## 7 Conclusions  
This work gives an investigation of a biomedical sensor for human well-being. In order for proper functioning of the sensor, the semiconductor arrangement should be examined for all the parts. Hereby, the FBGs have been examined in detail regarding their portrayal, adjustment and specialized investigation. Utilizing the algorithmic scheme for the specific device variables, the framework has been successfully analyzed in detail. The FBGs have been controlled via Petri network modelling scheme, and the measurement of wavelength difference between the set and Bragg wavelengths reveals negligibly small values.  
Afterwards, the tunable coupler has been examined that controls the operation of the FBGs by a piezoelectric actuator and micrometer screw. The coupler has been thoroughly characterized by the schematic arrangement in Figure 7. This system is controlled by LabView, and the measurement scheme is implemented according to the pseudocode developed in Algorithm 1. This helps to analyze the maximum value of the output power of the coupler in relation to the position of the micrometer screw and the applied voltage. Since the sensor is destined for the wavelength regime in NIR, the coupling ratio is measured at three different wavelengths, namely 1542 nm, 1538 nm and 1546 nm, respectively. These results of the coupling ratio reveal that the wavelength-selective coupling is negligible, and can be used with complete accuracy for the biomedical sensor setup. A scenario with a wavelength difference of 1.57 nm has been investigated in detail, with a consistent output power, and the effect of various values of intensity ratio on RIN, thereby justifying the sensitivity of the sensor's operation, and providing highly reliable piece of information, likewise mentioned in [31].  
A comparison of RIN results with earlier outcomes provides a close contrast between the values which is quite encouraging [17; 72]. We now attempt to check the values of RIN at different values of SOA injection current and temperature. This would certainly help in maintaining the sanctity of the results, thereby providing the biomedical sensor with optimal accuracy during its operation. As remarked earlier, since the modes are highly sensitive, we plan to use metamaterials in the future to confine them in our nanocavity. In this perspective, the setup would be amended with the aid of Metal Insulator Metal Insulator (MIMI) structures that could supposedly assist in the coupling and confining gap surface plasmons trough the evanescent wave which produced by surface plasmon polaritons, using the techniques that have been nicely developed in [26; 27].  
**Author Contributions:** Conceptualization, U.M.; methodology, U.M. and S.N.; software, F.A. and A.Z.; validation, U.M.; formal analysis, U.M. and F.A.; investigation, U.M. and U.G.; resources, U.M., F.A. and U.G.; data curation, U.M. and F.A., writing--original draft, U.M. and F.A.; writing--review and editing; U.M., F.A., M.R.A., H.E., Y.K., M.K.E., M.A.Q., A.A., S.N. and U.G.; visualization, U.M.; supervision, U.M. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The authors are greatly indebted to the vendors of the equipment involved, as well as the technical team in our clean room, for providing worthwhile suggestions and moral support during the entire work.  
**Conflicts of Interest:** The authors declare no conflict of interest.