Forced Opto-Electronic Oscillators Using Efficient PBG Based Phase Modulators

Abstract

Forced opto-electronic oscillators (OEO) using self-injection locking (SIL) and self phase locking (SPLL) have demonstrated high stability local oscillators and low jitter clock signals for a variety of RF applications. The standard OEO takes advantage of the amplitude modulation of an optical carrier using Mach-Zehnder modulators (MZM) using LiNbO 3 (LN) substrates. A Sagnac loop topology is proposed to convert phase modulation to intensity modulation (PM-IM) in the forced OEO. The phase sensitivity of the phase modulator and its losses is a critical component in overall performance of the OEO, and particularly for the forced oscillation OEOs using self-injection locking (SIL) and self-phase locking (SPLL). Integrated Si-Photonics phase modulators (PM) using electro-optic (EO) polymers and Si-Ge Bi-CMOS RF driver has added benefits of smaller size and lower cost systems. A higher modulation efficiency and bandwidth of the EO polymer based PM is demonstrated by slow wave structures of photonic bandgap (PBG) with a $\mathbf{V}_{\pi}$ of 1.38V and insertion loss (IL) of 1.6dB compared to LN based systems of 3V with IL of 4dB. The predicted phase noise performance for the PBG based PM is estimated to be −160dBc/Hz at 10kHz offset over X-band.