Design and characteristics of multi-hundred-core optical-fiber cable for use in subscriber feeder lines

This paper describes a design method for optical-fiber cable consisting of optical-fiber ribbons encased in loose tubes. The influence of excess fiber length on optical loss in a loose tube is evaluated and the required clearance is obtained. The optimum combination of the clearance and the tube stranding pitch is obtained in order to suppress fiber strain. The tube dimensions are also discussed and are determined to protect fiber ribbons from lateral load. A 600-fiber-structure cable is manufactured according to the obtained design results; the transmission and mechanical performances are confirmed to be excellent.