FOUR-FIBER HOT-STANDBY RING

PULSAR offers several network management options for the protection of critical communications channels in the event of a link or node failure. The four-fiber-dual counter-rotaring ring option utilizes two pairs of fibers between all adjacent nodes. One of the fiber pairs is used as the main communication path and the other pair is used as a hot standby or redundant path which is shared by all nodes in the loop. A break in the primary path between two nodes initiates rerouting of all 24 channels through the standby fibers. The rerouted signal travels in the opposite direction around the ring to arrive at the node on the opposite side of the break. This procedure reliably reconnects all channels affected by the break. The signals are automatically returned to the main fibers when the normal path has been restored. Unlike traditional path-switched schemes, the four-fiber-counter-rotating ring allows the user to make use of the fullT1 bandwidth between each adjacent station.

All 24 time slots between any two locations can be reused any number of times around the loop.

The system provides fast service restoration with complete reconfiguration in less than 50ms for most applications. High reliability is maintained by continuous monitoring of the standby fibers to ensure availability in the event of a fiber link or node failure.

Example Operation:

One or both of the main fibers between Station A and Station B break. Terminal A and/or Terminal B receive low signal alarms on the main fibers. This directs both Terminals A and B to switch to the standby path in the opposite direction. The affected data is passed through Stations C and D to complete the broken circuits. When low signal alarm has been cleared, transceivers at Terminal A and B will switch back from the standby fibers. If only the standby fibers are broken, no rerouting occurs and a minor system alarm is initiated.