Apparatus and method for measuring exit velocity of a gun round

An apparatus for measuring exit velocity of a round from a muzzle of a gun barrel, comprising:

• a first optical fiber comprising a first fiber optic Bragg grating (FBG) circumferentially attached to the gun barrel at the muzzle and a second FBG circumferentially attached to the gun barrel further from the muzzle than the first FBG thereby defining an axial linear distance between the first and second FBGs, the first and second FBGs being oriented perpendicular to a longitudinal axis of the gun barrel;
• a coupler that receives one end of the first optical fiber;
• a light source connected by a second optical fiber to the coupler for supplying light to the first optical fiber;
• a third optical fiber comprising an FBG notch filter, the third optical fiber being connected to the coupler to receive light reflected from the first optical fiber;
• a notch filter mount attached to the gun barrel, the FBG notch filter being disposed in the notch filter mount;
• a photodetector connected to an end of the third optical fiber;
• and
• data processing electronics electrically connected to the photodetector.