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In Fig a the sensitivity
In Fig. 5 (a), the sensitivity of the proposed PCF is greatly enhanced by the increasing air filling ratio. Air filling ratio (dc/˄1) is varied by 0.70, 0.65 and 0.57 and the calculated sensitivity at λ=1.33μm is 44.63, 38.61 and 29.91% respectively; the confinement loss is 2.477×10, 4.021×10 and 6.636×10dB/m respectively for Water. At a core diameter dc=0.63μm, the proposed O-PCF shows better propagation characteristics for Water, Ethanol and Benzyne analytes at λ=1.33μm; the calculated sensitivity is 44.73%, 46.67%, and 47.35%; and the confinement loss is 3.897×10, 6.266×10, and 2.282×10dB/m respectively. From Fig. 5, it receptor tyrosine kinase is acquitted that sensitivity increases by the increment of air filling ratio and confinement loss is vice versa. So another optimal parameter dc=0.63μm of 5-ring O-PCF is chosen for further investigation. Fig. 6 (a) and (b) depicts the sensitivity and confinement loss of the proposed fiber for the pitch (˄1) variation keeping air filling ratio (dc/˄1) constant. Three pitches (˄1=0.7, 0.8 and 0.9μm) are considered and ˄=2.4μm and d=1.75μm remain unchanged. Now keeping the air filling ratio fixed, the pitch (˄1) and core diameter (dc) are varied. It is evident from Fig. 6 that the highest sensitivity and lowest confinement loss are shown at ˄1=0.9μm and dc=0.63μm for all analytes. So for better propagation characteristics, core pitch value of 0.9μm is recommended here for further investigation procedure. Fig. 7 (a) and (b) illustrates the scenario of changing sensitivity and confinement loss of proposed O-PCF as the variation of the inner most ring air hole diameters for ˄=2.4μm, dc/˄1=0.7, and ˄1=0.9μm. The relative sensitivities at λ=1.33μm for d=1.75μm, 1.68μm and 1.60μm are 47.58%, 44.93%, 42.85%; 48.73%, 46.51%, 44.45% and 49.97%, 47.31%,45.22% for Water, Ethanol and Benzyne analytes respectively. In order to support the numerically investigated results represented in Fig. 7 (a), by increasing the diameter of the inner most air holes the sensitivity can be greatly enhanced. One remarkable reason is from Fig. 7 (b) which states that confinement loss is dramatically unchanged. The confinement loss for the proposed O-PCF is 2.47705×10, 2.67705×10, and 2.27705×10 dB/m; 2.07451×10, 2.37451×10, and 1.77451×10 dB/m; 7.58542×10, 7.88542×10 and 7.18542×10 dB/m for Water, Ethanol, and Benzyne analytes respectively keeping other parameters constant like Fig. 7(a). Almost all sensing applications, higher sensitivity and lower confinement loss through a wide range of wavelength are mostly acceptable essential parameters for designing PCF structure. In this research, plasmolysis is proved that higher sensitivity and lower confinement loss levels can be gained by the proposed O-PCF compared to previous demonstrated O-PCF structure [33] as well as H-PCF and S-PCF structures. The proposed O-PCF structure\'s sensitivity has been increased to 45.05%, 46. 87%, 47.35% from 20.05%, 21.55%, 22.50% respectively for all three analytes at λ=1.33μm. Similarly confinement loss is also improved to 6.63622×10dB/m, 2.28217×10dB/m, 5.28542×10dB/m from 5.55×10dB/m, 5.65×10dB/m, 5.75×10dB/m respectively. Fabrication issues of the proposed O-PCF structure are the most important topic through the experimental point of view. The fabrication process of the proposed O-PCF may not be easy due to micro cored holes. Not only fabrication criteria can be overcome due to technological advancement but also analytes can be entered into the fiber without damages of the fiber\'s integrity. Several techniques are introduced to fill the air holes with liquid. But the major complexity will be raised in the core region of the proposed structure. The Selective-filling technique was proposed by Huang et al. [38] which is able to fill all cladding holes as well as the micro core holes. Xiao et al. [39] and Cordeiro et al. [40] proposed techniques that were smoothly used to fabricate various PCF structures with liquid at core holes. Lastly the complexity of fabrication will be less due to large air hole diameters and their uniformity with the proposed O-PCF structure [39–40]. Now Sol–gel technique has been applied to remove the complexity of fabrication for any kind of microstructured optical fiber as well as PCF with different types of air hole shapes and sizes [41]. So the proposed PCF can be successfully fabricated using the Sol–gel technique.