  Quantum technology requires the creation and control over single photons as
an important resource. We present a single photon source based on a single
molecule which is attached to the end-facet of an optical fiber. To realize a
narrow linewidth, the system is cooled down to liquid-helium temperatures. The
molecule is optically excited and its fluorescence is collected through the
fiber. We have recorded an excitation spectrum, a saturation curve and analyzed
the contributions of Raman background fluorescence. This presents to date the
crucial limit for the introduced device. The single photon nature is proven by
an anti-bunched auto-correlation recording, which also shows coherent Rabi
oscillations.
