Recent developments in fiber optic sensors for monitoring civil structures have been of great help for engineers dealing
with these structures. After literature survey it is observed that while using fiber optic sensor system for health
monitoring of civil structures not much attention is given to the core quality of the fiber, types of coating on fiber,
implementing methodologies, handling of fiber optic sensors and their long term effect on reliability of the performance
of the monitoring system. These issues are important because the structural conditions, stress level and environment in
which fiber optic sensors are placed are different from telecommunication industry. In this paper issues related to long
term structural health monitoring of civil structures are investigated. The issue of the fatigue property of optic fiber is
discussed since reversal bending of the fiber may cause adverse effect on the light carrying capacity of the fiber. Other
long term structural health monitoring (SHM) issues such as life of fiber, strain transfer process from fiber core to
coating, calibration of fiber and selection of fiber are also discussed based on the experiments carried out for successful
implementation of long term health monitoring of civil structures. The main objective of these experiments is to come up
with comprehensive long term structural health monitoring system for strain measurement.
In recent years, it is becoming more common to use fiber optic sensors (FOS) in the structural health monitoring (SHM)
sector, especially in the civil engineering field. A number of surface-mountable sensor system for FOS have been
developed in the past years, the recent development of Brillouin Optical Time Domain Reflectometry (BOTDR) was a
great evolution towards the SHM system development, it inspired the new edge of FOS SHM system. Different from the
traditional monitoring instruments, it provides distributed, long distance, real-time, interference free and high
accuracy/precision measurement data. It is now possible to achieve "continuous" measurement data and this SHM
technique is applicable in area that is inaccessible. The research aims to solve the problems which exist in the
convergence measurement using the conventional measuring methods, however, there is still a gap between the lab
experiments and field applications. Limited research has been conducted on how to maximize its possible applications
due to its brittle and fragile material nature. A number of additional considerations for a successful pairing of these two
must be taken into account for successful field applications. This article provides a short review on underground
monitoring techniques and FOS SHM systems. The focuses is on examine (i) the feasibility and effectiveness of different
BOTDR sensors installation methods (ii) the suitable commercially-available o sensing cable for underground
application (iii) the sensing performance of customized sensor protection package BOTDR sensor that manufactured
involving layers of fiber reinforced composites. This research serves a bridge in between the technology advancement to
the creation of a structure health monitoring system with practical application, numerical simulation and theoretical
analysis aspects, and also to provide the insights into the mechanisms of BOTDR.
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