This paper presents an optical double-ring resonator system of which the design and analytical model are demonstrated to be useful as a novel force in micro-Newton measurement-sensing devices based on optical sensors. The sensing application can be accomplished by changing the optical filtering characteristic of an optical resonance structure such as the ring resonator system. Together with the concept of stress/strain and the elastic modulus of the waveguide material, the relationship between a slightly different value in the exerted force acting on the sensing unit and a difference in the waveguide length can be evaluated. Indeed, changing the optical path length (the waveguide length) causes the difference in peak spectrum of the filtering signals obtained from a ring resonator system. Hence, by measuring the spacing shift between the sensing and setting peak signal in the considered channel, the measurement of a slightly different value in the exerted forces on the sensing unit can be achieved. From the simulation results, an exerted force in small-scale ranges from 10 µN to 50 µN have been evaluated by measuring a spacing shift between the peak signals ranging from 35 pm to 225 pm. In this study, the potential of using such a double-ring resonator device for a force in micro-Newton sensing application is studied and discussed.