Patent ID: 7242867

Claim:
A synchronization apparatus for a SONET/SDH cross connect switch having an ingress stage, a center stage, and an egress stage, comprising: a main synchronization module operatively connected to the center stage and receiving a synchronization reference, said main sync module locking on to the synchronization reference to generate a sync signal in phase with the synchronization reference, said main synchronization module encoding a frame sync signal within the sync signal being generated; an optical sync interface operatively connected to said main sync module and to the ingress and egress stages, said optical sync interface converting the sync signal into an optical sync signal, said optical sync interface distributing the optical sync signal to the ingress and egress stages; said optical sync interface recovering the sync signal from the optical sync signal at the ingress and egress stages after optically transmitting the optical sync signal to the ingress and egress stages; a secondary synchronization module operatively connected to said optical sync interface, said secondary synchronization module extracting the encoded frame sync signal encoded within the recovered sync signal and generating a system clock from the recovered sync signal; said secondary synchronization module comprising a phase lock loop module outputting a frequency multiplied system clock in phase with the system clock to ingress and egress switch fabrics; said phase lock loop module comprising an EXOR phase comparator operatively connected to a controllable oscillator, said EXOR phase comparator comparing phases of the frequency multiplied system clock and the system clock and outputting a phase difference to said controllable oscillator, wherein said controllable oscillator outputs the frequency multiplied system clock.