Ultrasonic waves can penetrate into opaque media, such as metals and ceramic, which has become an important testing tool for ultrasonic safety monitoring. Compared with traditional piezoelectric-based ultrasonic sensors, optical fiber ultrasonic sensors exhibit strong anti-interference, strong multiplexing, high sensitivity, and broadband frequency response, which has applications in structural nondestructive detection and electric power system. Aiming at the characteristics and detection methods of acoustic emission signals in safety monitoring, we mainly review optical fiber ultrasonic sensing technologies and applications in ultrasonic safety monitoring. Furthermore, the sensing mechanisms, detection methods, and existing issues are analyzed. The next step will focus on the discussion of the future research direction and potential applications.