TOLERANCE ANALYSIS OF ALIGNING AN ASTIGMATIC LASER-DIODE WITH A SINGLE-MODE OPTICAL-FIBER

A general method of analyzing misalignment tolerance of coupling light from an astigmatic laser diode to a single-mode fiber is described, W e apply the method to derive the 3 dB tolerances caused by longitudina l, lateral, and angular misalignments in the optimal conditions for tw o kinds of coupling schemes, One is by the use of a rotationally symme tric optical system, and the other by a rod which is a special case of utilizing a rotationally asymmetric optical system, In the latter cou pling case, the misalignment caused by a laser is found to have a much less 3 dB tolerance in the vertical direction than that caused by a f iber.