Optimization of analog optical link performance: First minimize the noise figure

The authors have amassed the reported measured noise figure and spurious-free dynamic range data for analog optical links operating between 1 MHz and 100 GHz. We have observed that, in most cases, efforts to increase the dynamic range have resulted in an undesired increase in the noise figure as well. This would not be unduly problematic if broadband preamplifiers with sufficiently high dynamic range were commercially available. Using the advertised performance of commercial amplifiers, however, we find that pre-amplification of analog optical links to achieve acceptable noise figure in most cases reduces the dynamic range to a level below that of links that have low noise figure without a pre-amplifier. We conclude, therefore, that minimization of noise figure without a preamplifier is of paramount importance, and efforts to “linearize” links will yield true system improvements only after significant advancements in the state of the art of amplifier and/or optical link technology are achieved.