Abstract
In this paper, we demonstrate a fiber Bragg grating sensor for bio-chemical
detection. In the sensor area, the fiber has been chemically etched to the core with a
diameter of 7 μm. Due to increased index contrast, the etched-core fiber Bragg
grating supports multiple guided modes which respond differently to the refractive index
of the surrounding medium, temperature and the strain. An asymmetric adiabatic taper is
created between the etched and the unetched parts of the fiber resulting in excitation
of both the symmetrical and the asymmetrical modes which can be interrogated with an
erbium doped fiber amplifier amplified spontaneous emission source. The sensor is
integrated with a Polydimethylsiloxane (PDMS) microfluidic channel for introduction of
chemicals to be tested. A refractive index sensitivity of 92 nm/riu was achieved using
the 3rd order mode. Further the sensor can simultaneously measure the refractive index,
temperature and strain to an accuracy of 1 × 10<sup>-4</sup>, 0.32°C
and 10 με assuming a wavelength resolution of 0.01 nm. By using signal
processing, these resolutions can be improved by a factor of 10.
© 2011 IEEE
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