We present a novel graphical approach for evaluating the performance of analog photonic links employing an external intensity modulator biased at quadrature. A single graph is sufficient to grasp the engineering tradeoffs among noise figure, third-order spurious-free dynamic range, and RF gain for various values of half-wave voltage and dc photocurrent.
[Show abstract][Hide abstract] ABSTRACT: Radio-frequency (RF) photonics provides increased or previously unavailable capabilities for many military platforms and applications. As compared to electronic approaches, photonics offers increased transmission distances in antenna-remoting applications, unrivaled bandwidth in signal-processing and other electromagnetic-warfare applications, and decreased size and weight in numerous military platforms. In addition, fiber optics as a transmission medium offers invulnerability to electromagnetic interference and near-complete electrical isolation. We describe advances in the theoretical understanding of analog-photonic systems made at NRL in 2007, along with the accompanying record-setting performance demonstrated in our experiments. We have applied our expertise to the design and implementation of two state-of-the-art prototype systems for military antenna-remoting and electromagnetic-warfare applications. Each of these prototypes and their significance are described below.
[Show abstract][Hide abstract] ABSTRACT: Free-space optical (FSO) links typically carry digital data over short to moderate distances (100m - 50 km). From a military perspective, FSO links have the advantages of low probability of interception, inherent anti-jam capability and a reasonable degree of covertness. In certain applications it is desirable to minimize size, weight and power of the transmitter and this pushes the designer to eliminate power-hungry digitizers and to transmit raw analog, instead of digital, information. However, the transmission of analog signals presents significant technical challenges due to strong fluctuations in received optical power resulting from atmospheric turbulence. In this case the standard RF link properties of gain, noise factor, and linearity must be described entirely in statistical terms. In this paper we present preliminary experimental results from a short (500m), single-tone, 5 MHz analog FSO link and compare the data to theoretical predictions. Theory suggests, and our preliminary experimental results confirm, that the statistical properties of all the RF performance metrics of a FSO analog link are determined entirely by the statistical properties of the received optical power. We show that the distribution of values of RF link parameters can be obtained directly from the distribution of received optical power, without the need for modeling the received power with a continuous function.
Proceedings of SPIE - The International Society for Optical Engineering 05/2009; DOI:10.1117/12.818153 · 0.20 Impact Factor
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