Abstract: Chromatic dispersion is determined based on the arrival times of different frames of data in a wavelength division multiplexed (WDM) system having an optical communication link. Namely, a first frame is transmitted on a first optical channel, which is supplied to the optical communication link. A second frame is then transmitted on a second optical channel and the transmission time difference between the two frames is obtained. At a receive end, the difference in arrival times of the two frames is measured to obtain a relative time delay between the first and second frames and used to determine a chromatic dispersion.

Abstract: A temperature-compensated fiber grating package which provides a temperature dependant stress on a fiber Bragg grating to substantially compensate for temperature dependant variations of the Bragg wavelength. The package includes a base, a fiber grating bonded to the base, and a strut. The base is formed from a high thermal expansion material, and includes first and second spaced arms separated by a base portion. The strut is constructed from a low thermal expansion material is disposed between the first and second arms. The ends of the strut engage the interior surfaces of the arms to form left and right fulcrum points. The fiber grating is secured between the first and second arms. As temperature increases, the high thermal expansion material of the arms expands at a greater rate than the low thermal expansion material of the strut. The top portion of at least one of the arms thus pivots inward about a fulcrum point to place the temperature-dependant negative strain on the grating.

Abstract: In a wavelength division multiplexed system, optical frequencies are assigned in accordance with a channel plan conforming to an International Telecommunications Union (ITU) grid whereby every third channel position in the grid is vacant. As a result, both four wave mixing (FWM) and cross phase modulation (XPM) are reduced using ITU standard frequencies. In addition, a low bandwidth expansion factor (BEF) can be achieved.

Abstract: Consistent with the present invention, a tunable laser emits a monitoring signal which is combined with the WDM channels typically at the transmit side of a WDM system. At each monitoring point along the WDM system, the WDM channels are filtered out, the monitoring signal is sensed, and desired systems parameters (e.g., gain flatness, dispersion, PMD and OSNR) are measured. Accordingly, a single tunable element, i.e., the tunable laser, can be provided, thereby reducing costs. Moreover, system performance can be ascertained regardless of whether WDM channels are present.

Abstract: Consistent with the present invention, programmable input and output buffers are provided on each port of each stage of a distributed system in order to reduce data skew and preserve data synchronization. The programmable buffers provide the ability to add delay to data paths having less skew to compensate or match the skew associated with data paths having greater skew. Accordingly, the programmable buffers can equalize data skew and preserve data synchronization at each stage in the distributed system. As a result, individual stages can be placed farther apart, thereby facilitating larger distributed systems.

Abstract: An optical filter aligner/separator device for retaining optical filters in a desired position, the optical filters having an optical filter height, the device includes: a top frame having a top frame cut out section; a bottom frame having a bottom side and a bottom frame cut out section, the bottom frame coupled to the top frame, the bottom frame cut out section aligning with the top frame cut out section; and a wire mesh disposed between the top frame and the bottom frame, the wire mesh disposed at the cut out section, the wire mesh having a height from the bottom side of the bottom frame that is less than the optical filter height.

Abstract: A method for tensioning and positioning a fiber optic cable includes providing and securing a first portion of the fiber optic cable in a first support with a first clamp. A second portion of the fiber optic cable is then provided in a second support, and secured thereto with a second clamp. A cam contacting the second support is then rotated, thereby rotating the second support due to its weight and the weight of the second clamp. The rotation of the second support creates a gravity-assisted moment arm that uniformly and repeatably tensions and positions the fiber optic cable. After the fiber optic cable is uniformly tensioned and positioned, a refractive-index grating may be etched in the glass optical fiber portion of the cable. Once the grating is etched, the cable may be removed by reversing the method.

Abstract: Systems and methods consistent with this invention allow for each node within one or more rings to obtain connection and topology information from other nodes within these rings. In such a system, each node is able to maintain connection table and topology tables for each node and each ring within a ring network. In particular, such information can be kept current because this scheme allows for dynamic updating of connection and topology information in real time. With such current information, a node is able to utilize this information to execute such operations as squelching connections on a protect line and timeslot interchange. In addition, by supporting timeslot interchange, the ring can be managed as more than a single logical entity as well as can have better bandwidth management utilization.

Abstract: A unidirectional ring operates in accordance with a call setup procedure in which a single node on the ring, referred to herein as the “hub node,” simultaneously (i) processes call setup information from and provides call setup information to an ATM network, and (ii) controls the call setup operations of the nodes on the ring. When a source node that is part of the ring initiates a call, the node directs a call setup message to the hub node. The hub node determines if there is sufficient bandwidth available on the ring for the call. If so, the hub node passes the call setup message to the ATM network, and simultaneously multicasts call setup information to the nodes on the ring. While the call setup message is progressing over the ATM network in a conventional manner, the nodes on the ring simultaneously set up the associated virtual path and/or virtual circuit and send back connection information to the hub node.

Abstract: A connect and disconnect assembly for connecting and disconnecting a laser diode having leads to a printed circuit board (PCB). The assembly includes a heatsink having a base plate portion and fins extending from and integral with the base plate portion. The heatsink further includes spacer sleeves extending from a side of the base plate portion opposing the fins. The heatsink connects to the printed circuit board by providing mount screws through the heatsink and spacer sleeves which are received in mount holes formed in the PCB. The laser diode connects to the base plate portion of the heatsink. Laser support blocks connect with the heatsink and support opposing sides of the laser diode. Each laser support block is provided with a dielectric gasket. When the heatsink is mounted onto the PCB, the laser diode leads are forced against corresponding pads provided on the PCB for electrically connecting the laser diode to the PCB.

Abstract: An optical fiber ring is provided carrying a plurality of WDM optical signals, each at a respective one of a plurality of wavelengths. Each optical signal carries data associated with a corresponding group of TDM add/drop multiplexers coupled to an optical path spaced from the optical fiber ring. The optical signals are extracted from the fiber ring with optical add/drop multiplexers, and the data carried by the optical signals is then supplied to the corresponding group of TDM add/drop multiplexers. Accordingly, instead of assigning an optical add/drop multiplexer to each TDM add/drop multiplexer, the optical add/drop multiplexers are assigned to respective groups of TDM add/drop multiplexers. As a result, optical loss as well as cost of the WDM ring are minimized.

Abstract: At least one protection line is shared among SONET rings. Identification and availability information of the shared protection line is distributed among the switches of the SONET rings using K-byte data in the SONET overhead.

Abstract: In accordance with an aspect of the present invention, a circuit is provided which is configured to recover clock and data streams from an incoming signal. The circuit comprises a multiplexer having first and second inputs, and an output. The first input is configured to receive the incoming signal, and the second input is configured to receive a reference clock signal, while the output selectively supplies one of the incoming and reference clock signals. A toggling circuit, such as a flip-flop, and a frequency multiplier circuit are further provided which are coupled to the multiplexer output. A filter circuit is coupled to the frequency multiplier circuit, and the output of the filter circuit is coupled to a second input of the toggling circuit. Moreover, the output of the filtering circuit corresponds to the recovered clock stream, and an output of the toggling circuit corresponds to the recovered data stream.

Abstract: The present invention provides a remodulating channel selector for a wavelength division multiplexed optical communication system. The remodulating selector receives a WDM input signal, selects a particular optical channel from the WDM signal and places the information from the selected signal onto a newly-generated optical output signal. The wavelength of the output optical signal can be the same as or different from one of the optical channels which comprises the WDM input signal. When used in a WDM optical communication system with remodulators at the transmission input, the remodulating selectors provide complete control over the interfaces with optical transmitters and receivers, permitting use with a broad range of optical equipment.

Abstract: A clock signal is received. A synchronization signal is compared to the clock signal to determine whether the synchronization signal is asserted within a predetermined period of time with respect to clock signal cycles. The synchronization signal assertion is used to synchronize a circuit to an external event, if the synchronization signal assertion is received within the predetermined period of time. If the synchronization signal assertion is not received within the predetermined period of time the circuit is not synchronized.

Abstract: In accordance with the present invention, optical channels to be demultiplexed are supplied to first and second optical fibers via an optical splitter. Low loss interference filters, for example, coupled to the first and second optical fibers, select respective groups of channels. Each group of channels is next demultiplexed with sub-demultiplexers into individual channels, each of which is then sensed with a corresponding photodetector. Although the optical splitter introduces an optical power loss at the input to the demultiplexer, the interference filters and sub-demultiplexers create little additional loss. As a result, the total power loss associated with the present invention is significantly less than that obtained with a conventional n channel demultiplexer based on a 1×n splitter. Accordingly, large numbers of channels, e.g., in excess of forty can be readily demultiplexed and detected.

Abstract: A dispersion compensating element having a substantially uniform spectral nonlinearity is described. The dispersion compensating unit is thus suitable for incorporation into high speed wavelength division multiplexed (WDM) optical communication systems. Several examples of dispersion compensating elements are discussed, each of which comprising at least one segment of dispersion compensating fiber.

Abstract: A system with predefined primary and secondary routes sets up corresponding virtual circuits over both routes. A destination node maintains primary and secondary sets of routing tables that contain, respectively, routing information over each of the rings for every virtual circuit. A destination node disables the appropriate entries in the routing tables for the non-selected route, such that the node ultimately discards the traffic received over that route. To switch a virtual path, and thus all of the virtual circuits included therein, from the selected route to the nonselected route, the destination node disables and enables the appropriate entries in the primary and the secondary routing tables, to switch from using the set-up virtual circuits on the selected route to using the set-up virtual circuits on the non-selected route. To detect an event that triggers protection switching, such as path failure, the system uses “Continuity OAM cells” to provide path status information to the nodes.

Abstract: Consistent with the present invention, in-fiber Bragg gratings are used to demultiplex optical signals in a WDM optical communication system. The in-fiber Bragg gratings also perform dispersion compensation of the selected optical signals. As a result, additional segments of DCF for further dispersion compensation are rendered unnecessary. Improved performance is thus achieved with an inexpensive and simplified system design.

Abstract: A heat sink module consistent with the present invention includes a heat pipe for efficient heat transfer heat away from a semiconductor pump laser. The heat pipe heat sink occupies less space than a conventional heat sink, and the condenser portion of the heat pipe heat sink can be easily manufactured using an extrusion process.