Silicon RF-Photonic Filter and Down-Converter

Abstract

An RF-photonic filter and down-converter system based on a compact and fully tunable silicon optical filter has been demonstrated and analyzed. Its frequency down-conversion was implemented using optical heterodyne detection with an injection locked laser. This system filters a 1.25 GHz-wide signal with > 20 dB filter rejection and a very broad 20 GHz center tuning range. The frequency down-conversion process is operated in a low-IF mode to avoid laser low frequency noises. Measured system Spurious-Free Dynamic Range (SFDR) of 94.3 dB*Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sup> has been limited by the optical losses from I/O coupling and measurement setup. We examined experimentally that 105.3 dB*Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sup> SFDR is achievable if the encountered optical loss were reduced to the filter's intrinsic loss. Based on the excellent agreements between measured and simulated results, we explore the critical improvements of the silicon photonic devices needed for the system to achieve 118 dB*Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sup> SFDR and briefly review the status of the component technologies.