微小化布拉格光纖光柵之製作與量測

Abstract

一般光纖光柵是採用直徑125微米的單模光纖製作，而若是製作縮小化光纖光柵則是採用氫氟酸對已經製作完成的125微米的光纖光柵進行蝕刻去除掉光纖外層的纖衣部分。利用此種製作方式製作出的光纖光柵，光纖纖核大小依然保持不變。 我們使用125微米的單模光纖當預型體，然後採用我們研究小組所研發的改良式抽絲系統，再將光纖抽細，並將它拿來製作光纖光柵。與傳統氫氟酸蝕刻的光纖光柵不同的地方，在於光纖纖核的直徑會在抽拉過程中，隨著外層纖衣直徑而變化。由於纖核直徑變小,而導致纖核局限係數降低。我們在製作光纖光柵時同時觀測共振波長的飄移知道纖核局限係數對光纖中等效折射率變化的影響。 在我們的研究中縮小化光纖光柵溫度靈敏度10 pm/℃比傳統125微米光纖光柵的對溫度的靈敏度為11.6 pm/℃還要低。縮小化的光纖光柵對張力靈敏度為1.2 pm/με，比125微米光纖光柵的靈敏度1.0 pm/με高。

Traditional Fiber Bragg Gratings (FBGs) are fabricated using 125 μm single-mode fibers. In order to miniaturize the size of an FBG, the common method is to use hydrofluoric acid (HF) to etch 125 μm FBG. The core size of the FBGs made by this method is therefore unchanged. In this thesis, 125 μm fibers are used as preforms and drawn to smaller sizes by the homemade modified drawing system that our group developed. The difference between our method and traditional HF-etching approach is that in our experiment the core diameter would change linearly with the outer cladding diameter during the drawing process. The core power confinement factor would decrease due to the decrease of the core diameter. We can see the influence of core power confinement to the effective index change in the fiber core by in situ monitoring of the resonance wavelength drift during the grating writing process. In our work, the temperature sensitivity of miniaturized FBGs is 10 pm/℃, which is lower than that of a 125 μm FBG, 11.6 pm/℃. The strain sensitivity of miniaturized FBG is 1.2 pm/με, which is higher than that of a 125 μm FBG 1 pm/με.