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1 In optical communication systems employing direct detection at the receiver, intensity modulations such as on–off keying (OOK) or pulse-position modulation (PPM) are commonly used to convey the information. Consider the possibility of applying space-time coding in such a scenario, using, for example, an Alamouti-type coding scheme [1]. Implicit in the(More)
1 The structure of an optimal adaptive array receiver for ground-based optical communications is described and its performance investigated. Kolmogorov phase screen simulations are used to model the sample functions of the focal-plane signal distribution due to turbulence and to generate realistic spatial distributions of the received optical field. This(More)
A modification of the traditional pulse-position modulation (PPM) scheme typically employed on the optical direct-detection channel is proposed that allows for significantly improved information throughput and bandwidth advantage. The scheme sends a multitude (K) of pulses per symbol interval and as such provides a signal constellation whose size, for a(More)
It can be argued that optical communications had its origins in ancient times, where modulated sunlight was often used to convey information over large distances. For example, mirrors have been used to create bright flashes of light in certain directions, producing a form of on–off modulation. Similarly, blankets used to cover a signal fire periodically(More)
The use of radial basis function (RBF) networks and least squares algorithms for acquisition and fine tracking of NASA's 70-m-deep space network antennas is described and evaluated. We demonstrate that such a network, trained using the computationally efficient orthogonal least squares algorithm and working in conjunction with an array feed compensation(More)
A new technique for evaluating the performance of quantum signals observed in the presence of noise is described and evaluated. The quantum theory for detecting coherent-state signals has been developed previously; however, the quantum signal-plus-noise problem has received little attention due to its complexity. Here we develop a discrete approximation to(More)