Quartz-glass Optical Fibre Time to Fracture at Small Bending Radiuses

Standards and specifications for optical fibres specify such parameter as “macrobending loss”, i.e. macrobends are regulated only by attenuation increase. The paper shows by means of mathematical calculation that small bending radius of optical fibre significantly reduces the time to its fracture. To ensure the smooth operation of fibre-optic communication lines it is necessary that the bending radius of the optical fibre that passed the proof-test with 1 % stain does not exceed a value equal to 62.25 mm, and for the optical fibre that passed the proof-test with 2% strain - 36.5 mm. With smaller bending radiuses, mechanical loads on optical fibres exceed the permissible values, which leads to a decrease in time to its fracture. When designing a fibre-optic communication line to predict its uninterrupted service life, it is necessary to take into account the bending radiuses to which optical fibres are subjected for a long time.