  Telecom C-band single photons exhibit the lowest attenuation in optical
fibers, enabling long-haul quantum-secured communication. However, efficient
coupling with optical fibers is crucial for these single photons to be
effective carriers in long-distance transmission. In this work, we demonstrate
an efficient fiber-coupled single photon source at the telecom C-band using
InAs/InP quantum dots coupled to a tapered nanobeam. The tapered nanobeam
structure facilitates directional emission that is mode-matched to a lensed
fiber, resulting in a collection efficiency of up to 65% from the nanobeam to a
single-mode fiber. Using this approach, we demonstrate single photon count
rates of 575 $\pm$ 5 Kcps and a single photon purity of $g^2$ (0) = 0.015 $\pm$
0.003. Additionally, we demonstrate Hong-Ou Mandel interference from the
emitted photons with a visibility of 0.84 $\pm$ 0.06. From these measurements,
we determine a photon coherence time of 450 $\pm$ 20 ps, a factor of just 8.3
away from the lifetime limit. This work represents an important step towards
the development of telecom C-band single-photon sources emitting bright, pure,
and indistinguishable photons, which are necessary to realize fiber-based
long-distance quantum networks
