Expanded single mode fiber

@article{Chanclou2001ExpandedSM,
  title={Expanded single mode fiber},
  author={Philipe Chanclou and Philippe Gravey and Monique Thual},
  journal={OFC 2001. Optical Fiber Communication Conference and Exhibit. Technical Digest Postconference Edition (IEEE Cat. 01CH37171)},
  year={2001},
  volume={3},
  pages={WDD4-WDD4}
}
We present a solution to maintain an expanded mode in the extremity of a single mode fiber by using a piece-of multimode step index fiber. With a 25 /spl mu/m spot size, the average connection loss is 0.36 dB (without Fresnel reflection) for a multimode section length inferior to 5 cm. This process is particularly suitable for expanded beam connectors and fiber matrices.