system for generating a differential group delay between two orthogonal modes of polarization and a control unit of the polarization controller. A chromatic dispersion compensator applies compensation which is adjusted dynamically to optimize the quality of the received optical signal. Applications include long-haul optical transmission on standard fibers.

Abstract: A predistortion generator for coupling in-line with a non-linear device produces an output predistorion signal of useful amplitude, but with low composite triple beat and cross modulation distortions. The predistortion circuit comprises a distortion circuit which utilizes the non-linear current flowing through at least one diode, to provide a desired amount of signal attenuation bandwidth. The distortion generator circuitry is always matched to the non-linear device, thereby ensuring a frequency response that is predictable and predefined.

Abstract: Part of the invention is a method for electronic equalizing an optical transmitter comprising the following steps.

Abstract: To transmit a digital signal over an optical fiber link, the digital signal is modulated onto an optical carrier using frequency shift keying modulation at a modulation index of h<0.5. Under the impact of a non-linear transmission effect in the optical fiber, the use of a modulation index h<0.5 leads to an increase in maximum permitted launch power of the optical signal, increased receiver sensitivity and an increased spectral efficiency.

Abstract: An analog optical link (10) that provides high-fidelity over bandwidths greater than 1 GHz is presented. The analog optical link (10) includes a transmitter (18) having an optical modulator (20) and a receiver (16) having an optical demodulator (12). In one embodiment, the modulator (20) is a phase modulator (20) and particularly a pre-emphasis phase modulator (20) that operates as a frequency modulator at low frequencies. The demodulator (12) is a frequency demodulator (12) that includes a feed-forward function for cancelling noise.

Abstract: A distortion monitor for a non-linear device is provided. The control circuit includes an input coupleable to receive a signal from the non-linear device and a first frequency monitor coupled to the input. The frequency monitor monitors the level of one of even and odd order distortion at a first frequency and creates a first signal indicative of the level of the distortion without the use of a pilot tone.

Abstract: A light source with a broadband frequency-periodic output spectrum for digital spectrally coded data, whereby the light source consists of a solid state laser that is frequency-modulated or phase-modulated within one bit period.

Abstract: An optical transmitter having a function which compensates for wavelength dispersion is provided with a plurality of light sources for outputting light having wavelengths that differ from one another. Before the optical transmission system begins operating, the wavelength of light output to an optical transmission line is varied by changing over the light sources in order to detect a wavelength whose transmission characteristic is optimum with regard to wavelength dispersion exhibited by this optical transmission line. During system operation, the light having the detected optimum wavelength is output to the optical transmission line.

Abstract: An optical transmission system comprises a transmitter 1 having an optical source 2 adapted to emit light, a modulator 4 operable to modulate the light to produce a modulated optical signal and a dispersion element 8 adapted to apply dispersion to the modulated optical signal. The optical signal being modulated by the application of predetermined chirp thereto and the modulated optical signal having predetermined dispersion applied thereto, such that the signal is discernible at a point, along either a positive or negative dispersion fibre 16, in a range between a minimum and a maximum distance relative to the transmitter 1.

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.