Contents I. Introduction
The Internet of Things (IoT) is an expanded network based on the Internet, which aims at realizing the interconnection between objects and humans via combining various information sensor devices with the Internet [1]. Everything could be intelligently sensed, recognized, and managed by a sensing device that connects through the IoT to form a huge network. That is to say, electronic sensors are now playing a primary role in connecting the objects and humans. WiFi, mobile cellular networks, and Bluetooth have been applied as a tool to transmit large amounts of data for human’s intelligent identification. However, limited by the capabilities of wireless channels, the data transmission of the IoT is still a huge challenge for smarter world [2]. In addition, numerous electronic sensors need to be deployed, which is a time-consuming and laborious task. In order to overcome those problems, the distributed optical fiber sensing technique provides a potential for information transmission and sensors deployment in IoT [3]. Optical fiber shows the most powerful information transmission capability, through which large amounts of sensing data can be easily transmitted [4]–[7]. In distributed optical fiber sensing, optical fiber itself as an effective sensing array can be viewed as a collection of a massive number of virtual sensors. Thus, a large number of information sensors are deployed once the sensing fiber is laid [3]. Temporal and spatial mapping of the environmental quantities, such as temperature, vibration, and strain can be detected by the optical fiber sensing technology [8], [9]. In addition, power supply is not required for each sensor, thus ensuring high energy efficiency in distributed optical fiber sensing. Compared with the traditional electronic counterpart, optical fiber sensors are not limited by the signal bandwidth as the information of each sensor is extracted from the backscattered lights sharing the same bandwidth. Also, the distributed optical fiber sensing technique provides a promising alternative to electronic sensors, benefitted from their distinct advantages of high detection sensitivity, fast response, resistance to electromagnetic interference, and low cost owing to the characteristics of optical fiber materials [10]. The phase-sensitive optical time-domain reflectometry (-OTDR)-based distributed optic-fiber sensing technique has been employed to help build up the smart city by measuring the acoustic wave and vibration [3]. However, this technology has limited spatial resolution on the order of meters due to the wide pulse width. In addition, most state-of-the-art -OTDR systems are developed for dynamic measurements such as vibration by extracting amplitude variation of signals within a given period of time instead of static measurements, in which signal amplitude remains almost unchanged over a given period of time, including the strain and temperature, which are key parameters in the health monitoring of object structures. Thus, developing a new distributed optical fiber sensing technology to realize multiparameter and high spatial resolution measurement is of great significance for the IoT-applications.
