Abstract: Whispering gallery mode fiber laser driven by evanescent wave is used to tie two fibers with different diameters parallel
along their axes to form a pair of coupled asymmetric cylindrical microcavities. According to the Wiener effect, only when both cavities
are resonant at a certain frequency can laser radiation occur, and the free spectrum of the coupled asymmetric microcavities will be
expanded a lot and thereby the single mode laser radiation is realized. By changing the size of the coupled asymmetric microcavity, the
single-mode laser radiation under different conditions is obtained, and the coupling efficiency of the coupled asymmetric microcavity is
studied. The experimental results show that the coupling efficiency of the asymmetric microcavity composed of small and medium
diameter fibers and small diameter difference fibers is high.

Key words: evanescent wave, whispering gallery mode, Wiener effect, coupling efficiency