如今，工業和技術中常用的傳感器之一包括基於光學的傳感器。在光學傳感器中，光纖由於其特性具有有趣的作用和廣泛的應用原因。除了抗電磁干擾的安全性和良好的信噪比外，易於製造的小尺寸和低重量傳輸使光纖成為瞄準光學傳感器的良好選擇。為此目的，與早期技術相比，發現成本效益和簡單具有更大的吸引力。這項工作提出了控制纖芯對光纖中包層的作用。
LLPFG 在應變下的行為以及確定該行為的決定性因素，通過利用 KrF 準分子激光輔助的能量和化學蝕刻的持續時間來控制燒蝕區的周期和深度，通過實驗優化。通過控制蝕刻的持續時間和入射激光的能量，我們能夠獲得特定的直徑。 LLPFG 的深度和邊緣可以根據激光器的蝕刻缺口和蝕刻過程的持續時間進行控制，這反過來又可以快速估計實現拉伸載荷所需的包層直徑。週期為 610 μm 的 LLPFG 在光纖直徑為 60 μm、光柵深度為 26 μm 時的諧振衰減波長為 1551 nm，最大諧振衰減為 26.489 dB，並且隨著光纖的增加，LLPFG 的靈敏度會有所提高。直徑減小。
在下一步中，檢查不同彎曲光纖的可變長度和直徑 (CLD) 行為。提出了一種基於光纖彎曲結構的濕度和溫度測量傳感器。該傳感器涉及一種新的設計和使用 CLD 的彎曲光纖的簡單製造，以在傳輸光譜中產生獨立的馬赫 - 曾德干涉 (MZI) 下降。與雙模和多模光纖相比，單模 CLD 彎曲光纖干涉傾角對直徑變化更敏感。在進一步的步驟中，傳感器在 60–90% 的 RH 範圍內呈現 275 pm/RH% 的相對濕度 (RH) 靈敏度，在 30–120°C 的範圍內具有 44.9 pm/°C 的溫度靈敏度。通過在設計中植入可變直徑，這可以應用於環境濕度和溫度的特定變化。

Nowadays, one of the commonly used sensors in industry and technology and nano included optical-based sensors. Among optical sensor, fiber optics have interesting role and widely application cause of their properties. Beside of safety against electromagnetic interference and good ratio of signal to noise, Ease of fabrication of small size and low weight transmission enable fiber optics as a good choose to target optical sensors. In this purpose finding cost effective and simple have more attraction in comparison earlier techniques. This work presented the role of control of core to cladding in fiber optics.
The behavior of LLPFG under strain and the decisive factors in determining that behavior experimentally optimized by utilizing the energy of a KrF excimer laser-assisted and the duration of the chemical etching to control the period and depth of the ablation zone. By controlling the duration of etching and the energy of the incident laser, we were able to obtain specific diameters. The depth and edge of the LLPFG could be controlled depending on the etched notch of the laser and the duration of the etching process, which in turn enabled quick estimation of the cladding diameter needed to achieve tensile loading. The LLPFG with a period of 610 μm showed a resonant-attenuation wavelength of 1551 nm and a maximum resonance-attenuation of 26.489 dB at a fiber diameter of 60μm and grating depth of 26μm, and the sensitivity of the LLPFG would be increased when the fiber diameter was decreased.
In next step the behavior of changeable length and diameter (CLD) for different bent fiber inspected. A sensor based on the bent structure of fiber optics for humidity and temperature measurement has been presented. The sensor involved a new design and simple fabrication of bent fiber optics with CLD in generating independent Mach-Zehnder Interference (MZI) dips in the transmission spectrum. The single-mode CLD bent fiber interference dip was more sensitive to diameter changes in comparison to two-mode and multi-mode fibers. In a further step, the sensor presents Relative Humidity (RH) sensitivity of 275 pm/RH% in the RH range of 60–90% and a temperature sensitivity of 44.9 pm/◦C in the range of 30–120 ◦C. With changeable diameter implanted in the design, this can be applied in the specific variation of humidity and temperature of the environment.

ABSTRACT III
ACKNOWLEDGEMENTS V
CONTENTS VI
LIST Of SYMBOLS X
LIST OF FIGUERS XII
TABLES XVIII
CHAPTER 1: INTRODUCTION 1
1.1 Research motivation 1
1.2 Targets 3
1.3 Layout of thesis 3
1.3.1 Fabrication a LLPFG 3
1.3.2 Ratio of core to cladding during etching process, which enabled the sensor to more sensitivity under loading 4
1.3.3 Inspect and monitoring ratio core and cladding in bent fiber optics which unable to reach more sensitive diameters to changes of humidity and temperature 4
1.4 Chapter Contents Review 5
Chapter Two: Basic Theory of fiber optics and FBG and LPFG 7
2.1 Introduction 7
2.2 Wave Propagation 7
2.3 Theory of Coupling Mode 12
2.3.1 Polarization in periodic refractive index modulation 15
2.4 Phase match condition 17
2.5 Long period fiber grating (LPFG) 22
2.5.1 Review of laser assist Etching LPFG 23
2.5.2 Review of the manufacture of long-period fiber grating sensors 32
by Excimer laser 32
2.6 Sensitivity of LPFG 39
2.6.1 Temperature Sensitivity of LPFG 40
2.6.2 Strain Sensitivity of LPFG 41
2.7 Bent fiber 42
2.7.1 Review of bent fiber sensor 43
2.7.2 Review of bent fiber to measurement temperature and humidity 44
2.7.3 Theory of bent fiber 45
2.7.4 Mach-Zehnder Interferometer (MZI) 48
Chapter 3: procedure and fabrication method 51
3.1 fabrication and procedures of LLPG 51
3.1.1 Preparing of LLPFG 52
3.1.2 Optical adjustment 53
3.2 Laser-assisted etching process of long-period optical fiber 55
3.3 Laser-assisted etching by chemical reactions 57
3.3.1 Chemical etching by solution acid 57
3.3.2 3D geometry of LLPFG 58
3.4 bent fiber 60
3.4.1 Fabrication and experiment setup of CLDs 60
3.4.2 Comparison CLDs bent fiber with faraday mirror and CLDs series 63
3.5 Summery 64
Chapter 4: Result of discussion 65
4.1 dependency of depth to acid solution and laser power 65
4.2 Saturation points of etching process 68
4.3 Loading sensitivity of LLPFG 70
4.3.1 Dependency of transmission spectrum of LLPFG to diameter 73
4.3.2 Dependency of transmission spectrum of LLPFG to force 74
4.4 Inspection of NLPFGs under different polarization 75
4.5 Bent fiber 78
4.5.1 initial data of multi-mode CLDs bent fiber 78
4.5.2 initial data of two modes CLDs bent fiber 80
4.5.3 Initial data of single mode CLDs 81
4.5.4 Effective range of diameter and length on CLDs bent fiber 85
4.6 CLDs sensitivity to temperature 89
4.7 CLDs sensitivity to humidity 91
4.8 Producibility and productivity 94
4.9 summery 99
Chapter 5: Conclusion and future work 99
5.1 Conclusion 100
5.2 Future work 101
Publication 102
References 103

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