  Optical interfaces for quantum emitters are a prerequisite for implementing
quantum networks. Here, we couple single molecules to the guided modes of an
optical nanofiber. The molecules are embedded within a crystal that provides
photostability and, due to the inhomogeneous broadening, a means to spectrally
address single molecules. Single molecules are excited and detected solely via
the nanofiber interface without the requirement of additional optical access.
In this way, we realize a fully fiber-integrated system that is scalable and
may become a versatile constituent for quantum hybrid systems.
