A protective ferrule for an end-firing optical fiber arrangement combines a spherical or rounded shape with a planar end. The combination of the spherical or rounded shape and planar end provides protection for the working channel of an endoscope or catheter through which the fiber is inserted while confining and minimizing erosion of the active surface area of the fiber. The protective ferrule of may be fitted to the end of the optical fiber by the steps of heating the ferrule to expand an inside diameter so that it fits over the end of the fiber, with subsequent cooling of the ferrule causing it to contract and create a compression fit.
