Analysis of bending loss in single-mode optical fiber with low-cost setup

Optical fibers are essential for global communications, but bending loss remains a key factor limiting performance. We investigated how bending radius, wavelength, and number of turns influenced signal attenuation in a commercial single-mode fiber. We hypothesized that, at a fixed radius and wavelength, bending loss would increase linearly with the number of turns, while loss per turn across different radii would increase exponentially, with higher wavelengths exacerbating optical losses. To test this, we coiled fiber samples at different radii and measured output power at 1310 nm and 1550 nm using an optical power meter. Our results showed that at a given radius and wavelength, total loss increased linearly with the number of turns, while loss per turn across radii followed an exponential dependence. In addition, output power at 1550 nm exhibited higher losses than at 1310 nm at the same bend radius, confirming the predicted wavelength sensitivity. To interpret these trends, we obtained an analytical expression by fitting experimental results that captured bending-loss dependence on bend radius and wavelength. Fitting our data to an exponential model provided parameters that were qualitatively consistent with theoretical predictions, though the experimental wavelength dependence was weaker than expected. Overall, our results demonstrated that bending loss follows an exponential dependence on radius and is wavelength-dependent, with experimental trends qualitatively matching theoretical predictions. These findings underscore the value of combining low-cost experiments with analytical modeling to study fundamental properties of optical fibers and may help inform fiber routing decisions, especially in areas where bending attenuation matters.