## 1 Introduction  
Coal mining methods include the underground mining method and open-pit mining method. More than 90% of coal resources in China are obtained from underground mining. After a long period of large-scale coal mining, shallow resources are increasingly exhausted. The coal mining depth continues to extend at the rate of 10-25 m per year. The average mining depth is about 700 m and the deepest mine exceeds 1500 m [1]. The deep roadway has the characteristics of a fast deformation rate, large deformation and serious bottom drum, which significantly increases the maintenance cost of the roadway and puts forward higher requirements for the support technology. From the perspective of engineering practice, the strata behavior characteristics of roadways in different mines and different regions of the same mine are poorly similar, which is difficult to form guiding support technology. Therefore, it is necessary to construct a surrounding rock pressure monitoring system, which can collect the pressure data in real time to define a reasonable and economic support scheme. Bolt support is a widely used active support method, which contributes to great economic benefits for Chinese coal enterprises [2]. With the wide application of bolt support, many scholars are devoted to the study of its mechanical characteristics and supporting mechanism through different detection methods. In reference to [3, 4, 5], the stress wave non-destructive detection method, electromagnetic method, and infrared radiation detection method were used to detect the quality of rock bolts. Nowadays, it is widely recognized to monitor the axial force of the anchor rod by the dynamometry bolt. According to the different measurement principles, the conventional force-measuring anchors could be divided into two types: the electric measuring type and mechanical measuring type. The force measuring bolts equipped with a resistance strain gauge were one type of the electric measuring type, which were also the most common in engineering practice. [PERSON] et al. studied the stress distribution law and supporting mechanism of the force measuring bolts in the process of rock mass deformation. The force measuring bolts were installed manually and instrumented five pairs of symmetrical strain gauges [6]. The above detection methods had the following drawbacks: they were susceptible to external interference, complicated signal processing, unable to achieve real-time monitoring, unable to achieve distributed measurements, and unfavorable to long-distance information transmission. Hence, this paper aims to study a new type of force-measuring bolt, and construct a surrounding rock pressure monitoring system. Coal mine technicians only need to check the axial force of the bolt in the ground command center, and there is no need to arrange special personnel to collect the data on site. In the early 1970s, the optical fiber sensing (OFS) technology that used light waves as carriers for sensing and measurements came into being. The OFS technology was suitable for real-time online detection and has been applied to the underground engineering of coal mines, which initially realized the measurement of rock settlement and underground excavations, support loads, surrounding rock mass stress, and disaster prediction [7; 8; 9; 10]. Some scholars carried out research on the detection of the bolt body. [PERSON] et al. [11] studied the performance of the bolt under pull-out loading using the pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA) and fiber Bragg grating (FBG) sensing technologies. [PERSON] et al. [12] designed a full rod FBG force-measuring bolt and system based on the principle of fiber grating sensing to continuously monitor the axial force of the bolt over a long period of time. However, [PERSON] and [PERSON] neglected the influence of binders on the sensing characteristics of the FBG force-measuring bolt. [PERSON] et al.