• When When the emitting area of the source is smaller than the core area of fiber, the power coupling efficiency becomes poor. In order to improve the coupling efficiency miniature lens is placed between source and fiber. Microlens magnifies the emitting area of source equal to core The power coupled increases by a factor equal to magnification factor of lens.

(See Fig. 4.4.1 on next page.)


  • Important types of lensing schemes are :
  1. Rounded – end
  2. Spherical – surfaced LED and Spherical-ended fiber.
  3. Taper ended
  4. Non imaging
  5. Cylindrical lens,
  6. Imaging


Fig. 4.4.1 shows the lensing schemes.


  • There are some drawbacks of using
  1. Complexity
  2. Fabrication and handling
  3. Precise mechanical alignment is