Alcatel

Nec Corporation

S&eacute;bastien Bigo

Yann Frignac

Thomas Ducellier

Erwan Pincemin

Olivier Leclerc

Wilfried Idler

Roland Mestric

Giovanni Bellotti

Gilles Vendrome

A frequency allocation scheme for optical channels transmitted via a WDM transmission line with alternating left side and right side filtering for adjacent channels, with alternating channel spacing of A and B, where A<B, and with two sets of channels orthogonally polarized.

Frequency allocation scheme and transmission system for polarization and wavelength division multiplexed signals with left and right side filtering

The invention relates to a wavelength division multiplex transmission system; for one channel, the spectral interval between adjacent channels on one side is different from the spectral interval between adjacent channels on the other side. A demultiplexing filter is used which attenuates more strongly the spectrum of the channel on the side on which the spectral interval between adjacent channels is smaller. The invention improves spectral efficiency and retains frequencies chosen from a grid of regularly spaced frequencies.

Wavelength division multiplex transmission system using asymmetrical filtering

The invention relates to a method of reducing the intensity distortion induced by cross phase modulation in a wavelength division multiplexed optical fiber transmission system comprising a transmission line made up of a plurality of optical fiber segments with repeaters interposed between successive optical fiber segments, the transmission system having N different wavelength channels, where N is an integer greater than unity. In each repeater interconnecting first and second consecutive fiber segments, a time offset is introduced between the channels in such a manner that compared with the inlet of the first optical segment, the (n&plus;1) and the n channels are offset by &tgr; at the inlet to the second fiber segment, where n is an integer less than or equal to N, where &tgr; is selected to be greater than zero and less than a value that eliminates correlation between the intensity distortion contributions of each fiber segment.

Method of reducing intensity distortion induced by cross phase modulation in a WDM optical fiber transmission system

A wavelength division multiplex optical signal regenerator is inserted between two optical fiber sections of a wavelength division multiplex fiber optic transmission system including a transmission line made up of a plurality of optical fiber sections and providing N channels at different wavelengths where N is an integer greater than 1. The regenerator includes a demultiplexer for demultiplexing wavelength division multiplexed optical signals onto N individual channels, and a multiplexer for multiplexing optical signals at the output of the N individual channels into multiplexed optical signals. Each individual channel includes a saturable absorber for reshaping the optical signals of each channel, and a delay line. The length of each delay line is chosen to introduce a total delay &tgr;n&Prime; between the (n&plus;1)th channel and the nth channel to obtain a time shift of &tgr;n between the (n&plus;1)th channel and the nth channel.

Wavelength division multiplex optical signal regeneration method

The invention relates to an optical fiber transmission system using soliton signals and wavelength division multiplexing. To reduce the effects of collision-induced jitter on the soliton channels, the invention proposes to interchange the wavelengths of the channels of the multiplex at least once, so as to invert the sign of the residual frequency variation induced by the asymmetrical collisions on the signals of the channels. The invention is applicable in particular to transmission systems implementing a frequency allocation scheme that guarantees that the bit times of the various channels are synchronous at regular intervals.

Reducing collision-induced jitter by wavelength interchange in an optical fiber transmission system using soliton signals and wavelength division multiplexing

The invention relates to apparatus for limiting noise in the &ldquo;zeros&rdquo; of optical RZ signals, the apparatus comprising a birefringent fiber for mutually spectrally offsetting the signals as a function of their intensity, and a filter for filtering the offset signals. The filter attenuates the pulses that correspond to &ldquo;zeros&rdquo;, but passes the pulses that correspond to &ldquo;ones&rdquo;. The invention makes it possible to limit the noise in the &ldquo;zeros&rdquo; of an RZ signal.

Apparatus for limiting noise in the zeros of RZ optical signals

In the invention, a stream (S) of solitons enters a Sagnac interferometer ( ) with an offset semiconductor amplifier (A) and the amplifier is controlled by an optical synchronization signal (Y) that is amplitude-modulated at a frequency which is half a bit frequency of the stream, the offset of the amplifier in said interferometer and the parameters of said synchronization signal being given values such that two adjacent solitons of said train are transmitted with their optical phase relationship inverted. The invention finds an application in fiber optic telecommunications networks.

Device and method for regenerating a train of solitons

The invention relates to a regenerator using optical phase modulation in an optical fiber transmission system using soliton signals. According to the invention, the soliton signal is modulated by a clock in a modulator which is itself contained in an interferometer; the output signal from the interferometer has intensity that is representative of the phase difference between the clock and the soliton signal, and is therefore suitable for use in controlling the phase of the clock. In an embodiment, the interferometer is a Sagnac interferometer constituted by a non-linear optical loop mirror, and the modulation is distributed phase modulation in the transmission fiber. This enables the clock to be synchronized in simple manner.

Regenerator with optical modulation for optical fiber transmission systems using soliton signals

The invention provides a regenerator for very high rate solitons, the regenerator comprising a non-linear loop mirror or NOLM receiving the soliton signal and modulating it with a control signal. The regenerator also comprises a device for generating the control signal by beats between two light sources, with the frequency of at least one of the two sources being variable and servo-controlled as a function of the modulated soliton signal, e.g. as a function of its power, or servo-controlled by means of an optical phase-lock loop. This provides a soliton regenerator in which the electronic components operate at low frequency only, while being capable of regenerating a soliton signal at a very high rate.

Growing community of inventors

Palaiseau, France

Sébastien Bigo

Growing community of inventors

Palaiseau, France

S&eacute;bastien Bigo

Sébastien Bigo