One or more nanotaper coupling waveguides formed within an optical
substrate allows for straightforward, reproducible offset launch
conditions to be achieved between an incoming signal and the core region
of a multimode fiber (which may be disposed along an alignment fixture
formed in the optical substrate), fiber array or other multimode
waveguiding structure. Offset launching of a single mode signal into a
multimode fiber couples the signal into favorable spatial modes which
reduce the presence of differential mode dispersion along the fiber. This
approach to providing single mode signal coupling into legacy multimode
fiber is considered to be an improvement over the prior art which
required the use of an interface element between a single mode fiber and
multimode fiber, limiting the number of propagating signals and
applications for the legacy multimode fiber. An optical switch may be
used to select the specific nanotaper(s) for coupling into the multimode
fiber.