Free-space optical communications research and demonstrations at the US Naval Research Laboratory

Abstract

Free-space optical communication can allow high-bandwidth data links that are hard to detect, intercept, or jam. This makes them attractive for many applications. However, these links also require very accurate pointing, and their availability is affected by weather. These challenges have limited the deployment of free-space optical systems. The U.S. Naval Research Laboratory has, for the last 15 years, engaged in research into atmospheric propagation and photonic components with a goal of characterizing and overcoming these limitations. In addition several demonstrations of free-space optical links in real-world Navy applications have been conducted. This paper reviews this work and the principles guiding it.

Optomechanical antennas for on-chip beam-steering

“…As a special case, this enables multiple optical wavelengths to be sent to and received from a single angular spot. Such functionality may prove useful in the realization of free-space communication links [11,38], (holographic) video displays [14,39], remote sensing [40][41][42], and coherent imaging [43,44].…”

“…When incorporated with phase-shifters into an array, they can steer in two dimensions [3][4][5][6][7][8]. These integrated beamsteering systems are of a size, weight, and cost surpassing the motorized optical gimbals currently used with free-space optical systems for lidar, optical wireless communication [9,10], and free-space optical interconnects [11]. The growing presence of autonomous systems, such as self-driving cars, motivates the development of massmanufacturable photonic systems.…”

Shipborne Acquisition, Tracking, and Pointing Experimental Verifications towards Satellite-to-Sea Laser Communication

“…The divergence angle of very narrow communication beams requires both communicating sides to maintain extremely high dynamic alignment accuracy. With the ultimate aim of realizing a global-scale laser communication for practical use, many significant achievements have been made in the past decades, such as the demonstration of links for building-to-building communication [3,4], airborne applications [5][6][7], inter-satellite applications [8,9], satellite-to-ground [10][11][12][13][14][15][16], and ship-to-ship communication [17][18][19]. However, currently, most of the experiments only involve space and ground communication links or short-distance communication between ships.…”

Surface-normal electro-optic-polymer modulator with silicon subwavelength grating

“…Having inherent compatibility with dense 2-D array integration, they have found wide range of potential applications, including high-capacity optical interconnects [1,2], freespace optical communications [3], dynamic beam forming and adaptive optics [4,5]. Surface-normal modulators based on liquid crystals and micro-electromechanical systems (MEMS) are relatively mature; but their operating speed is typically in a range from kHz up to MHz [4,5,6].…”

“…Surface-normal modulators based on liquid crystals and micro-electromechanical systems (MEMS) are relatively mature; but their operating speed is typically in a range from kHz up to MHz [4,5,6]. On the other hand, high-speed surface-normal intensity modulators with bandwidth beyond GHz range have been demonstrated by using multiple-quantum-well (MQW) semiconductor materials [1,2,3]. These devices, however, require complicated epitaxial structures and are inherently absorptive, which makes them unsuitable for some applications.…”