There is described a method for terminating an optical fiber within a proximal portion of a guidewire tubing. The guidewire tubing has an outside diameter and comprises a lumen. The method comprises centering the optical fiber relative to the outside diameter of the proximal portion of the guidewire tubing. The optical fiber and the inside of the lumen define an average gap there between. The average gap around the optical fiber is between 1 μm and 100 μm for allowing a substantial displacement of the optical fiber inside the lumen during the centering.