Abstract: A system for transmitting a return to zero type optical pulse stream includes an optical line and arrangements for amplifying and reshaping pulses distributed along the length of the line. The mean chromatic dispersion of the fiber of the line is of the normal type and the reshaping arrangements include a modulator that is synchronized to the pulse stream that it receives and that applies amplitude modulation to reshape the pulses temporally and phase modulation that is decreasing at the start of a pulse and increasing at the end of a pulse to reshape the pulses spectrally. The reshaping arrangements further include a band-pass filter.

Abstract: The method of transmitting a sequence of binary-coded information modulates the phase and the polarization of soliton pulses in such a manner that phase alternates between pairs of successive pulses, and the absolute value of the phase angle difference between two successive soliton pulses remains constant over the entire pulse train. The pulse train is transmitted by applying the method. Emission and reception apparatuses implement the method. The method is applicable to transmitting information over long distances.

Abstract: A system for transmission of a digital signal on a transmission line with an optical on-line amplification. The transmission line is formed by a plurality of optical fiber sections and a plurality of optical amplifiers. Each of the optical amplifier is interposed between two adjacent optical fiber sections. The system includes at least one device for on-line compensation of the distortions induced in the digital signal, notably by the noise and the propagation on the transmission line. The on-line compensation device includes at least one bandpass optical filter having a passband whose value is substantially lower than that of the passband of the digital signal before transmission, and at least one saturable absorbent element that is a non-linear passive optical element having an absorption that depends decreasely on the optical power.

Abstract: In a system for the long-distance transmission of a digital signal on a fiber-optic transmission line connecting a transmitter station and a receiver station, the digital signal has rising edges and descending edges between two predetermined signal levels, respectively representing the two binary values that can be assumed by the digital signal, the transmitter station comprising: device for the amplitude modulation of the digital signal, delivering an amplitude modulated signal; device for the modification of the instantaneous optical frequency of the amplitude modulated signal, at the instants corresponding to the rising and descending edges of the digital signal.