A wireless communication system can comprise two or more antennas that interfere with one another via free space coupling, surface wave crosstalk, dielectric leakage, or other interference effect. The interference effect can produce an interference signal on one of the antennas. A cancellation device can suppress antenna interference by generating an estimate of the interference signal and subtracting the estimate from the interference signal. The cancellation device can generate the estimate based on sampling signals on an antenna that generates the interference or on an antenna that receives the interference. The cancellation device can comprise a model of the crosstalk effect. Transmitting test signals on the communication system can define or refine the model.

Method and system for antenna interference cancellation

A return-to-zero pulse optical communication system includes fast saturable absorber means (F1,DSF) to provide substantially zero average dispersion in a single amplifier span (SIF,DSF) to reduce the effect of timing jitter an provide considerably enhanced propagation distances.

Optical communication systems

A multilevel optical receiver (150) can comprise a plurality of comparators (405) that generally correspond with the number of levels in a multilevel data stream. Each comparator (405) can be individually controlled and fed a decision threshold in order to decode a multilevel signal. The multilevel optical receiver (150) can generate a statistical characterization of the received symbols in the form of a marginal cumulative distribution function (CDF) or probability density function (pdf). This characterization can be used to produce a set of e-support estimates from which conditional pdfs are derived for each of the transmission symbols. These conditional pdfs may then be used to determine decision thresholds for decoding the received signal. The conditional pdfs may further be used to continuously estimate the fidelity or error rate of the received signal without the transmission of a testing sequence. The e-supports may further be used to automatically control the gain on the receiver.

Method and system for decoding multilevel signals

Signals propagating in one communication channel can generate crosstalk interference in another communication channel. A crosstalk cancellation device can process the signals causing the crosstalk interference and generate a crosstalk cancellation signal that can compensate for the crosstalk when applied to the channel receiving crosstalk interference. The crosstalk cancellation device can include a model of the crosstalk effect that generates a signal emulating the actual crosstalk both in form an in timing. The crosstalk cancellation device can include a controller that monitors crosstalk-compensated communication signals and adjusts the model to enhance crosstalk cancellation performance. The crosstalk cancellation device can have a mode of self configuration or calibration in which defined test signals can be transmitted on the crosstalk-generating channel and the crosstalk-receiving channel.

Method and system for crosstalk cancellation

Data throughput rates are increased in an optical fiber communication system without requiring replacement of the existing optical fiber in a link. Channel throughput is increased by upgrading the components and circuitry in the head and terminal of an optical fiber communication system link. Aggregate throughput in a fiber optic link is increased beyond the range of conventional Wavelength Division Multiplexed (WDM) upgrades, while precluding the necessity of replacing existing fiber plants. The increase in system throughput is achieved by using advanced modulation techniques to encode greater amounts of data into the transmitted spectrum of a channel, thereby increasing the spectral efficiency of each channel. This novel method of increasing transmission capacity by upgrading the head and terminal of the system to achieve greater spectral efficiency and hence throughput, alleviates the need to replace existing fiber plants. Spectrally efficient complex modulation techniques can be supported by interface circuits with an increased level of signal processing capability in order to both encode multiple bits into a transmitted symbol and decode the original data from the received symbols.

Increasing data throughput in optical fiber transmission systems

A system for very-long-distance transmission of a digital signal between a transmitter station and a receiver station, wherein the transmitter and receiver stations are connected by a monomode optical fiber with negative chromatic dispersion at the operating wavelength of the system, having a length of at least one thousand kilometers. The receiver station comprises device to compensate for the distortions due to the non-linear effects and to the chromatic dispersion introduced by the transmission line, the compensation device carrying out a positive chromatic dispersion of the received signal, the amplitude of the positive chromatic dispersion being a function notably of the amplitude of the negative chromatic dispersion induced by the optical fiber as well as of the mean on-line optical power of the signal transmitted on the optical fiber.

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

A system for transmission of a digital signal on a transmission line with an optical on-line amplification. The transmission line is formed by a plurality of optical fiber sections and a plurality of optical amplifiers. Each of the optical amplifier is interposed between two adjacent optical fiber sections. The system includes at least one device for on-line compensation of the distortions induced in the digital signal, notably by the noise and the propagation on the transmission line. The on-line compensation device includes at least one bandpass optical filter having a passband whose value is substantially lower than that of the passband of the digital signal before transmission, and at least one saturable absorbent element that is a non-linear passive optical element having an absorption that depends decreasely on the optical power.

Optical fiber transmission system with compensation for line distortions

A system for very-long-distance transmission of a digital signal between a transmitter station 21 and a receiver station 25, wherein the transmitter and receiver stations are connected by a monomode optical fiber 22 with negative chromatic dispersion at the operating wavelength of the system, having a length of at least one thousand kilometers. The receiver station comprises means to compensate for the distortions due to non-linear effects (e.g. the Kerr effect) and to the chromatic dispersion introduced by the transmission fiber, the compensation means carrying out a positive chromatic dispersion of the received signal, the amplitude of the positive chromatic dispersion being a function notably of the amplitude of the negative chromatic dispersion induced by the optical fiber as well as of the mean on-line optical power of the signal transmitted on the optical fiber. The compensation means may comprise at least two adjustable diffraction gratings, fiber sections of positive chromatic dispersion separated by optical amplifiers, or, as shown, a fiber section 23 of positive chromatic dispersion.

Optical fiber transmission system

Le domaine de l'invention est celui de la transmission numerique tres longue distance sur fibre optique. L'invention concerne un systeme de transmission tres longue distance d'un signal numerique entre une station d'emission (21) et une station de reception (25), dans lequel lesdites stations d'emission (21) et de reception (25) sont reliees par une fibre optique (22) monomode a dispersion chromatique negative a la longueur d'onde de fonctionnement du systeme, d'une longueur (LT o t ) d'au moins mille kilometres, et ladite station de reception (25) comprend des moyens de compensation des distorsions dues a la combinaison des effets non-lineaires et de la dispersion chromatique introduits par ladite ligne de transmission, lesdits moyens de compensation realisant une dispersion chromatique positive du signal recu, l'amplitude de ladite dispersion chromatique positive etant superieure ou egale a l'amplitude de la dispersion chromatique negative induite par ladite fibre optique.

Systeme de transmission tres longue distance sur fibre optique a compensation des distorsions a la reception.

L'invention concerne un systeme de transmission d'un signal numerique sur une ligne de transmission avec une amplification optique en ligne, ladite ligne de transmission etant constituee d'une pluralite de troncons de fibre optique (1) et une pluralite d'amplificateurs optiques (2), chacun desdits amplificateurs optiques (2) etant intercale entre deux troncons de fibre optique (1) adjacents, ledit systeme comprenant au moins un dispositif de compensation en ligne (3) des distorsions induites sur ledit signal numerique notamment par le bruit et la propagation sur ladite ligne de transmission, Selon l'invention, ledit dispositif de compensation en ligne (3) comprend: - d'une part, au moins un filtre optique passe-bande (4) presentant une bande passante substantiellement inferieure a la bande-passante dudit signal numerique avant transmission; et - d'autre part, au moins un element absorbant saturable (5) qui est un element optique passif non-lineaire presentant une absorption dependant de maniere decroissante de la puissance optique.

Jean Baptiste Thomine

Papers

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

Optical fiber transmission system with compensation for line distortions

Optical fiber transmission system

Systeme de transmission tres longue distance sur fibre optique a compensation des distorsions a la reception.

Système de transmission sur fibre optique à compensation des distorsions en ligne.