Wideband analog photonic links: some performance limits and considerations for multi-octave implementations

Abstract

High-performance analog photonic links are discussed and the prevalent modulation formats are highlighted. Because of its multi-octave and millimeter-wave potential, special attention is given to intensity modulation with direct detection (IMDD) employing an external Mach-Zehnder modulator (MZM). The theory for IMDD is reviewed and some experimental results are discussed. Two limiting factors in multi-octave IMDD implementations are quantified. The MZM bias requirements in order to remain third-order limited are shown to be very stringent in high-performance links. Photodiode nonlinearities, perhaps the most inhibiting factor in present-day wideband analog photonics, are cast in terms of output intercept points and tied to the IMDD link performance.