Signal Acquisition with Photon-Counting Detector Arrays in Free-Space Optical Communications

TL;DR

This paper analyzes the pointing and acquisition process in free-space optical communications using photon-counting detector arrays, deriving bounds and optimizing parameters to improve acquisition time performance.

Contribution

It introduces a maximum likelihood detection approach and derives bounds on detection and acquisition times, highlighting the advantages of detector arrays over single large detectors.

Findings

Array of smaller detectors outperforms single large detector in acquisition time

Derived bounds on missed detection and false alarm probabilities

Optimized beam radius minimizes mean acquisition time

Abstract

Pointing and acquisition are an important aspect of free-space optical communications because of the narrow beamwidth associated with the optical signal. In this paper, we have analyzed the pointing and acquisition problem in free-space optical communications for photon-counting detector arrays and Gaussian beams. In this regard, we have considered the maximum likelihood detection for detecting the location of the array, and analyzed the one-shot probabilities of missed detection and false alarm using the scaled Poisson approximation. Moreover, the upper/lower bounds on the probabilities of missed detection and false alarm for one complete scan are also derived, and these probabilities are compared with Monte Carlo approximations for a few cases. Additionally, the upper bounds on the acquisition time and the mean acquisition time are also derived. The upper bound on mean acquisition time is minimized numerically with respect to the beam radius for a constant signal-to-noise ratio scenario. Finally, the complementary distribution function of an upper bound on acquisition time is also calculated in a closed form. Our study concludes that an array of smaller detectors gives a better acquisition performance (in terms of acquisition time) as compared to one large detector of similar dimensions as the array.