A method to fabricate fiber Bragg grating (FBG) in an optical microfiber (OM) from a conventional photosensitive fiber is proposed in this letter. The cladding of a conventional photosensitive fiber is etched to 17 \mu m. The etched fiber is drawn to an OM 6 μm in diameter. The photosensitivity of the fabricated OM is effectively reserved. A FBG in the OM (MFBG) is successfully fabricated using a KrF excimer laser at a fluence of 400 mJ/cm2 through a phase mask with a pitch of 1 089.3 nm. The re
