摘要:
To increase the transmission length in an optical fiber, a method of transmitting digital data uses both power modulation and phase modulation of an optical carrier. To compensate the chromatic dispersion produced by the fiber, a phase-shift is applied to the wave within each time cell in which the optical power is low and that precedes or follows a cell in which the power is high. Applications include long-distance optical transmission using standard fibers.
摘要:
Transmission line sections in a connection comprise passive portions transmitting the signal without compensating for its natural attenuation and occupying 15% to 65% of the length of the section. They also include active portions that amplify the signal. The invention is particularly applicable to making intercontinental connections.
摘要:
A laser source supplies a primary laser beam. A phase grating generates two secondary beams from the primary beam so as to form interference fringes that are inscribed in an optical fiber by photo-refraction. An optical system of variable focal length varies the gap between the interference fringes so as to vary the pitch of the Bragg grating discretely for successive segments of the optical fiber. Means displace the primary laser beam and the optical fiber relative to each other by successive segments of said fiber. These means are synchronized with the variation of the focal length of the optical system. Application to telecommunications.
摘要:
An electrical power supply (20, 22) powers a semiconductor laser chip (2) under gain switching conditions so as to make the chip emit light pulses. The light pulses are compressed in a fiber (30) having negative dispersion, so that they constitute solitons. Their spectrum width is decreased by the fact that a gain segment powered by the power supply constitutes only a portion of the length of the resonant cavity of the chip. The invention applies to transmitting data over optical fibers.
摘要:
A semiconductor laser (2) constitutes a monolithic source whose intensity is modulated at a frequency lying in the microwave frequency range, typically 10-20 GHz to 100 GHz. It is based on coupling between the longitudinal modes of the laser, with intensity modulation being given by beats between the various modes of the laser. Optimization and control of the laser are made possible by splitting the optical cavity (6, 8, 10) of the laser into successive sections (20, 22, 24). The invention is particularly suitable for telecommunications applications.
摘要:
The object of the invention enables wavelength division multiplexed solitons conveyed by an optical fiber to be regenerated synchronously. The method uses clock recovery from the WDM signal, and synchronous modulation of the solitons at the clock rate recovered in this way. The locations for the optical modulators are selected to be at a distance between the transmitter and the first modulator or between successive modulators along the optical link such that the signals at different wavelengths are synchronous. The apparatus of the invention regenerates solitons in-line by synchronously modulating said solitons using an optical modulator, clock recovery, and multichannel filtering at the output from the modulator. In a particular embodiment, the telecommunications system of the invention also includes fiber lengths having different dispersion relationships depending on their position within the link, so as to achieve "dispersion management" within the link. The invention is applicable to optical telecommunications over great distances by means of solitons.
摘要:
An optical communication link with correction of non-linear effects comprises an optical fiber transmission line subject to chromatic dispersion and non-linear effects and correction means for limiting the disadvantageous consequences of this dispersion and/or these non-linear effects. The correction means comprise at the output of the transmission line a dispersion compensator adapted to apply dispersion in the opposite direction to and of lower absolute value than the dispersion due to the transmission line.
摘要:
The fibre is adapted to compensation of the chromatic dispersion and chromatic dispersion slope of an optical fibre with negative chromatic dispersion. It has, in a propagation mode other than the fundamental mode, a positive chromatic dispersion and a negative chromatic dispersion slope. The fibre can be used in compensation dispersion modules or as line fibre, in transmission systems using line fibre with negative chromatic dispersion.
摘要:
Optical pulses carrying information to be conveyed are routed, for each pulse, by the intensity of the pulse. The pulses may be solitons. The invention is particularly applicable to long distance communications.
摘要:
An amplifying fiber is connected at both ends to two respective pump-forming semiconductor lasers. The connections are made via two pump injection fibers and two multiplexers. According to the invention, each of the two pump injection fibers includes a respective photorefractive filter constituting a portion of the resonant cavity of the associated pump, and serving to separate the spectrum bands of the pumps. The invention is particularly applicable to optical fiber telecommunications networks.