Multi-Path Propagation in On-Chip Optical Wireless Links

Abstract

Optical wireless networks-on-chip (OWiNoC) are considered as a possible solution to overcome the communication bottleneck due to wired interconnects in modern chip multiprocessor systems. The efficient implementation of optical wireless links requires considering many different aspects, including analysis and deep understanding of the effects on the propagation of the electromagnetic field induced by the discontinuities that can be found in a realistic scenario. This letter aims at showing the impact determined by some of these discontinuities on optical links designed in Silicon-on-Insulator technology, exploiting simple point-to-point interconnections as a first example. Measurements and simulations confirm that multi-path phenomena, triggered by the multi-layer structure housing the antennas and the propagation paths, can have a serious impact on the link budget, with fading effects that may compromise the performance of the link. However, in the presented experimental results, thanks to a careful choice of the chip layer structure, received powers higher than those which could have been measured for optical links fabricated in an infinite homogeneous medium are observed, thus resulting beneficial for the connection's power budget.

A Ray Tracing Tool for Propagation Modeling in Layered Media: A Case Study at the Chip Scale

“…The prediction accuracy of the RT models presented in Sections II and III has been checked against PG measurements carried out at chip level by means of the measurement procedure outlined in Section IV [26]. Ray simulations have been run in the layered scenario outlined in Fig.…”

“…7) consists of a lower bulk of Silicon ( down = 675 μm) coated with a layer of SiO 2 (h SiO2 = 3 μm) further overlayed by a thin film of Silicon (h W = 220 nm), where standard Si waveguides and the antennas are etched. Waveguides and antennas are then covered by a thin layer (h A = 300 nm) of borophosphorous tetraethyl orthosilicate (BPTEOS), being easily planarized and showing a refractive index very close to Silica (Table 3) [26]. Finally, As the investigation is mainly oriented to propagation modeling, the antennas have been designed by simply tapering the silicon waveguides according to what discussed in [27].…”

“…Further details on the design of the optical wireless links and of the measurement equipment can be found in [22] and [26].…”

Reconfigurable Optical Wireless Switches for On-Chip Interconnection

“…Actually, the on-chip wireless communication occurs in a multilayered structure, typical of photonic integrated circuits. The medium discontinuities in on-chip optical wireless scenarios, can lead to multi-path propagation phenomena, shown by the authors in [30]. Multiple reflections cause fluctuations on the received power (increasing where interference is constructive, fading where destructive interference is taking place), requiring simulations of the complete device to optimize the configuration of the OWS.…”

Terahertz Channel Propagation Phenomena, Measurement Techniques and Modeling for 6G Wireless Communication Applications: a Survey, Open Challenges and Future Research Directions

“…Data rates of 0.95 Tbps were achieved by full-wave simulations in [177] for wireless on-chip communications that interconnect cores in a multiprocessor. In [178] the effects of multipath propagation on the link budget due to multi-layer housing structures for on-chip communications were studied and may prove to be beneficial if careful chip layer structure is considered.…”