Abstract: An arrangement and a method for testing a telecommunications circuit over Dense Wavelength Division Multiplexing (DWDM). A transmitter, which is optically coupled to the circuit, transmits a test-drive signal on the circuit. Through a network, a performance of the circuit is monitored at points along the circuit based on the transmitted test-drive signal.

Abstract: Fast on-line electro-optical detection of wafer defects by illuminating with a short light pulse from a repetitively pulsed laser, a section of the wafer while it is moved across the field of view of an imaging system, and imaging the moving wafer onto a focal plane assembly, optically forming a continuous surface of photo-detectors at the focal plane of the optical imaging system. The continuously moving wafer is illuminated by a laser pulse of duration significantly shorter than the pixel dwell time, such that there is effectively no image smear during the wafer motion. The laser pulse has sufficient energy and brightness to impart the necessary illumination to each sequentially inspected field of view required for creating an image of the inspected wafer die. A novel fiber optical illumination delivery system, which is effective in reducing the effects of source coherence is described.

Abstract: A system for measuring optical characteristics of a multiport optical device uses optical heterodyne detection and known port-specific transmission delays to simultaneously monitor multiple ports of the multiport optical device with a single receiver. An embodiment of a system includes a splitter configured to split a swept optical signal into a reference signal and a test signal and a test system input, connectable to the multiport optical device, for transmitting the test signal to the multiport optical device. The test system also includes an optical combiner and a receiver. The optical combiner is connectable to the multiport optical device to receive a first portion of the test signal having a first port-specific transmission delay and to receive a second portion of the test signal having a second port-specific transmission delay.

Abstract: The invention relates to a simple and relatively inexpensive way of determining the optical bit rate of an optical signal, which is based on the fact that different percentages of the signal will be transmitted through a narrow-band optical filter depending on the bit rate. Increasing the bit rate of an optical signal results in a broadening of the channel spectrum, therefore, if the optical filter is designed with a passband thinner than all (or all but one) of the channel widths, then signals with different bit rates will have distinctive amounts of transmitted light relative to the amount of input light. In the preferred embodiment the optical signal is divided into two sub-beams by a beam splitter, and one of the sub-beams is passed through the optical filter. The power of filtered sub-beam is compared to the power of the unfiltered sub-beam to provide a ratio, which is compared to one or more predetermined values indicative of the bit rate.

Abstract: A method for measuring the signal quality of an optical data signal is provided. To measure the signal quality, and in particular the signal-to-noise ratio of an optical data signal which has data-free time intervals, the signal strength of the transmitted optical data signal is measured during a data transmission. The signal strength of the noise signal is determined during the data-free time intervals. The signal-to-noise ratio is determined and used as a criterion for the signal quality of the optical data signal.

Abstract: The present invention relates to an automatic retrieval method of a wavelength-division multiplexed (WDM) ring network to the normal state after recovery of a failure. More specifically, the present invention relates to an automatic retrieval method of a WDM ring network to the normal state after recovery of a failure by inducing a lasing by making the gain of the closed loop larger than 1 using the fact that the recovered section in the ring network forms a closed loop immediately after the recovery of the failure.

Abstract: A method for automatic initialization of an optical network is provided. A network management system (NMS) performs remote determination of span losses and sets the operating points of network components. The initialization method comprises remotely and automatically setting target gains of optical amplifiers and signal power levels at transmitters and receivers to required operating values. The methods for initialization of the optical network of the embodiments include gain excursion minimization (GEM) for individual channels passing through amplifiers and/or pre-emphasis of the optical link, where channel powers at the transmitters are biased to compensate for the effects of optical amplifiers gain ripple.

Abstract: A central equipment is connected by at least two optical fibers to a decentralized optical equipment and the central equipment creates an optical auxiliary signal which is transmitted together with an optical payload signal from the central equipment to the decentralized equipment. The optical auxiliary signal that is received in the decentralized optical equipment is rerouted and transmitted back to the central optical equipment via another optical fiber in addition to a second payload signal, and the reception of the optical auxiliary signal is optically monitored in the central optical equipment to determine if there is a breakage in either one of the fibers extending to the unit.

Abstract: A system for image data communication in military aircraft between a graphics processor computer, referred to as the computer node, and weapons carried on wing pylons, referred to as remote nodes, includes a hub connected via fiber pairs to the computer node and to the remote nodes. The hub includes a number of port bypass switches connected in a bypass loop so that each port bypass switch conveys data between the computer node and the hub or between the remote node and the hub when in a first state, and each port bypass switch conveys data within the bypass loop in the hub, i.e. bypassing its node, when in a second state.

Abstract: An optical transmitter-receiver that does not have a harmful effect on the human eye when an optical fiber is disconnected from the apparatus and is able to determine easily when the fiber has been reconnected. A normal signal detector and a dummy signal detector determine when a signal from another optical transmitter-receiver is no longer received due to disconnection of an optical fiber. This result switches an output switch and causes a second reference voltage to be transmitted to an optical output automatic controller, thereby reducing the power of a laser diode. At the same time, a signal switch provides a dummy signal having a low frequency to the laser diode in place of the normal signal, resulting in output of a dummy optical signal. At this time, the other optical transmitter-receiver also outputs a dummy optical signal. When the optical fiber is reconnected, the dummy signal transmitted from the other optical transmitter-receiver is detected.

Abstract: A nonlinear optical crystal is composed of 2-adamantyl-5-nitorpyridine (AANP) allowing the type 2 phase matching to the sampling light and a measuring object light, emitting a sum frequency light of the measuring object light and the sampling light, with the polarization directions thereof being perpendicular to each other, when the sampling light and measuring object light multiplexed by a multiplexer are entered. When the sum frequency light is emitted through the nonlinear optical crystal, a control portion controls the polarization direction of the sampling light so as to be parallel to a predetermined reference axis located within a plane perpendicular to a phase matching direction of the nonlinear optical crystal. The predetermined reference axis is a single axis maintaining parallelism with the crystal axis of the nonlinear optical crystal even if the wavelength of the inputted light is changed.

Abstract: An optical network analyzer for measuring an optical characteristic of an object to be measured, including: a first multiplexer for multiplexing a first optical signal which has transmitted the object to be measured, and a second optical signal having a frequency different from the first optical signal, and for outputting a third optical signal; a first photoelectrical converter for converting the third optical signal into a first electric signal; and a phase measurement block for comparing phases of the first electric signal and a first reference signal.

Abstract: Optical networks using wavelength division multiplexing (WDM) techniques require innovative methods of maintaining network connectivity data and for identifying and isolating network faults. The present invention discloses such methods using a signal processor for installation at each node for retrieving upstream connectivity data from an out-of-band signal, updating the data and returning it to the out-of-band signal for use by downstream elements. A central network monitor periodically requests updates from each node of the connectivity data maintained by it in the form of messages transmitted along the out-of-band signal. When the various payload signals carried along the network are modulated with in-band signals carrying data which identifies the source and wavelength of the payload, this data can be combined with the updated connectivity data to identify network faults and raise alarms for transmission along the out-of-band signal to the central network monitor.

Abstract: While a discrimination level is scanned by a discrimination section, an average-value detecting section detects the average value of the discrimination output. This yields a distribution function of an input signal. Further, a differentiation section performs a differential process to acquire a probability density function. Average values or dispersion values of, for example, the mark level and space level of the input signal are computed from the distribution function and the probability density function. Accordingly, a Q value as a quality parameter can be obtained.

Abstract: The present invention relates to a technology of an IP node for transferring IP packets accommodated in a wavelength division multiplexing optical signal.

Abstract: An optical communication system is provided that includes first and second optical transmitters/receivers remotely located with respect to one another and which are coupled together by first and second optical transmission paths for bidirectionally transmitting optical information therebetween. First and second optical amplifiers are respectively disposed in the first and second optical transmission paths. At least one loop-back path optically couples a portion of a WDM optical signal from the first to the second transmission path. The loop-back path includes a filter for transmitting a monitoring channel but not a data channel included in the optical signal portion traversing the loop-back path.

Abstract: A tuning system for use in a receiver of an optical transmission system. The receiver includes a data channel transporting a data signal and a monitoring channel transporting a copy of the data signal. The tuning system includes a processing module for processing the copy of the data signal to generate a control signal conveying tuning information. This tuning information is used by the receiver to alter an operating point of the receiver on the data channel. The operating point of the receiver that is susceptible to be altered by the control signal is a decision threshold applied on the data signal to discriminate one binary value from another binary value on the data channel of the receiver. This approach allows, when required or desired, tuning of the system while the system is in service. This is possible since the tuning of the system is performed using the monitoring channel, and does not disturb nor corrupt the actual data being transported on the data channel.

Abstract: An optical wavelength division multiplexing (WDM) device comprising optical components that are integrated together to provide an optical WDM that does not require circulators, that has simplified alignment and that is relatively low in cost. The WDM device comprises an integrated port separator, a dispersive element and a reflector. The integrated port separator comprises various optical components, that spatially separate the polarization components of a light beam input through an input port of the integrated port separator. The spatially separated polarization components are output from the integrated port separator and impinge on the dispersive element, which spatially separates the wavelengths associated with the polarization components impinging thereon. The spatially separated wavelengths then impinge on the reflective element and are reflected with angles of polarization that depend on the state of the reflective element.

Abstract: An optical communications system is adapted for connection to an optical fiber link of an optical communications network. The system obtains a fiber identifier respecting the optical fiber link; a respective optimum setting of one or more parameters of the optical communications system; and adjusts a respective value of each parameter in accordance with the respective optimum setting. The fiber identifier can be obtained from a value of at least one fiber transmission property of the optical fiber link. The fiber transmission property value is used to search a look-up table of class definitions, each class definition including a respective class identifier and at least one corresponding characteristic transmission property value. A class identifier is selected as the fiber identifier from the class definition for which each characteristic transmission property value most closely matches a corresponding fiber transmission property value.

Abstract: Control information is embedded in the signal passing through an optical amplifier by varying the power level of that amplifier's pumped laser source. Connection discovery for a given optical port can then be performed by detecting variations in the optical signal present on that given port and then attempting to match these with the variations assigned to each of the optical amplifiers. If a match is found, then the optical amplifier connected to the given port can be identified. As a result, the need to physically handle the fiber in order to effect connection discovery is eliminated, rendering the process faster, safer and more reliable. Also, the present invention advantageously allows a connection discovery function to be invoked from a remote location.

Abstract: A data communication system includes circuitry to assure components respond to variations in the time length of the valid data window or “eye” of the high speed data communication signal. A self-test portion of the system periodically injects the effects of phase jitter into the data communication signal to assure the system performs properly.

Abstract: In a spatial transmission optical transceiver, signals of two lines from a feeder-affixed twisted pair line 17 which is a data transmission line based on IEEE1394 standard are converted to signals of one line by a code conversion circuit 14, and further converted to optical signals and emitted to space by a optical transmitter 15. The optical signal transmitted through the space is converted to an electrical signal by a optical receiver 16. The code conversion circuit 14 receiving the electrical signal of one line thus converted to signals of two lines, and transmits the signals onto the feeder-affixed twisted pair line 17. The electrical signal from the optical receiver 16 is input to an interception and insertion/removal detection circuit 13 to detect the presence or absence of the optical signal and judge whether the received signal is a reflection signal, thereby detecting the interception of a communication path and the insertion/removal of a signal line connected to a confronting optical transceiver.

Abstract: A arrangement is described for transmitting, radiating and receiving high-frequency signals. The arrangement is comprised of a system connected to a transmitting and receiving device (3) which includes at least one high-frequency element (1) capable of guiding electromagnetic waves and a first signal cable (5) extending parallel thereto. To improve the service reliability of the arrangement, a second signal cable (6) which is also connected to the transmitting and receiving device (3), is arranged parallel to the high-frequency element (1) and maintains a significant spatial separation to the first signal cable (5).

Abstract: The present invention relates to prevention of erroneous connection in an optical network and, in particular, it provides an optical communication node having route switching function as well as an optical network system using the same in a wavelength division multiplex (WDM) network system. There is provided an optical communication node that is connected to a specific optical path in an optical network, said optical communication node having: an external network that is placed thereunder; and an interruption means for interrupting connection between said optical network and said external network, wherein said interruption means interrupts the connection until a sequence of changing a route is completed when the route setting of said optical path is changed.

Abstract: An optical signal repeater, in which an output level of each optical signal of WDM optical signals does not change even when the number of wavelengths of inputted WDM optical signals changes, amplifies WDM optical signals transmitted from an optical transmitter via an optical fiber transmission line. A pumping light source outputs pumping light used for amplifying the WDM optical signal. A multiplexer transmits the pumping light to an amplifier, and a splits the amplified WDM optical signals into two parts. A wavelength selection type reflector reflects only an optical signal having a specified wavelength in one part of the amplified WDM optical signals. An automatic output level controller controls the pumping light output from the pumping light source so that the power level becomes a designated level. A reflected optical signal transmitter transmits the optical signal having the specified wavelength reflected to the automatic output level controller.

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

Abstract: A polarization scrambler and a polarization mode dispersion (PMD) compensation system compensate for PMD on an active optic fiber. The polarization scrambler scrambles a state of polarization of an optical signal that carries user information. The PMD compensation system then receives the optical signal over the active optic fiber. The PMD compensation system measuring a differential group delay and principal states of polarization of the PMD in the active optic fiber. The PMD compensation system then determines a modification of the optical signal based on the differential group delay and the principal states of polarization of the PMD. The PMD compensation system modifies the optical signal in the active optic fiber to compensate for PMD based on the determination of the modification. The PMD compensation system then transmits the optical signal.

Abstract: A method for checking a ring optical network line for data transmission between a plurality of network subscribers in a motor vehicle, wherein one network subscribers carries out a master function, wherein, apart from the optical network line, there is a further communication line which has a star structure. The network subscribers having the master function is arranged in the centre of the star structure and is connected directly via the communication line to every other network subscribers. The optical network line is checked by the network subscriber having the master function outputting a start signal to the individual network subscribers. The individual network subscribers acknowledge the start signal for the network subscribers the master function via the communication line. After the start signal, the network subscriber having the master function outputs an initialization signal via the optical network line.

Abstract: The present invention relates to a method of monitoring the transmission of optical signals including a step of inserting a monitoring signal (S) more particularly suited to monitoring the quality of service. During the transmission of optical signals each carried by a predefined wavelength defining a transmission channel (Ci), said signals are grouped onto the same fiber in a band (B) of channels. The method then includes a step of simultaneously modulating said signals grouped in the band of channels using the monitoring signal to be transmitted, so that each of the signals constitutes a carrier of the monitoring signal.

Abstract: Vulnerability of an optical network to channel impairments or the like, is addressed by utilizing real-time monitoring and control of prescribed optical channel impairments. The impairments are compensated for by employing an optimization process in the optical network such that the optical signals from the source or sources of the impairments are controllably adjusted at any particular node in the network. The optical signals are attenuated more or less at the source node of the associated optical channel in order to optimize performance of the corresponding optical channel in the network. A variable optical attenuator (VOA) is used at the &lgr; laser source of optical channel having the impairment to obtain the attenuation. The optical signal impairment is measured at a receiving node and the source node of the associated optical channel is determined.

Abstract: A wavelength division multiplexing ring network is constructed using a simple architecture and a fewer number of hardwares between the nodes compared with the conventional ring network. Each node is structured so that any number of multiple waves can be processed, and a fault in the network or within a node is resolved by providing a path-based protection so that switching can be performed without disrupting other nodes or even within one node.

Abstract: The present invention relates to a local node for use in a synchronous optical network ring. The local node includes a group of working transmission lines and a protection line, for connecting to a remote node. The local node further includes a control unit for monitoring the working transmission lines and, upon detection of a data transmission impairment over a particular working transmission line, invoking a protection switch event causing re-routing of optical signals from the particular working transmission line to the protection line. Should the control unit detect simultaneous data transmission impairments over two or more working transmission lines, the control unit will choose to protect a particular working transmission line on the basis of a user-defined priority scheme.

Abstract: A method, and optical network management system is provided for monitoring an optical transmission system, including detecting degradation of an electrical signal converted from an optical signal transported via a plurality of optical network elements within the optical transmission system. The method, and optical network management system additionally perform the step of correlating the degradation in the electrical domain with degradation of the optical transmission system in an optical domain based a plurality of threshold values associated with an optical performance parameter corresponding each of the optical network elements. The method, and optical network management system further perform the step of determining whether a cause of the degradation in the electrical domain stems from one or more of the optical network elements according to the correlation.

Abstract: A method, and optical network management system is provided for monitoring an optical transmission system, including assigning a plurality of threshold values corresponding to a performance parameter associated with the optical transmission system. The method, and optical network management system further perform the step of identifying degradation of the optical transmission system based on which of the threshold values being exceeded.

Abstract: The present invention relates to supervisory signalling for optical communications equipment. More particularly, it relates to a method and apparatus for supervisory signalling relating to submarine optical communications equipment on a submarine optical communications system.