Abstract: The present invention relates to an optical communication network and to a network element for use in such a network. The network element comprises a plurality of receivers (70-76) for receiving optical communication signals, a plurality of transmitters (54-62, 82-86) for transmitting optical communication signals, and a plurality of network connections, each network connection having an individual signal impairment characteristic. The pluralities of receivers (70-76) and transmitters (54-62, 82-86) are adapted to employ a plurality of different modulation schemes (64, 66). Furthermore, the pluralities of receivers (70-76) and transmitters (54-62, 82-86) are assigned to the network connections as a function of the individual signal impairment characteristics.

Abstract: The invention relates to a time division and wavelength division multiplex optical switching node for use in an optical communications network (2), which node combines a set of time division multiplex packets (8-1, 8-2, . . . , 8-i) into a wavelength division multiplex packet (18) to form a composite wavelength division multiplex packet, in particular by conferring on each time division multiplex packet (8-1, 8-2, . . . , 8-I) a respective appropriate multiplexing wavelength (&lgr;1, &lgr;2, . . . , &lgr;i), for example a wavelength specific to each time division multiplex packet. The invention has applications in high bit rate optical networks in particular, in which it offers versatility and transparent use of the different multiplexing modes.

Abstract: A device for compensating the polarization dispersion suffered by an optical signal when it is transmitted by an optical line includes a polarization controller. It generates a differential time delay between two orthogonal polarization modes and controls the polarization controller so that it converts the signal transmitted by the line into a compensated optical signal. If the quality of the compensated optical signal remains below a reference quality the device modifies the state of polarization of the optical signal. Applications include long distance optical transmission via standard fibers.

Abstract: To optimize the resources of an optical transmission network using wavelength division multiplexing, assigning carrier frequencies to signals to be transmitted consists in associating N sets of optical frequencies of the comb with N respective ranges of consecutive error rate values, each of the sets comprising frequencies generating a mean error rate in the associated range, defining a measured signal transmission constraint level that is a function of the transmission constraint parameter(s) and may take N distinct values referred to as constraint values, associating the N constraint values in increasing order respectively with the N sets of frequencies in decreasing order of the error rate values of the associated N ranges, assigning any signal to be transmitted a constraint value obtained by applying the measurement, and assigning the signal to be transmitted a carrier frequency belonging to one of the sets of frequencies that is associated with a constraint value at least equal to the constraint value as

Abstract: A method of measuring the error rate of an optical transmission system transmitting a signal by detecting the signal, and asynchronously sampling the signal at a frequency independent of the bit rate of the signal to obtain K samples of the signal at respective times t1 to tK, where K is an integer greater than or equal to 2. The eye diagram of the signal, the error rate of the signal and the bit time of the signal are then computed.

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 present invention relates to an optical cross-connect unit of multigranular architecture (1000) including a first stage (100) for switching wavelength bands and including an optical switching matrix for switching wavelength bands, demultiplexing and multiplexer means (10 to 20′)for demultiplexing and multiplexing wavelength bands, a second stage (200) for switching wavelengths and including a switching matrix for switching wavelengths, and demultiplexing and multiplexer means (30 to 60′) for demultiplexing and multiplexing wavelengths. The first matrix of the invention includes a series of first optical switching submatrices (1, 2) disposed in parallel and the second matrix of the invention includes a series of second switching submatrices (3, 4) disposed in parallel.

Abstract: To increase the bit rate at which and the distance over which data can be transmitted by optical fiber, polarization dispersion is compensated by means of a polarization controller, a system for generating a differential group delay between two orthogonal modes of polarization and a control unit of the polarization controller. A chromatic dispersion compensator applies compensation which is adjusted dynamically to optimize the quality of the received optical signal. Applications include long-haul optical transmission on standard fibers.

Abstract: The present invention is a device to increase the bit rate and distance at which data can be transmitted by optical fiber. The device compensates the polarization dispersion of the line by processing a received optical signal with the use of a polarization controller, the generation of 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 using the redundant data. The application of the device is to long-haul optical transmission, in particular over stranded fibers.

Abstract: Known optical power equalizers receive an optical main input signal modulating between high and low input power levels. The optical power equalizers 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 that operates about its saturation range. The optical power equalizer receives an amplifier input signal, which has one or more modulated portions, and emits a modulated amplifier output signal. According to the invention the dependence of the gain-clamped semiconductor optical amplifier's gain on the power of the amplifier input signal is adjusted such that the high input power levels of the amplifier input signal are equalized into the one high output power level of the amplifier output signal.

Abstract: The invention provides an optical modulator for transmitting data encoded in NRZ mode by modulating the intensity of a light signal, the modulator including means for shaping the light signal including shaping means for producing a signal of low bandwidth from an input control signal, and a laser modulator having a transfer function favoring the extinction time of the resulting light 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. Switching the carriers at the subset level improves the quality of the output signal and limits the number of components for the same total quantity of information switched.

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: The optical switching device (100) includes:

Abstract: The present invention relates to a method of measuring the error rate of an optical transmission system transmitting a signal, said method comprising the following operations:

Abstract: The transmission system includes a first electro-optical modulator adapted to supply in response to an input electrical signal a controlled phase optical signal having an optical power modulated between low levels and high levels and a phase shift within each time cell that contains a low power level. To make it more flexible to use, the system includes a second electro-optical modulator controlled by the input signal and optically coupled to the first electro-optical modulator to apply to said controlled phase optical signal complementary power and/or phase modulation so as respectively to modify its extinction ratio and/or to apply a transient “chirp” to it.

Abstract: The invention relates to a reconfigurable optical switching system for selectively coupling one or more frequencies of first and second input wavelength division multiplex signals (WDM1, WDM2) consisting of N channels to first and second output ports (O1, O2). The invention also relates to a variable and reconfigurable optical delay circuit comprising said optical switching system associated with an optical delay loop. The input frequency division multiplex optical spectra (WDM1, WDM2) are therefore divided by a first demultiplexer (Demux) to a plurality of interleaved stages of optical switches (D, C, A and B) which selectively feed a plurality of input ports (Mi) of a multiplexer (Mux), which then uses its routing properties to implement in particular the complex reconfigurable multiple 2×2 frequency switching function.

Abstract: A decision system for a modulated electrical signal delivered by a converter in response to a received modulated optical signal compares the amplitude of the electrical signal to a reference level, measures an average amplitude of the electrical signal, and generates the reference level as a function of the result of such measurements so that the “reference level/average amplitude” ratio can be adjusted to a predetermined constant value different from 1. Applications include receivers for optical packet transmission systems.

Abstract: A multi-user optical fiber communications system uses spread spectrum code division multiple access techniques to achieve better bandwidth utilization. Each channel of the system is provided with light source that is temporally and spectrally modulated by an encoder. Modulation is accomplished by first passing the data through a pulse modifier to obtain a stream of shortened pulses with a reduced duty cycle. The modulated light is coupled to a fiber and data are recovered by the decoder. The source includes a superluminescent fiber source that is split multiple times and amplified in a hierarchical manner to produce a plurality of like sources. The like sources are decorrelated by adding delays to the different sources. Each of the encoders includes an encoding mask having a first code that encodes the optical signal. Light, spatially encoded by the mask and temporally modulated with data, is transmitted over a fiber link with the signals of other users and received by a decoder.

Abstract: A device for compensating the polarization dispersion suffered by an optical signal when it is transmitted by an optical line includes a polarization controller. It generates a differential time delay between two orthogonal polarization modes and controls the polarization controller so that it converts the signal transmitted by the line into a compensated optical signal. If the quality of the compensated optical signal remains below a reference quality the device modifies the state of polarization of the optical signal. Applications include long distance optical transmission via standard fibers.