Performance improvement of an optoelectronic oscillator by modifying the optical characteristics of a multimode laser diode

Abstract

This paper presents a substantial improvement on the electrical performance of a microwave optoelectronic oscillator (OEO) by modifying the intermodal separation of a multimode laser diode (MLD). The Free Spectral Range (FSR) of the OEO is controlled by implementing an optical filter that allows manipulating the optical spectrum of an MLD. For this goal, a section of birefringent optical fiber is placed between two crossed polarizers as an optical filter. The intermodal separation of the MLD is varied using a suitable length of birefringent optical fiber. A set of stable microwave signals in the frequency range of 0–12 GHz is obtained. The performance evaluation for the microwave signal centered at 2.93 GHz shows a phase noise as low as −118.06 dBc/Hz at 10 kHz offset frequency and a Q factor of 1.40 × 109 for an optical delay line of 13 km.