Abstract: The invention relates to an optical demultiplexing system for separating frequency bands of a frequency-division multiplex, said system comprising a 1 to n first cyclic demultiplexer for demultiplexing said multiplex into n interleaved frequency combs each comprising m channels and a second cyclic demultiplexer for separating the channels of said n interleaved combs to obtain m consecutive bands comprising n consecutive frequencies, characterized in that said second multiplexer is an m to m cyclic demultiplexer having n input ports connected to respective output ports of said 1 to n first cyclic demultiplexer and in that the numbers n and m are mutually prime numbers.

Abstract: An optical packet node for receiving and transmitting optical packets is presented, which comprises: a multiwavelength band splitting device for splitting received optical packes transmitted via multiwavelength bands into at least three groups, each group including one multiwavelength band, a multiwavelength band combining device for combining said at least three groups of multiwavelength bands, at least two optical packet add drop multiplexers, each optical packet add drop multiplexer being placed between said multiwavelength band splitting device and said multiwavelength band combining device, and each optical packet add drop multiplexer serving to add and to drop at least one individual wavelength to a respective group of a multiwavelength band, and a load balancing stage being connected to at least two of said optical packet add drop multiplexers, to provide an interconnection between at least two wavelength bands.

Abstract: A selective frequency extractor is disclosed which forwards one or more selected frequencies of a wavelength division multiplex input signal consisting of N channels to one output port and all the other frequencies to another output port. A reconfigurable frequency add and drop multiplexer is also disclosed. The input signal is divided up by a first demultiplexer and routed to a plurality of interleaved stages of optical switches for selectively feeding a plurality of input ports of a multiplexer, whose routing properties are then used for extracting one or more frequencies from the input signal or for reconfigurable frequency add and drop multiplexing.

Abstract: A differential group delay generator includes a polarization splitter which splits an input signal into two components having orthogonal states of polarization, and an adjustable delay system for receiving one component. For high accuracy and a fast response, the adjustable delay system includes an adjustable phase modulator for applying phase modulation to the carrier wave of the component to supply an intermediate signal carried by a modified center wavelength, and a delaying dispersive component receiving the intermediate signal and supplying a delayed signal. Applications include polarization dispersion compensation in long-haul optical transmission, especially via standard fibers.

Abstract: The invention refers to an optical power equalizer. Known devices receive an optical main input signal modulating between high and low input power levels. They emit an equalized optical main output signal modulating between high and low output power levels, where at least one of the two sets of high and low power levels is equalized to one high or one low output power level. Such devices can comprise at least one gain-clamped semiconductor optical amplifier, adjusted to work about its saturation range, receiving an amplifier input signal, consisting of one or more portions of which at least one is modulated and emitting a modulated amplifier output signal. According to the invention the dependence of the GC-SOA's gain on the power of the amplifier input signal is adjusted in such a way, that the high input power levels of said amplifier input signal are directly converted into the one high output power level of said amplifier output signal.

Abstract: A transmission system and a transmitter for optical signals is proposed with a laser and a modulator for modulating the signal by supplying a controlled phase optical signal having optical power modulated between low levels and high levels respectively corresponding to said first and second modulation levels of the input signal, and a phase shift within each time cell that contains a low power level and which precedes or succeeds a cell that contains a high power level and an optical pass band filter that filters the modulated signal.

Abstract: The invention relates to a switch (112) for optical signals and which has a number of outputs at least equal to the number of inputs and include means whereby an input signal is routed to at least one of those outputs. Each input receives information modulating optical carriers at different wavelengths. The switch (112) includes means (12611, 12612, . . . , 126NB) for grouping all the carriers received into non-contiguous subsets of carriers (G11, . . . , G1B, . . . , GN1, . . . , GNB) and means (1291, 1292, . . . , 129NB) for selecting blocks of carriers from the same subset of carriers. The information corresponding to each subset of optical carriers is thus routed in blocks to the same subset output.

Abstract: A method and a device for compensating the polarization mode dispersion (PMD) of a transmitted optical signal comprise means of a polarization controller (3) coupled to a differential group delay (DGD) generator (5). The polarization controller (3) is controlled by a feedback loop, said feedback loop implementing an optimisation algorithm to optimize a feedback parameter of the output signal of the DGD generator (5). The algorithm takes into account the state of polarization (SOP) of an optical signal determined from the output signal of the polarization controller (3)) or from the output signal from the DGD generator (5).

Abstract: To increase the bit rate and distance of transmission of data by optical fiber, the system compensates polarization dispersion of the link by means of a polarization controller, a differential delay generator for generating a differential delay between two orthogonal polarization modes and a control unit for the polarization controller. It further includes a chromatic dispersion compensator inserted in the link and which applies a fixed value of compensation which minimizes the error rate of the signals received after transmission. Application to long-haul optical transmission via standard fibers.

Abstract: To increase the bit rate at which and the distance over which data can be transmitted by optical fiber, the device compensates the polarization dispersion of the line by processing the received optical signal by means of a polarization controller, means for generating a differential group delay between two orthogonal polarization modes and a control unit for the polarization controller. The data that is sent is redundant to enable detection of errors affecting the data received and the control unit is adapted to minimize the error rate calculated in real time by means of said redundant data. Application to long-haul optical transmission, in particular over standard fibers.

Abstract: 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.

Abstract: The invention concerns a system for compensating polarization dispersion of channels in a wavelength-division multiplex signal. In accordance with the invention, the system comprises a plurality of cascaded polarization control modules respectively associated with said channels and a common differential delay generator. Each polarization control module comprises a drop and insert multiplexer for extracting the signal from the associated channel from the input multiplex signal and inserting a modified channel supplied by a polarization controller. The system further comprises a control loop for controlling the polarization controllers in response to the optical properties of the channel signals at the output of the differential delay generator and obtaining a compensated multiplex signal.

Abstract: In order to increase the distance over which binary data can be transmitted over an optical fiber, the device compensates for fiber-generated chromatic dispersion by modulating the emitted light wave both in power and in phase, in such a manner as to ensure that there is a phase shift of close to 180.degree. within each binary cell for which the optical power is low but not zero. The device comprises a Mach-Zehnder type interferometer made on a substrate of III-V elements and designed so that in the absence of electrical voltages being applied to its electrodes it establishes destructive interference. A control circuit applies control voltages to the electrodes which voltages have DC components that are substantially equal, with at least one of the control voltages being the result of superposing a bias voltage on a filtered signal obtained by lowpass filtering an input electrical signal. The invention is applicable to long distance transmission over standard optical fibers.

Abstract: In a transmission system, a control circuit (4) receives an input binary sequence (T) representing data to be transmitted. The circuit encodes the sequence using a phase alternation code which differs from the phase inversion duobinary code in that the phase shifts applied to a carrier wave are less than 90 degrees. For this purpose, a semiconductor chip (3) includes a laser transmitter and an electro-absorption modulator having two segments. The chip generates said carrier wave and modulates it using the encoded sequence. An optical fiber (54) conveys the modulated wave. And a detector diode (58) receives the conveyed wave and performs intensity discrimination thereon so as to restore the input binary sequence.

Abstract: 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.