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: A method for routing traffic in a network comprising a plurality of nodes and a plurality of data lines that extend between adjacent ones of said nodes, the traffic being formed of traffic connections between pairs of nodes referred to as terminal nodes, comprises the steps of a) selecting a pair of said terminal nodes and determining a shortest path between them (S1-S4); b) selecting (S6) a new node from said plurality which is not part of the path and inserting (S8) the new node between two adjacent nodes of the path; c) repeating step b) until at least all terminal nodes are included in the path; d) routing at least part of said traffic on said path (S11-S14).

Abstract: An optical packet node for receiving and transmitting optical packets is disclosed. A multiwavelength band splitting device splits received optical packets transmitted via multiwavelength bands into at least three groups, each group including one multiwavelength band. A multiwavelength band combining device combine the three groups of multiwavelength bands. At least two optical packet add drop multiplexers are placed between the multiwavelength band splitting device and the multiwavelength band combining device. Each optical packet add drop multiplexer adds and drops at least one individual wavelength to a respective multiwavelength band group. A load balancing stage is connected to the optical packet add drop multiplexers to provide an interconnection between at least two wavelength bands.

Abstract: The routes for transmitting optical signals between the nodes (N1-N6) of a transparent network are selected according to the estimated error rate (ERe) values presented by the signals received after being transmitted along these routes. To limit the number of measurements to be made before the network is commissioned, a function (G) relating to the parameters characteristic of the network's optical links is used. This function is an interpolation function providing, for each set (QoT) of parameters associated with a given route, a corresponding estimated error rate (ERe) value. To evaluate the accuracy of the interpolation, during the network's operation, error rate measurements are performed, relating to signals effectively transmitted along given routes, and these measurements serve either to readjust the margin of uncertainty to be applied to exploit the estimated error rates (ERe), or to modify the function (G) to improve its interpolation accuracy.

Abstract: A device (D) is dedicated to controlling auxiliary paths (CP, SC) in a hybrid optical communications network comprising a multiplicity of hybrid nodes (NO) including switching means (CM1) and color converter means (CM2) and interconnected by transmission lines. The device comprises processor means (MT) adapted, in the event of a fault on at least one of the transmission lines carrying a connection and at the ends of which are two hybrid nodes (NO) adapted to effect switching in opaque mode, to command the switching means (CM1) of at least one of the hybrid nodes (NO) to switch the optical signals taking the connection to a selected auxiliary path independent of color and passing through said nodes, where applicable after color conversion of the optical signals by the associated converter means (CM2).

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: 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: 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: Dispersion-shifted monomode optical fibers have an effective mode surface area greater than 65 .mu.m.sup.2 by optimization of the geometrical characteristics that characterize the fibers.

Abstract: Dispersion-shifted monomode optical fibers have an effective mode surface area greater than 65 .mu.m.sup.2 by optimization of the geometrical characteristics that characterize the fibers. The fibers have substantially zero chromatic dispersion in the vicinity of 1.55 .mu.m, and they include an optical core having a central portion, a first layer having an index lower than the index of the central portion, and a second layer having an index higher than the index of the first layer and higher than the index of the optical cladding.

Abstract: Light pulses carrying data in binary form to be transmitted are injected into a transoceanic line fiber in which they pass through amplifiers imparting Gordon-Haus jitter to them. In accordance with the invention, a compensation fiber is disposed at the output of the line fiber so as to apply negative chromatic dispersion to the pulses so as to compensate their jitter in part before they are processed in a receiver. The invention applies to telecommunications.

Abstract: In an optical frequency marking method and a frequency channel communication network using this method, an optical reference frequency is scanned across a scanning band to produce frequency coincidences with a monitored frequency which constitutes the frequency to be marked. During each scanning half-cycle it effects a go path and a return path according to a known law to produce a go frequency coincidence and a return frequency coincidence. A marker interval is measured which is the time elapsed between said two coincidences. This interval marks the monitored frequency and enables said frequency to be locked by comparison with a set point interval. The invention finds a particular application in the marking and stabilization of carrier frequencies of a closely-spaced different frequency channel network.

Abstract: An optical communication link with correction of non-linear effects comprises an optical fiber transmission line subject to chromatic dispersion and non-linear effects and correction means for limiting the disadvantageous consequences of this dispersion and/or these non-linear effects. The correction means comprise at the output of the transmission line a dispersion compensator adapted to apply dispersion in the opposite direction to and of lower absolute value than the dispersion due to the transmission line.

Abstract: According to the invention, messages to be transmitted between user terminals interconnected by a transmission network are classified into "heavyweight" messages and "lightweight" messages. The heavyweight messages, i.e. messages containing a large quantity of data, are transmitted over the network in message frequency channels attributed to respective heavyweight messages, while the lightweight messages are transmitted over a shared channel common to the lightweight messages.

Abstract: In a method of the invention an emission wave (F(2P-1)) which is to be positioned within the spectrum relative to an external wave (F(2P-2)B) is modulated. Said external wave is mixed with one of the side waves that results from said modulation (F(2P-1)A) and the emission wave is positioned in response to variations in the frequency of a beat signal (F(2P-2)BE) that results from said mixing. The invention applies in particular to implementing an optical fiber communications network.

Abstract: Calls are made in known manner between terminals in the form of information-carrying modulation applied to emission waves that travel along common transmission lines. An emission frequency (F(2P-1)) is allocated to each terminal for each call. According to the invention, a marking wave is supplied to all of the terminals while no call is yet being set up, thereby marking an emission frequency. When a new call is being set up, the marked frequency is allocated for the new call to at least one of the terminals that are to participate in the call. The invention is particularly applicable to communications by means of optical fibers.

Abstract: The emission frequencies (F(1) . . . F(2P)) used for simultaneous communications form a stack extending from a fixed based frequency (F(0)) to a top of stack frequency (F(2P-1), F(2-P)). At the beginning of each call, the emission frequency (F(2P-1)) used for the call is at the top of the stack. During the call, said emission frequency is maintained by being servo-controlled to a predetermined spectrum distance (DF) beyond a lower support frequency (F(2P-2)) providing such a frequency can be detected. When such a frequency cannot be detected, the emission frequency is shifted progressively towards the base frequency. The invention is particularly applicable to communications between the peripherals of computer systems.

Abstract: In a long-haul optical communication line the fibers to be made into the line are grouped into pairs such that the two fibers in each pair have substantially symmetrical chromatic dispersion relative to a mean value of the chromatic dispersion of all the fibers of the line. These two fibers are thereafter connected consecutively into the line. The invention finds an application in telecommunications.

Abstract: Dispersion-shifted monomode optical fibers have an effective mode surface area greater than 65 &mgr;m2 by optimization of the geometrical characteristics that characterize the fibers.