  The development of efficient sources of single photons and entangled photon
pairs emitting in the low-loss wavelength region around 1550 nm is crucial for
long-distance quantum communication. Moreover, direct fiber coupling and
electrical carrier injection are highly desirable for deployment in compact and
user-friendly systems integrated with the existing fiber infrastructure. Here
we present a detailed design study of circular Bragg gratings etched in InP
slabs and operating in the telecom C-band. These devices enable the
simultaneous enhancement of the X and XX spectral lines, with collection
efficiency in NA=0.65 close to 90% for the wavelength range 1520-1580 nm and
Purcell factor up to 15. We also investigate the coupling into single mode
fiber, which exceeds 70% in UHNA4. Finally, we propose a modified device design
directly compatible with electrical carrier injection, reporting Purcell
factors up to 20 and collection efficiency in NA=0.65 close to 70% for the
whole telecom C-band.
