Link analysis for a liquid lens beam steering system, the miniature optical steered antenna for intersatellite communication: MOSAIC

Abstract

Laser communications can enable more efficient and higher bandwidth communications across longer distances than conventional radio frequency (RF) systems. However, beam divergence angles for laser systems are narrower than typical RF systems, and require precise pointing, acquisition, and tracking systems to establish and maintain the link. In addition, typical lasercom links are point-to-point, and not capable of multicast or broadcast. Conventional pointing and tracking (PAT) systems use mechanical gimbals or fast-steering mirrors. Mechanical gimbals may not meet the size, weight, and power (SWaP) constraints for small spacecraft, particularly for multiple concurrent spatially diverse beams. Fast-steering mirrors while compact and efficient have limited aperture size, and many would be needed to provide multiple links over a hemisphere.The Miniature Optical Steered Antenna for Intersatellite Communications (MOSAIC) aims to provide nonmechanical pointing and tracking using liquid lenses, allowing a wide field-of-view and support for multiple concurrent links. Initial work with commercially available liquid lenses showed that liquid lenses can be used in a space environment and assessed spatial coverage. In this work, we model a transmitter using three liquid lenses. One on-axis lens provides focusing capability. Two off-axis and perpendicular lenses provide beam steering, with a fisheye lens amplifying the effect. This provides near-hemispherical pointing up to 170 degrees. We investigate beam quality and divergence using a Zemax model and conduct a link analysis dependent on the beam steering angle and rotation angle. A 25 Mbps link with 200 mW transmit power at 1550 nm (optical C band) and 16-ary pulse position modulation (16-PPM) can be maintained up to 28 km separation with 3 dB margin for an Optotune EL-16-40-TC liquid lens. Losses are primarily due to the liquid lenses limiting aperture size to 16 mm. We also consider the impact of diffusers for increasing numerical aperture through a simple ray transfer analysis and experimental results.

MOEMS-based Lens-Assisted Beam Steering for Free-Space Optical Communications

“…Various methods are used to perform these functions, including gimbals [12], fast steering mirrors (FSMs) [13], adaptive optics [14], RF-FSOC hybrids [15], and others. Many technologies for steering the optical beam have been developed, including small micro-electromechanical system (MEMS) mirrors or mirror arrays [16] - [18], liquid lenses or variable focal length lenses [19] - [21], optical phased arrays [22] [23], liquid crystal electro-optic scanners [24], and image-based beam steering [25] - [27].…”

Optical performance of commercial liquid lens assemblies in microgravity

“…The MOSAIC project seeks to construct a compact, nonmechanical lasercom transceiver with integrated beam steering for small satellites using liquid lenses. 2,3,5,6 The transceiver design is based on a previous design by Zohrabi 7 that utilizes a single on-axis liquid lens for divergence control and two additional liquid lenses offset in x and y for 2D steering; it was initially proposed for light detection and ranging (LIDAR).…”

“…This work is part of the development for the miniature optical steered antenna for intersatellite communication (MOSAIC) project, which aims to utilize liquid lenses for a hemispherically steering lasercom terminal for small satellites, for which reliable operation in the space environment is required. The MOSAIC project seeks to construct a compact, nonmechanical lasercom transceiver with integrated beam steering for small satellites using liquid lenses 2 , 3 , 5 , 6 . The transceiver design is based on a previous design by Zohrabi 7 that utilizes a single on-axis liquid lens for divergence control and two additional liquid lenses offset in x and y for 2D steering; it was initially proposed for light detection and ranging (LIDAR).…”

Optical Performance of Commercial Liquid Lens Assemblies in Microgravity

“…3 This work is part of development for the Miniature Optical Steered Antenna for Intersatellite Communication (MOSAIC) project which aims to utilize liquid lenses for a hemispherically steering lasercom terminal for small satellites, for which reliable operation in the space environment required. 1,2,4,5 The MOSAIC project aims to utilize liquid lens arrays for beam steering and laser communication on small satellites. The project seeks to construct a compact, nonmechanical lasercom transceiver with integrated beam steering for small satellites using liquid lenses.…”

“…The transceiver design is based on a previous design by Zohrabi 6 utilizing a single on-axis lens for divergence control and an additional two lenses offset in x and y for 2D steering, initially proposed for LIDAR. Additionally, this work is part of a broader space environment evaluation effort including ionizing radiation testing and vacuum power handling performance, for which more details can be found in the full study by Kacker 5 -in summary, commercial liquid lenses from Corning Varioptic and Optotune perform well during TVAC testing, do not show gross discoloration when exposed to ionizing radiation equivalent to 10 years of low Earth orbit, and can handle over 2 W of laser power in vacuum without damage. Liquid lenses have applications in machine vision, 3, 7 phone cameras, 8 microscopy, 9 optical communications [10][11][12][13][14] and more due to their compactness and depending on the lens technology, low power.…”