Optical Fiber Communications 4th Edition by Gerd Keiser

Exercise 19

Consider an optical fiber transmission star coupler that has seven inputs and seven outputs. Suppose the coupler is constructed by arranging the seven fibers in a circular pattern (a ring of six with one in the center) and putting them against the end of a glass rod that serves as the mixing element.
( a ) If the fibers have 50-m core diameters and 125-m outer cladding diameters, what is the coupling loss resulting from light escaping between the output fiber cores Let the rod diameter be 300 m. Assume the fiber cladding is not removed.
( b ) What is the coupling loss if the fiber ends are arranged in a row and a 50-m × 800-mm glass plate is used as the star coupler