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Chip-Scale Optical Receivers for Communications


OBJECTIVE: Develop a small SWAP-C (chip-scale) optical receiver that overcomes current limitations such as field-of-view (FOV) and pointing and tracking (PAT) enabling communications for highly mobile vehicular and personal/on-body applications. DESCRIPTION: The radio frequency (RF) spectrum, relied upon for wireless communications, is increasingly congested and subject to interference that reduces system performance. Obtaining the bandwidth necessary for the high data rates demanded by modern applications is extremely expensive within licensed bands, and permissible use of the unlicensed bands entails various design restrictions. Free space optics (FSO) systems that can communicate using lasers eliminate these problems since the optical bands are unregulated, and the extreme directivity of lasers prevent interference with nearby receivers. Furthermore, the large amounts of available bandwidth with this approach can offer very high data rates. Unfortunately, while current commercially available FSO systems are suitable for fixed-site point-to-point applications with mast/tower-mounting, they are unsuitable for highly mobile applications with stringent size, weight, and power (SWAP) requirements. Additionally, the high-cost of FSO makes it impractical to field in very large quantities for military use and rules out potential civilian applications. Photonic integrated circuit (PIC) based FSO address all of these problems. Designed to be fabricated on an integrated circuit, PIC-based FSO can achieve size and weight reductions of multiple orders of magnitude relative to traditional FSO designs, and, when fabricated in production quantities, the costs of these PICs are minimal compared to FSO system component costs. In addition, because optoelectronic techniques enabling extremely rapid beam-steering can be used instead of mechanical steering, chip-scale systems can support on-the-move applications. Because of these capabilities and attributes the use of chip-scale FSO holds great promise for incorporation into networks as a means to alleviate the growing demand for RF spectrum while providing high data rate communications in a low SWAP-C design. Although chip-scale FSO components have been fabricated and demonstrated at various levels of maturity, additional development of the components and receiver design is needed in order to realize the promise of the technology. Current designs are limited in field-of-view (FOV) especially across wide bandwidths and implementation of high-speed pointing and tracking (PAT) is limited. C5ISR Center seeks the design and development of a chip-scale optical receiver that overcomes these challenges and enables low SWAP-C high data rate communications for highly mobile applications. In particular, C5ISR Center seeks a wide FOV (>= 45 degrees) wide-bandwidth (1 – 10 GHz) receiver capable of pointing and tracking and high rates (<= 500 us slew time across FoV). This includes significant increases in field of view in both azimuth and elevation planes across high bandwidths (e.g. 1 – 10 GHz or higher) as well as the ability to support high-speed beam-tracking, node acquisition/network entry, and angle of arrival calculations. Work under this SBIR aligns with Army network S&T investments, including the Nova Specter project. PHASE I: During Phase I the selected company(s) will design a chip-scale optical receiver capable of beam-tracking for highly mobile applications (e.g. vehicles, drones). The design must support wide bandwidths (at least 1 GHz and ideally 10 GHz) over a wide field-of-view (>=45 degrees in azimuth and elevation) in a compact form-factor (<= 1 cm^3) and have a clear and well defined path towards full 360 degree coverage. A pointing and tracking (PAT) mechanism will be designed with high slew rates (<= 500 us across FoV) that maintains low probability of detection and does not incorporate a side-channel or locator beacon. For eye-safety, designs must operate between 1200 nm – 1700 nm. A report documenting the design will be delivered to the government at the end of Phase I. PHASE II: The Phase II effort will fabricate the chip-scale optical receiver and incorporate it into a demonstration/prototype communications system capable of demonstrating the ability to beam-track while sending high data rate communications (>1 Gbps). The optical receiver and demonstration/prototype communication system shall be delivered to the government at the conclusion of the Phase II effort along with a user’s guide and an interface control document documenting the physical, electronic, and signaling interfaces necessary to incorporate the optical receiver into a third party design. PHASE III DUAL USE APPLICATIONS: The Phase III effort will focus on commercialization of the technology, which could include civilian applications such as wireless access networks or drone communications. This will entail maturing and optimizing the chip-scale receiver from performance, cost, and ruggedization standpoints. This will also necessitate an innovative packaging design that incorporates a protective layer(s)/housing to prevent damage to the optical components and minimize the impact/likelihood of dirt, debris, condensation, water, or other obfuscating substances as well as scratches, cracks, or other damage to the protective covering. The Phase III system will produce a compact optical receiver with impactful capability for both Army/DoD and civilian applications. For the Army/DoD FSO based communications will enable significant advancement in network capacity and improvements in low probability of detection (LPD). This can be used for air-to-air, air-to-ground, as well as ground-to-ground applications such as inter-vehicular communications. The lack of spectrum approval required for the use of FSO will represent an enormous time savings for spectrum managers, and the ability to use optical spectrum for a much wider range of communications will enable RF spectrum to be conserved for where it is most needed (e.g. non-line-of-sight links). In the civilian sector chip-scale optical communications holds tremendous opportunities. Billions of dollars are spent by commercial companies to secure the use of RF spectrum. The ability to use the optical spectrum instead which entails no spectrum costs, can therefore save enormous amounts of money. In addition to communications, certain optical receiver designs can also be applied towards LiDAR, which is a key component in some approaches to autonomous vehicle technology. REFERENCES: 1. P. F. McManamon et al., "Optical phased array technology", Proc. IEEE, vol. 84, no. 2, pp. 268-298, Feb. 1996.; 2. Moshe Zadka et al., "On-chip platform for a phased array with minimal beam divergence and wide field-of-view", Optics Express, vol. 26, pp. 2528-2534, 2018.; 3. Michael Gehl, Galen Hoffman, Paul Davids, Andrew Starbuck, Christina Dallo, Zeb Barber, Emil Kadlec, R. Krishna Mohan, Stephen Crouch, Christopher Long, "Phase optimization of a silicon photonic two-dimensional electro-optic phased array", Lasers and Electro-Optics (CLEO) 2019 Conference on, pp. 1-2, 2019.; 4. Jie Sun et al., "Large-scale nanophotonic phased array", Nature, vol. 493, pp. 195-199, 2013.; 5. SungWon Chung et al., "A monolithically integrated large-scale optical phased array in silicon-on-insulator CMOS", IEEE J Solid-St Circ, vol. 53, pp. 275-296, 2018. KEYWORDS: Communications, Optoelectronics, Photonics, Photonic Integrated Circuits, Optical Phased Arrays, Free Space Optics
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