Abstract: In a switch fabric environment, which includes a buffer, packet data of different class-types from different sources is received, stored in the buffer, processed and outputted to its intended destination. As the buffer fills up, transmission from some of the data sources is stopped to avoid dropping of packets. To avoid packet loss, when the occupancy of the buffer reaches a first threshold value, further transmission of a first-class type of data is precluded from the particular source of that data then being received, while transmission from other sources of that same first-class type of data is not precluded from these other data sources until first-class type of data from such other sources is also received. Further, data of a second-class type is not precluded from being transmitted as long as the amount of data stored in the buffer remains below a second threshold, which is greater than the first threshold.

Abstract: A method and apparatus for recovering the time base of signals which change at periodic intervals is disclosed. The apparatus comprises gated voltage controlled oscillators (GVCO) that are alternated or exchanged, to reduce phase and frequency deviations in the recovered time base signal, such as the deviations induced by inherent GVCO differences. Each GVCO is stabilized by a respective phase locked loop. The respective GVCOs are gated only in response to a chosen polarity transition in the input signal, to make the circuit more tolerant of waveform distortions. More than two GVCOs may be used to provide improved frequency drift resistance. The circuit uses resynchronization control signals, such as the time slot signal in synchronous switching systems, to indicate resynchronization or reassignment of the GVCOs in gaps in the data transmission.

Abstract: An apparatus and method are disclosed for implementing a polarization-independent optical switch wherein switchable communication signals are retained in the optical mode while being switched between optical links in an optical communication network. The polarization-independent optical switch comprises polarization-dependent components which are advantageously arranged to switch arbitrary polarized light waves. The polarization-independent optical switch is achieved by splitting incoming arbitrary polarized light waves into two paths, a light wave with a TE radiation component and a light wave with a TM radiation component. The light wave with the TE radiation component is converted to a light wave with a TM radiation component. Both light waves having the TM radiation component are then switched in a polarization-dependent photonic switch device.