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 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: 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 network element locating system includes a network element locator and a network element position manager. The network element locator acquires geographical location information and stores it as position data. The network element position manger receives the position data, and provides the geographical location information of the network element in a user requested format. The acquisition of the geographical location information can be made at the time of installation of the network element, using a hand-held GPS device. Alternatively, the GPS device can be embedded in the network element. The position data is transmitted to the network element position manger on request, or whenever a certain type of fault occurs.

Abstract: A chromatic dispersion characterization system for an optical transmission path is based on setting the operating point (the DC bias) of an external modulator alternatively on the inverting and non-inverting characteristic of the modulator. A dispersion regime of choice may be selected based on the modulator's alpha parameter, and the BER information recorded against the respective values of the DC bias. This system can be used to determine when the net CD in a link is zero, i.e. the network provider has provisioned sufficient compensation to match the CD in the link. The link operates in a zero-dispersion regime when the quality of the received signal does not change between the two modes.

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 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: A return-to-zero (RZ) modulator for an optical transmitter comprises a Mach-Zehnder interferometer optically coupled with a light source for modulating a continuous wave generated the said light source with a drive signal. A drive circuit generates a drive signal for modulating the Mach-Zehnder device to generate an optical RZ pulse signal with adjustable width. The drive circuit comprises a trigger flip-flop for converting a non-return to zero (NRZ) signal to a modified drive signal. A method of generating an optical RZ pulse signal comprises converting a non-return to zero (NRZ) signal to a modified drive signal, and modulating a continuous wave from a light source with the modified drive signal to generate an optical RZ pulse signal. The width of the pulses in the optical RZ pulse signal is controlled by adjusting the rise and fall time of the modified drive signal.