Effects of the taper-joining of two single-mode fibers, where the fibers are first spliced by fusion, and are then heated and stretched to form the taper-joint, are analyzed and discussed. Due to reductions both in the lateral and angular offsets in the process of forming the taper, the loss can be reduced by one tenth, which is much smaller than that in the case where fibers are spliced after the formation of the taper. It is also pointed out that the joint must be kept straight to avoid the radiation loss due to curving of the joint. Finally, it is ascertained experimentally that the taper joint can be obtained by the arc-discharge method in both the splicing and the stretching processes.

By the derivative expansion method we solved a certain perturbation problem which well represents the phase lock loop. We derived the equation which describes the dynamics of a slowly varying parameter E, where E can be regarded as the averaged energy of the system approximately.

By refining the deconvolution technique proposed previously by the same authors for determining the impulse response of optical fibers, the time resolution has been improved. In some cases an impulse response consisting of several independent pulses is obtained; probably these pulses correspond to separate LP-mode groups.