METHOD FOR ADJUSTING COEFFICIENT OF COUPLING IN OPTICAL FIBER DIRECTIONAL COUPLER

摘要

PURPOSE:To relieve an eccentric core fiber having a parameter deviated from a design value by rotating the fiber after production to set intervals of cores. CONSTITUTION:Eccentric core fibers 1 and 2 are produced after a core diameter 2a, a specific refractive index difference DELTA, and a distance S from the outside peripheral surface of the fiber to the center of the core are so determined that a desired coupling coefficient K is obtained. Two eccentric core fibers 1 and 2 have outside peripheral surfaces brought into contact with each other, and one or both of them are rotated in this state to set the interval between cores 1A and 1B to a desired value (d). A preliminarily designed value is selected as this value (d) if the diameter 2a and the specific refractive index difference DELTAof cores 1A and 1B are as designed after production. If they are deviated from design values after production, the core diameter 2a and the specific refractive index difference DELTA after production are used to calculate again the interval between cores by which the desired coupling coefficient is obtained, and the value (d) is corrected to the calculated value.