Guo Tuan, Tam Hwa-Yaw, Krug Peter A, Albert Jacques
Photonics Research Center, Department of Electrical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China.
Opt Express. 2009 Mar 30;17(7):5736-42. doi: 10.1364/oe.17.005736.
A novel in-fiber structure for power-referenced refractometry with the capability to measure surrounding refractive index (SRI) as low as 1.33 is proposed and demonstrated. A short optical fiber stub containing a weakly tilted Bragg grating is spliced to another fiber with a large lateral offset. The reflection from this structure occurs in two well-defined wavelength bands, the Bragg reflected core mode and the cladding modes. The cladding modes reflect different amounts of power as the SRI changes, while the core-mode reflection from the same weakly tilted FBG remains unaffected by the SRI. The power reflected in the core mode band can be used as a reliable reference to cancel out any possible power fluctuations. The proposed refractometer with improved sensitivity for low SRI measurement together with the tip-reflection sensing feature, is a good candidate for sensing in chemical and biological applications.
提出并演示了一种用于功率参考折射测量的新型光纤结构，该结构能够测量低至1.33的周围折射率（SRI）。一根包含弱倾斜布拉格光栅的短光纤短截被熔接到另一根具有大横向偏移的光纤上。这种结构的反射发生在两个明确的波长带，即布拉格反射的芯模和包层模。随着SRI的变化，包层模反射不同量的功率，而来自同一弱倾斜光纤布拉格光栅的芯模反射不受SRI影响。芯模带中反射的功率可作为可靠的参考，以抵消任何可能的功率波动。所提出的折射仪对低SRI测量具有更高的灵敏度，同时具有尖端反射传感特性，是化学和生物应用传感的良好候选者。
