Optical Coherence Sensors in Multimode Fibers
| dc.contributor.author | Shi, Guannan | en |
| dc.contributor.committeechair | Zhu, Yizheng | en |
| dc.contributor.committeemember | Bailey, Scott M. | en |
| dc.contributor.committeemember | Wang, Anbo | en |
| dc.contributor.committeemember | Jia, Xiaoting | en |
| dc.contributor.committeemember | Pickrell, Gary R. | en |
| dc.contributor.department | Electrical Engineering | en |
| dc.date.accessioned | 2024-10-11T08:00:11Z | en |
| dc.date.available | 2024-10-11T08:00:11Z | en |
| dc.date.issued | 2024-10-09 | en |
| dc.description.abstract | Optical fiber sensors are widely applied in modern sensing systems. Taking advantage of the high sensitivity of optical interference, optical coherence fiber sensors, such as fiber Bragg gratings (FBGs) and Fabry-Perot interferometers (FPIs), have been investigated intensively and utilized broadly in optical sensing systems. Multimode fibers (MMFs) offer low coupling loss, high compatibility with various light sources, and insensitivity to ambient fluctuations, which are preferred for reliable and low-cost sensing systems. Therefore, the combination of optical coherence sensors and MMFs have facilitated and will continue to contribute to various optical sensor designs with desirable performances. This dissertation addresses the design and construction of optical coherence sensors in multimode fibers and presents several fully multimode fiber sensing systems with low coherence light source. Moreover, a theoretical analysis of fiber mode excitations, model coupling, and multimodal interference is conducted, and a numerical model is constructed to study the behaviors of optical coherence sensors in MMFs. With the femtosecond laser point-by-point inscription method, parallel fiber Bragg gratings (pFBGs), scattering array interferometers (SAIs), and densely multiplexable scattering array interferometers (DMSAIs) in sapphire fibers are proposed, fabricated and characterized, achieving excellent performance in multiplexed high temperature sensing. The study on SAI signals also revealed the unique coherence properties of MMFs. This work points out that the coherence properties in MMFs play a significant role in affecting the performances of optical coherence sensors, and such properties are closely related to both geometrical and optical properties of the fibers. This work also presents both theoretical and experimental tools to explore such properties and predict and test the performance of optical coherence sensors in MMFs, which is of great significance in the applications of such sensors in the real world. | en |
| dc.description.abstractgeneral | Optical fibers have been considered a powerful media that opened a new era in the field of telecommunication and optical sensing. Owing to their excellent resistance to chemical corrosion, immunity to electromagnetic interference, extremely low loss transmission at long distance, small size, and large aspect ratio, optical fibers are considered an ideal media to construct optical sensors. Optical coherence sensors are a very important type of optical fiber sensors that utilize the optical coherence property, such as interference, for sensing purposes. A lot of such sensors are generally constructed with single mode fibers (SMFs) owing to the high-quality coherence interaction supported by the fundamental-mode-only operation. Multimode fibers (MMFs), however, process high compatibility with various light sources owing to the high power-coupling efficiency because of large core size, which is desirable for industrial applications that requires low-cost and robust sensing systems. Meanwhile, the high modal volume of MMFs causes severe challenges on the design and fabrication of optical coherence sensors in MMFs. In this work, theoretical analysis of the mode excitation and coupling in MMFs is discussed, and a numerical model to simulate the behaviors of optical coherence sensors in MMFs is built. Then, using femtosecond laser point-by-point fabrication technique, parallel fiber Bragg gratings (pFBGs), scattering array interferometers (SAIs), and densely multiplexable scattering array interferometers (DMSAIs) are demonstrated and proven to be effective in multiplexable temperature sensing. Furthermore, using the numerical model and the SAI structures, coherence properties in MMFs are studied. This research may facilitate a deeper understanding of coherence properties in optical waveguides and support the design of novel fiber sensors that can be utilized in the real world. | en |
| dc.description.degree | Doctor of Philosophy | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:41500 | en |
| dc.identifier.uri | https://hdl.handle.net/10919/121326 | en |
| dc.language.iso | en | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | Optical fiber sensors | en |
| dc.subject | optical coherence | en |
| dc.subject | multimode fibers | en |
| dc.subject | sapphire fibers | en |
| dc.title | Optical Coherence Sensors in Multimode Fibers | en |
| dc.type | Dissertation | en |
| thesis.degree.discipline | Electrical Engineering | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |