| dc.description.abstract | Optical sensing methods have the capability of offering fast and precise measurements. However, they are not deployed to their full potential because they involve the use of complex equipment, frequent supervision and are complicated to use. For these reasons, industries often choose electronic solutions.
This project aims at demonstrating a new approach to optical sensing. It is based on square wave modulation of a laser that does not require costly equipment and is simple to use. The project was divided in three stages: theoretical demonstration, experimental validation and evaluation.
The theoretical approach introduces the retrieval of the transmission function spectra of a Fabry-Perot interferometer from the injected and transmitted photocurrent and the laser's average wavelength. Secondly, the experimental setup was deployed using a current-modulated laser diode and two photodiodes. An optical spectrum analyzer was used to retrieve the laser's average wavelength. The experiments validated square wave modulation since it was possible to retrieve a satisfactory shape and order of magnitude for the transmission function and a satisfactory shape for the derivative. The method's resolution was also successful and better than current available equivalent optical instruments. Finally, some improvements like raw data fitting and amplitude variations were tested.
In conclusion, this thesis is a contribution to proving square wave modulation as a valid optical interrogation method and gives an insight into future improvements. | |
