Optimum clearance design for a loose optical-fiber cable based on suppression of fiber strain

Theoretical and experimental investigations were made for fiber strain in a loose-type optical-fiber cable. Calculation formulae were derived for strain evaluation, including clearance in a loose-tube. Loose-type optical cables composed of five-fiber ribbons were manufactured and the strain characteristics were measured under tensile force, bending, and temperature change. The theoretical and experimental results were compared and strain reduction was confirmed due to the clearance. By using the results, a design procedure for optimum clearance has been shown, based on strain suppression under an allowable value for long-term use.