Abstract: The present invention provides an expandable and cost-effective high capacity optical communication system using wavelength-division-multiplexing, optical direction guide means and bidirectional transmission of data over an optical waveguide. The use of interleaved bidirectional data channels reduces the minimum spacing between data channels, permitting a greater number of channels over a single optical waveguide.

Abstract: A closed-ring transparent optical communication network that provides for protection of the principal communication channel of each supported wavelength and supports occasional traffic on a separate channel. In the case of a breakdown of or degradation in the principal channel, these communications are redirected to the occasional channel.

Abstract: A method and apparatus for managing state-of-polarization (SOP) controllers along an optical communications link. When the polarization-mode dispersion (PMD) in the link exceeds a preset limit as determined by a PMD compensator, the SOP controller is directed to change rotation angle in an arbitrary fashion. This shift is only undertaken after other indicators are examined to determine that PMD is the main problem affecting the link, and not simply a consequence of a separate problem that the SOP controller rotation angle should not try to fix. By reducing unnecessary SOP adjustments which can disrupt data traffic, the reliability of the optical link is improved.

Abstract: Feedback instabilities arising from interactions between automatic control loops at the amplifier nodes of an optical network are eliminated by restricting operation to a single amplifier node at a time. Amplifier node activation is accomplished using a global control signal which is sequentially passed from an upstream node through all of the nodes of the system. By controlling the state of the global control signal, an upstream node has operational priority over downstream nodes.

Abstract: Radio base stations subject each code-division multiplex signal to frequency conversion so as to vary each frequency thereof according to the radio base stations and then converts the signal to an optical signal before transmitting the same to a switching station. The switching station multiplexes the optical signals, subjects a signal obtained after multiplexing to optical-electrical conversion, and extracts the code-division multiplex signal from the respective electrical signal obtained after the conversion. Consequently, each signal to be demodulated by demodulating sections includes nothing but the code-division multiplex signal outputted from the radio base stations. Therefore, a code-division multiplex signal outputted from a desired base station is not disturbed by code-division multiplex signals outputted from the other stations as a noise as will be in a conventional system.

Abstract: Disclosed is a method for generating a duobinary signal which has the step of: modulating individually an intensity and a phase of a carrier wave. Also disclosed is a duobinary-manner optical transmitter which has: a laser device which outpus signal light; an optical intensity modulator which intensity-modulates the signal light according to a first data signal generated by dividing a data signal into two signals; a precoder which inputs a second data signal generated by dividing the data signal into two signals; and an optical phase modulator which phase-modulates the intensity-modulated signal light according to a signal which is obtained delaying 0.5 bit an output signal of the precoder.

Abstract: A wavelength division multiplex optical crossconnect system and add/drop multiplexer including a dense wavelength division multiplexed (DWDM) source which preferably includes a multiwavelength mode-locked (MWML) external cavity laser as a fundamental sub-circuit for optically crossconnecting several multi-wavelength data channels onto similar data channels having an interchanged set of optical wavelengths. The optical crossconnect architecture allows the rearrangement of multiple logical channels in a timely manner to support protection switching, traffic grooming, and other telecommunications network functions. The crossconnect architecture further supports multiple physical fibers into and out of the crossconnect, where each fiber carries multiple logical channels on multiple wavelengths of light which are assigned particular wavelength carriers, crossconnected onto any other physical fiber, and assigned another wavelength carrier.

Abstract: Methods and apparatus for safe and reliable telecommunication using a telecommunication network that employs substantially unguided, free-space, point-to-point, electro-magnetic radiation are provided. Most methods include the use of a retro-reflector near a transceiver assembly. The retro-reflector can be used to rapidly calibrate, align, and/or realign one or more assemblies by reflecting a beam of light back toward its source, providing an opportunity for optical detection of the reflected beam.

Abstract: We disclose a method for routing a set of demands in a ring network that comprises nodes interconnected by directed links, in which each demand may be routed clockwise or counterclockwise. According to our method, a linear program is solved to obtain a set of routing variables that minimize an objective function. Each routing variable corresponds to a respective one of the demands, and has a value, exemplarily, on the closed interval from 0 to 1. A value of 1 signifies, e.g., clockwise routing, and a value of 0 signifies counterclockwise routing. The objective function describes the value of a load, defined on each link and maximized over all links of the network, so that a solution of the linear program provides a minimum value of the maximized load. The method further comprises rounding the routing variables so that the value of each routing variable falls at 1 or 0. This rounding is carried out such that the maximized load does not exceed the previously-obtained minimum value of the maximized load.

Abstract: A optical circuit includes a variable-wavelength optical notch filter having a notch wavelength, which receives optical WDM signals to allow an optical signal of the notch wavelength to be reflected and another optical signal to pass through. A control signal is detected from the optical WDM signals, and the notch wavelength of the variable-wavelength optical notch filter is controlled based on the control signal. The notch wavelength may be determined according to the control signal and is further controlled based on a signal level of a reflected optical signal reflected by the variable-wavelength optical notch filter such that the signal level of the reflected optical signal is maximized.

Abstract: An optical interconnect transfers data between a plurality of processors. An input-ring array receivers a plurality of data modulated light beams. Each data modulated light beam has a plurality of light wavelengths and is associated with one of the processors. An output-ring array outputs a light beam to each processor. A plurality of prisms and optical element reflectors transfer light from the input-ring array to the output-ring array and uniquely rotates each wavelength of the transferred light.

Abstract: A nonimaging beam combiner and collimator. The nonimaging beam combiner and collimator can include at least two light sources that emit light of the same wavelength through a focus point and a nonimaging element that receives the light of the same wavelength after the focus point and collimates the light at the same wavelength through the atmosphere. The at least two light sources can include fiber light sources, optical fibers, gradient index lenses, fiber lasers or laser diodes. The collimator can include an input surface, a paraboloid surface located adjacent to the input surface, a conical surface located adjacent to the paraboloid surface, and an ellipsoid surface located adjacent to the conical surface and located on an opposite side of the collimator from the input surface. The paraboloid surface can include a total internal reflection surface.

Abstract: In a method of controlling a switching operation of an optical network for use in connection between an optical transmitter and an optical receiver through an optical switch is controlled by a switch controller, the optical receiver is given through the optical switch a sequence of combined optical signals which is formed by combining a sequence of optical signals with an additional sequence of optical signals. The additional sequence of the optical signals may be either a sequence of optical signals sent to another optical receiver or a sequence of dummy optical signals. The combined optical signal sequence has a time interval which is defined between two adjacent ones of the combined optical signals and which is shorter than a predetermined time interval of, for example, 1 millisecond. Such a combined optical signal sequence serves to avoid occurrence of an optical surge appearing when the time interval is longer than the predetermined time interval.

Abstract: A transceiver for the transmission and reception of high speed optical signals contains a detuning structure which reduces the gain for quarter wave radiation of Electro Magnetic Radiation (EMI). A conductive housing couples light energy from a source or a detector to an external fiber having a metallic ferrule. The conductive housing also is referenced to the chassis enclosure of the transceiver thereby attenuating the quarter wave radiator.

Abstract: A remote control device of an acousto-optic tunable filter includes an acousto-optic tunable filter, a surface acoustic wave control signal source and a control unit. The acousto-optic tunable filter receives an output light signals from an optical transmission line and has a control port to control and outputs state of the light signal received from the optical transmission line, based on a surface acoustic wave control signal received through the control port. The surface acoustic wave control signal source generates the surface acoustic wave control signal and is provided at a remote place from the acousto-optic tunable filter. The control unit receives information regarding the surface acoustic wave control signal generated by the surface acoustic wave control signal source and supplies the surface acoustic wave control signal to the control port of the acousto-optic tunable filter.

Abstract: An optical transmitting device which combines a plurality of signal lights, each having a different, corresponding, frequency, into a wavelength division multiplexed signal light. The frequencies are spaced apart from each other in a manner with eliminates the effects of four-wave mixing (FWM). More specifically, the difference in frequencies of any pair-combination of the signal lights is different from the difference in frequencies between any other pair-combination of the signal lights. Moreover, the plurality of signal lights include n signal lights having respectively corresponding frequencies f1 through fn arranged in order from f1 to fn along a frequency spectrum, where frequencies f1 through fn−1 have respectively corresponding integer spacing coefficients m1 through mn−1, and frequencies fi and fi+1 are separated by mi·&Dgr;fS−F, where i=1 to (n−1) and &Dgr;fS−F is a unit of spacing between frequencies.

Abstract: An optical crossconnect apparatus which includes one terminal connected to a transmission path from one optical transmission terminal station and another terminal connected to a transmission path from another optical transmission terminal station, a first optical signal switch having “M1” ports and “N1” ports, through which the optical signal can pass, a second optical signal switch having “M2” ports and “N2” ports, through which the optical signal can pass, and “L” optical signal repeaters, one end connected to the “N1” ports of the first optical signal switch, and the other end connected to the “N2” ports of the second optical switch. The “N1” and the “N2” ports are equal to “L” optical signal repeaters.

Abstract: There is disclosed a photoelectric conversion method, a light receiving circuit, and an optical communication system, in which even if an average received light level varies, a constant output level of demodulated signal can always be obtained. In the photoelectric conversion method, the light receiving circuit and the optical communication system of the present invention, a light signal is received by a light receiving diode and converted to an electric signal. An alternating component is removed and a direct current component is taken out by a low-pass filter to detect an average received light level of the light, a difference of the average received light level and a preset reference voltage is amplified by a differential amplifier to output a control voltage of a variable gain amplifier, and the electric signal is amplified with a gain corresponding to the control voltage by the variable gain amplifier to obtain a demodulated signal.

Abstract: A new method and apparatus provide efficient highly non-degenerate four-wave mixing (FWM) signal in a semiconductor quantum well microcavity device. The phase mismatch between beam incidence angle and microcavity resonance frequency is minimized by using obliquely incident pump and probe beams. The FWM device is used to implement a wavelength multiplexer, a demultiplexer, a packet wavelength multiplexer, a packet demultiplexer, a time division multiplexer, a time division demultiplexer, a wavelength converter, and a wavelength switch.

Abstract: In a control device for processing an optical supervisory transmission signal necessary for network management between transmission devices in a wavelength-multiplexed optical transmission system, there is provided a main signal device that amplifies a main signal light which is wavelength-multiplexed. A supervisory control device processes supervisory control information. A transmission path connects the main signal device and the supervisory control device. The supervisory control information is defined by mapping items of data of the optical supervisory transmission signal into an overhead defined in another optical transmission system. The main signal device converts the optical supervisory transmission signal dropped from the main signal light into the supervisory control information, which is sent to the supervisory control device. The supervisory control device processes the supervisory control information received as the overhead.