BOARD-LEVEL H-TREE OPTICAL CLOCK DISTRIBUTION WITH SUBSTRATE MODE HOLOGRAMS

This paper describes a design for a board-level System free-space opti cal clock distribution system implemented with Clock substrate mode ho lograms, The design uses an H-tree distribution scheme to balance prop agation delays for different clock paths on each board. The H-componen t provides four diffracted output beams with similar to 11% efficiency for each output, and the required laser power for the clock distribut ion system is calculated, To provide 80 clock fan-out signals for a fi ve-board system, the clock distribution system requires 4.7 mW of lase r power with 10 mu W of received optical power at each node, The misal ignment analysis for the free-space optical system is presented and de sign considerations are given, The factors causing clock skew and timi ng jitter in the optical clock distribution system are also examined, An experimental system was demonstrated with a 622-MHz clock signal di stributed with 36 ps of timing jitter and less than 10 ps of clock ske w.