Free-Space Optical Interconnects for Cable-Less Readout in Particle Physics Detectors

Particle physics detectors utilize readout data links requiring a complicated network of copper wires or optical fibers. Upgrades to such detectors may require additional bandwidth to be provisioned with limited space available to route new cables or fibers. In contrast, free-space optical interconnects will offer cable-less readout, thereby resulting in significant reductions of material and labor to install and manage the cables. A collaborative effort between Fermilab and Vega Wave Systems is pursuing the development of a unique free-space optical link design that utilizes the transparency of silicon at wavelengths including 1310 nm and multiple wavelengths used in standard telecommunications applications such as coarse wavelength division multiplexing (CWDM). The first step in the pursuit of that design is a proof that the concept may be viable. To that end, experiments have been performed to characterize the bit error rate performance of a prototype link over a free-space optical path and through doped silicon at multi-gigabit rates. These experiments have demonstrated that operation within acceptable bit error rates is possible using single and multiple wavelength transmission arrangements.