Angle selective fiber coupler.

@article{Barnoski1976AngleSF,
  title={Angle selective fiber coupler.},
  author={Michael K. Barnoski and R. J. Morrison},
  journal={Applied optics},
  year={1976},
  volume={15 1},
  pages={253-5}
}
Angle selective input coupling through the side of a slightly tapered section of Corning highly multimode fiber has been experimentally demonstrated for the first time. This coupling technique allows the possibility of fabricating bidirectional (duplex) couplers for systems employing single strands of multimode, low loss fiber.