METHOD FOR ADJUSTING COEFFICIENT OF COUPLING IN OPTICAL DIRECTIONAL COUPLER

摘要

PURPOSE:To adjust the coupling characteristic of a multicore fiber to a desired value even if the coupling characteristic of the fiber after production is deviated from the desired value, by reducing the multicore fiber. CONSTITUTION:The section of the multicore fiber is reduced to adjust a coupling coefficient K, namely, a coupling length Lc. The coupling coefficient K is depen dent upon an interval (d) between cores 2a and 2b and a spot size (w) of power in the core. Reduction of an outside diameter D of the multicore fiber causes reduction of the interval (d) between cores, increase of the coupling coefficeint K, reduction of the coupling length Lc, reduction of a core diameter (r), increase after every sloe reduction of the size (w), reduction after increase of the coupling coefficient K, and increase after reduction of the coupling length Lc successively. finally, the coupling length Lc is increased after reduced in accordance with reduction of the outside diameter D. That is, the multicore fiber is reduced to adjust the coupling characteristic to a desired value.