Optical Fiber Buffer for High‐Performance Broadband Switching

This paper presents an optical buffer shift register based on a set of fiber delay lines electrically‐controlled, to provide cell storage and queueing capabilities in high‐performance broadband switches satisfying ATM service requirements. The concept of multi‐wavelength cell buffering is adopted, to realise a partially shared buffer with a storage capacity equivalent to a set of single shift registers. The final system is well‐suited for photonic switches adopting time‐ and wavelength‐division multiplexing techniques to perform the routing functions inside the switching matrix. We have demonstrated both the suitability of optical fibers as signal delay lines and the use of semiconductor optical amplifiers as gates associated to passive splitters, to realise cell buffering and time‐switching. An experimental set‐up has been implemented at 600 Mbit/s, operating without guardbands between packets. Good performances were obtained in terms of gain and speed of the whole system: the slight penalty and time shifts observed show that the system synchronisation is very good, thus capable of allowing higher operating bit‐rates.