Optical pulse source, and a soliton optical transmission system including the source

A soliton optical transmission system including:

• an optical pulse source for supplying optical pulses on command, said optical pulse source comprising:
• an optical emitter for supplying a light wave;
• an electrically-controlled optical modulator receiving a light wave and having a threshold characteristic curve so as to transmit an optical pulse having a duration less than the duration of an electrical pulse applied to the modulator;
• and
• a control generator for supplying an electrical-type control signal for controlling the modulator, the generator supplying the signal in the form of a control pulse having firstly a leading edge from a base value to a maximum signal value and secondly a trailing edge returning to the base value, the modulator stopping said light wave when the signal has the base value, whereby the modulator transmits said light wave in the form of an optical pulse whose duration is defined by the control pulse;
• wherein said modulator is a modulator having a threshold and whose optical transmittance reaches a perceptible value only when said control signal exceeds a threshold lying between said base value and said maximum signal value;
• said control pulse having a leading edge and/or a trailing edge that is/are progressively sloping, whereby said optical pulse is shorter than the control pulse;
• an input circuit receiving data to be transmitted and controlling the source such that it supplies a succession of optical pulses, in which succession the time intervals between the optical pulses are representative of the data to be transmitted;
• a line fiber constituted by a very long optical fiber receiving said succession of optical pulses, and having both chromatic dispersion and a Kerr effect such that the dispersion and the Kerr effect compensate each other to maintain the shape of an optical pulse when the optical pulse has intensity, duration and spectrum width that are characteristic of a soliton in the fiber;
• and
• a receiver receiving the optical pulses transmitted by said line fiber and processing the received pulses to retrieve said data to be transmitted;
• and
• wherein said optical pulse source supplies said optical pulses in the form of said solitons of said line fiber.