Sk. Tewksbury et La. Hornak, OPTICAL CLOCK DISTRIBUTION IN ELECTRONIC SYSTEMS, Journal of VLSI signal processing systems for signal, image, and video technology, 16(2-3), 1997, pp. 225-246
Citations number
59
Categorie Soggetti
Computer Sciences, Special Topics","Engineering, Eletrical & Electronic","Computer Science Information Systems
Techniques for distribution of optical signals, both free space and gu
ided, within electronic systems has been extensively investigated over
more than a decade. Particularly at the lower levels of packaging (in
tra-chip and chip-to-chip), miniaturized optical elements including di
ffractive optics and micro-refractive optics have received considerabl
e attention. In the case of optical distribution of data, there is the
need for a source of optical power and a need for a means of modulati
ng the optical beam to achieve data communications. As the number of o
ptical data interconnections increases, the technical challenges of pr
oviding an efficient realization of the optical data interconnections
also increases. Among the system signals which might be transmitted op
tically, clock distribution represents a substantially simplified prob
lem from the perspective of the optical sources required. In particula
r, a single optical source, modulated to provide the clock signal, rep
laces the multitude of optical sources/modulators which would be neede
d for extensive optical data interconnections. Using this single optic
al clock source, the technical problem reduces largely to splitting of
the optical clock beam into a multiplicity of optical clock beams and
distribution of the individual clacks to the several portions of the
system requiring synchronized clocks. The distribution problem allows
exploitation of a wide variety of passive, miniaturized optical elemen
ts (with diffractive optics playing a substantial role). This article
reviews many of the approaches which have been explored for optical cl
ock distribution, ranging from optical clock distribution within lower
levels of the system packaging hierarchy through optical clock distri
bution among separate boards of a complex system. Although optical clo
ck distribution has not yet seen significant practical application, it
is evident that the technical foundation for such clock distribution
is well established. As clock rates increase to 1 GHz and higher, the
practical advantages of optical clock distribution will also increase,
limited primarily by the cost of the optical components used and the
manufacturability of an overall electronic system in which optical clo
ck distribution has been selectively inserted.