Abstract: An exemplary photo-electronic frequency multiplier (100) includes an intervening optical signal generator (10), a pair of photo-electronic conversion circuits (21, 22), a differential amplifier circuit (30), and a signal processing circuit (40). The intervening optical signal generator includes a light source (11), a first mirror (12), a first reflector (14), a second reflector (15), an optical phase modulator (16), and a second mirror (13). The intervening optical signal generator is for generating two intervening optical signals. Each photo-electronic conversion circuit is for converting one intervening optical signal into an electronic signal. The differential amplifier circuit is for multiplying the difference between the two electronic signals and outputting an amplifying signal. The signal processing circuit is for processing the amplifying signal to generate a signal having a plurality of frequency multiplications.

Abstract: The signal converter of the present invention receives a multichannel video signal and converts the video signal into a microwave signal, the phase of which has been modulated with the video signal. The signal converter includes: a laser light source; a modulating section for modulating the phase of output light of the laser light source with the multichannel video signal and modulating the intensity of the output light with the microwave signal; and a light receiver for receiving the output light modulated by the modulating section and for outputting the microwave signal, the phase of which has been modulated with the multichannel video signal.

Abstract: In accordance with the invention, an optical data transmission system of enhanced flexibility is provided by sub-band multiplexing of a WDM channel. Specifically, an exemplary optical data transmission system comprises an optical source for generating a plurality of frequency spaced optical tones within at least one WDM channel, a plurality of modulators for modulating the tones, and an optical transmission fiber for receiving and transmitting the modulated tones. An advantage of this system is that the tones are coherent. As a consequence, the need for guard bands is substantially reduced, and more flexible coding systems can be used to achieve a higher level of integration. For example, both amplitude and phase coding can be applied to the sub-band signals.

Abstract: An optical spike is generated at an arbitrarily selected location within an arbitrary optical link. The optical spike is generated by deriving a spike signal having a plurality of components, and launching the spike signal into the a transmitter end of the optical link. An initial phase relationship between the components is selected such that the involved signal components will be phase aligned at the selected location. In order to achieve this operation, the initial phase relationship between the components may be selected to offset dispersion induced phase changes between the transmitter end of the link and the selected location. One or more optical spikes can be generated at respective arbitrarily selected locations within the link, and may be used for performance monitoring, system control, or other purposes.

Abstract: A fiber optic communication system comprising: an optical signal source adapted to produce a frequency modulated signal; and an optical spectrum reshaper (OSR) adapted to convert the frequency modulated signal into a substantially amplitude modulated signal, wherein the optical spectrum reshaper is adapted to compensate for at least a portion of a dispersion in a transmission fiber; and further including a transmission fiber coupled to the optical source, a receiver and a decision circuit coupled to the transmission fiber.

Abstract: With a single laser light source, the line width of a beat signal is set to a few tens of kHz or less without it fluctuating over time, and the frequency thereof is set as desired. CW light from a CW laser light source is input into an electroabsorption modulator to which a sine wave electrical signal is applied. A modulation sideband which is made up from line spectra at separations equal to the modulation frequency is generated from the electroabsorption modulator. An optical fiber for higher-order soliton compression broadens the optical spectrum width, and increases the number of line spectra. A tunable wavelength filtering device which is made up from optical fiber gratings and optical circulators chooses two of the line spectra, which are combined by an optical coupler with their beat signal being heterodyne wave detected by a photo-detector.

Abstract: A termination device for use in a WDM-SCM PON system can effectively support a multi-channel integration function of a WDM/SCM PON system.

Abstract: An optical transmitter includes an optical modulator, an optical coupler, a crosspoint monitoring unit, a reference-value setting unit, and a bias circuit. The optical coupler splits an optical signal output from the optical modulator into a plurality of optical signals. The crosspoint monitoring unit receives part of the optical signals, and monitors a crosspoint of the optical signal output from the optical modulator. The reference-value setting unit sets a bias reference value to be assigned to the optical modulator based on an output of the crosspoint monitoring unit so that the crosspoint is constant. The bias circuit applies a bias to the optical modulator based on the bias reference value.

Abstract: An object of the invention is to clear up factors in deterioration due to optical reflection and to provide an optical transmission apparatus and an optical transmission system in which a superior optical transmission characteristic can be obtained for analog signals even if a reflection phenomenon occurs in an optical transmission line. There are provided a frequency converter (3) for converting the frequency band of a to-be-transmitted electric signal into a predetermined frequency band higher that this frequency band, and a semiconductor laser (4) serving as an electro-optic converter for performing electro-optic conversion upon the frequency-converted electric signal.

Abstract: There is provided a fiber optic system comprising: a multi-wavelength source adapted to generate frequency modulated signals having different wavelengths, ?1, ?2, . . . , ?n; and an arrayed waveguide grating adapted to convert the multiplicity of frequency modulated signals into a multiplicity of substantially amplitude modulated signals, and spatially combine the different wavelengths ?1, ?2, . . . , ?n. And there is provided a method for transmitting an optical signal through a fiber comprising: operating a multi-wavelength source so as to generate frequency modulated signals having different wavelengths, ?1, ?2, . . . , ?n; passing the frequency modulated signals through an arrayed waveguide grating so as to convert the frequency modulated signals into substantially amplitude modulated signals, and spatially combine the different wavelengths ?1, ?2, . . . , ?n; and passing the substantially amplitude modulated signals into the fiber.

Abstract: Systems for wireless communication may select a photonic signal to generate a carrier frequency for wireless communication. In an illustrative example, the selected photonic signal may have sidebands with a frequency difference corresponding to a carrier frequency within one of multiple predetermined carrier frequency bands. In some implementations, each of the predetermined carrier frequency bands may contain a local minimum signal attenuation characteristic over a signal path of the wireless communication. For example, the selection of the photonic signal may be based on predetermined selection criteria such as error information, and/or signal path conditions (e.g., atmospheric humidity level, noise, signal strength). Apparatus for performing such methods may include a wireless communication system with a transmitter and/or receiver.

Abstract: A method of transmitting an optical communications signal, comprising receiving a first signal, encoding the signal with a differential or duobinary encoding scheme, encoding the signal with an oscillating signal component, and sub-carrier modulating the signal onto a sub-carrier of an optical carrier signal. The invention also relates to corresponding systems and apparatuses.

Abstract: An optical frequency modulated transmitter includes a plurality of separately phased-controlled slave lasers, the outputs of which are combined to form a single output beam of the transmitter. A master optical oscillator outputs an optical signal for injection locking the plurality of slave lasers, the optical signal being frequency modulated directly in the master optical oscillator or externally thereof. Additionally, a method of frequency modulating an optical beam is disclosed using a plurality of slave lasers. Each of the slave lasers has an output, the outputs of which are combined to form the optical beam. The plurality of slave lasers is injection locked to an optical output of a master oscillator. The optical output of the master oscillator is frequency modulated before the optical output is applied to the plurality of lasers. Each slave laser of the plurality is phased controlled relative to other slave lasers of the plurality.

Abstract: An optical RZ transmitter comprises an optical signal source and a pair of electro-optical modulators in tandem, one arranged to receive a NRZ electrical data signal and the other a clock signal at the data rate of the data signal. The phase difference between the data signal and the clock signal is controlled by adding a first dither signal to a bias signal applied to the modulator receiving the data signal, and a second dither signal, having a different frequency, to the phase difference. The amplitude of variations in the power of the optical output signal corresponding to cross-modulation of the first and second dither signals is detected and the phase difference is controlled in response to the detected amplitude.

Abstract: An optical modulator is overdriven to increase its nonlinearity and therefore improve its response as it pertains to differential phase shift keyed (DPSK) transmission and a method of operating the same. In one embodiment, the MZM includes an MZM drive circuit coupled to the electrodes and configured to deliver to the electrode a DPSK drive signal bearing digital data and having a voltage that exceeds a normal drive voltage of the MZM by at least about 20%.

Abstract: A data modulation apparatus is proposed that includes a data modulator (20) for modulating data onto an optical signal at a predetermined bit rate. The resulting encoded optical signal is phase modulated by a phase modulator (50) that is driven by at least one waveform of a frequency that is 1/n of the predetermined bit rate, where n is an integer greater than 2. The application of a phase modulation at a frequency of a third or less of the bit rate of a digital data signal increases the non-linear tolerance of a transmission system by reducing the effect of non-linear pulse-to-pulse interactions. Moreover, this increase in non-linear tolerance is significantly better than that obtained by a phase modulation at one half of the data bit rate, while the implementation of a phase modulator at this lower frequency reduces the complexity of the transmitter.

Abstract: A method for transmitting digital data includes splitting a coherent optical carrier having a subcarrier into mutually coherent optical carriers, producing corresponding sequences of phase shifts in each of the mutually coherent optical carriers, and then, interfering the mutually coherent optical carriers. The interfering produces an output optical carrier whose subcarrier has modulated inphase and quadrature components with a corresponding sequence of pairs of values. The pairs of values of the modulated inphase and quadrature phase components produced by the interfering correspond to a sequence of coordinate pairs for the signal points the 4-PSK 2D, 16-QAM 2D, or 16-PSK 2D constellation.

Abstract: There is provided a fiber optic transmission system, comprising: an optical signal source adapted to produce a frequency modulated signal; and a multi-ring resonator optical spectrum reshaper (OSR) adapted to convert the frequency modulated signal into a substantially amplitude modulated signal. And there is provided a method for transmitting an optical signal through a fiber comprising: producing a frequency modulated signal; passing the frequency modulated signal through a multi-ring resonator optical spectrum reshaper (OSR) so as to convert the frequency modulated signal into a substantially amplitude modulated signal; and passing the substantially amplitude modulated signal into the fiber.

Abstract: A 90 degree Alternate-Phase (AP) on-off keying (OOK) transmission format for high bit rate, long-haul optical transmission systems employing a chirped or a chirp-free pulse stream generated by a pulse generator (e.g., Mach Zehnder modulator) driven by mixing two electrical signals—one for intensity modulation and another for pulse modulation. These electrical signals may be two properly skewed sinusoidal electrical signals at half the desired data rate thereby generating a pulse stream in which the maximum optical phase modulation occurs at the intensity peak of each pulse and is 90 degrees out of phase with its nearest neighbors.

Abstract: An apparatus for accelerating assessment of an optical transmission system using Bit Error Rate (BER) tests calculates Q-factors for at least two different extinction ratios from measured test BER values, and extrapolates to determine a Q-factor for an operational extinction ratio, whereby the operational BER value for the operational extinction ratio can be calculated.

Abstract: The present invention relates to a device for detecting or generating and modulating optical signals, and having an angular dispersive element arranged to change angles of the optical signals or carrier and/or reference rays brought to interference.

Abstract: An optical transmitter comprises an amplitude modulation unit performing amplitude modulation of only a one-side amplitude of a main signal with a low-frequency signal having a predetermined frequency. An optical modulator receives an input signal generated after the one-side amplitude modulation, and modulates an incoming light in response to the received signal in accordance with a predetermined modulation-characteristic curve to output an optical output signal. An operating point control unit applies a predetermined bias voltage to the optical modulator to control a level of the input signal substantially applied to the modulation-characteristic curve so that the one-side amplitude of the main signal is applied to a minimum portion of the modulation-characteristic curve of the optical modulator.

Abstract: Processing a received optical signal in an optical communication network includes equalizing a received optical signal to provide an equalized signal, demodulating the equalized signal according to an m-ary modulation format to provide a demodulated signal, decoding the demodulated signal according to an inner code to provide an inner-decoded signal, and decoding the inner-decoded signal according to an outer code. Other aspects include other features such as equalizing an optical channel including storing channel characteristics for the optical channel associated with a client, loading the stored channel characteristics during a waiting period between bursts on the channel, and equalizing a received burst from the client using the loaded channel characteristics.

Abstract: A method and system for transmitting information in a wavelength division multiplex (WDM) or other suitable multichannel optical communication system includes receiving a multichannel signal having a symbol rate and comprising a plurality of non-intensity modulated optical information signals. The non-intensity modulated optical information signals have a minimum channel spacing comprising a multiple of the symbol rate within 0.4 to 0.6 of an integer. The non-intensity modulated optical information signals are separated from the multichannel signal and each converted into an intensity modulated optical information signal using an asymmetric interferometer. A data signal is recovered from the intensity modulated optical information signal.

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

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

Abstract: An optical transmitter-receiver is provided which is suitable for a high-speed optical communication system. A high-frequency electric line on a mounting substrate becomes a traveling-wave electrode of a semiconductor optical element equivalently by the following steps: separately manufacturing the mounting substrate having the high-frequency electric line, and the semiconductor optical element for which high-frequency design has been applied beforehand; and then bonding and mounting of drive electrodes of the mounting substrate and the semiconductor optical element through a soldering material. In addition, it is also possible to have a configuration in which not only junction down mounting of high-frequency semiconductor optical elements, but also that of an electronic element for electrically driving and controlling a light source such as a semiconductor laser and for electrically driving and controlling a high-frequency semiconductor optical element, is performed on the mounting substrate.

Abstract: A communication system comprises a phase encoder, a phase shifter, and a modulator. The phase encoder receives user data and phase encodes the user data to form an encoded signal representing the user data. The phase shifter shifts a phase of the encoded signal to generate a phase shifted signal. The modulator receives a first optical signal and modulates the first optical signal with the encoded signal and the phase shifted signal to form an optical single sideband signal representing the user data. The modulator then transmits the optical single sideband signal representing the user data.

Abstract: A transmitter for optical communication systems includes a source of optical radiation, a source of complex non-information signals, and a modulator unit in communication with the source of optical radiation. The modulator unit is also in communication with the source of complex non-information signals. The modulator has an input adapted to receive information-bearing signals.

Abstract: The invention relates to optical communications using techniques for providing efficient high speed polarization bit interleaving. One common architecture for high-speed time-division-multiplexing employs two modulators having a same bit rate, wherein two separately modulated streams of data bits are combined into a high-speed single serial stream of data bits, instead of providing a single higher-cost higher-speed modulator. The present invention has found with the availability of fast data modulators, that polarization bit interleaving can be employed more efficiently for higher speed data transmission in optical network systems by providing an optical modulator including a single data modulator, rather than multiplexing different data streams from different modulators.

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 transmitter enables output of high-power light signals while effectively suppressing occurrence of the nonlinear optical phenomena, particularly, SBS, and an optical communication system provided therewith. The optical transmitter comprises a modulation signal source for outputting modulation signals of the frequency not more than 20 kHz, a semiconductor laser source for outputting laser light amplitude-modulated according to the modulation signals from the modulation signal source, an optical amplifier for amplifying the laser light from the semiconductor laser source, and a modulation depth control system for controlling a ratio of an amplitude modulation depth of amplified laser light outputted from the optical amplifier to an amplitude modulation depth of the laser light outputted from the semiconductor laser source.

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: An RF-lightwave transmitter performs successive conversions of an information-bearing input signal in order to generate an output signal suitable for transmission in a wireless communications system. The transmitter includes a high-efficiency FM laser connected to a FM discriminator. In operation, the laser converts an RF signal into a frequency-modulated optical signal, and the discriminator converts this signal into an amplitude-modulated optical signal. The discriminator performs its conversion using a high slope-efficiency linear transfer function which ensures that the AM optical signal varies in accordance with a desired operational performance. The transmitter also includes a photodiode which converts the AM signal output from the optical discriminator back into an RF signal for transmission. Experimental results demonstrated that a transmitter of this type is able to realize greater than 10 dB RF insertion gain at less than 0 dBm optical power, with a high spurious-free dynamic range and low noise.

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

Abstract: 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: In a multi-channel video optical transmission system comprising an optical transmitter and an optical receiver, a frequency modulation function incorporated pilot signal generating unit is provided in the optical transmitter to generate a pilot signal frequency-modulated. This frequency-modulated pilot signal is superimposed on a multi-channel video signal inputted thereto and is converted into a frequency-modulated signal in a frequency modulator, and is transmitted through an optical fiber to an optical receiver in a state converted into an optical signal in a semiconductor laser device. In the optical receiver, the optical signal is again converted into an electric frequency-modulated signal in a light-receiving device and, after amplified in an amplifier, is demodulated in a frequency demodulator, thereby regenerating the multi-channel video signal before the input to the frequency modulator.

Abstract: A method and system for demultiplexing non-intensity modulated wavelength division multiplexed (WDM) signals includes receiving a WDM signal having a plurality of non-intensity modulated optical information signals. A plurality of the non-intensity modulated optical information signals are converted to intensity modulated signals while the plurality of non-intensity modulated optical information signals are multiplexed in at least a portion of the WDM 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: The device includes an oscillator (1) to generate an electrical signal of a predetermined frequency and a signal divider (2) to split the electrical signal into first and second signals. The frequency of the second signal is tripled by tripler (3) and the tripled second signal is recombined with the first signal at signal adder (9) to produce a combined electrical signal. This combined electrical signal drives a Mach-Zehnder modulator (10).

Abstract: A wavelength Division Multiple Access (WDMA) free space broadcast technique for optical backplanes and interplanar communications for providing free space optical interconnects between multiple circuit cards in a computer system or networking device which is compatible with existing electrical backplanes. Current equipment can easily be upgraded in the field to take advantage of this new approach by simply replacing existing printed circuit boards, without requiring a complete redesign of the copper backplane.

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: A branch portion 101 branches an inputted electrical signal into an in-phase signal and an opposite phase signal which have an opposite relation as to a phase. A first FM laser 104 converts the in-phase signal into an optical frequency-modulated signal (a first optical signal) having a center wavelength ?1 and then outputs the resultant signal. A second FM laser 105 converts the opposite phase signal into an optical frequency-modulated signal (a second signal) having a center wavelength ?2 and then outputs the resultant signal. The two optical signals are combined and then inputted into an optical-electrical converting portion 106. The optical-electrical converting portion 106 subjects the inputted optical signals to optical heterodyne detection by its square-law detection characteristic, and outputs a beat signal between the two optical signals which is a wide-band FM signal at a frequency corresponding to a wavelength difference ??(=|?1??2|) between the first optical signal and the second optical signal.

Abstract: The present invention relating to a device and method for multiplication of repetition frequency in optical pulse trains. The device and the method multiply repetition frequency of optical pulse train generated with ML-FRL with high stability. The device comprises an optical fiber ring composed of optical fibers, an optical amplifier and a modulator for optically modulating, and an electric signal generator generating high frequency signals. The device generates an optical pulse train of repeating frequency of fm, when applying electric signals of frequency of fm to the modulator. In addition to the construction, the stabilized optical pulse generator comprises a filter passing through frequencies of integer multiple of the applied modulation frequency fm, and a composite cavity composed of a plurality of optical fibers of which lengths are different each other.

Abstract: A system which improves wavelength tolerance, compensates dispersion in a simple way, reduces limitation of the fiber input power is disclosed. The operation includes receiving a clock signal from a system clock source; modulating a single mode optical signal based on the clock signal and generating an optical pulse signal having two longitudinal modes, the frequency interval thereof being n×B, n being a natural number and B being a transmission speed; generating a partial response signal by converting a binary NRZ signal from a digital signal source in synchronism with the system clock source; and modulating the optical pulse signal based on the partial response signal, and outputting a binary RZ modulated signal. The binary RZ modulated signal is input into a receiver, where two partial response components in the optical spectra of the input signal are divided, and one or both of the components are received.

Abstract: A method and apparatus are provided for transmitting and receiving multiple RF/microwave subcarriers on a single optical wavelength over an optical link. The method includes the steps of modulating a plurality of RF/microwave subcarrier frequencies with a respective communication signal and modulating an optical carrier wave with the plurality of modulated RF/microwave subcarrier frequencies.

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: 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 method and system for optimization of an optical transmissions signal which is modulated with a binary data signal, wherein a control device ensures that the operating point and the modulation signal of a Mach-Zehnder modulator are set optimally, with the fundamental frequency and/or the first harmonic frequency of the transmission signal being selected for this purpose, and an optimum setting is reached when the amplitude of the fundamental frequency has reached a maximum value and the amplitude of the harmonic frequency has reached a minimum value.

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