losses in a 5 mm length of fiber core are 30 db 1000 200 1 5 10 u2212 4 db u2248 3 5 10 u2212 5 if we launch 20 mw of light into the end of the optical fiber a 5 mm section irradiates 20 3 5 10 u2212 5 mw 0 7 u03bcw and the detector detects 16 of this radiation p core 0 7 0 16 u03bcw u2248 0 1 u03bcw the sensitivity of the detector is approximately 0 04 u03bca u03bcw therefore the current realized by radiation from the fiber core in the detector is approximately i core 0 1 0 04 u03bca 4 10 u2212 3 u03bca we have assumed that all losses in the core are radiation which is not accurate the most substantial portion of loss in the fiber core is due to absorption therefore the actual detected signal should be several times lower than the above estimation we were not able to find specifications for losses in the cladding of the single mode fiber used since the cladding is not considered to be a light guiding medium the purpose of the cladding is to provide conditions under which essentially total internal reflection occurs in the core our rough estimation is that losses in the cladding in the form of light mostly propagating into free space about the cladding are 30 100 db m if one takes the lower limit 30 db m the same calculation as for the core yields losses in 5 mm 30 db 200 0 15 db u2248 0 035 typically when coupling light from the.