  Efficient sources of individual pairs of entangled photons are required for
quantum networks to operate using fibre optic infrastructure. Entangled light
can be generated by quantum dots (QDs) with naturally small
fine-structure-splitting (FSS) between exciton eigenstates. Moreover, QDs can
be engineered to emit at standard telecom wavelengths. To achieve sufficient
signal intensity for applications, QDs have been incorporated into 1D optical
microcavities. However, combining these properties in a single device has so
far proved elusive. Here, we introduce a growth strategy to realise QDs with
small FSS in the conventional telecom band, and within an optical cavity. Our
approach employs droplet-epitaxy of InAs quantum dots on (001) substrates. We
show the scheme improves the symmetry of the dots by 72%. Furthermore, our
technique is universal, and produces low FSS QDs by molecular beam epitaxy on
GaAs emitting at ~900nm, and metal-organic vapour phase epitaxy on InP emitting
at 1550 nm, with mean FSS 4x smaller than for Stranski-Krastanow QDs.
