Effect of Bending Radius and Bending Location on Insertion Loss in Single Mode Fibers and Polarization Maintaining Fibers

This paper shows the effect of bending radius and bending location on Insertion Loss (IL) in Single Mode Fibers (SMFs) and Polarization Maintaining Fibers (PMFs). Five FC/UPC PMF patchcords were tested for the effect of bending radius on IL, by being coiled from 0 (as reference) to 5 loops at bending radii of 7.5 mm to 17.5 mm in a step of 2.5 mm. Based on the significant IL changes at 7.5-mm radius and no change starting at 15-mm radius, these two radii were chosen for the study of bending location. Fifteen patchcords (5 FC/UPC PMF, 5 LC/UPC PMF and 5 LC/UPC SMF) were coiled for 1 full loop located at 20 cm to 100 cm in a step of 10 cm. At 7.5-mm radius, PMFs reveal their major IL variations strongly depending on bending location, while SMFs have minor variations. In contrast, no IL variations are observed at 15-mm radius for both PMFs and SMFs. This radius was then selected for the final study on a number of coils. All 15 patchcords were coiled up to 15 loops at 15-mm radius. The results exhibit insignificant IL increase for PMFs, but a small increase proportional to the number of coils for SMFs. Consequently, the benefit of these IL studies will validate the proper testing conditions for SMF and PMF patchcords, especially in PMFs, where the measurement of Polarization Extinction Ratio is correlated with IL.