Fiber Bragg grating sensors for structural and railway applications

Abstract

Historically, due to the high cost of optical devices, fiber-optics sensor systems were only employed in niche areas where conventional electrical sensors are not suitable. This scenario changed dramatically in the last few years following the explosion of the Internet which caused the rapid expansion of the optical fiber telecommunication industry and substantially driven down the cost of optical components. In recent years, fiber-optic sensors and particularly fiber Bragg grating (FBG) sensors have attracted a lot of interests and are being used in numerous applications. We have conducted several field trials of FBG sensors for railway applications and structural monitoring. About 30 FBG sensors were installed on the rail tracks of KowloonCanton Railway Corp. for train identification and speed measurements and the results obtained show that FBG sensors exhibit very good performance and could play a major role in the realization of "Smart Railway". FBG sensors were also installed on Hong Kong's landmark TsingMa Bridge, which is the world longest suspension bridge (2.2 km) that carries both trains and regular road traffic. The trials were carried out with a high-speed (up to 20 kHz) interrogation system based on CCD and also with a interrogation unit that based on scanning optical filter (up to 70 Hz). Forty FBGs sensors were divided into 3 arrays and installed on different parts of the bridge (suspension cable, rocker bearing and truss girders). The objectives of the field trial on the TsingMa Bridge are to monitor the strain of different parts of the bridge under railway load and highway load, and to compare the FBG sensors' performance with conventional resistive strain gauges already installed on the bridge. The measured results show that excellent agreement was obtained between the 2 types of sensors.

Real Time Monitoring of Railway Traffic Using Fiber Bragg Grating Sensors

“…Additionally, the possibility of remote operation is key in the railway environment. Previous works using FBG sensors for railway applications have been reported [3][4][5]. These works showed the possibility to assess the health of the rail and wheels using FBGs.…”

State-of-the-Art Review of Railway Track Resilience Monitoring

“…When compared to electrical strain gauges, FBGs present clear advantages such as long life time (more than 30 years), electrical immunity, ease and cost of installation. One of the first applications of FBG sensors in railways was accomplished in the monitoring system of the Tsing Ma Bridge [64,65], for measuring the temperature and structural response of cables, girders and bearings during train crossings. Another pioneer railway industry project in successfully adopting this sensing technology was carried out at the KCRC railway line in Hong Kong for detecting trains and measuring their speed and weight.…”

Real-Time Train Wheel Condition Monitoring by Fiber Bragg Grating Sensors

“…Typical wavelength changes of FBG written in standard single-mode fiber at 1550 nm region due to mechanical strain and temperature variation are ∼1 pm/με and ∼11 pm/ • C, respectively. Because of its compact size, low optical loss, self-referencing, and wavelength multiplexing capability, FBG sensors have been widely applied in a wide range of condition monitoring applications [9,[15][16][17][18][19]]. …”

“…In addition, the system allows inservice and real-time monitoring of wheel condition, which is attractive to the railway industry. Moreover, the system can also be integrated with other railroad FBG sensing applications [9][10][11][12][13] that have been reported previously.…”