Abstract: The present disclosure relates to systems and methods for fast digital signal processor (DSP) optical receiver recovery, namely for optical modems configured on a client side. This approach can be used in optical protection switching (OPS) applications to allow switching between two client links fast, i.e., within 50 ms. A receiver (Rx) digital signal processor (DSP) in an optical receiver includes circuitry configured to detect traffic is interrupted on a current link, enter a holdoff period, and one of i) receive good traffic during the holdoff period and ii) have the holdoff period expire that causes a notification to a host device and retrain to acquire an optical signal.

Abstract: A method and apparatus for adjusting a symbol decision threshold at a receiver in a communication network enables the receiver to be adapted to more correctly receive symbols as transmitted by a transmitter. In one embodiment, a received bit imbalance is detected by a receiver prior to error correction and after error correction to determine whether an error component of the received signal contains larger numbers of ones or larger numbers of zeros. Where the transmitter scrambles the signal prior to transmission, the receiver will also scramble the signal after error correction and prior to counting the number of zeros or ones. Any imbalance between the number of transmitted and received ones or zeros is used as feedback to adjust threshold values used by detectors to fine tune the manner in which the receiver interprets incoming signals.

Abstract: A method and apparatus for adjusting a symbol decision threshold at a receiver in a communication network enables the receiver to be adapted to more correctly receive symbols as transmitted by a transmitter. In one embodiment, a received bit imbalance is detected by a receiver prior to error correction and after error correction to determine whether an error component of the received signal contains larger numbers of ones or larger numbers of zeros. Where the transmitter scrambles the signal prior to transmission, the receiver will also scramble the signal after error correction and prior to counting the number of zeros or ones. Any imbalance between the number of transmitted and received ones or zeros is used as feedback to adjust threshold values used by detectors to fine tune the manner in which the receiver interprets incoming signals.

Abstract: Provided is a method and apparatus for segmenting packets into cells of variable sizes in order to facilitate the parallel transport of data symbols common to a single packet through a composite medium made up of a number of lanes. According to the invention the method of segmenting packets results in cell sizes that efficiently use the available capacity and minimize the complexity of any additional apparatus required in the receivers used to reassemble the packets from the variable-sized cells. Additionally, the invention could be advantageously combined with the Generic Framing Procedure (GFP) as defined in ITU-T G.7041/Y.1303 that was ratified December 2001.

Abstract: A system and method for clock synchronization in a network having one or more asynchronous data links is provided. A clock signal is propagated through, at the physical layer, a sequence of network devices linking a source network device to a destination network device of the network. Each asynchronous data link between the source network device and the destination network device is adapted to receive an incoming clock signal from the previous network device and then provide a clock signal synchronized to the received clock signal to the next network device of the sequence. At the same time, each network device of an asynchronous segment of the network can continue to transmit packets of data asynchronously. By locking the link-based frequency on a per link bases, the receiver clocks located at the edge of a network can be tied directly to a primary source located in the core network.

Abstract: A method and apparatus for minimizing starvation of a station in a ring networked environment includes allocating a tax to each of the stations in the ring, and, for each packet that is to be transited though the ring, providing bandwidth to the station in the form of a tax packet, which allows the station to have ring access.

Abstract: A packet-aware time division multiplexing (TDM) switch includes one or more ingress ports, one or more egress ports, a TDM switching fabric, and a bandwidth manager. Ingress ports are capable of distinguishing packets. The TDM switching fabric has persistent connections which provide connectivity between each ingress port and each egress port. Packets received at an ingress port are transmitted to one or more egress ports using TDM over one or more switching fabric connections. The congestion of each connection is monitored, and the capacity of the connection may be automatically adjusted based on the monitored congestion. Congestion may be indicated by a utilization of the connection or by a degree to which a buffer for storing packets to be sent over the connection is filled. Statistical multiplexing may be used at ingress ports and/or egress ports in order to eliminate idle packets. The utilization of the switch for data traffic may thus be improved over conventional TDM switches.

Abstract: A control system enables transport of payload data across a dual counter rotating ring (DCRR) network having two or more nodes, each node providing access to the DCRR network by a respective local area network (LAN) subtending the node. The control system comprises a topology learning entity operative within each node for monitoring individual, links of the DCRR, discovering the active topology of the DCRR, communicating topology changes to other nodes in the DCRR, and informing frame forwarding and learning processes of the topology to enable failover to redundant resource upon detection of a network component failure. A frame forwarding process selects a shortest path route between a source and a destination node in the DCRR, and forwards frames to the destination node via the selected shortest path route. An address learning process inspects a source medium access control (MAC) address in each received frame to learn a shortest path route for each MAC address.

Abstract: Provided is a method and apparatus for segmenting packets into cells of variable sizes in order to facilitate the parallel transport of data symbols common to a single packet through a composite medium made up of a number of lanes. According to the invention the method of segmenting packets results in cell sizes that efficiently use the available capacity and minimize the complexity of any additional apparatus required in the receivers used to reassemble the packets from the variable-sized cells, Additionally, the invention could be advantageously combined with the Generic Framing Procedure (GFP) as defined in ITU-T G.7041/Y.1303 that was ratified December 2001.

Abstract: A fairness scheme is disclosed for managing data flow between nodes in a bi-directional ring network. A method in accordance with the invention controls the output bandwidth of nodes in a bi-directional ring network by: identifying a congested span comprising a head node having a congested downstream link, and a plurality of chain nodes contributing to the congestion in the downstream link: adjusting the output bandwidth of the head node as a function of the congestion in the downstream link; and adjusting the output bandwidth of the chain nodes as a function of the congestion in the downstream link.

Abstract: A communications system is provided having SONET communications channels extending between first and second locations. The channels include pairs of forward and reverse channels for carrying traffic in normal operation between first and second locations and a protection channel for carrying traffic of one channel in the event of a fault. Each pair of forward and reverse channels is provided on a shelf at each location, the shelves having the same relative position at both locations and the protection channel is provided on a protection shelf. The protection channel includes, between the first and second locations, a forward optical link and a reverse optical link and at each of the first and second locations, a single protection loop, coupling the forward and reverse optical links, that forms the protection channel.