  Non-classical light sources based on a single quantum emitter are considered
as core technology for multiple quantum network architectures. A large variety
of sources has been developed, but the generated photons remained far from
being utilized in established standard fiber networks. Here, we report a
week-long transmission of polarization-entangled photons from a single
InAs/GaAs quantum dot over a metropolitan network fiber. The emitted photons
are in the telecommunication O-band, favored for fiber optical communication.
We employ a polarization stabilization system overcoming changes of
birefringence introduced by 18.23km of installed fiber. Stable transmission of
polarization-encoded entanglement with a high fidelity of 91% is achieved,
facilitating the operation of sub-Poissonian quantum light sources over
existing fiber networks.
