A new type of optical fiber has been developed. It is made with all pure silica in both the core and cladding. This is possible because the cladding is a micro porous silica produced by a modified sol-gel technology. The formation and characteristics of this new optical fiber type are described. In particular the optical and mechanical properties are illustrated and described. The strength and fatigue of these optical fibers are very good, even without additional protective jackets. Unjacketed fibers have mean Weibull strengths in bending of 6.5 to 7.6 GPa with Weibull slopes in the 40 to 60 range. Fatigue results for fibers tested in ambient air, ambient water and boiling water are presented. The dynamic and static fatigue parameters are around 20. The micro porous structure of the sol-gel cladding provides sites for attaching different moieties which could activate biochemical reactions or be useful as sensing sites. Based on preliminary experiments, some possibilities are presented. In general this new structure can provide opportunities for as yet unidentified applications where chemicals and or light must be brought in close contact with body tissue to effect beneficial reactions there.