Abstract: A transmission system is provided that recognizes occurrence of a fault efficiently so that the workability and quality of service can be improved. An optical amplifier part amplifies an optical main signal. A fault occurrence recognizing part detects a pump light used for an opposing device via an optical fiber transmission line to which an optical main signal is sent by the repeater. If the pump light is not detected, the fault occurrence recognizing part recognizes occurrence of a fault. A light cutoff control part stops the optical amplifying part outputting an amplified signal so that the light cutoff control in only one of two directions is performed when a fault occurs.

Abstract: Disclosed herein is a signal transmission method in a wavelength-division-multiplex (WDM) transmission system. The WDM transmission system comprises a first WDM terminal for transmitting a WDM signal, a second WDM terminal for receiving the WDM signal, and an optical add-drop multiplexer (OADM) node for transmitting to a network element an optical signal of a specific wavelength of the WDM signal which is transmitted between the first and second WDM terminals. The WDM signal is transmitted from the first WDM terminal to the second WDM terminal regardless of whether an optical signal is added or dropped at the OADM node. The network element employs an optical signal of an idle wavelength of the WDM signal that has no transmission data, to transmit another transmission data that is transmitted by the network element.

Abstract: An optical amplifier to which an optical output power automatic attenuation circuit according to the present invention is applied, comprises: one amplifier board to and from which a WDM light is input and output; and a plurality of booster boards which supply pumping lights to the amplifier board, an ID pattern generated in an ID pattern generating circuit disposed in each of the booster boards is superposed on the pumping light to be sent to the amplifier board, an electric signal indicating a monitoring result of the pumping light in a light receiver disposed on the amplifier board is transmitted to each of the booster boards, it is detected in an ID coincidence detection circuit in each of the booster boards whether or not a received ID pattern contained in the electric signal is coincident with the generated ID pattern, and a connection condition of an output fiber is judged according to the detection result so that an output level of the pumping light is controlled.

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: A system and method for forwarding fault information in an optical network is disclosed. Responsive to a fault being detected at a node, the fault information is forwarded to the destination node in the form of a loss-of-signal condition by turning off laser transmitters used to propagate the signal towards its destination. Thus, a node or other network element not capable of generating an alarm signal consistent with an established alarm signaling protocol, such as a SONET alarm indication signal (AIS) or an SDH multiplexer section alarm indication signal MS-AIS, may still forward the fault condition to a downstream element.

Abstract: A wavelength division multiplex transmission system with substantial functions for avoidance of defects is provided. The system comprises an optical transmission device and an optical receiving device. The optical transmission device comprises an operating-system optical transmission unit and a standby-system optical transmission unit, and distributes transmission signals to be transmitted among a plurality of wavelength components, converts the signals into WDM signals, and transmits the WDM signals to a WDM transmission network. The optical receiving device comprises an operating-system optical receiving unit and a standby-system optical receiving unit, and restores WDM signals from the WDM transmission network into transmission signals.

Abstract: The present invention implements open fiber control in an optical transceiver. During normal operation, the transceiver transmits signals through a connection to an optical network. When the connection is intact, the total power transmitted can be greater than the eye-safety limit. When the connection breaks, the transceiver detects the loss of signal and disables transmissions over all channels except for one. The transceiver continues transmission on the single enabled channel at an eye-safe level. When the connection is fixed and a signal reappears, the transceiver detects the signal reappearance and re-enables all channels that had previously been disabled. By allowing the transceiver to transmit with greater optical power when the connection is intact, an increased data rate and longer transmission distances can be achieved. At the same time, safety is preserved, because transmissions drop to acceptable power levels whenever a break is detected.

Abstract: An optical communication system and method for starting up and shutting down the system to ensure safety during repair of a fiber break are disclosed. A technique for shutting down an optical communication system having spans of optical transmission fiber interspersed serially between optical transformation sites and a plurality of amplifier sites includes shutting down both amplifiers on either side of a fiber disruption and both amplifiers in the same amplifier sites serving transmission in an opposite direction, followed by deactivation of all amplifiers within the same optical line between optical transformation sites. During startup, amplifiers enter an operating mode to ignore a system shutdown signal, an amplifier at a terminal site is forced on, and then successive amplifiers step through an intermediate safe power level before reaching full operating power.

Abstract: Power of scattered light separated from an optical transmission path is monitored, part of the excitation light is separated and power thereof is monitored, power of reflected light which passes in a direction opposite to a direction in which signal light passes through the optical transmission path is monitored, and, when monitored power of an excitation light reaches a predetermined determination value, whether or not any loss point occurs is determined, based on a ratio between the monitored power of the scattered light and the monitored power of the reflected light.

Abstract: A method and system for transmitting infra-red (IR) signals through power lines. An IR signal may be received and substituted with a corresponding RF signal. The RF signal may be placed on a power line network in one location and removed by a high-pass filter at a second location. The RF signal may be converted back to the corresponding IR signal.

Abstract: A system and method for identifying one or more characteristics of an optical signal, in which a transmitter is operable to transmit an optical signal and a receiving unit is operable to receive the optical signal. The transmitter has a laser for generating the optical signal and an encoding unit adapted to control the laser to activate and deactivate the optical signal during a laser shutdown state based on a predetermined code. The receiving unit has an optical receiver optically coupled to the transmitter by a light transmission medium and is operable to receive the optical signal from the transmitter. The receiving unit also has a decoder measuring at least one of an active time of the optical signal and the inactive time between active times of the optical signal. The decoder determines at least one of the one or more characteristics of the optical system based on at least one of the active time or the inactive time.

Abstract: A parallel optical module is constructed to include a plurality of photodetectors (MD1, MD2) which detect output lights of a plurality of arbitrary channels of a laser light source (3) having a plurality of channels, a plurality of detection and control loops which detect and control intensities of output lights of the laser light source based on detection signals from the plurality of photodetectors, and a control circuit (1) which stops output of the laser light source when an intensity of output light detected by at least one of the plurality of detection and control loops does not satisfy a predetermined standard.

Abstract: A method for standby switching in optical transmission devices is provided, wherein, in addition to a working signal and a protection signal, respective control signals with information concerning the allocation state are transmitted and evaluated at the receiving end. The control signals are transmitted via a monitoring channel even when the useful signal is switched off.

Abstract: An apparatus and method are disclosed for visualizing an automatic laser shutdown (ALS) state. An operator is informed of the ALS state by transmitting a visible light with weak power, to an optical fiber, that effuses from the cut position of the optical fiber. The operator recognizes the cut position of the optical fiber by comparing the power of the ALS visible light reflected from the cut surface of the optical fiber and that of the transmitting ALS visible light, and thus restores the cut optical fiber at the recognized position.

Abstract: An OPC generates a pump light having the wavelength &lgr;s with a power larger than a threshold for generating a nonlinear effect in an optical fiber for a main signal having the wavelengths &lgr;1 through &lgr;4 transmitted from an OS, and wavelength-multiplexes the generated light with the main signal. When the pump light induces a nonlinear effect, a signal light having the wavelengths &lgr;1′ through &lgr;4′ is generated symmetrically to a main signal having the wavelength &lgr;1 through &lgr;4 about the pump light on a wavelength axis. Thus, in a wavelength multiplexing system designed based on an eight-wave transmission, a signal light can function as a compensation light even when only four waves are used at the initialization of the system, thereby compensating for the characteristics of the system operations. Furthermore, the system is effective in cost because it simply requires an OPC for generating a pump light regardless of the number of compensation lights to be generated.

Abstract: A communication path impairment detection module for connection to a duplex optic communication link is provided. The duplex optic communication link includes an outgoing communication path and an incoming communication path, each being characterized by a data channel and an optical service channel. The communication path impairment detection module includes a first port and a second port suitable for coupling to the outgoing and incoming communication paths respectively. The communication path impairment detection module is responsive to impairment of the data channel and of the optical service channel in the incoming communication path to impair the data channel and the optical service channel in the outgoing communication path.

Abstract: A method and apparatus for detecting if an optical module has been disconnected from a fiber span or if there has been a break in the span, and for automatically reducing the output signal level of the optical module such that the output signal level is within an acceptable safety limit. Also disclosed is a system and technique for automatically resetting a Raman pump unit once the source of an optical leak has been located and addressed.

Abstract: A method and apparatus are provided to ensure that laser optical power does not exceed a “safe” level in a DC coupled open loop parallel optical link in the event that a fiber optic ribbon cable is broken or otherwise severed. A duplex parallel optical link includes a transmitter and receiver pair and a fiber optic ribbon that includes a designated number N of channels that cannot be split. The duplex transceiver includes a corresponding transmitter and receiver that are physically attached to each other and cannot be detached therefrom, so as to ensure safe, laser optical power in the event that the fiber optic ribbon cable is broken or severed. Safe optical power is ensured by redundant current and voltage safety checks, and the corresponding low duty cycle signal is generated by a safety pulse generator in the safety channel.

Abstract: The invention provides a network system for laser processing, comprising at least two laser devices and a workstation with a laser processing head which can be operated safely. A first light guide leads from the first laser device to a first connection element, associated with which is a first communication connection element connected to the laser controller of the first laser device. A second light guide leads from the second laser device to a second connection element, associated with which is a second communication connection element connected to the laser controller of the second laser device. The laser processing head can be connected to one of the connection elements by a mating connection part. A safety circuit of the workstation ensures that each laser controller releases the shutter switch only if the safety circuit is connected to the communication connection element connected to the respective laser controller.

Abstract: In the method and apparatus for providing an optical fiber interconnect, a transmitter transmits an optical signal through an optical fiber. The transmitter does not transmit to a controller, information about the power of the transmitted optical signal near the input end of the fiber. The controller receives an indication of the power of a returned portion of the transmitted optical signal. The controller causes the lowering of the power of the transmitted optical signal to a predetermined level based the received indication.

Abstract: A method and apparatus are disclosed for terminating optical links in an opticalnetwork based on performance requirements. The present invention forces the termination of the received optical signals at each node only on the protection ring and does not force termination on the working ring, unless necessary to satisfy performance requirements. A signal on an end-to-end light path on the working ring is terminated only when required by engineering rules, such as signal-to-noise requirements. Specifically, the present invention does not force terminate an end-to-end light path on the working ring at a given node (or on a link between two nodes) unless the signal will fail to meet certain criteria, such as a minimum optical signal-to-noise ratio, at the next node.

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 single-chip integrated circuit, sometimes called a controller, controls operation of a transceiver having a laser transmitter and a photodiode receiver. The controller includes memory for storing information related to the transceiver, and analog to digital conversion circuitry for receiving a plurality of analog signals from the laser transmitter and photodiode receiver, converting the received analog signals into digital values, and storing the digital values in predefined locations within the memory. Comparison logic compares one or more of these digital values with predetermined setpoints, generates flag values based on the comparisons, and stores the flag values in predefined locations within the memory. Control circuitry in the controller shuts off the laser transmitter in response to comparisons of signals with predetermined setpoints that indicate potential eye safety hazards.

Abstract: An automatic optical power management system for use with an optical communications system includes a light source residing in a first circuit pack and adapted to emit light at a nominal power level only absent receipt of an indicator signifying a loss of signal resulting from a fiber discontinuity relating to the first optical fiber, wherein the nominal power level is of sufficient magnitude to violate laser safety guidelines in the event of the fiber discontinuity. A redundant detection system includes a first optical detector residing in the first circuit pack, and a second optical detector residing in a second circuit pack that is optically adjacent to the first circuit. A redundant response system communicates an indicator signifying loss of signal from the first and second optical detectors to the light source upon detection of loss of signal by either detector.

Abstract: The present invention provides a method of monitoring a transmission fiber including the steps of transmitting a monitor signal on the transmission fiber in a direction opposite to the propagation of traffic signals on the transmission fiber, at an optical amplifier connected to the transmission fiber detecting the monitor signal and automatically shutting down the optical amplifier in response to a predetermined change in the detected monitor signal. The invention facilitates a faster shut down of amplifiers when a fault occurs than is currently available because it shuts down the amplifier feeding directly into the area of broken fiber first rather than last as in conventional communication systems.

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: 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: 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 method of routing of signals through an optical network involves determining a route through the network for which the power level within each branch of the network along the route is below a threshold power level which is a function of the fiber characteristics of the branch. This threshold power is the power below which a fiber fuse can not be initiated. This method enables power levels within a network to be controlled such that the threshold power is not exceeded, and a fiber fuse will not be initiated. The invention provides a network controller for carrying out this method.

Abstract: The invention refers to a safety procedure for optical fiber systems. Such systems are widely used in telecommunication to transport optical signals between a transmitter terminal and a receiver terminal. By the invented safety procedure the optical input power fed into said optical fiber system is automatically shut off or at least reduced in case of an unintended escape of light from at least one fiber. A safety interface, provided in the transmission line detects changes of the total optical output power in at least one fiber and initiates a shut-down of the input power as soon as a decrease of the total output power is detected, that exceeds a predefined value within a predefined time window. Thus the slope of the total output power is measured and evaluated rather than its absolute value.

Abstract: In an optical receiver circuit chip, which constitutes an optical fiber link and converts a received optical signal into an electrical signal for communication, shutdown function is added to a bias circuit, which supplies power to an internal circuit such as a photodiode, amplifiers, a comparator and a buffer. Furthermore, a shutdown control circuit is provided in order to cause the bias circuit to perform a shutdown control in response to whether or not a plug for a transmission medium such as an optical fiber is inserted to a corresponding jack and in response to an shutdown signal inputted to a shutdown input terminal in accordance with user's operation. Therefore, the shutdown control can be realized with lower cost and smaller substrate space compared with a case where a regulator IC is separately used.