Recent progress on 3-D integrated intra-chip free-space optical interconnect

In this paper, the authors compare the energy efficiency of a WDM-based optical interconnect similar to and the proposed intra-chip free-space optical interconnect FSOI system to illustrate the advantages of the approach. The operation wavelength of the WDM-based systems is chosen to be 1550 nm, while the FSOI system still uses 980 nm. To emphasize the effects of photonic devices and optics design, the transceiver circuits is excluded from the calculation, which would be similar in both cases. To simplify the calculation, the PDs in both systems are assumed to have 100% quantum efficiency and adequate bandwidth to support 10-Gbps data rate, which gives the WDM system unfair advantage.