point not shown and the cladding removed to near the core at the second point fiber 12 can be coiled or elongated the ablation source should be pulsed to prevent deep melting of fiber 12 the loss due to the ablation process can be monitored in various ways fiber 12 can be a single mode or a multimode fiber if fiber 12 is a single mode fiber it is preferable to provide a single mode monitor source 23 ablation should be stopped before reaching the core in order to preserve the low loss waveguide properties of the core evanescent fields of the core guided energy extend significantly into the cladding region 20 ablation should be terminated when a small portion of the evanescent fields are coupled out through the remaining cladding a 0 1 db to 0 3 db loss will indicate that about 5 microns of cladding will remain above the core 20 and will generally be a good time to terminate ablation if one desires more energy to be coupled out it is preferable to extend the length of the ablated region rather than cut to less than 5 microns from the core the general cross section of a fiber 11 with.