We present the first demonstration of telecom fiber-based quantum key distribution using single photons from
a quantum dot in a pillar microcavity. The source offers both telecommunication wavelength operation at 1.3
microns and Purcell enhancement of the spontaneous emission rate. Several emission lines from the InAs/GaAs
quantum dot are identified, including the exciton-biexciton cascade and charged excitonic emission. We show an
order of magnitude increase in the collected intensity of the emission from a charged excitonic state when temperature
tuned onto resonance with the HE11 mode of the pillar microcavity, as compared to the off-resonance
intensity. Above- and below-GaAs-bandgap optical excitation was used and the effect of the excitation energy
on the photoluminescence investigated. Exciting below the GaAs-bandgap offers significant improvement in the
quality of the single photon emission and a reduction of the multi-photon probability to 0.1 times the value for
Poissonian light was measured, before subtraction of detector dark counts, the lowest value recorded to date
for a quantum dot source at a fibre wavelength. We observe also the first evidence of Purcell enhancement of
the spontaneous emission rate for a single telecommunication wavelength quantum dot in a pillar microcavity.
We have incorporated the source into a phase encoded interferometric scheme implementing the BB84 quantum
cryptography protocol and distributed a key, secure from the pulse splitting attack, over standard telecommunication
optical fibre. We show a transmission distance advantage over that possible with (length-optimized)
uniform intensity weak coherent pulses at 1310 nm in the same system.