title: Broadband and wide-range feedback tuning scheme for phase-locked loop stabilization of tunable optoelectronic oscillators.
abstract: In this Letter, we propose and experimentally demonstrate a novel broadband and wide-range feedback tuning scheme for phase-locked loop (PLL) stabilization of tunable optoelectronic oscillators (OEO). The proposed scheme was realized in a simple and feasible way based on a dual-parallel Mach-Zehnder modulator (DPMZM) and optical bandpass filter (OBPF). The wide RF phase-shift range and broadband performance of the proposed scheme were demonstrated theoretically and experimentally, which ensured OEO's wide operating temperature range and tunability in PLL stabilization. As a result, PLL stabilization for OEO was achieved at different oscillating frequencies and the long-term stability was greatly improved without any thermal control. The measured overlapping Allan deviation of PLL-locked OEO reached lower than 10⁻¹⁰ after 1000-s averaging time, which was four orders of magnitude better than the free-running OEO. The phase noise performance was also improved at low-offset frequencies and remained the same at high-offset frequencies.
authors.forename: Xingyuan
authors.initials: X
authors.lastname: Xu
authors.forename: Jian
authors.initials: J
authors.lastname: Dai
authors.forename: Yitang
authors.initials: Y
authors.lastname: Dai
authors.forename: Feifei
authors.initials: F
authors.lastname: Yin
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhou
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Li
authors.forename: Jie
authors.initials: J
authors.lastname: Yin
authors.forename: Qunyang
authors.initials: Q
authors.lastname: Wang
authors.forename: Kun
authors.initials: K
authors.lastname: Xu