Guest editorial microwave photonics

W E ARE pleased to provide our readers a special issue on microwave photonics in the JOURNAL OF LIGHTWAVE TECHNOLOGY (JLT). Microwave photonics is an interdisciplinary field that studies the interaction between light wave and electrical wave for the generation, processing, control and distribution of microwave signals by means of photonics. For the last few years, extensive research activities have been carried out throughout the world and excellent research results have been achieved. This special issue is intended to provide a venue for our researchers to report their latest findings and results in microwave photonics, covering microwave photonic devices, sub-systems, systems, and networks. In particular, recent advances in integrated microwave photonics and microwave photonics techniques for 5G are highlighted. This special issue has 9 invited articles and 47 contributed articles, with 10 from Americas, 26 from Asia-Pacific and 20 from Europe. The invited articles were selected from the topscored, post-deadline or invited papers presented at the 2017 International Topical Meeting on Microwave Photonics (MWP 2017) held on October 23–26 in Beijing, China. All papers were reviewed with a rigorous selection process with the help and support from our dedicated reviewers. Integrated microwave photonics is the focus of this special issue. Seven out of the nine invited articles are directly related to integrated microwave photonics. Specifically, Zhang et al. reported a silicon-based photonic integrated optoelectronic oscillator, and Hao et al. reported an InP-based photonic integrated optoelectronic oscillator; both papers were post-deadline papers of MWP 2017. Lo et al. reported an InP-based monolithically integrated microwave synthesizer. Perez et al. reported a photonic integrated programmable true-time delay network for microwave photonics. A high-quality tunable microwave photonic filter based on integrated optical phase lock loop was reported by Balakier et al. A coherent LiDAR based on CMOS-compatible photonic integrated circuit was reported by Martin et al. Solutions to characterize wideband optical discrete or on-chip devices for microwave photonic system applications were reported by Zhang et al. The last two invited papers reported microwave systems using discrete components, including one by Zou et al. to demonstrate a microwave photonic system for high-speed railway applications, and the other by Onori et al. to demonstrate a broadband tunable microwave receiver based on photonic direct conversion.