Abstract: Providing a common broadcast channel in a WDM (wavelength division multiplexed) system is accomplished by applying a pulsed light source to a dispersive delay line, and also applying the light source to each of M delay lines, such that the Mth delay line has a delay of (M-1) time slots, where M is a nonnegative integer representing the number of time slots to be provided for the broadcast channel. The dispersive delay line spreads the spectrum of the pulsed light source across the desired bandwidth of the WDM system to provide a wide-spectrum signal, and this wide-spectrum signal may then be modulated to provide a plurality of WDM channels. The M delay lines provide delayed pulses that may be modulated to provide a common broadcast channel for reception on a plurality of WDM receivers.

Abstract: An optical transmitter/receiver transmits and receives optical signals between terminal devices of a network which are connected by a twisted pair cable with a feeder line. The optical transmitter/receiver has an electric connector for connection to the twisted pair cable, a peak holding circuit for detecting whether there is an optical signal in an optical fiber based on an output signal from an optical receiver, and a biasing circuit for applying a bias voltage to the twisted pair cable. The biasing circuit applies a bias voltage to a twisted pair of the twisted pair cable if there is an optical signal in the optical fiber, and stops the application of the bias voltage to the twisted pair if there is no optical signal in the optical fiber. The terminal devices are capable of detecting insertion or removal of the twisted pair cable or the optical fiber.

Abstract: An optical communication apparatus having a light receiving element 11 for receiving optical signals including an optical signal calling for communication start and an optical communication circuit 13 which includes an amplifier circuit amplifying the photocurrent generated by the light receiving element 11, performs predetermined processing necessary for the optical communication, and outputs a communication terminating signal upon termination of the optical communication, wherein there is provided a first circuit 15 capable of always supplying a bias voltage to the light receiving element 11, turning off a power source 29 for the optical communication circuit by making use of the communication terminating signal when it is outputted, and turning on the power source by making use of the photocurrent Ip generated by the light receiving element when the light receiving element receives the optical signal calling for communication start, whereby the power saving in the standby state can be made more effective c

Abstract: An optical interface device for applying a light signal to a port of device under test and analyzing the signals leaving each of the ports on the device. The device to be tested has at least two such ports. An interface device according to the present invention includes a plurality of optical couplers having first, second, third, and forth ports. Each of the optical couplers transfers a first fraction of a first optical signal received at the first port to the second port and a second fraction of that optical signal to the third port. In addition, each of the couplers transfers a fixed fraction of a second optical signal entering the second port to the fourth port. There is one such optical coupler for each of the ports of the device to be tested at any given time, the second port of that optical coupler being coupled to that port during testing.

Abstract: The BER is used as a parameter for evaluating the performance of an optical transmission system. Performance of optical systems is also defined by the Q factor, which indicates the signal-to-noise ratio of the electric signal regenerated by the receiver. In the absence of distortion, Q is univocally determined by the BER. Q is calculated using an estimated BER measured with the path under normal conditions of operation, and a distortion-free Q is determined in the same operating point of the system. The distortion penalty for the path is obtained by comparing the measured Q with the distortion free Q. In addition, the distortion penalty for a transmitter-receiver pair, and a distortion penalty for a transmission link between the transmitter and receiver may be determined.

Abstract: Optical emitting head including a laser and an external optical modulator. The modulating signal is modulated by an electrical signal proportional to 1-e, e being the noise power superimposed onto the laser signal, before being applied to the optical modulator. The invention is suitable for fibre optical transmission applications.

Abstract: An optical time-domain reflectometer (OTDR) launches pulses of light into a link or a system of multiplexed links and records the waveform of pulses reflected by the seals in the link(s). If a seal is opened, the link of cables will become a discontinuous transmitter of the light pulses and the OTDR can immediately detect that a seal has been opened. By analyzing the waveform, the OTDR can also quickly determine which seal(s) were opened. In this way the invention functions as a system of active seals. The invention is intended for applications that require long-term surveillance of a large number of closures. It provides immediate tamper detection, allows for periodic access to secured closures, and can be configured for many different distributions of closures. It can monitor closures in indoor and outdoor locations and it can monitor containers or groups of containers located many kilometers apart.

Abstract: An optical switch includes a semiconductor gain medium and inputs for an optical control signal applied to the semiconductor gain medium. The switch has a pair of arms (31, 32) arranged in a Mach-Zehnder configuration. A semiconductor gain medium (SOA1, SOA2) is connected in each arm. A fixed phase shifting element PE is also connected in one arm. Control signals are applied to each of the semiconductor gain media. There is a delay between the control signals selected so that a desired one of the optical pulses experiences a differential phase shift and so we switch to a different output of the multiplexer. In one example, the semiconductor gain media are provided by discrete semiconductor devices sandwiched between a pair of planar substrate on which waveguides forming the other components of the switch are formed. The switch may be used for demultiplexing OTDM signals.

Abstract: In an optical head for optical beacon, a prism 5 is arranged immediately after light emitting elements 1 of an optical head 10 in light radiating directions of the light emitting elements 1, so that the paths along which light rays travel immediately after the radiation can be curved by the prism 5. As a result of this configuration, if the index of refraction of a material of which the prism 5 is made and the angle of a slope of the prism 5 are set to proper values, the light rays can be injected from the prism 5 to an optical head 10 on the side of a light receiving element 2 in arbitrary directions. Further, a surface 21 of a body 13 in which a transmission window 14 is formed is so shaped as to be inclined backward with respect to the travelling direction of an automobile from an upper edge a to a lower edge b.

Abstract: In a transmission system, a control circuit (4) receives an input binary sequence (T) representing data to be transmitted. The circuit encodes the sequence using a phase alternation code which differs from the phase inversion duobinary code in that the phase shifts applied to a carrier wave are less than 90 degrees. For this purpose, a semiconductor chip (3) includes a laser transmitter and an electro-absorption modulator having two segments. The chip generates said carrier wave and modulates it using the encoded sequence. An optical fiber (54) conveys the modulated wave. And a detector diode (58) receives the conveyed wave and performs intensity discrimination thereon so as to restore the input binary sequence.

Abstract: A photonics package, and methods for its use are disclosed. In one configuration, a collimating lens is disposed between a photonics device and a ferrule containing two optical fibers. Preferably, one of the fibers delivers an optical signal to the photonics device, and the other fiber receives an optical signal from the photonics device. The fibers within the dual-fiber ferrule are located off of the optical axis of the lens so that light emanating from the signal-delivering fiber will be imaged onto the photonics device at a slight angle from the normal and may be reflected at the same angle for coupling into the signal-receiving fiber Preferably, the photonics device is situated at the Fourier plane to facilitate coupling reflected light into the signal-receiving fiber. The function of the photonics package varies with the included photonics device.

Abstract: An optical network in which data signals are encoded with a wavelength corresponding to the address of the signals includes at least one point therein, a data routing switch (1) which comprises: a wavelength comparator (3) for example a Brag grating or a notch filter that will receive data signals and has associated therewith a characteristic wavelength so that it will send the data signal along a gate enabling line (5) or not in accordance with the relationship between the data signals encoding wavelength and the characteristic wavelength of the comparator, and a gate (7) which transmits or blocks the data signal in response to the presence or absence of the data signal in the gate enabling line and a number of data routing switches having different characteristic wavelengths so that routing of the data is determined by which switch characteristic wavelength matches the data encoding wavelength.

Abstract: A programmable wavelength router having a plurality of cascaded stages where each stage receives one or more optical signals comprising a plurality of wavelength division multiplexed (WDM) channels. Each stage divides the received optical signals into divided optical signals comprising a subset of the channels and spatially positions the divided optical signals in response to a control signal applied to each stage. Preferably each stage divides a received WDM signal into two subsets that are either single channel or WDM signals. A final stage outputs optical signals at desired locations. In this manner, 2.sup.N optical signals in a WDM signal can be spatially separated and permuted using N control signals.

Abstract: Channels are assigned in an optical bus network, including N nodes connected in series to one another by way of a pair of optical fibers, which facilitate simultaneous, two-way communication between all nodes of the bus network. A second pair of optical fibers, which directly connect the first and second nodes of the bus network, is adapted, after protective switching, to maintain the communication in the event of an interruption in the first pair of fibers. Each transmitter on the bus network transmits a certain network channel. Each receiver on the bus network receives a certain wavelength channel and allows other wavelength channels to pass to the next node. The channel which is received by a receiver in a node is entirely removed from the network, whereafter the channel can be re-used for transmission of information between two other nodes.

Abstract: In order to reduce its switching time, the delay apparatus comprises a coupler and a multiplexer provided with n inlets set respectively to n distinct wavelengths. Inlets of the multiplexer are coupled respectively to outlets of the coupler via wavelength conversion apparatuses, and via delay lines all of which are different. Each conversion apparatus has an amplifying optical gate function and delivers to the corresponding inlet of the multiplexer a wave carried by the wavelength associated with said inlet. The invention also concerns apparatus for synchronizing channels of a wavelength multiplex using the variable delay apparatus. Application in particular to synchronizing optical packets in a switched optical network.

Abstract: A display unit is rotatably supported on an apparatus body of a portable electronic apparatus, by a hinge portion. The display unit has a hollow boss projecting into the apparatus body, and the boss is engaged with the apparatus body to be rotatable around the rotation center axis of the hinge portion. An inner hole in the boss communicates with the inside of the display unit and with the inside of the apparatus body, thereby forming a communication path coaxial with the rotation center axis. In the apparatus body, there is provided a light emission element for emitting image data to be transmitted to the display unit, in form of an optical signal into the communication path. In the display unit, there is provided a light receive element for receiving the optical signal from the light emission element through the communication path.

Abstract: This network, intended for the transmission of information in optical form, wavelength multiplexed, comprises nodes (N1, N2) linked to each other by at least one optical fiber (F1), at least one wavelength being treated in each node. The system comprises unit (OF1, OF2, OS1, OS2) for superimposing on the information, for at least one wavelength per node, a surveillance signal whose frequency is outside the transmission band and, in each node, a surveillance circuit (CS1, CS2) for sampling at least one part of the surveillance signals, elaborating surveillance information in function of this part and sending this information to the processing units of the network. Application in optical telecommunications.

Abstract: Provided are an optical amplifier, for amplifying a light signal; first and second light dividers, optically connected to an output terminal of the optical amplifier; and first and second light receivers, for receiving light divided by these light dividers. A variable wavelength filter is located between the first optical coupler and the second optical couler. In addition, provided are a filter driver, for sweeping a center wavelength that passes through the variable wavelength filter; a counter circuit, for counting output peaks of the second light receiver; and an output controller, for controlling an output of the optical amplifier so as to maintain a constant output by the first light receiver. The output controller employs a voltage output by the count circuit as a reference voltage for controlling changes in the light output power of the optical amplifier that are in consonance with the value held by the counter, i.e., in consonance with the number of signal light wavelengths.

Abstract: An optical modulating method and an optical modulating device for optical time division multiplexing (OTDM). The optical modulating device comprises, for example, an optical switch for generating first and second optical clocks according to a carrier beam output from a light source, optical modulators for respectively switching on/off the optical clocks by data signals to thereby generate first and second signal beams, an optical multiplexer for combining the signal beams to generate an OTDM signal, and prechirp circuit for controlling, for example, the optical clocks so that the OTDM signal has a chirp parameter adapted to an optical transmission line. This optical modulation device is suitable for high-speed transmission and allows chromatic compensation.

Abstract: An optical telecommunication unit includes a shielded case having a size adapted for mounting upon a standard open-rack frame, wherein the shielded case includes a rear panel carrying an interconnection pattern, a plurality of plug-in connectors provided on the rear panel at an inner side thereof in electrical connection with the interconnection pattern for holding plug-in units forming an optical telecommunication apparatus inside the optical telecommunication unit, wherein the optical telecommunication unit carries a plurality of interface connectors on the rear panel in electrical connection with the interconnection pattern for accepting external interconnection cables, and a rear cover is provided on the shielded case so as to cover the rear panel.