一种新型的光纤锥形耦合器

A Novel Tapered Fiber Optical Coupler

提出了一种光纤波导折射率渐变的新型锥形（Taper）耦合器件，其原理是基于光纤中Ge缺陷在紫外光照射下而产生的光致折射率的变化。利用光纤在高压、低温下渗氢技术使单模光纤的光致折射率变化△n达6×10-3数量级；通过控制曝光条件就可以在光纤中产生一定规律的锥形结构，使单模光纤的模场半径由4．8μm缩小到3．2μm。由耦合波理论分析表明该器件具有较好的基模传输特性。

A novel fiber optical tupered coupler is proposed with its waveguide refractive index gradually changing, induced by germania defects under the UV irradiation. The refractive index change An of 6 ×10-3 in the, single- mode communications fiber is achieved in our experiment by means of pre-treating the fiber in high-pressure and lowtemperature environment. A particular index tuper profile function is obtained by delicately controlling the exposure conditions, and the mode field radius (MFR) is reduced from 4. 8 um to 3. 2 um in single-mode fibers. The coupled wave theory analysis show that the taPered coupler is capable of excellent transmission for fundamental mode with very small mode conversions.