Improving SOA direct modulation capability with optical filtering

Abstract

Semiconductor optical amplifiers (SOAs) have been receiving intense interest for use as external modulators in a variety of fundamental and advanced applications. However the employment of these modules for the target purpose is hindered by their limited modulation bandwidth. Motivated by this fact, in this invited paper we review the main outcome of our recent research on enabling the direct modulation of SOAs with improved performance at enhanced data speeds. In this context we present experimental and theoretical results that we have obtained by exploiting different types and combinations of optical filters. These filters include the birefringent fiber loop (BFL), either alone, in cascade with another BFL or assisted by an optical bandpass filter (OBPF), and a passive single microring resonator (MRR). To this end we demonstrate the capability of the schemes to efficiently overcome the pattern-dependent response of the directly modulated SOA and enhance the quality characteristics of the encoded signal.