Coupling efficiency between ball lens capped laser diode chip and single mode fiber

Laser diodes are one of the key devices in the optical fiber communication system. Alignment and coupling is an application prerequistite between laser diode and single mode fiber. Coupling efficiency is analyzed theoretically between laser diode, ball lens and single mode fiber. The theory coupling efficiency with working distance are obtained under different optical system parameters, such as, the separation between the laser diode and the ball lens, refractive index and diameter of ball lens. Alignmnet and coupling experiments are done on the optical system for the coupling efficiency with working distance, and the maximum coupling efficiency is located at 2400 μm. The simulation to get high coupling efficiency, namely minimize spherical aberration, the laser diode should be put as close to the ball lens as possible and choose the ball lens with high refractive index and small diameters, which can be explained by Gaussian lens law.