**4. Discussion**

Figure 8 presents the comparison of the different sensitivities obtained in each case. As can be seen, the displacement sensitivity of the two interferometers with the Vernier effect (60 ± 1 nm/μm) is two-fold the one obtained with the single interferometer (29.2 ± 0.3 nm/ μm), with the same FSR. In addition, when the two interferometers are optimized, the maximum sensitivity obtained is 254 ± 6 nm/μm corresponding to an *M*factor of 1071 and a *MVernier* of 1.9. Therefore, the sensor using the enhanced Vernier effect was more efficient than the traditional Vernier effect besides the fact that the maximum sensitivity obtained was 24 times higher than the SPR-based sensor for a micrometric range [13]. Furthermore, the Vernier effect allows a sensor whose implementation is easier to be obtained because the performance depends on the relation between the interferometers and not on the specific length of each FPI. Thus, it is possible to develop giant sensitivities in ranges where the sensitivity of a single interferometer is low.
