While attempting to clearly resolve the difficulty of long cable, recent works have developed wireless sensor networks (WSN) to monitor debris flows [21] and landslides [22].Fiber-optic sensors have been developed recently for detecting various physical signals, including strain, temperature, and acceleration [23]. Owing to their light weight, immunity to electromagnetic interference, high sensitivity and extremely low optical loss, fiber-optic sensors are promising for use in monitoring debris flows or similar natural disasters, which usually occur in mountainous regions far from available electricity sources. Fiber-optic Inhibitors,Modulators,Libraries sensors use fibers to transmit light signals. Light waves generated by a light source are guided by an optical fiber to the measurement area.
Differences in the physical variables, including strain, acceleration and temperature, can affect the light characteristics. Hence, changes in physical variables can be Inhibitors,Modulators,Libraries determined by demodulating the variation in light characteristics. Despite their use for monitoring in various fields, fiber-optic sensors have seldom been applied to monitor debris flows or other related natural disasters. Pei et al. [24] developed two fiber-optic sensing systems for monitoring landslides and debris flows. Their systems monitored debris flows by installing two steel pipes on the trench bank and then fixing a metal net crossing the section of the trench. FBG strainometers were glued at the bottom of the pipes to detect the pipe deformation induced by debris flows.
In this work, commercial fiber optical products, such as a FBG (Fiber Bragg Grating) accelerometer, coupler, and demodulator, are combined to set up Inhibitors,Modulators,Libraries a fiber-optic sensing system for monitoring ground vibrations generated by debris flows. Based on field tests, the performance of the proposed fiber-optic sensing system is compared with Inhibitors,Modulators,Libraries those of conventional systems using geophones or microphones. Following confirmation of the feasibility of the proposed system, fiber-optic sensing systems are deployed along Ai-Yu-Zi Creek and Chu-Shui Anacetrapib Creek in Nautou County (Central Taiwan) for monitoring debris flows.Following a brief review of the principles of the FBG accelerometer and the multiplexing method, this work presents a novel fiber-optic sensing system for monitoring debris flows. Next, based on field tests, the SNR values of the proposed system are compared with those of monitoring systems using a geophone or a microphone.
Finally, the sensitivity of the proposed fiber-optic sensing system along creek banks is examined via further field tests.2.?Fiber-Optic Sensing Techniques and Multiplexing MethodAn FBG sensor utilizes the variation of the periodic refraction selleckbio index in a fiber section to reflect the light of a unique wavelength from a broadband light source [25]. The period of the grating structure is called the grating pitch, �� (Figure 1).