It is shown that the dispersion in transmission characteristics of a ring resonator designed with silicon-on-insulator waveguides in all-pass configuration can be enhanced significantly by increasing interaction length of the directional coupler. This in turn helps to single-out highly extinct resonance(s) at and around the critically coupled wavelength. Such a device is found to be useful for a wide range of refractive index sensing for the cladding materials/analytes (1.0 < nc ≤ 2.0). As a proof of concept, the sensor devices were fabricated and characterization results are shown to be consistent with theoretical prediction. The fabricated devices have been also used successfully to determine unknown refractive index of a given analyte (Newport F-IMF-150) with an error limit of δn ∼ 1.67 × 10-2 RIU. Analyzing experimental results, it is shown that the limit of detection can be further reduced (≤ 10-3 RIU), if the perimeter of the ring is increased without compromising the round-trip waveguide loss. The superiority of such a sensor device lies in its simpler design rule, easier operation, wider range, and nearly accurate detection mechanism. © 2016 IEEE.