Alignability of optical interconnects

A theory for analyzing the alignability, the degree of difficulty of aligning the devices and light beams, of a given optical interconnection system is developed. From various experiments it has been found that the alignment of a basic optical interconnect consisting of one beam and one device is a random process, N(0,σ). The standard deviation of alignment is inversely proportional to the overall cost measure modeled as a function of the time spent, the skill of operators, positioning devices, degrees of freedom in positioners, etc. In an incoherent interconnect, Pf = prob (alignment with at least f% power coupling) = 1 exp[−(d + s +fs/50)2/2σ2], where d and s are the radii of the device and the spot, respectively, and d ⪰s. The alignability of the interconnect, A = ∫ Pf df. Aincreases with the device size and the overall cost measure indicating that alignment gets better if more money is spent or larger devices are used. Practical optical systems consisting of many optical paths and devices, such as, optical crossbar switches, can be modeled as series and parallel combinations of many independent basic interconnects. Thus, overall alignability of a large interconnect = IIAi, of all the component interconnects. From this concept of alignability guidelines for the design and deployment of optical interconnects can be developed.