Abstract: An emitter of optical signals for optical fibers includes an electroabsorption modulator downstream of a laser and a Mach-Zhender modulator downstream of the electroabsorption modulator and controlled by at least one clock to eliminate for each pulse of the resulting signal from the first modulator a portion of signal in a time range including the rising edge and in a time range including the falling edge.

Abstract: An emitter of optical signals for optical fibers includes an electroabsorption modulator downstream of a laser and a Mach-Zhender modulator downstream of the electroabsorption modulator and controlled by at least one clock to eliminate for each pulse of the resulting signal from the first modulator a portion of signal in a time range including the rising edge and in a time range including the falling edge.

Abstract: A method of making an optical transmission system safe, the system including a transmission optical fiber and emitting an optical wanted signal, transmitting a transmitted optical signal containing the wanted optical signal and optical noise, sampling a portion of the transmitted optical signal constituting a monitoring optical signal, and analyzing the power of the monitoring optical signal to deduce, as a function of the power of the monitoring optical signal, whether the transmission optical fiber is broken. The method isolates in the monitoring optical signal a first signal containing only the noise and a second signal containing the noise and the wanted signal and compares the power of the first and second signals and to deduce that the transmission optical fiber is broken if the ratio of the power of the second signal to the power of the first signal is substantially equal to 1.

Abstract: An optical transmission method and device consisting of coding a binary data pattern (SI) to be transmitted in the form of a second binary signal (SM), by differential coding; filtering the second binary signal (SM) to obtain a duobinary signal (SMF having three meaningful values (-1, 0.+-..epsilon., +a) and a narrower bandwidth; and modulating an optical carrier according to the values assumed by the filtered signal (SMF), the modulated carrier having a maximal amplitude to represent the maximal value (+a) and the minimal value (+a) of the duobinary signal (SMF), the phase of the modulated carrier being shifted by .theta..sub.1 and .theta..sub.2 =.theta..sub.1 +180.degree., respectively, and a minimal amplitude to represent values (0.+-..epsilon.) near 0 if the duobinary signal. The method of this invention is suitable for long distance fiber-optic transmissions.

Abstract: A system for re-establishing the transmission quality of a digital information transmission link including amplifier equipments in the event of failure of one or more amplifier equipments includes, associated with at least one of the amplifier equipments, a gain control device for varying the gain of the amplifier equipment in order to compensate for deterioration of the receive signal-to-noise ratio following failure of at least one other amplifier equipment. An error corrector coder at the send end of the link operates on the digital information to be transmitted and an error corrector decoder at the receive end of the link operates on the received digital information. The error corrector code used by the error corrector coder and decoder reduces or eliminate residual errors at the receiving end associated with residual deterioration of the receive signal-to-noise ratio not compensated by varying the gain.