The impact of the exposure of the cavity to liquid of the different next, where in this experiment exposure has been set by the length of the loop, is shown in Fig. . Experimental data and numerical analysis agree well. The RI of the liquid in the loop was 1.34025 RIU while that of the background liquid was 1.33296 RIU. Due to Taylor dispersion in the connection tube, the liquid in the sample loop is slightly diluted and the simulations show that the ultimate concentration (and thus RI) reaches only 85% of its full value for the smaller volume loop. Taylor dispersion is the process through which the difference in flow velocity along the radial direction of the tube leads to a smearing out of the concentration distribution along the direction of the flow . When the concentration/RI of the liquid coming from the loop increases, the wavelength corresponding to the transmission minimum follows and its value decreases. For shorter loop, in agreement with the simulations the shift in resonance wavelength is only about 85% of the value for the longer loop.