Phase noise performance of optoelectronic oscillator using optical transversal filters

Narrowband RF filtering is required for stabilization of optoelectronic oscillators and forced oscillators. An optical transversal filter is proposed to perform narrowband RF filtering in opto-electronic (OEO) oscillators by realizing a Mach-Zehnder interferometer (MZI) at RF frequency of 8.8GHz. This 1
^st
order optical filter is realized utilizing various lengths of SMF-28 fiber and 3dB couplers to perform RF filtering in the optical domain. With proper delay length, arm amplitude balance, and filter implementation, a stable filter with large null depth can be achieved. A tuning of 33kHz/nm is also achieved using standard fiber dispersion at 1550nm. The phase noise measurements of standard OEO are performed using this transversal filter with excellent results.