Fiber Bragg Grating Sensors-Based In Situ Monitoring and Safety Assessment of Loess Tunnel

Table 1

Specifications for the SM125-500 [33].

Specifications	SM125-500
Number of optical channels	4 (8 & 16 available)
Wavelength characters
Range	1510–1590 nm
Accuracy	1 pm
Stability	1 pm
Repeatability	0.5 pm at full speed and 0.2 pm with 10 averages
Dynamic range	50 dB
Scan frequency	1 Hz (2 and 5 Hz available)
Typical sensor spacing	>2x sensor bandwidth
Optical connectors	FC/APC (E2000 available)
Operating temperature	0° to 50°C