From these results, it can be observed that the greatest RI sensitivity of the proposed configuration was with CLF of 50 μm diameter and 25 mm length. It represents the minimum portion of the light transmitting via the fiber that induces highest evanescent fields, causing in an improvement of optical interaction between the surrounding RI light and the fiber-guided. Corresponding to MMI principle, the length and diameter of CLF would influence the output spectra and too there is an optimum length for every diameter to preserve the self-imaging and reduction the losses. As illustrated in figure 9 the linear fitting coefficient (R2) is 0.998 for SCS fiber configuration with 50 μm diameter and 25 mm length, which exhibits an excellent RI sensing features of the SCS-based sensor.