Alcatel

Avanex Corporation

Alcatel Submarine Networks

Olivier Leclerc

Emmanuel Desurvire

Patrick Brindel

Bruno Lavigne

Denis Penninckx

Jose Chesnoy

S&eacute;bastien Bigo

Sebastien Bigo

Catherine Martinelli

Alex Bombrun

Frédéric Seguineau

Jean-Baptiste Pomet

Frederic Seguineau

Jean-Luc Moncelet

Fabien Seyfert

A wavelength converter for binary optical signals includes an interferometer structure () for generating an output signal by modulating a received local signal (LS) according to the modulation of a fUrther received first input signal (IS). When such interferometer structures () are operated in a standard mode it is known in the art to control the power of the input signal such that the extinction ratio of the output signal is kept minimal. The invention also controls the power of the input signals to achieve the minimal extinction ratio when the wavelength converter and in particular the interferometer structure () is operated in a differential mode receiving two input signals.

Wavelength converter

A method for remodulation of a modulated optical signal is disclosed which uses a disturbed line signal and an optical clock signal derived from the undisturbed original line signal modulated with the bitrate frequency feeding both signals in a Raman amplifying fiber connected to at least one Raman pump running the clock signal as Raman pump wavelength for the line signal.

Method for remodulation of a modulated optical signal and device for remodulation and transmission system

A synchronous optical regenerator applies intensity modulation and phase modulation. The phase modulation is effected after the intensity modulation by the crossed Kerr effect in a Kerr fiber. The clock used for the phase modulation is obtained by injecting a continuous wavelength into the intensity modulator. The regenerator therefore includes a multiplexer coupling continuous light with the signals transmitted, an intensity modulator modulating the signals transmitted and the continuous light, and a Kerr fiber phase modulating the transmitted signals by crossed phase modulation with the intensity-modulated continuous light. Applications include wavelength division multiplex transmission systems.

Synchronous optical regenerator using intensity modulation and phase modulation by the crossed kerr effect

The present invention propose to use an optical multiplexer associated with an optical clock as a wavelength converter. Each RZ coded tributary will be carried by a single wavelength (channel) passively interleaved with the others without interferometric interaction hence achieving a not necessarily perfect OTDM. This input data stream as optical data signal composed of different wavelengths is then launched on at least one data access of said optical multiplexer used as a wavelength converter. An optical clock at the desired bit-rate is launched on the probe access of said optical multiplexer synchronously to the multi-wavelength data stream. At the output, the initial clock wavelength is converted on data signal using the gain conversion property of the optical multiplexer. In such a way, a data stream of substantially higher bit-rate is obtained while due to a very precise synchronization a lost of data is minimized.

All-optical high bit-rate multiplexer

A demultiplexer for an optical time-division multiplexed digital signal, which has a signal wavelength &#x3bb;and is transmitted with a bit rate B, is described. It comprises a Raman active optical medium, a pump source for generating a periodic optical pump signal having a pump wavelength &#x3bb;and a periodicity of B/n where n is an integer &#x2267;2, and a coupler for coupling the digital signal and the pump signal into the Raman active optical medium. The new demultiplexer exploits the non-linear Raman gain response of the Raman active medium to a high power pump signal and has a narrow time window and a high extinction ratio.

Demultiplexer for optical time-division multiplexed signals

To delay optical signals precisely and continuously in a very small dynamic range, a device for applying a time-delay to optical signals includes a first phase modulator to receive an input optical signal carried by an original center wavelength and to apply a first stage of phase modulation to the carrier wave of the input signal to supply a first intermediate signal carried by a modified center wavelength, a delaying dispersive member having chromatic dispersion to receive the first intermediate signal and to supply a second intermediate signal, and a second phase modulator to receive the second intermediate signal and to apply a second stage of phase modulation to the carrier wave of the second intermediate signal to supply an output signal carried by the original center wavelength. Applications include optical telecommunication systems, in particular converting wavelength division multiplexed signals into time division multiplexed signals and regenerating wavelength division multiplexed signals.

Device for applying time-delays to optical signals

Double filtering fiber optic soliton signal transmission system

An optical module advantageously uses optical conversion fibers not only for a single channel but for sets of channels that are, in a specific way, selected from a multi-channel wave division multiplex (WDM) grid. The sets of channels are defined such that four wave mixing is negligible or has a negligible effect. The optical module has a demultiplexer, a multiplexer, and parallel optical conversion fiber portions that are arranged between the demultiplexer and the multiplexer. Each of the parallel optical conversion fiber portions has a specific dispersion map and transmits a different set of channels of the multi-channel WDM grid. These channels are regularly spaced from each other.

Optical module for multi-channel wavelength multiplexing

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 an optical fiber transmission system using soliton signals with wavelength division multiplexing in which the wavelengths, &lgr; to &lgr; , of the various channels of the multiplex are selected in such a manner that at least one point of the transmission system, the difference between the bit times of any two channels of the multiplex is substantially a submultiple T/N of the clock period. The invention proposes placing a synchronous modulator at said point to modulate the soliton signals at a frequency N/T which is a multiple of the soliton clock frequency 1/T. In a frequency allocation scheme that ensures that the bit times of the channels are synchronous at an interval ZR, this makes it possible to modulate all of the channels at intervals that are submultiples of Z by using modulation frequencies that are multiples of the clock frequency.

Optical fiber transmission system using soliton signals with wavelength division multiplexing

Repairing undersea optical fiber transmission systems using soliton signals with wavelength division multiplexing

In a wavelength-division multiplex fiber optic soliton signal transmission system the wavelengths of the multiplex are chosen to assure a relative slippage between the channels at a given interval substantially equal to a multiple of the bit time. At one point of the transmission system at least, the soliton pulses of the various channels have a temporal offset relative to a given reference such that, on distributed optical modulation by a clock that is input at this point, for each channel, the extremum of the non-linear phase profile induced by the clock, integrated over the modulation length, coincides with the center of the bit time. In a system of this kind distributed optical modulation can be applied to all the channels of the multiplex by a single sinusoidal signal. The modulation can be effected in a non-linear optical loop mirror or in the transmission fiber itself.

Optical regeneration for wavelength-division multiplex soliton signal

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.

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Saint Michel S/Orge, France

Olivier Leclerc