Abstract: The is directed to extending wavelength routing on a metro network subtended off an optical agile network. Flexibility on the subtended metro network is obtained by either tuning the head-end transmitter on a metro wavelength that is the operating wavelength of the route to a specified tail-end node (tunable source, fixed wavelength-route dependency) or/and tuning a specified route to the metro wavelength (fixed source, tunable wavelength-route dependency). The routes may be tuned at one or both ends.

Abstract: A wavelength exerciser is used for evaluating connections in an agile network. The exerciser operates at some or all switching nodes of the network, by first detecting the paths available between the respective node and all remaining nodes. For each available path, the exerciser selects some or all wavelengths that can carry the traffic all the way along the path. It can operate both during SLAT and/or during network normal operation. When the network carries live traffic, the wavelengths used on the test connections are wavelengths that are not used at the respective moment by the user traffic. The exerciser verifies the switch architecture and the access architecture, and also collects information about the performance of all paths, so as to speed-up the path-connection matching process and to increase the chances of successfully establishing the connection along the selected path.

Abstract: A line amplification system connected on the fiber between two flexibility sites of a wavelength switched network is built with a number of modules that can be arranged in a line amplifier, preamplifier and postamplifier configurations. The line and preamplifiers include a Raman module and a two-stage EDFA module provided with mid-stage access. A dynamic gain equalizer is connected in the mid-stage in the line amplification configurations. As well, dispersion compensating module may be connected in the mid-stage whenever/if needed. A line monitoring and control system operates the line amplification system so that all channels traveling along a link have substantially the same power, in the context of channels being added and removed to/from the line arbitrarily.

Abstract: A device for measuring dispersion of a link between two switching nodes of an optical network comprises a phase measuring unit PMU for determining a first phase of a data signal traveling on a first wavelength &lgr;1, and a second phase of the same data signal traveling on a second wavelength &lgr;2, received consecutively over the link under measurement. A dispersion measurement controller controls operation of the phase measuring unit and characterizes the dispersion of the link at a wavelength of interest &lgr;=(&lgr;1+&lgr;2)/2, based on the first and second phases. The PMU includes a frame detector for determining a first and a second rotation signal indicative of the digital offset between the first and second test clocks with a respective frame start, and a phase detector for measuring the phase of these test clocks with respect to a static reference. The static reference is provided by the same data signal transmitted continuously over a reference wavelength.

Abstract: An agile network is provided with a layered control system for maintaining a network-wide target performance parameter (e.g. power) along all end-to-end connections. A connection is controlled at the physical layer using optical control loops that have a concatenated response based on a set of loop time constants. The network is separated into gain based span loops and power based switch loops; each link has a gain profile, and requires a per-wavelength power target as the output power target for the switch loop at the start of the link. Use of achievable gain for the span loops allow to optimize the performance of the link. Use of individual achievable power targets allows each switch loop to autonomously ramp on and off channels without causing interference with existing and other ramping channels. A loop control uses a model-based rules block, to distribute control signals to an optical section encompassing a plurality of optical components.

Abstract: A line amplification system connected on the fiber between two flexibility sites of a wavelength switched network is built with a number of modules that can be arranged in a line amplifier, preamplifier and postamplifier configurations. The line and preamplifiers include a Raman module and a two-stage EDFA module provided with mid-stage access. A dynamic gain equalizer is connected in the mid-stage in the line amplification configurations. As well, dispersion compensating module may be connected in the mid-stage whenever/if needed. A line monitoring and control system operates the line amplification system so that all channels traveling along a link have substantially the same power, in the context of channels being added and removed to/from the line arbitrarily.

Abstract: A Raman module comprises a detecting unit for measuring the output power of a WDM signal traveling along a fiber section, and a spectral gain estimating unit for determining an estimated vector gain Gainmeas based on the output power alone. The Raman pump signal is controlled with a gain GainRA evaluated based on the estimated gain Gainmeas so that all channels have a similar gain. The spectral gain estimating unit comprises a fiber gain model and an input signal adjust unit. The model receives the output power, assumes a predicted input power for each channel and provides a corresponding estimated output power for each channel. The input signal adjust unit adjusts the predicted input power based on an error signal provided by the model. The gain is then calculated from the predicted input powers and the estimated output powers. The detecting unit demultiplexes a fraction of the WDM signal into n sub-band and detects sub-band optical power PB1, . . . PBn.

Abstract: A device for measuring dispersion of a link between two switching nodes of an optical network comprises a phase measuring unit PMU for determining a first phase of a data signal traveling on a first wavelength &lgr;1, and a second phase of the same data signal traveling on a second wavelength &lgr;2, received consecutively over the link under measurement. A dispersion measurement controller controls operation of the phase measuring unit and characterizes the dispersion of the link at a wavelength of interest &lgr;=(&lgr;1+&lgr;2)/2, based on the first and second phases. The PMU includes a frame detector for determining a first and a second rotation signal indicative of the digital offset between the first and second test clocks with a respective frame start, and a phase detector for measuring the phase of these test clocks with respect to a static reference. The static reference is provided by the same data signal transmitted continuously over a reference wavelength.

Abstract: An out of band vehicle for an optical network is used for transporting overhead (OH) data between 3R network elements, irrespective of the format or/and rate of the OH data. At the first 3R network element, the OH data is up-converted at a frequency fch, and the resulting signal is combined with the traffic and transmitted to a second 3R network element. The inverse operation is effected at the second 3R network element by down-converting the combined signal. The frequency fch is selected to be in a null of the traffic spectrum, so as to not interfere with the traffic.

Abstract: Dispersion is measured for an end-to-end link using two carrier wavelengths with a phase-synchronized signal modulated on each, and a single receiver that detects the BER of the combined fields. The power ratio of the two fields is chosen such that the weaker field modulates the eye of the stronger field, leading to slight periodic eye closure BER(&tgr;)≅BER(&tgr;+TB) whenever the relative group delay changes by the bit period TB. The magnitude of the relative group delay can therefore be inferred from the undulated BER response as a function of the wavelength detuning. A fit function is selected for the group delay response and the dispersion parameter D and dispersion slope S are calculated from this fit function after the function parameters are determined.

Abstract: A method for engineering of a connection in a WDM photonic network with a plurality of flexibility sites connected by links comprises calculating a physical end-to-end route between a source node and a destination node and setting-up a communication path along said end-to-end route. An operational parameter of said communication path is continuously tested and compared with a test threshold. The path is declared established whenever the operational parameter is above said margin tolerance. The established communication path is continuously monitored by comparing the operational parameter with a maintenance threshold. A regenerator is switched into the path whenever the operational parameter is under the respective threshold, or another path is assigned to the respective connection.

Abstract: The path selection and wavelength assignment to a selected path are performed by mapping the wavelength reach to the demand distribution (agile reach) resulting in a 50-60% increase in the network reach. The network reach is further increased (about 2.2 times) when on-line measured performance data are used for path selection and wavelength assignment. The connections may be engineered/upgraded individually, by optimizing th eparameters of the entire path or of a regenerator section of the respective path. The upgrades include changing the wavelength, adjusting the parameters of the regenerator section, controlling the launch powers, mapping a certain transmitter and/or receiver to the respective wavelength, selecting the wavelengths on a certain link so as to reduce cross-talk, increasing wavelength spacing, etc.

Abstract: A method for engineering of a connection in a WDM photonic network with a plurality of flexibility sites connected by links comprises calculating a physical end-to-end route between a source node and a destination node and setting-up a communication path along this end-to-end route. An operational parameter of the communication path is continuously tested and compared with a test threshold. The path is declared established whenever the operational parameter is above the margin tolerance. The established path is continuously monitored by comparing the operational parameter with a maintenance threshold. A regenerator is switched into the path whenever the operational parameter is under the respective threshold, or another path is assigned to the respective connection. An adaptive channel power turn-on procedure provides for increasing gradually the power level of the transmitters in the path while measuring an error quantifier at the destination receiver until a preset error quantifier value is reached.

Abstract: The architecture for a photonic transport network provides for separation of passthru channels form the drop channels at the input of a switching node. A wavelength switching sub-system then switches the passthru channels, without OEO conversion. The drop channels are directed to broadband receiver of choice using a broadcast and select drop tree. The add channels are inserted at the output side of the node, using tunable transponders. In addition, a passthru channel may be OEO converted if signal conditioning and/or wavelength conversion are necessary. The transponders, regenerators and transceivers are not wavelength specific, allowing flexible and scaleable network configurations. This structure provides for fast provisioning of new services and ‘class of service’ network recovery in case of faults.

Abstract: A n×n transparent photonic switch TPS for an optical communication network uses wavelength selective elements connected in the switch fabric, to allow channels to pass, or to block channels from passing according to a network-wide routing connectivity data. The WSE may be a two-port blocker, in which case all input and output ports of the TPS are provided with 1:(n−1) splitters/combiners for providing internal routes between all pairs of input I(i) and output O(j) ports. The WSE may be assembled using wavelength selective switches WSS, or combinations of WSSs, splitters/combiners and circulators.

Abstract: The method of monitoring the quality of an optical signal at the site of a 2R or 1R regenerator, without performing a clock recovery operation, is based on slicing the recovered voltage with a threshold voltage, manipulated according to a pattern, and averaging the output of the slicer. An eye diagram is simulated by a diagram representing the average voltage versus the threshold voltage.

Abstract: A unidirectional or bidirectional node for use in an optical communications network, a network consisting of such nodes. The node comprises one or more optical couplers as well as either or both of drop circuitry connected to an output port and add circuitry connected to an input port. This allows for changes to the wavelength plan without interruption of the ring traffic. If add circuitry is used, the wavelengths in the filtered add signal should be distinct from those of the incoming signal on the main optical path which is merged with the add signal. When separate fibers are used for transmitting and receiving data between a hub and nodes in a ring, the through loss of the couplers is reduced for upstream couplers, which increases the available loss to be assigned to the fiber.

Abstract: A configuration for a transport node of a telecommunication system comprises a pair of transparent mux/demuxs provided at two sites and connected over a high rate span. The T-Muxs provide continuity of all tribs and maintain a lower bit rate linear or ring system through the higher bit rate span. The lower bit rate linear or ring system operates as if it were directly connected without the higher bit rate midsection. For the forward direction of the traffic, the T-Mux comprises a multi-channel receiver for receiving a the trib signals and providing for each trib signal a trib data signal and a trib OAM&P signal. The data signals are multiplexed into a supercarrier data signal and the OAM&P signals are processed to generate a supercarrier OAM&P signal. A supercarrier transmitter maps the supercarrier data signal and the supercarrier OAM&P signal into a supercarrier signal and transmits same over the high rate span. Reverse operations are effected for the reverse direction of traffic.

Abstract: A unidirectional or bidirectional node for use in an optical communications network, a network consisting of such nodes. The node comprises one or more optical couplers as well as either or both of drop circuitry connected to an output port and add circuitry connected to an input port. This allows for changes to the wavelength plan without interruption of the ring traffic. If add circuitry is used, the wavelengths in the filtered add signal should be distinct from those of the incoming signal on the main optical path which is merged with the add signal. When separate fibers are used for transmitting and receiving data between a hub and nodes in a ring, the through loss of the couplers is reduced for upstream couplers, which increases the available loss to be assigned to the fiber.

Abstract: Architectures for a synchronous transport network of a telecommunications system using transparent transport capabilities are presented. The telecommunications network comprises a pair of transparent multiplexers (TMuxs) connected over a bidirectional high speed span for transparently transporting high rate traffic. Each TMux consolidates traffic from a plurality (I) of linear systems or a plurality of bidirectional self-healing rings, each ring (Ki) having a ring rate Ri and at least two nodes (Ai, Bi). In another configuration, each TMux subtends a plurality of rings, such TMuxes being adapted for connection as ring nodes in a high-speed ring. The upgrades obtained with TMuxes in both the linear and ring configurations provide for per span relief for fiber exhaust where no changes to the existing systems are desired. As well, the bandwidth of an existing system may be increased on a per-span basis or the equipment count may be reduced.