Characteristic beam parameters in diffracted field of fiber end face

Abstract

The mode field radii in the near field and the angular radii of the far field divergence defined by second moment and differential operator algorithm and the beam propagation factor defined by second moment algorithm were presented to describe the characteristic beam parameters in the diffracted field of the fiber end face comprehensively. In the condition of paraxial approximation, the simple relationship of the beam parameters hinged on the beam propagation factor were educed. The verdict that beam propagation should be more than 1 for fiber was presented. The beam parameters can be calculated accurately from the mode field distribution of the fiber, or from the diffraction frequency spectrum distribution in the far field, which is experimentally measurable exactly. The above principles and findings can serve as theoretical basis for measuring and computing the characteristic parameters of fiber. The analytic functions and scopes of the characteristic beam parameters in the diffracted field of LP01 mode step index fiber were deduced.