Abstract: A method of providing reset logic in high availability computer systems is disclosed. The illustrative embodiment of the present invention uses probability theory in combination with redundant processors and components to ensure system availability. Detected errors are verified, and malfunctioning processors or components are then changed to a reset state that functionally removes them from the system. Detected errors which can not be verified result in the processor or component that incorrectly detected the error being placed in a reset state. The use of redundant components and processors enable standby processors to be activated to take the place of reset processors quickly enough to maintain system availability.

Abstract: An optical receiver circuit includes a differential limiter amplifier receiving a binary electrical waveform generated by an optical-to-electrical converter receiving an optical communications signal. Low-pass filter circuits are coupled to differential outputs of the limiter amplifier to obtain the average DC values of the mirror-image output signals. The outputs of the low-pass filter circuits are provided to a differential amplifier to obtain the difference between these average DC values. The output of the differential amplifier is provided to an integrator circuit whose slowly-varying output is provided to the limiter amplifier to establish a switching threshold for distinguishing logic “0”s from logic “1”s in the received data signal. The switching threshold is automatically adjusted in response to varying operation conditions such as changes in the received optical signal power.

Abstract: A system and method is provided for using a first data channel to pass working data and a second data channel to pass error correction information. For example, this second data channel may be defined along a redundant data path. For example, this error correction information may be forwarded error correction (FEC) information such as Hamming code information or any other type of error correction information. Use of the redundant path to forward FEC information provides several advantages: 1) the FEC information can be used to correct bit errors that occur within the system, making the system high-quality and more reliable and 2) use of the protected path provides an efficient method to constantly monitor the quality of both the working and redundant path. Monitoring is accomplished by using the FEC information on the redundant path in conjunction with the information on the working path to accurately count the number of errors that occur on the working and redundant paths.

Abstract: A method of adding wavelengths to an “in-service” WDM optical network system carrying live traffic. The method divides the wavelength into groups and adds each group of wavelengths into the working system in a parallel way by determining the desired TX launch power change for each wavelength from a predetermined value and applying the power changes for the group all together. When the system performance degradation happens after wavelengths addition, a wavelength power balance method according to another aspect of this invention can be applied to optimize the system performance. The power balance method first identifies the wavelengths to be optimized and classifies the wavelengths into controllable and reserved wavelengths; the total power available for wavelength adjustment is then determined; for each controllable wavelength, the required TX launch power which will bring the wavelength to meet the desired performance is determined and applied.

Abstract: An optical transmission system with two counter propagating wavelength division multiplexed (WDM) optical signals carried by an optical fiber transmission line, has a first Raman pump for launching a first beam of pump energy for amplifying both WDM signals so that the first beam counter-propagates with respect to a first WDM signal The system also includes a second Raman pump for launching a second beam of pump energy for amplifying both WDM signals so that the second beam counter-propagates with respect to a second WDM signal.

Abstract: A method and apparatus for detecting if an optical module has been disconnected from a fiber span or if there has been a break in the span, and for automatically reducing the output signal level of the optical module such that the output signal level is within an acceptable safety limit. Also disclosed is a system and technique for automatically resetting a Raman pump unit once the source of an optical leak has been located and addressed.

Abstract: A method and apparatus are disclosed for spreading the component signals of a groomed input circuit through a three-stage CLOS switch network. The spreading algorithm includes sequentially evaluating each midstage switching module as to the availability of a connection between an assigned source switching module and an assigned destination switching module having sufficient spare bandwidth to accommodate one or more of the component signals. A load sharing algorithm can be used to spread the component signals among the midstage switching stages. In this way the available bandwidth of each of the midstage switching modules is evaluated for each of the component signals and each component signal is routed through the midstage switching module having the largest available bandwidth.

Abstract: A method for improving the bit error rate of a modulated optical signal transmitted over single mode fiber is provided. The modulating voltage supplied to a single arm or alternatively to both arms of a Mach-Zehnder modulator is increased to result in a reduced extinction ratio of the modulated optical signal. This results in an optimum optical signal with a reduced bit error rate at a receiver coupled to the Mach-Zehnder modulator.

Abstract: An apparatus for hindering the collection of dust and particulate matter within unutilized housings or ports of hardware component chassis is provided. A port filler baffle for occupying a port within a chassis includes a panel assembly sized and dimensioned to fit within the port of the chassis. A bracket couples with the panel assembly. An aperture filler couples with the bracket. The aperture filler is disposed to hinder particulate intrusion into the unutilized port of the chassis. When the panel assembly is mounted in the chassis, the aperture filler presses against the unutilized port, substantially blocking access to the inside of the port, thus hindering particulate intrusion and keeping the port clean.

Abstract: An active control system and method for controlling the position and/or properties of optical components in an optical switch of an optical communications network is provided. The active control system utilizes a power-sharing scheme to provide an array of supervisory signals, which are directed through the switch to monitor and control the optical components. The supervisory signals are produced by combining the light signals emitted by an array of external light sources, and subsequently splitting the combined signal equally to form the supervisory signals.

Abstract: In a network having a trace capability, a method to track the connectivity of the network uses the trace messages. A network manager creates a list of ports in the network and uses that list to track the connectivity. For each port, the manager first checks whether there is a current connection and if it finds one, records the connection. For the unconnected ports, the manager enables the transmission of a trace message that identifies the transmitting port. When a trace detected message is received from a port, the network manager updates the list of ports with the connection just reported and disables the trace message that was detected. A port sending a trace message that is not detected is marked as not connected in the list. The method is useful in high bandwidth circuit-based networks, such as optical networks, composed of links of many types and utilizing differing protocols.

Abstract: A method and apparatus for controlling the attenuation level of a semiconductor VOA relative to an absolute temperature of the VOA without the use of a power monitor is provided. The method includes the step of providing a variable optical attenuator for attenuating the optical signal. The variable optical attenuator is instructed to maintain the desired attenuation level of the optical signal. The temperature of the variable optical attenuator is periodically sensed, and a required voltage level is determined to achieve the desired attenuation level based at least partially on the periodically sensed temperature of the VOA. The method can further include the step of increasing and decreasing a voltage to the VOA to achieve the required voltage level and thus the desired attenuation level.

Abstract: A method of dispersion compensation for an optical network divides the optical fiber transmission line into sections located between a pair of re-configurable nodes. For each section, at either one of the pair of nodes, wavelengths are classified into a first set of added waves, a second set of dropped waves and a third set of express waves. A first predetermined dispersion compensation is provided to the third set of express waves so that the third set of express waves have a second predetermined dispersion. Methods for determining linear and nonlinear impairment parameters so that the optical parameters due to both linear and nonlinear transmission impairments of each section can be independent obtained and disseminated throughout the network.

Abstract: An interface device having a plurality of ports with a plurality of speed configurations for a serial backplane with 2-pair copper transmission lines, has a plurality of high speed Ethernet ports and a plurality of Gigabit Ethernet ports. A switch mechanism for selecting between the high speed Ethernet ports and the Gigabit Ethernet ports will connect the selected port to the serial backplane via the 2-pair copper transmission lines.

Abstract: A method and apparatus for executing narrow channel spaced dense wavelength division multiplexing (“DWDM”) includes an optical multiplexor/demultiplexor with channel add/drop having a first circulator and a second circulator. A first fiber Bragg grating couples with the first circulator and the second circulator. A second fiber Bragg grating couples with the second circulator. The fiber Bragg gratings separate optical signals in an interleaved manner. The optical multiplexor/demultiplexor with channel add/drop further includes at least one optical filter in communication with the first circulator. The system can further include at least one optical filter in communication with the second circulator as well. The optical filters are spaced apart a greater distance with respect to channel spacing than the channels passing through the system. However, the unique combination of the circulators and fiber Bragg gratings allow the filters to function at the wider spacing to add/drop channel signals.

Abstract: An apparatus for supporting and protecting the optical backplane that permits adequate cooling of electronic components near the optical backplane and maintains optical connectors of the optical backplane in a predetermined and substantially static arrangement is provided. A cartridge for supporting and arranging an optical backplane includes a base. An upper portion couples with the base. The upper portion has one or more optical connector slots for supporting one or more optical connectors of the optical backplane. The optical backplane mounts within the upper portion such that the upper portion together with the base bends the optical backplane to a curvature having a radius of curvature within a predetermined acceptable range.

Abstract: A method and apparatus for in-circuit biasing of a modulated laser and bit error rate testing of an optical transmitter and/or optical receiver under the control of a test controller. The test controller is communicably coupled to an interface of a module under test, as well as to external test equipment. The test controller modifies operational parameters of the modulated laser, in order to obtain a desired output power and to obtain a predetermined extinction ratio. The operational parameters of the laser include a laser bias current, an electro-absorption modulator offset bias current and a modulation depth. The disclosed test controller also determines whether the optical transmitter and/or receiver exhibit acceptable bit error rates. The disclosed test controller uses a variable optical attenuator, in combination with an erbium-doped fiber amplifier (EDFA) to control an optical signal to noise ratio for a signal terminating at either the transmitter or the receiver of the optical transceiver under test.

Abstract: A method for shared distributed mesh optical network restoration includes defining a set of attributes for the links, which further includes globally disseminated and locally kept attributes. The method further includes finding a SRLG-disjoint diversely routed paths, including allocating resources by updating attributes along the links on the backup path. The fault recovery process is started by first detecting and propagating the fault to the tail end of the faulty path, starting from tail end node, for each node along the faulty path. Recovery information is then passed to an egress port. An OXC is configured, updating reserved resource by modifying the attributes for each involved link. Further fault information is disseminated to the network.

Abstract: A network device includes latches disposed between control outputs of control logic such as a field-programmable gate array (FPGA) and control inputs of functional elements through which network traffic flows. The control logic generates a latch enable signal that controls the operation of the latches. The latch enable signal is in a latching state to maintain the latches open during normal operation. During an upgrade, the control outputs may take on incorrect or indeterminate values, due to entering a high-impedance state. Therefore, during the upgrade the latches are closed, maintaining the pre-upgrade values on the inputs of the functional elements and preventing the control logic outputs from affecting operation of the device. After re-programming is complete and the control outputs are in a determinate state, the latches are re-opened. A pullup/pulldown circuit is used to maintain the latch enable signal in a latching state during the upgrade.

Abstract: A method and apparatus for variable optical attenuation is disclosed. A variable optical attenuator is provided having a housing. Within the housing, a filter is mounted on a drive shaft of a motor such that the drive shaft passes through a substantially center point of the filter. The filter has a monotonically increasing filter gradient that begins at a lower optical density and gradually increases in optical density in a diametrical pattern. An input optical fiber provides a light signal to be attenuated. The input optical fiber introduces the light signal, which passes through a first collimator, through the filter, through a second collimator, and to an output optical fiber which exits the housing. When activated, the motor rotates the drive shaft to position the filter to a desired attenuation position for attenuating the light signal.