Folded optical design for high fidelity atmospheric emulation with a spatial light modulator

Abstract

Atmospheric emulators based on spatial light modulators offer the ability to test atmospheric propagation effects on a laser communication component's performance in the laboratory setting. To create a high-fidelity atmospheric emulator, details of the optical design are key. This paper discusses the optical design choices and refinements that enabled the creation of a system that was verified to recreate multi-layer turbulence with high fidelity up to D/r0 =50. Optical design choices that affect the fidelity discussed in this paper include the characteristics of the input laser, the spatial light modulator, the holograms, the image relay optical components, and the spatial filter. Also included in this paper is a comparison of the chosen folded optical layout to an alternative angled layout.

Fiber-detector subsystem loss comparison for a ground-based photon-counting optical receiver

“…We quantify the additional loss in both systems by using the NASA Glenn Research Center's Arbitrary Light Field Generator (ALF-G), depicted in Figure 3. This system has been described in detail elsewhere, 17,18 but we will summarize the salient features here. As shown in Figure 3, a linearly polarized fiber-coupled 1550 nm laser is collimated with an 80 mm focal length collimator to form a 14.5 mm diameter beam.…”

A real-time optical ground receiver for photon starved environments

“…After the VOA, the light is delivered via a fiber to the Arbitrary Light Field Generator (ALF-G) 15,16 , which is used to generate a flat-top beam profile. At the output of the ALF-G, the flat-top beam is focused into the receiver fiber interconnect.…”