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: Techniques for coupling output laser beams from multiple lasers into multiple fibers and using a collimating lens and a steering mirror to individually couple the laser beams from the fibers to a laser control system.

Abstract: The invention relates to an optoelectronic arrangement having a laser component. There are provided: a cooling device of small design for cooling the laser component down to a constant temperature, a device for the direct optical detection of the emitted wavelength of the laser component, whose signal is used to control the cooling device, and a package of small design with an extent of at most 6.5 mm perpendicular to the optical axis of the laser component and in which the above named components are arranged. The invention also relates to a method for controlling the emitted wavelength of a laser component.

Abstract: An optical wavelength locking system is provided that includes a plurality of optical signal generating units for generating optical signals corresponding to a plurality of channels, and an optical wavelength locking unit for receiving the optical signals corresponding to the plurality of channels and sequentially controlling a wavelength fluctuation exhibited by the optical signal of each channel. Since one optical wavelength locking unit is used for a plurality of optical sources, production costs are reduced, a better utilization of available space can be achieved and the reliability of the system is improved.

Abstract: Method and apparatus for synchronizing two different types of modulators in an optical transmission system includes a first modulator generating an optical pulse train, a second modulator encoding data onto the optical pulse train, an optical filter resolving upper and lower modulation sidebands of the optical data and an analyzer measuring the optical power of modulation sidebands and converting the received optical power of the sidebands into a control signal for synchronizing the two modulators. A wedged etalon is the filter element selecting the USB and LSB from the optical data spectrum. The analyzer contains photo-detectors measuring the optical power of the filtered USB and LSB and an electronic differential amplifier producing a control signal based upon photo-detector output. The phase shifter, in response to the control signal, adapts the temporal delay of the first modulator to reduce differences between the power levels of the upper and lower sidebands.

Abstract: A method and system for modulating an optical signal to encode data therein. The method comprises the steps of directing the optical signal through a filter mechanism having a passband function including a center wavelength, and modulating the center wavelength of the optical signal to establish a difference between the center wavelengths of the filter mechanism and the optical signal to represent a data value. With the preferred implementation of the invention, a transmit device is used to encode the data in the optical signal, and a receive device is provided to decode the signal. The transmit device modulates the center wavelength of the optical signal to establish a difference between the center wavelength and a predefined wavelength to encode data in the optical signal, and the transmit device then transmits the optical signal. The receive device receives the optical signal from the transmit device and processes that signal to identify the encoded data.

Abstract: The invention describes methods and systems for monitoring the performance of an optical network by marking a group of optical signals with a set of identification tags which are unique to network characteristics. In the preferred embodiments, fiber identification (FID) and bundle identification (BID) tags are encoded into optical signals by marking an optical signal with low frequency dither tones whose frequencies are unique to the fiber section and to a bundle of fibers respectively. Detecting of the FID and BID tones provides more effective and accurate monitoring of performance of the optical network and allows determining of the network topology, e.g. paths of optical channels and traffic load through different fiber sections in the network. Other sets of hierarchically arranged identifiers encoded into optical signals have also been proposed, including band, conduit, city, region, country, etc. identifiers, as well as identifiers related to network security and service characteristics.

Abstract: An object of disclosed technology is to control lasing wavelengths so that a wavelength shift does not occurs. Another object is to permit wavelengths of a light source for wavelength division multiplexing optical-fiber communication system to be variable in response to an ITU-TS grid. A means for achieving the objects is as follows: locating an etalon in a light path of diode laser light, which is a parallel plane wave changed by a collimator lens; generating a wavelength error signal from a difference between both of divided pieces of light from transmitted light or reflected light; and locking a wavelength of a diode laser device according to the wavelength error signal.

Abstract: First and second carrier modulators each modulate a carrier having a different frequency from each other with a baseband input signal. First and second variable wavelength optical modulators each convert the modulated signal into an optical signal having a first or second wavelength. An optical multiplexer multiplexes the optical signals, and sends a multiplexed signal to an optical transmission line. A wavelength separator individually outputs wavelength components of the multiplexed signal. First and second optical receivers each convert these wavelength components into an electrical signal. First and second filters each pass only the signal components of each different frequency. First and second burst demodulators each demodulate the modulated signal. With such a structure, a large-capacity optical communication apparatus which is capable of simultaneously using the same wavelength without requiring wavelength management in optical transmitting circuits can be achieved at a low cost.

Abstract: A system and method for improving the transmission quality of a WDM optical communications system begins by determining the bit-error rate for an optical channel before forward error correction is performed at a receiver. The pre-corrective bit-error rate is fed back through a feed back circuit that includes a parameter adjustment module which adjusts an optical signal parameter based on the bit-error rate. As examples, the signal parameter may be a channel power, dispersion, signal wavelength, the chirp or eye shape of an optical signal. The feedback circuit may also adjust various parameters within the WDM system, including amplifier gain, attenuation, and power for one or more channels in the system. By adjusting these parameters based on a pre-corrective bit-error rate, transmission quality is improved and costs are lowered through a reduction in hardware.

Abstract: A tunable dispersion compensator whose passband center wavelength changes when the amount of dispersion compensation is changed is suitably adjusted. The relationship between temperature for keeping the center wavelength constant and the amount of dispersion compensation is stored in advance. After controlling the amount of dispersion compensation to achieve best or optimum transmission quality, the amount of dispersion compensation is converted into temperature in accordance with the stored relationship and, based on that, the temperature is controlled to keep the center wavelength constant.

Abstract: A transmitter subsystem generates an optical signal which contains multiple subbands of information. The subbands have different polarization. For example, in one approach, two or more optical transmitters generate optical signals which have different polarization. An optical combiner optically combines the optical signals into a composite optical signal for transmission across an optical fiber. In another aspect, each optical transmitter generates an optical signal containing both a lower optical sideband and an upper optical sideband (i.e., a double sideband optical signal). An optical filter selects the upper optical sideband of one optical signal and the lower optical sideband of another optical signal to produce a composite optical signal.

Abstract: A system for matching a optical filter characteristic of a first filter tunable in wavelength with an optical first signal comprises a modulator for modulating at least a part of the first signal with a modulation signal before being applied to the first filter. An analyzing unit derives a control signal for tuning the first filter by analyzing the modulated first signal after passing the first filter in conjunction with the modulation signal.

Abstract: The present invention relates to an optical sender applicable to WDM (wavelength division multiplexing), and a primary object of the present invention is to prevent interchannel crosstalk in WDM. The optical sender includes a light source for outputting a light beam, an optical modulator for modulating the light beam in accordance with a main signal to output an optical signal, and a unit for shutting down the optical signal when receiving at least one of a power alarm relating to on/off of power supply and a wavelength alarm relating to the wavelength of the light beam.

Abstract: In optical filter systems and optical transmission systems, an optical filter compresses data into and/or derives data from a light signal. The filter way weight an incident light signal by wavelength over a predetermined wavelength range according to a predetermined function so that the filter performs the dot product of the light signal and the function.

Abstract: An optical module according to the present invention includes: a light-emitting device that outputs laser light; a temperature adjustment unit that adjusts a wavelength of the laser light outputted from the light-emitting device so as to be locked at a predetermined wavelength; a wavelength monitor unit that receives laser light outputted from the light-emitting device by allowing the laser light to pass through an optical filter provided above the temperature adjustment unit and monitors the wavelength thereof; a package for sealing the light-emitting device, the temperature adjustment unit, and the wavelength monitor unit into the inside thereof; and a package temperature detection unit for detecting a temperature of the package, in which the temperature adjustment unit adjusts an oscillation wavelength of the laser light outputted from the light-emitting device to the predetermined lock wavelength based on a signal outputted from the wavelength monitor unit, and a signal from the package temperature detect

Abstract: The influences on transmission quality caused by chirp and self-phase modulation are at least largely corrected by way of an optimally set operating point of the modulator (2). Suitable criteria are obtained in control loops in order to maintain the optimal setting.

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 optical multiplex communication system includes a transmission part and a receiving part, wherein the transmission part includes a transmission quality detecting part which measures and transmits a transmission quality information for the channels based on a request from the transmission part; the receiving part includes a variable optical attenuation part controls the optical signal level for the channels, an optical level setting part controls the variable optical attenuation part based on a setting value, a setting control part adding the setting value to the optical level setting part based on a request for setting.

Abstract: A method and system for tuning channel spacing for a wavelength division multiplexing (WDM) transport system includes determining a spectrum width for a channel. A bandwidth of a group of base channels covering the spectrum width for the channel is allocated to the channel. A passband of a channel filter at a center frequency of the group is adjusted to correspond to the spectrum width of the channel.

Abstract: The present invention aims to provide a WDM optical communication system that can arrange efficiently optical signals of a plurality of bit rates at different wavelength spacing.

Abstract: An improved analog optical system which provides improved dynamic range as well as sensitivity relative to known analog optical systems. The analog optical system includes a Mach-Zehnder modulator (MZM) operated with a low bias to improve sensitivity. In accordance with an important aspect of the invention, the optical system utilizes two optical wavelengths with two effective bias points to cancel even ordered distortion associated with low biasing. Two lasers having different wavelengths are applied to the Mach-Zehnder modulator by way of a wavelength division multiplexer (WDM). Alternately, a single laser producing two optical carriers having different wavelengths could be used in place of the two single wavelength lasers and the WDM. The modulator bias control circuit forces two optical carriers to two bias points on opposite sides of the minimum bias point thus, providing equal modulation depth with opposite sign on each of the two optical carriers.

Abstract: The present invention provides an optical transponder with an add/drop operation function of optical channels, which combines operating functions of adding and dropping type optical transponders in accordance with mounting of a digital wrapper to simultaneously process two optical channels. The optical transponder receives an optical signal, converts the optical signal into electrical signal, adds maintenance information, monitoring information, and error correction information to each of the converted signals, and detects the maintenance information, monitoring information, and errors contained in each of the signals. Furthermore The optical transponder corrects the detected errors, and transmits the signals having the maintenance information, monitoring information, and error correction information and the signals of which errors are corrected.

Abstract: Disclosed is a multi-wavelength locking method for a wavelength division multiplexing (WDM) optical communication network, and in particular, a multi-wavelength locking method and apparatus for a WDM optical communication system that can lock wavelengths of optical signals by producing pilot tones by applying a sine-wave current to a plurality of transmission lasers having different wavelengths, passing the optical signal through a Fabry-Perot etalon filter, and then Fourier-transforming the filtered optical signal.

Abstract: A high efficiency optical feedback modulator and method of operation are provided. The high efficiency optical feedback modulator (30) includes an optical modulator (52) and an optical feedback system (54). The optical modulator (52) includes first and second optical inputs (66a, 68a) and first and second optical outputs (66b, 68b). The optical feedback system (54) is coupled between the second optical output (68b) and the second optical input (68a). The second optical input (68a) receives an optical feedback signal (70) from the optical feedback system (54). The first optical input (66a) receives an input light beam (56). The input light beam (56) and the optical feedback signal (70) are modulated with an electronic input signal (26a) to produce a high modulation depth optical signal (36) output from the first optical output (66b).

Abstract: A system and method for optimizing performance characteristics of optical networks. The system and method exploits a wavelength-locked loop servo-control circuit and methodology that enables real time adjustment of optical signals in accordance with attenuation characteristics of an optical transmission channel. Particularly, the invention enables alignment of optical signal center wavelengths and optical wavelength selective devices exhibiting a peaked passband function in optical networks utilizing information included in first derivative and second derivatives of dither modulated optical signals extracted from a feedback signal provided in the wavelength-locked loop servo-control circuit.

Abstract: Highly efficient control of laser frequency is provided. An optical channel monitor is coupled to a composite WDM signal resulting from the multiplexing of outputs from multiple laser sources. The monitor determines the frequency of each laser and this measurement is used to provide feedback for laser frequency control. In this way a single optical channel monitor can provide frequency control for numerous WDM channels, greatly reducing the cost and space required. Monitoring capability may be provided to individual channels as needed.

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: An optical channel monitor is described, the optical channel monitor includes an optical input port, a photodetector disposed in an optical path communicating at least intermittently with the optical input port, an optical filter disposed in the optical path between the optical input port and the photodetector, and an optical band splitter disposed in the optical path between the optical filter and the photodetector. The optical filter is a multibandpass filter, such as a scanning Fabry-Perot filter. The optical channel monitor also comprises a reference light system for providing a calibration standard against which an optical signal input through the input port may be compared. The channel monitor finds application in optical transmission systems including wavelength division multiplexed (WDM) optical communication systems.

Abstract: A WDM transmitter comprising an array of M pump lasers multiplexed by an M×N multiplexer, in the form of a coupler, and used to feed an array of N optically pumped fiber lasers emitting at wavelengths ?1, ?2, . . . ?N. The parameter M determines the number of pump lasers as well as the number of inputs of the pump-multiplexing coupler and can be smaller or equal to parameter N that determines the number of optically pumped lasers. The fiber laser outputs are passed through N isolators before entering N modulators were the signals are monolithically modulated. The outputs of the modulators are passed through an array of N tunable attenuators. Finally all the individual channel outputs are recombined into a single output in a combiner. The output will typically lead to an optical network. The proposed architecture may also be used for optical amplifiers, especially fiber-based optical amplifiers.

Abstract: A wavelength stabilizing apparatus utilized in an optical communication system for controlling a light wave output from a tunable optical component is disclosed. The wavelength stabilizing apparatus includes a coarse-tuning element, a fine-tuning element, and a servo element. When the wavelength stabilizing apparatus is used, the light wave output from the tunable optical component is directed into the coarse-tuning element and the fine-tuning element, respectively, and then transformed into electric signals to be received by the servo element. Particularly, the electric signals from the coarse-tuning element are served as basis for coarse-tuning and channel recognition of the light wave output from the tunable optical component while the electric signals from the fine-tuning element are served for fine-tuning and servo control of the light wave output from the tunable optical component.

Abstract: The present invention relates to a method for generating a single-sideband optical signal. According to the method, as data signals having a 90-degree phase difference with respect to input data signals, which are NRZ signals at 10 Gb/s, 0.5-bit delay data signals are generated by a 0.5-bit delay circuit for obtaining a delay corresponding to ?/2 of the bit period of the input data signal. An SSB optical signal produced from the data signals and the 0.5-bit delay data signals is generated through an optical filter. Further, to eliminate a residual intensity-modulated component, the generated SSB optical signal is fed back to appropriately adjust the center frequency of the optical filter. The carrier output frequency of a semiconductor laser can be adjusted instead of the center frequency of the optical filter. When an RZ signal is used as an input data signal, a 0.25-bit delay circuit is used.

Abstract: First and second carrier modulators each modulate a carrier having a different frequency from each other with a baseband input signal. First and second variable wavelength optical modulators each convert the modulated signal into an optical signal having a first or second wavelength. An optical multiplexer multiplexes the optical signals, and sends a multiplexed signal to an optical transmission line. A wavelength separator individually outputs wavelength components of the multiplexed signal. First and second optical receivers each convert these wavelength components into an electrical signal. First and second filters each pass only the signal components of each different frequency. First and second burst demodulators each demodulate the modulated signal. With such a structure, a large-capacity optical communication apparatus which is capable of simultaneously using the same wavelength without requiring wavelength management in optical transmitting circuits can be achieved at a low cost.

Abstract: An optical transport system that uses tunable filters to vary the central wavelengths and spectrum widths of channels within the system to more efficiently use the bandwidth of the fiber. Higher bit rate channels may be divided into multiple lower bit rate channels, and lower bit rate channels may be combined to form higher bit rate channels.

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: The invention pertains to a method for determining and/or controlling the transmission wavelengths of transmission elements of an optical wavelength division multiplex transmission unit, in which the output signals of several optical transmission elements (7) with respectively one optical transmission spectrum (15) of different center wavelength (ësj) are respectively fed to one optical input (E2, E4, . . . , En1) of an optical wavelength monitoring and coupling unit (3) that combines the output signals into a wavelength division multiplex signal on one or more optical output(s) (A), with the wavelength monitoring and coupling unit (3) being designed such that an optical path, on which a narrow-band high-pass filtering or low-pass filtering takes place, exists between one, more or all inputs (E2, E4, . . . , En-1), to which the output signal of a transmission element (7) is fed, and one or more additional inputs (E1, E3, . . . , En) that are not connected to transmission elements (7).

Abstract: An optical module for use in detecting a plurality of different wavelengths by making use of the multiple wavelength selectivity of an etalon. The optical module includes a semiconductor laser, a lens for converting a beam emitted from the semiconductor laser into a substantially parallel beam, a beam splitter for splitting the converted beam into a reflected beam and a transmitted beam, and a light-receiving element disposed such that one of the split beams is incident thereupon through an etalon, wherein a center of the reflected beam from the etalon occurring as the beam is incident upon the etalon is arranged to return to a region other than a beam-emitting portion of the semiconductor laser.

Abstract: A system and method for optical power transient control and prevention in communication networks. An optical signal propagating on a network is demultiplexed into individual spectral bands, e.g. at an OADM, and an optical power monitor point is included into each band. A separate idler laser is provided for each OADM band. The power output of each laser is adjusted such that it compensates for the signal power lost from each band. The wavelength of each laser is chosen to fall within the associated OADM spectral band, but outside of the window of individual signal wavelengths, so that it may propagate through the network without causing deleterious interference at the receiver.

Abstract: A method and apparatus for monitoring and controlling each of at least one optical signal sources within a WDM system by using beat frequencies derived by combining portions of the optical signals provided by the optical signal sources and a reference optical signal.

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: Method and apparatuses for compensating for wavelength drift in a fiber-optic laser transmitter includes 1) controlling a temperature within the optoelectronic assembly at a defined level; 2) driving the optoelectronic assembly to emit light, wherein the emitted light has a wavelength that is within a channel of operation, the channel of operation including a range of wavelengths centered around a channel center wavelength; 3) accessing from memory within the optoelectronic assembly a control value associated with the temperature of the optoelectronic assembly at defined points within an operational lifetime of the optoelectronic assembly; and 4) recalculating the defined level by reference to the control value, whereby a wavelength of the optoelectronic assembly is maintained within the channel of operation despite an expected drift of wavelength.

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: The optical transmitter includes a semiconductor laser device, and an optical modulator region optically connected to the semiconductor laser device and having the function of modulating the output light from the semiconductor laser device. The operating temperature of the optical modulator region is changed without changing the oscillation wavelength of the semiconductor laser device.

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 wavelength stabilization module having a light-receiving element array and a method of manufacturing the same are disclosed.

Abstract: A multichannel WDM transmission system incorporates a plurality of WDM optical sources with stabilized wavelengths and light intensity. Efficient stabilization of these characteristics is achieved by modulation of WDM sources by distinguishing low frequency electrical signals in a range between 1 and 4 kHz and modulation depth in a range between 1% and 5% that are used as WDM source identifiers. After the modulated outputs of the WDM sources are multiplexed and filtered, a Fourier transform of total light intensity may be obtained. Digital feedbacks provide stabilization of both the wavelength and light intensity of each WDM optical source.

Abstract: A system for locking the operating wavelength of an optical transmission source, the system including: a pattern of nanostructures being optically coupled to the optical transmission source and adapted to perform notch filtering; at least one photodetector optically coupled to the pattern of nanostructures; and, at least one controller operatively coupled to the photodetector and optical transmission source to operate the optical transmission source responsively to the at least one photodetector.