Etched-Core Fiber Bragg Grating Sensors Integrated With Microfluidic Channels

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^-4, 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.