An optical fiber treatment system having a side fire output tip (114, 210, 300) for transmitting high power laser energy in medical treatments, said output tip (114, 210, 300) comprising: an optical fiber (106, 202, 302), having a fiber core and a cladding layer (208, 306), for transmitting high power laser energy, said optical fiber (106, 202, 302) also having an input end and an output end; wherein a ratio of said cladding layer's (208, 306) diameter to said core's diameter (the clad/core ratio) is a least as great as 1.2; said output end of said optical fiber (106, 202, 302) being of a predetermined length, said output end (114, 308) being the fiber core and the cladding layer (208, 306) over said predetermined length, said output end having a side firing surface (220, 310) formed thereon; a capillary tube, said capillary tube for attachment to said output end on an outer most surface of said cladding layer (208, 306), said capillary tube having a hole at a proximal end for the acceptance of said output end of said optical fiber (106, 202, 302), having a sealed end section being formed from a distal end section of said capillary tube, and also having an output area therein where said laser energy passes through said tube; a void, said void being located between said side fire surface (220, 310) and said sealed end section; characterised in that said capillary tube is fused to said outer most surface of said cladding layer along the predetermined length of said cladding layer (208, 306); wherein refractive indices at a clad-tube interface of said tube and of said Or outer surface area of said cladding layer (208, 306) are matched to minimize or eliminate Fresnel reflections at this clad-tube interface, the cladding layer (208, 306) and the tube being mechanically and optically continuous at the clad-tube interface; and wherein said clad-tube interface is free of gaps or bubbles. an optical fiber (106, 202, 302), having a fiber core and a cladding layer (208, 306), for transmitting high power laser energy, said optical fiber (106, 202, 302) also having an input end and an output end; wherein a ratio of said cladding layer's (208, 306) diameter to said core's diameter (the clad/core ratio) is a least as great as 1.2; said output end of said optical fiber (106, 202, 302) being of a predetermined length, said output end (114, 308) being the fiber core and the cladding layer (208, 306) over said predetermined length, said output end having a side firing surface (220, 310) formed thereon; a capillary tube, said capillary tube for attachment to said output end on an outer most surface of said cladding layer (208, 306), said capillary tube having a hole at a proximal end for the acceptance of said output end of said optical fiber (106, 202, 302), having a sealed end section being formed from a distal end section of said capillary tube, and also having an output area therein where said laser energy passes through said tube; a void, said void being located between said side fire surface (220, 310) and said sealed end section; characterised in that said capillary tube is fused to said outer most surface of said cladding layer along the predetermined length of said cladding layer (208, 306); wherein refractive indices at a clad-tube interface of said tube and of said Or outer surface area of said cladding layer (208, 306) are matched to minimize or eliminate Fresnel reflections at this clad-tube interface, the cladding layer (208, 306) and the tube being mechanically and optically continuous at the clad-tube interface; and wherein said clad-tube interface is free of gaps or bubbles.