Research on miniature
photonics sensors, known as fibre Bragg grating sensors, is being put
to test on Hong Kongs landmark Tsing Ma Bridge.
grating (FBG) sensors are created inside fibres that are commonly used
in optical communication systems and can be used to measure temperature
and strain on structures. A feature of the tiny sensors is that many can
be created at points along a single length of optical fibre up to 50km
long and measurements can be taken from either end of the fibre link.
FBG interrogation system using sensors to measure strain at five positions
along a railway track.
number of sensors required for Tsing Ma Bridge is about 100. Researchers
at The Hong Kong Polytechnic University under Principal Investigator Prof
Hwayaw Tam, have designed and built two innovative systems; one can interrogate
12 sensors located more than 25 km away and has a sensitivity to stress
of 0.3 microstrains.
systems have a broadband light source that illuminates the FBG sensors,
detects the reflected light and measures its wavelength to determine the
induced strain. The sensors behave like mirrors, reflecting narrow bands
strain cause the sensors to reflect different wavelengths. Another significant
result of the research was the development of FBG sensors that can withstand
temperatures up to about 600OC, an important advance for systems measuring
this type of sensor could only be used to measure temperatures to about
300OC before itself being destroyed.
Prof Hwayaw Tam: email@example.com