Abstract: The present invention provides a method of dispersion compensation comprising the steps of:

Abstract: A circuit having two optical amplifiers each of which comprises a pump source, an active medium such as an optical fiber, and means for recovering pump energy that is unused in its active medium so that said energy can be reinjected into the other amplifier. The recovery means is such that in each amplifier, reinjection is performed in the direction opposite to the direction in which the main pump energy is injected. By way of example, each amplifier includes a recovery terminal constituting both an outlet for the unused pump energy and an inlet for reinjection the pump energy as recovered from the other amplifier. A single conductor provides an optical link between the recovery terminals of the two amplifiers. The circuit can be used in a repeater for long distance transmission of optical signals, in particular for undersea transmission.

Abstract: A device for assessing the transmission quality of an optical amplifier includes a coupler for sampling on the upstream side of the amplifier equipment relative to the direction of propagation of the optical signal to be amplified by the amplifier equipment part of the power of an optical signal propagating in the direction opposite to the propagation direction and corresponding to that part of the noise generated by the amplifier equipment transmitted in the direction opposite to the propagation direction. It also includes a coupler for sampling on the downstream side of the amplifier equipment relative to the propagation direction part of the power of an optical signal propagating in the propagation direction and corresponding to the optical signal after amplification by the amplifier equipment superimposed on that part of the noise generated by the amplifier equipment and transmitted in the propagation direction.

Abstract: A method of transmitting signalling along a bidirectional digital transmission link consists in transmitting from an intermediate equipment of the link a signalling message in two parts. One is a characterizing part the form of which depends on the signalling type and which is substituted for data of one of the digital bit streams carried by the link in the direction from one of the terminals referred to as the processing terminal. The other is a localizing part whose form is independent of the signalling type and which is substituted for data of the digital bit stream carried by the link in the direction towards the other, so-called relay terminal. The relay terminal responds by sending an acknowledgement message to the processing terminal, the time-delay of this relative to the characterizing part being used to identify the sending equipment. A signalling message transmission circuit controls switching circuits inserted into the paths of the digital bit streams carried by the link.

Abstract: Apparatus for implementing a remote signalling method which consists in momentarily replacing the transmitted digital data stream by a remote signalling message which is built up from not more than n identical and nonconsecutive sequences of N bits, with the first sequence of each message being present on each occasion that a message is sent, and with the remaining n-1 sequences of each message representing, by their presence or absence, the values 0 or 1 of n-1 digits in a binary number encoding remote signalling data. FIG. 2 shows a circuit for transmitting a remote signalling message from an equipment along a very high data rate digital link, which equipment is provided with a circuit (6') for detecting and handling alarms, and a circuit (3) for recovering the bit rate from the digital stream.

Abstract: The method consists in momentarily replacing the data transmitted by a digital data link with a digital message comprising two non-consecutive sequences, with the first sequence being a prefix sequence and the other sequence being a suffix sequence. The period of time separating the prefix and suffix sequences is variable and encodes remote signalling data. FIG. 2 shows a message transmitter circuit fitted in digital link equipment for operation at a very high data rate, and provided with a circuit (6') for detecting and handing alarms and with a circuit (3) for recovering the bit rate from the digital stream. A pattern generator (10) serves to generate a 1000 pattern and its 0111 complement from the recovered check rate. An oscillator (20) has a period which defines the time interval separating the prefix sequence and the suffix sequence.

Abstract: The method consists in momentarily replacing the data in a transmitted digital data stream by a remote signalling message which is built up from consecutive sequences, each of which is obtained by repeating a specific binary pattern chosen from a plurality of possible binary patterns which are generated from the second and fourth sub-harmonics of a clock signal at the bit rate of the digital stream, and from logical combinations thereof. FIG. 2 is a circuit diagram of a transmitter circuit for transmitting a remote signalling message. Said transmitter circuit is located in equipments on a very high data rate digital link, which equipments include a circuit (6') for detecting and handling alarms, and a circuit (3) for recovering the bit rate from the digital stream. Divide-by-two circuits (10, 14) and a logic gate (16) serve to generate three kinds of pattern from the recovered clock rate, namely: 0101, 0011, 1000.