Optical communication refers to the communication mode with optical signal as a carrier. With the development of laser and optical fiber, optical communication has also made great progress and has penetrated into every aspect of our daily life. However, the continuous growth of bandwidth and high-quality service demand has brought unprecedented challenges to optical communication network; thus, it is imperative to find new solutions to meet the new challenges. Due to its powerful computing power, artificial intelligence (AI) is applied in optical communication to improve its performance [1, 2]. The combination of artificial intelligence technology and optical communication technology may promise great potential and start a new stage of optical communication and optical network. This Special Issue aims to discuss advanced analytical tools and new technologies for next-generation fiber optical communication systems and networks. It focuses on the latest advances and future prospects from basic theory to applications, as well as devices, subsystems, and networks. Topics covered include nonlinear fiber optics, advanced devices, AI and deep learning applications in optical fiber communication, and optical network control and management, etc. Seven research articles and one communication paper are included in this Special Issue.

More specifically, passive optical networks are discussed. Zehri, M. et al. proposed a dynamic bandwidth allocation (DBA) algorithm [3]. In time-and wavelength-division multiplexing (TWDM) technology, the laser tuning time (LTT) delay is often ignored when evaluating the performance of dynamic bandwidth allocation (DBA) mechanisms. The DBA algorithm takes LTT into account and is capable of dynamically processing bandwidth and converting the laser wavelength of an optical network unit. By introducing the longest processing time, the first scheduling discipline (LPT) algorithm can reduce the queue delay by 73% compared to interleaved polling with an adaptive cycle time (IPACT) and 33% compared to the WFQ algorithm, which has high practical significance. Free-space optical communication (FSOC) has the advantages of fast communication speed, strong anti-interference ability, and high security. The use of a FSOC system on unmanned aerial vehicle (UAVs) will help improve communication capabilities and eliminate its strict requirements for electromagnetic environment. Zhang, Y. et al. established an electromagnetic immune FSOC system for UAV control link [4]. The system has great antiturbulence, anti-vibration, and anti-flight interference performance. Moreover, it achieves the goal of miniaturization without using a gimbal mirror system, a beacon camera system, and a four-quadrant photodetector (QPD), allowing the system to be used in situations where small FSOC devices are required, such as satellite–submarine communication. In the field of improving optical communication performance, Yin, H. et al. proposed a method to realize frame synchronization based on Hough transform (HT) methods [5].