System of very-long-distance digital transmission by optical fiber with compensation for distortions at reception

A system for a very-long-distance transmission of a digital signal between a transmitter station and a receiver station, wherein said transmitter and receiver stations are connected by a monomode optical fiber with negative chromatic dispersion at an operating wavelength of the system, having a length of at least one thousand kilometers, said optical fiber inducing a negative chromatic dispersion and non-linear effects, a combination of said non-linear effects and of said negative chromatic dispersion giving distortions to the digital signal received by said receiver station, and wherein said receiver station comprises compensation means for compensating for said distortion, said compensation means being connected to said monomode optical fiber, said compensation means carrying out a positive chromatic dispersion of said received signal, an amplitude of said positive chromatic dispersion being a function notably of an amplitude of the negative chromatic dispersion induced by said optical fiber as well as of a mean on-line optical power of said signal transmitted on said optical fiber, and wherein said compensation means include at least two fiber sections with positive chromatic dispersion chosen from a set of fiber sections having at least two different lengths, so as to adjust said amplitude of the positive chromatic dispersion.

A system for a very-long-distance transmission of a digital signal between a transmitter station and a receiver station, wherein said transmitter and receiver stations are connected by a monomode optical fiber with negative chromatic dispersion at an operating wavelength of the system, having a length of at least one thousand kilometers, said optical fiber inducing a negative chromatic dispersion and non-linear effects, a combination of said non-linear effects and of said negative chromatic dispersion giving distortions to the digital signal received by said receiver station, and wherein said receiver station comprises compensation means for compensating for said distortions, said compensation means being connected to said monomode optical fiber, said compensation means carrying out a positive chromatic dispersion of said received signal, an amplitude of said positive chromatic dispersion being a function notably of an amplitude of the negative chromatic dispersion induced by said optical fiber as well as of a mean on-line optical power of said signal transmitted on said optical fiber, and wherein said compensation means includes at least one set of at least two diffraction gratings mounted so as to induce said positive chromatic dispersion.