A Fiber Bragg Grating-Based Condition Monitoring and Early Damage Detection System for the Structural Safety of Underground Coal Mines Using the Internet of Things

Table 1

Specifications of SM125-500 interrogator [30].

Specifications	SM125-500
Number of optical channels	4
Scan frequency	2 Hz
Wavelength range	1510–1590 nm
Wavelength scalability; accuracy	1; 1 pm
Dynamic range	50 dB
FBG sensor capacity	60–120
Full spectrum measurements	Yes
Repeatability	0.5 pm at full speed and 0.2 pm with 10 averages
Optical connector type	FC/APC
Operating temperature range	0 to 50°C
Operating humidity	95%
Power consumption at 112 VDC	20