Optoelectronic oscillator with delay elements in optical and RF domain

This study describes the generation of microwave signals by an optoelectronic oscillator, OEO. The delay of the OEO was made in the optical domain as well in the radio frequency (RF) domain. The constructed OEO was proposed for embedded applications, which requires low components volume, e.g., small size. Aimed at greater thermal stability and the application in embedded systems, a shorter acceptable optical fiber length was used as delay element. This enables to obtain an RF signal with the phase noise values according with the technical specifications. The total value of the OEO delay is completed with a delay in the RF domain. The benefits of this setup include the possibility of using inexpensive components and commercially available bandpass filter. Fiber optic section with length of 200 meters, coaxial cable and a filter with 15 MHz of bandwidth were used. The output characteristics of the OEO were a microwave signal at 2.022GHz, an intensity of 10.5dBm and a phase noise equal to −118.7dBc/Hz for an offset of 100 KHz and −102.2 dBc/Hz for an offset of 10 KHz.