Tunable Microwave Frequency Comb Generation Based on Actively Mode-Locked OEO

• Published in: IEEE photonics technology letters Vol. 35; no. 5; pp. 221 - 224
• Main Authors: Li, Yan, Wang, Muguang, Gao, Pufeng, Zhang, Jing, Yin, Bin, Wang, Chuncan, Fan, Guofang
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.03.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: active mode-locking; Bandwidth; Bragg gratings; Frequency modulation; Microwave filters; Microwave frequencies; Microwave frequency comb; Microwave photonics; Optical communication; Optical fibers; Optical modulation; Optical reflection; optoelectronic oscillator; Optoelectronics; Oscillation modes; Phase modulation
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2023.3234391

A novel photonics-assisted method for tunable microwave frequency comb (MFC) generation based on an actively mode-locked optoelectronic oscillator (AML-OEO) is proposed and experimentally demonstrated in this letter. Two key factors for the proposed system, periodic gain modulation and widely tunable center frequency, are implemented by an externally introduced intensity-modulated optical signal and a microwave photonic filter (MPF) based on the phase-shifted fiber Bragg grating (PS-FBG) respectively. Unlike a conventional OEO with only one dominant oscillation mode, an AML-OEO operates in a stable multimode oscillation state and thus can generate MFC signal. Through simply adjusting the center frequency of the PS-FBG-based MPF, the center frequency of the generated MFC changes accordingly. In the proof-of-principle experiment, two sets of MFC signals with center frequency tuning from 3.5 GHz to 6.5 GHz and frequency intervals of 1.02 MHz and 340.46 kHz are generated.