Adaptive detector arrays for optical communications receivers

Abstract

The structure of an optimal adaptive array receiver for ground-based optical communications is described and its performance investigated. Kolmogorov

Coherent optical array receiver for PPM signals under atmospheric turbulence

“…High performance quantum-limited operation of optical detector arrays can be achieved with current technology in the two different ways previously mentioned, namely by the use of photon-counting detector arrays (Vilnrotter et al, 2002) and by the use of optical mixing prior to detection. It has been determined that focal plane arrays that sample the spatially degraded signal fields, together with high-speed signal processing to implement the real-time combining algorithms, provide the necessary capability for optimizing receiver performance when direct detection is employed.…”

“…It has been determined that focal plane arrays that sample the spatially degraded signal fields, together with high-speed signal processing to implement the real-time combining algorithms, provide the necessary capability for optimizing receiver performance when direct detection is employed. This technique has been evaluated through analysis and laboratory simulation with high-gain photoncounting PMT arrays and shown to provide approximately 3-5 dB gain over a large area single-detector PMT receiver covering the same FOV when operating in turbulent and high-background environments (Vilnrotter et al, 2002). However, currently available PMT arrays have low quantum efficiency (less than 10%) at the wavelengths of interest (1.064 micrometers).…”

Two-element optical array receiver concept demonstration

“…2. Electrical pulses from each N × N focal-plane detector array are processed in the FPA electronics card of each telescope to determine the total number of detected photons per sample time, and to extract local information such as telescope pointing updates and instantaneous estimates of the focal-plane intensity distribution to further reject background photons via adaptive focal-plane processing, as described in [6]. Digital samples then are constructed at each telescope to facilitate transfer to a central array combiner assembly, which compensates the sample streams to remove possible delay variations before combining, thus maximizing the signal energy in each signal slot and simultaneously minimizing the pulse widths.…”

Free-Space Optical Communication Impaired by Angular Fluctuations

“…A number of techniques have been proposed to mitigate turbulence-induced intensity fluctuations [3]- [9]. Spatial diversity is an attractive approach and substantial performance gain can be achieved by using direct detection with spatial diversity at both transmitter and receiver sides [3].…”

“…The effect of link geometry on the diversity and multiplexing gain of a multi-beam FSO system is investigated in [8]. Moreover, in [9], an adaptive array receiver is employed to enlarge the receiver field-of-view (FOV) as well as to reduce the amount of background noise collected by the receiver.…”