Modulation of annular light distribution by mechanical fiber scrambler

The far-field pattern of fiber output beam changes dramatically due to different positions and angles of the input beam on fiber. This paper studies the change of the fiber-s output beam when the axis of input beam is shifted a small angle off the axis of optical fiber through the anlysis of the fiber-s output distribution. Fiber coupling theory indicates that the fiber macrobending leads to mutual coupling of fiber mode, so an improvement of fiber transmission with a mechanical scrambler which gives certain pressure to bend parts of fiber is designed. The collected output spots in different off-axis angles and scrambling degree are taken by median filtering and Gaussian fitting approaches. The scrambling effects are measured mainly through the profile of radial intensity distribution as well as its fitting degree of Gaussian distribution and the change of the energy ratio between different output focal ratio and input.