| 摘要 |
PURPOSE:To improve coupling efficiency by varying the refractive index distribution of the core of an optical fiber gradually in a transition area near its slab waveguide from a cylindrical symmetrical square-law distribution to a square- symmetrical uniform distribution type while holding the total number of modes constant. CONSTITUTION:The transition area 3 which varies gradually in refractive index distribution from the cylindrical GI type to the square SI type is formed between the optical fiber 1 and slab waveguide 2 and the core varies from a cylindrical shape to a polygonal shape. The variation of the core in the transition area 3 is gentle and the total number of modes is constant. The slab waveguide 2 is considered to be (n) square waveguides in lateral abutting relation while a lateral clad which isolates individual waveguides is removed in terms of heat insulation. Therefore, there is no lateral clad in the slab waveguide 2, so light inone optical fiber spreads into the clad and light of opposite sides is all distributed to the optical fiber 1. Thus, the coupling efficiency is improved. |
