Simulation and measurement of radiation loss at multimode fiber macrobends

A ray-tracing model for simulating light propagation in bent multimode fibers is described. The model takes modal effects into account. Calculations of the bend loss using this model are compared with measurements. Reasonable agreement with measured bend losses is obtained by including a realistic modal power distribution (MPD) in the simulation. For situations in which the power per mode in each principle mode group is constant, the simulations predict fractional loss curves as a function of the normalized group number m/M that are independent of wavelength. These curves can be used to predict bend losses in other constant radius bends as long as the MPD is known. The emission pattern of the radiated light has been calculated and qualitative agreement with the measured pattern found. It is suspected that the differences between simulation and experiment might be explained if the exact shape of the fiber in the bend were known and taken into account