Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

Browse

Filters

2014 - 201912020 - 20211

Settings

Author: search.filters.author.Yüksel Aldoğan, KıvılcımSubject: search.filters.subject.Fiber optics

Search Results

Now showing 1 - 2 of 2
  • Master Thesis
    Development of Simulation Tool for Fbg-Based Phase-Otdr Vibration Sensors
    (Izmir Institute of Technology, 2021) Yüksel Aldoğan, Kıvılcım; Yüksel Aldoğan, Kıvılcım; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Over the last twenty years, phase-sensitive optical time-domain reflectometer based distributed vibration sensors have attracted increasing attention as a research topic and commercial product. Due to their capability to detect external perturbations along fiber in real-time, they have found applications in several sectors such as oil\&gas pipeline monitoring, border security, transportation, and so on. Recently, the implementation of fiber Bragg gratings into these systems has become popular in order to improve sensing performance and several system configurations adopting a wide range of signal processing techniques have been presented. In this thesis, a simulation tool for distributed vibration sensing systems based on FBG-based phase-sensitive optical time-domain reflectometry is developed. In this context, firstly, the operation principle of optical time-domain reflectometry and system parameters affecting the performance are investigated. Secondly, fiber Bragg grating structures and their implementation into phase-sensitive optical time-domain reflectometer based vibration sensors are studied. By utilizing the one-dimensional impulse response model, fiber Bragg grating implementation-related problems, spectral shadowing crosstalk and multiple reflection crosstalk, and different sensor configurations are analyzed. Based on this model, the numerical simulation tool is developed by constructing fiber, fiber Bragg grating, and probe pulse structures. The operation of the developed simulation tool is verified by comparing obtained results with theory. Then, the capabilities of the developed tool are demonstrated by conducting several simulations with conventional Phase-OTDR and FBG-based Phase-OTDR configurations.
  • Master Thesis
    Analysis and Modelling of a Novel Approach for the Interrogation Unit of Fiber Bragg Grating Sensors Using Optical Frequency Domain Reflectometry Techniques
    (Izmir Institute of Technology, 2014) Pala, Deniz; Yüksel Aldoğan, Kıvılcım; Yüksel Aldoğan, Kıvılcım; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The main purpose of this thesis is to demonstrate the feasibility of using polarization properties of FBGs interrogated by OFDR for quasi-distributed sensing applications. A fiber Bragg grating (FBG) is a constant and periodic refractive index value modulation within the core along an optical fiber. This modification is generally obtained by exposing the fiber core of a photosensitive optical fiber to an intense ultraviolet (UV) interference pattern. At the fabrication process of Bragg gratings, only one side of the fiber expose to UV light. As a result, refractive index change is not constant at the cross section of fiber. This non-uniformity on the refractive index gives rise to photo-induced birefringence which combines with the birefringence resulting from the slightly elliptical shape of the optical fiber and creates a global birefringence value. In the presence of the birefringence, the reflection (transmission) spectrum of Bragg grating is degenerated into two reflection (transmission) spectra corresponding to a pair of orthogonal polarization modes (x and y modes). The ratio between maximum and minimum optical transmitted power of these modes are defined as Polarization Dependent Loss (PDL). We analyzed the reflection spectrum, transmission spectrum and the PDL of the cascaded FBGs interrogated by an OFDR by the way of simulations. Based on the simulation results, we demonstrated the feasibility of a novel FBG interrogation method which can be implemented in quasi-distributed strain sensors embedded into composite materials.