Abstract: An optic fiber adapted for ultrasound imaging of the lumen of a vessel comprising: an inner core for transmitting light having an index of refraction that changes responsive to acoustic energy incident thereon; a ring core concentric with the inner core for transmitting light; a cladding material between the inner and ring cores that has an index of refraction smaller than the index of refraction of the material from which the inner core is formed; and at least one acoustic transducer comprising absorbing material formed on the surface of the ring core that absorbs optical energy transmitted along the ring core and generates ultrasound responsive thereto.