Abstract
The transmission spectrum of a ring resonator enclosing a -phase shifted fiber Bragg grating (-FBG) shows a spectral feature at the Bragg wavelength that is much sharper than resonance of the -FBG alone, and that can be detected with a simple integrated cavity output technique. Hence, the resolution of any sensor based on the fitting of the -FBG spectral profile can be largely improved by the proposed configuration at no additional fabrication costs and without altering the sensor robustness. A theoretical model shows that the resolution enhancement attainable in the proposed closed-loop geometry depends on the quality factor of the ring resonator. With a commercial grating in a medium-finesse ring, a spectral feature 12 times sharper than the -FBG resonance is experimentally demonstrated. A larger enhancement is expected in a low-loss, polarization maintaining setup.
© 2015 Optical Society of America
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