Abstract: In an optical communication system in which cable-television signals and subscriber-assigned tele-communication signals are transmitted over a passive optical network (4, 5) to at least one optical network termination (6), each optical network termination (6) requires two optical-to-electrical transducers. An optical network termination (6) is disclosed which requires only one optical-to-electrical transducer (24). The system has two transmitting devices (1, 2) which each transmit a respective optical signal (O.sub.TV, O.sub.D). In the second transmitting device (2), a second electric signal (S.sub.D), whose energy occupies a second frequency band (FB2), is processed in such a way that the energy is concentrated in a subband lying outside the first frequency band (FB1) of a first electric signal (S.sub.TV). The optical-to-electrical transducer (24) in the optical network termination (6) converts the received optical signals (O.sub.TV, O.sub.D) to an electric multiplex signal (E.sub.

Abstract: An optical transmission system which permits long-distance, ultrafast, high-capacity optical soliton transmission by suppressing timing jitter with simple means. In an optical transmission system which uses a transmission line composed of an optical fiber for transmitting therethrough a lightwave signal having digital information added to a return-to-zero lightwave pulse and a plurality of optical amplifying repeaters for compensating for losses by the optical fiber and in which the pulse compression effect by the nonlinear optical effect on the optical pulse and the pulse expansion effect by the dispersion effect are compensated, at least one optical band limited element which has a flat group delay characteristic near the center frequency is disposed in the transmission line at intervals of a period Z equal to the soliton period Z.sub.sol and the product, aB.sub.sol.spsb.

Abstract: A transmission and reception module for a bidirectional optical communication and signal transmission includes a light transmitter having a first lens coupling optical element, and a light receiver. A fiber connection has a second lens coupling optical element for a common optical waveguide. A beam splitter is disposed in a free beam path. A common housing surrounds the foregoing. The light transmitter, the beam splitter and the fiber connection as well as the light receiver which is orthogonal thereto, are disposed axially symmetrically.

Abstract: An automatic gain control circuit for use in a multichannel RF system using fiber optic links. The circuit samples the power levels from a number of attenuated RF signals simultaneously and adjusts the gain in all of the channels by the amount required to keep the highest power channel below a predetermined power level determined by the power capacity of the fiber optic link while maintaining the signal strength relationship between the attenuated signals as was existing between the RF input signals.

Abstract: A bidirectional optical bus and bus interface. Each functional unit (35, 37) includes an active coupler (60, 70) for each bus line (40a, 40b) with which it is to interface. Each coupler is a four-port device, controllable to assume a desired one of at least two states characterized by different coupling coefficients. In the first state, a significant fraction (possibly all) of the light incoming to the first port (65a) is coupled to the fourth port (65d) and a significant fraction of the light incoming to the second port (65b) is coupled to the third port (65c). In the second state, most of the light incoming to the first port is coupled to the second port with a small fraction coupled to the fourth port, and most of the light incoming to the second port is coupled to the first port with a small fraction coupled to the third port.

Abstract: An optical packet switch which receives data packets and switches those data packets in the optical domain without using recirculation devices is provided. The switch staggers the data packets in time to avoid packet collisions within the switch. The switch includes two stages that are coupled by optical delay lines. The non-blocking stages include a scheduling stage and a switching stage. Incoming data packets are received at the scheduling stage and are output to appropriate optical delay lines. The scheduling stage and the delay lines ensure that the data packets do not collide when the packets are switched at the switching stage of the optical switch.

Abstract: A phase-modulated carrier wave is injected into a line fiber (4) by a semiconductor laser source (8, 10) to carry digital data to be transmitted. An optimum value for a permanent parameter of the carrier wave, in particular the phase deviation thereof, must be redefined from time to time because of drift in the characteristics of the source. This is done on the basis of the variations in the power of a diffracted wave that is caused to return via the fiber by Brillouin scattering in response to an incident wave emitted for this purpose by the same source. Application to telecommunications networks.

Abstract: In a light transmission device operable in response to a sequence of input digital signals to produce an output light beam, a modulated light beam is produced from a laser device as a result of frequency shift keying carried out under a designed modulation index and is transmitted as the output light beam on one hand and is sent to a Fabry-Perot interferometer on the other hand to produce an optical output beam which has an output level deviated in dependence upon a variation of a modulation index relative to the designed modulation index. A feedback signal is fed back to a drive circuit which is supplied with the input signals and which is operable to control the laser device. The feedback signal serves to adjust the modulation index of the laser device to the designed modulation index. A controller may be included to control a central frequency of the output light beam by producing a bias signal which is added to the feedback signal.

Abstract: An optical transmission system utilizing at a transmitter (100) continuous phase frequency shift keyed modulation of a laser (14) and a coherent heterodyne receiver (200) therefor, the system including at the transmitter means for imposing (18,12) a low frequency modulation on the transmitter optical power and frequency deviation and at the receiver means for extracting (28) from the receiver AGC control signal a replica of the low frequency modulation, means for demodulating (32) the modulated frequency deviation of the received optical signal synchronously with respect to the extracted low frequency signal, means for deriving (34) from the demodulated signal an error signal and a control system responsive to the error signal to control the receiver local oscillator (22) frequency.

Abstract: When a communication network system is constructed using an optical fiber as a transmission path, a node which transmits a signal may receive its own transmission signal upon reflection of an optical signal on the transmission path. When access control to a network is performed by a CSMA/CD method, the reflection signal may be erroneously detected as a signal sent from another node, and a collision which has not actually occurred may be detected. In order to avoid this, a reflection signal component of the transmission signal must be removed from a reception signal. For this purpose, a time-inverted signal of the transmission signal, and the reception signal are modulated, and the modulated signals are then input to a convolver, thereby obtaining a convolution integral value between the two signals.

Abstract: According to an optical receiver of the present invention, an optical input signal is converted to an electric signal by a photoelectric element, and amplified by an amplifier. Thereafter, a band frequency is restricted by a low pass filter, and a peak value of a bottom level of the band-restricted pulse signal is detected. Then, an offset voltage is added to the detected value, thereby a compare reference value is generated. The output of the amplifier is compared with the compare reference voltage by a comparator, thereby data is discriminated.

Abstract: An optical communications system comprises a transceiver arranged to provide two-way communication over an optical communications channel (3). The transceiver comprises a semiconductor light source (4) and a detector (5). The semiconductor light source (4) provides optical signals for transmission via the optical communications channel (3), and the detector (5) detects optical signals received via the optical communications channel and converts said optical signals into electrical signals. Means (2)a, (2)b) are provided for modulating the output of the semiconductor light source (4) with an RF carrier having a first frequency. Said electrical signals are passed through filter (8) adapted to filter out signals at said first frequency.

Abstract: An optical repeater OFF-state supervisory method includes the steps of: converting an input optical signal into an electrical signal; monitoring a level of the input optical signal from a monitored value when converted into the electrical signal; monitoring whether an input optical signal to an optical repeater is in an OFF state or not; detecting that the input optical signal has been in an OFF state; and changing the monitored value to a predetermined fixed monitored value.

Abstract: A fiber optic sensing apparatus is provided to measure the relative reflections of two temporarily displaced signals. One of the signals is a reference signal and the other signal represents the magnitude of a sensed variable. A reference mirror is disposed at a preselected position along an optical fiber between a transmitter/receiver and a sensor mirror. The transmitter provides an energy pulse into a first end of the optical fiber. When the energy pulse encounters the reference mirror, a first portion of the energy pulse is reflected back toward the receiver which is located at the first end of the optical fiber. The remaining portion of the energy pulse continues toward the sensor mirror. A second portion of the energy pulse is reflected by the sensor mirror. The second portion is of a magnitude that is analogous to the sensed parameter. Fiber optic delay lines are provided between the reference mirror and the transmitter/receiver and also between the reference mirror and the sensor mirror.