  Nitrogen-vacancy (NV) defect in diamond is a very promising tool for numerous
sensing applications like magnetometry or thermometry. In this paper, we
demonstrate a compact and convenient device for magnetic field imaging where a
commercial single mode photonic crystal fibre is directly coupled to a
commercial CVD ppm diamond. We managed to excite and detect efficiently the
luminescence from an ensemble of NV centres and also to perform Electron Spin
Resonance (ESR) experiments where the NV hyperfine structure is perfectly
resolved under continuous excitation and measurement.
