Abstract: An AC-coupled receiver is provided which allows data with long periods of no signal sent on a fiber optic bus to be received without the normally required preamble. The receiver provides a voltage signal which is AC-coupled to one side of a differential amplifier with a delayed voltage signal AC-coupled to the other input of the differential amplifier. If the time constant of the AC coupling network is much longer than the signal baud time, low-frequency variations at the two inputs of the differential amplifier will be nearly identical and the low frequency signals will effectively cancel each other.

Abstract: An optical regenerator includes a clock recovery circuit which recovers an optical clock signal from a received deteriorated optical data signal. The recovered optical clock signal is used to generate a new optical clock signal. The new optical clock signal and the received deteriorated optical data signal are applied as an input signal and control signal, respectively, to a Sagnac switch which encodes the new optical clock signal with the encoded information of the deteriorated optical data signal thereby regenerating a clean optical data signal.

Abstract: An optical communication method and network system includes a base station for generating a plurality of beams having different wavelengths, an optical transmission line for transmitting the plurality of beams emitted by the base station, an optical transmitter, connected to the optical transmission line, for selecting one of the plurality of beams transmitted through the optical transmission line and modulating the selected beam in accordance with a signal to be transmitted, and an optical receiver, connected to the optical transmission line, for receiving the signal transmitted using the selected beam.

Abstract: A wavelength-stabilizing method for use with an optical communication system capable of transmitting and receiving information by means of signal light between a pair of stations each having a coherent optical transmitter and a coherent optical receiver. This method is characterized in that each station transmits signal light while controlling its wavelength at the coherent optical transmitter and receives the incoming signal light together with the local light at a wavelength adjusted in accordance with the wavelength of the incoming signal light.

Abstract: A method of linearizing a modulator (1) having two parallel-coupled sub-modulators (2, 3). The complete transmission function of the modulator includes parameters which relate to power division (A, 1-A) of a non-modulated carrier wave (P.sub.in) and a relationship (B) between the activation degree of the sub-modulators (2, 3). The transmission function is simplified and series-expanded with two higher-order terms, each having a respective coefficient. An expression for intermodulation distortion is calculated with the aid of the series-expansion and with control signals (V1, V2) having two or three frequencies. The signs of the coefficients are determined so that the terms having these coefficients will mutually counteract their respective distortion contributions, and limited search regions for the parameters (A, B) are calculated with the aid of the sign-determined coefficients.

Abstract: A casing for use in a television set has a U-shaped frame for firmly supporting the cathode ray tube and a chassis arrangement for supporting a circuit arrangement for driving the cathode ray tube. An escutcheon is secured to the frame at a position in front of a screen of the cathode ray tube. A protection cover is connected to the frame for covering the cathode ray tube. Thus, the frame, chassis arrangement, escutcheon and protection cover taken together define an integral unit which is a semi-completed product that can be shipped from a factory. The casing further has a cabinet provided over the protection cover for covering and decorating the appearance the television set, and a back cover for enclosing the integral unit in the cabinet. The cabinet and the back cover can be applied at a local distribution station in accordance with the desire of the user.

Abstract: An optical data network, in which data is exchanged between an active central unit (CU1) and subscriber line units (DU1, DU2, DU3, . . .) using the time-division multiplexing method. The reliability is considerably enhanced by parallel connection of a back-up central unit (CU2). In order to permit a disruption-free switchover between the central units (CU1, CU2), the latter have controllable delay devices (TDL1, RDL1, TDL2, RDL2), so that the delays of the signals to and from the subscriber line units (DU1, DU2, DU3, . . . . ) can be matched with the aid of a special line unit (SDU).

Abstract: The invention is a system and method for improving the signal-to-noise ratio of an electrical data signal transmitted between two electronic modules. An electrical data signal from a first module is amplified by an electrical amplifier to produce an amplified electrical data signal. The electrical amplifier is supplied by a power distribution network. The amplified electrical data signal has a power level sufficiently low such that the electrical amplifier does not cause significant disturbances in the power distribution network so that a plurality of the electrical amplifiers can be proximately located and operated concurrently without significant noise coupling occurring between the electrical amplifiers through the power distribution network. The electrical data signal is then converted to an optical data signal for transmission to a second module. The optical data signal is transmitted to the second module through an optical path where it is optically amplified.

Abstract: An IFF device comprises a beam generator for directing an unmodulated beam at a target. The target has a plurality of retro-reflectors mounted on it. These retro-reflectors have internal reflecting surfaces for reflecting the unmodulated beam penetrating the retro-reflector. A device is associated with the internal reflecting surfaces for modulating the beam at a predetermined frequency so that the reflected beam emerging from the retro-reflector is modulated at the same frequency. A tuner is positioned in the path of the reflected modulated beam and tuned to predetermined frequency, so that if the tuner receives a signal, it indicates the target is friendly.

Abstract: An optical distributor which comprises M inputs (M>1) each receiving signals. M modules (MT1 to MT4) are connected to the M inputs and each simultaneously process N consecutive signals (N>1). N optical couplers (CO1 to CO4) each having M inputs and 1 output are connected to one of the N outputs. A control means (G) controls the modules and enables the distributor to scramble the signals so that a given signal reaches a given output of the distributor. Each module electronically demultiplexes the N consecutive signals, time rearranges the demultiplexed signals in accordance with the output of the distributor imposed by the control means for each of these signals, transposes the latter into optical form at N different wavelengths and switches each transposed signal to the desired output of the distributor. Such a device finds particular application in optical telecommunication system.

Abstract: The present invention relates to a method for detecting external influence on an optical cable. The invention can be used as a sensor in an intrusion alarm, in which case the cable is buried and an alarm is triggered when someone treads on it. The invention can also be used as a surveillance system for an optical cable transmitting information. The method means that coherent radiation for surveillance purposes is transmitted in multimode in an optical fibre. On the receiver side the surveillance radiation is then split into two beams, that are plane-polarized in two different directions. Then the amplitude and/or frequency content of each beam is detected. A signal which is a measure of their amplitude and/or frequency relation is formed from this. Finally an alarm function is initiated when the signal exceeds predetermined values in time and/or level.

Abstract: A photovideo camera takes visual images formed on negative films and/or positive films to obtain video signals corresponding to the visual images. The camera unit of the photovideo camera can be focused after determining a desired angle of view by zooming, without changing the desired angle of view. In focusing the lens unit, only the master lens of the focusing lens system of the lens unit is moved.

Abstract: An electro-optical modulation system comprising an optical modulator for pulse-modulating an incoming light beam in response to a pulsed RF input signal and to a bias signal and for producing a pulse-modulated optical output which is characterized by a plurality of enveloped pulses, optical detector for producing an electrical signal which is representative of the output from the optical modulator, average detecting device for producing pulse envelope signals which are representative of the envelopes of the pulses, and a bias control circuit, using a plurality of pulse envelop signals, for producing the bias signal as a function of the pulse envelopes.

Abstract: In an optical self-muting network, N optical splitters are associated respectively, with N inlet terminals for splitting an optical signal from the associated inlet terminal into M replicas of the optical signal. M optical combiners, associated respectively with M outlet terminals, combines N optical signals incident thereon into a combined optical signal and couples it to the associated outlet terminal. M sets of N optical gates are connected between the N optical splitters and the M optical combiners. Each optical gate allows passage of an optical signal incident thereon when it timely coincides with an electrical signal applied thereto. A controller supplies a gate control electrical signal to the optical gates of each set during M successive intervals. Contention between optical packets simultaneously incident on the optical gates of the same set is resolved by the controller.

Abstract: An apparatus for reading data from each of a plurality of image duplicating devices comprises a plurality of image duplicating devices each having a two-way communications port for receiving and transmitting data and a processing device electronically coupled to the two-way communications port of each of the image duplicating devices for receiving information from and transmitting information to each of the image duplicating devices. The apparatus allows each image duplicating device to be operated simultaneously with the processing device.

Abstract: A logarithmic video detector/r.f. limiter amplifier provides an amplitude-limited r.f. carrier version of an input signal. The amplitude-limited signal is either employed directly or is coupled to a mixer that produces a down-converted constant-amplitude signal which is applied to a first optical modulator which in turn is coupled to an optical source. The optical modulator is coupled to an optical fiber that carries the frequency component of the input signal at a first light wavelength. The amplifier also supplies a signal which is dependent upon its logarithmic detector response that represents the amplitude component of the input signal. This signal is supplied to a VCO which drives a second optical modulator which is coupled to a second optical source and produces an optical signal of a second light wavelength. In a first embodiment, both optical signals are supplied to the receiver over the same optical fiber link.

Abstract: The optically-based frequency synthesizer for generating an electric output signal at a preselected frequency having a given period that can be changed over a wide band of frequencies for communication purposes, comprises a modulator having an input for receiving a command signal, and an output for generating a current driving signal having a DC component, and a modulating component formed of an AC signal having a predetermined time period which is an integer multiple of the period of the preselected frequency, and an amplitude responsive to the command signal, a laser having an input for receiving the current driving signal, the coherent light signal having a given coherence time; optical isolators for receiving the light signal emitted by said laser; a splitter having an input optically connected to the isolators; a first optical path having an end optically connected to the splitter; and a second optical path having an end optically connected to the splitter, and a delay means along its length, the time de

Abstract: An optical detector for use in detecting digital optical signals has an optical fiber coupler which splits a received optical signal into two signal portions. The coupler has unequal length output fibers so that one signal portion impinges upon an associated photodetector delayed relative to the other. The photodetectors are connected in series nonopposed when the delay is equal to the bit period of the optical signal the output of the detector is the differential code (dicode) of the received signal which can be recovered by a high input impedance, i.e. integrating, amplifier. By forming the dicode in the optical domain in this manner large DC and AC dynamic ranges are obtained without linearity constraints on the optical transmission source that apply when the optical signal is transmitted as a dicode.

Abstract: An optical transmitting and receiving system for connection to an optical bidirectional transmission path comprises a transmitter and a pair of coherent receivers sharing a local oscillator. The transmitter and receiver and connected to the transmission path via a hybrid circuit. The hybrid circuit is provided with a first polarisation splitter, a nonreciprocal polarisation rotator and a second polarisation splitter. A connection of the first polarisation splitter and a connection of the second polarisation splitter form, respectively, the input connection for the transmitter and the bidirectional connection of the hybrid circuit. The input and output of the nonreciprocal polarisation rotator are connected between the first and second polarisation splitters. The receivers are connected to separate outputs of the polarisation splitters.

Abstract: A system for optical communication between first and second optical terminal stations, containing a plurality of working optical transmission lines each for connecting between the first and second optical terminal stations, a protection optical transmission line. Each of the first and second optical terminal stations contains a plurality of working pieces of optical terminal equipment, connected to the respective working optical transmission lines, a protection piece of optical terminal equipment connected to the protection optical transmission line, and a plurality of bidirectional optical signal paths, provided corresponding to the respective working pieces of optical terminal equipment, and each operative to connect the corresponding working piece of optical terminal equipment to the protection piece of optical terminal equipment.