Optical fiber cables using V-grooved cylindrical units: High performance cables

Some practical and theoretical aspects of a V-grooved cylindrical cable (high performance optical fiber cable) are now being developed in several countries. Design of cables is important, because bendings may cause distortions. In order to limit micro-bending losses in an optical fiber cable, it is possible to modify parameters relating to the fiber or the cable. Some of the possibilities are: to decrease the core diameter in order to decrease the attenuation coefficient; to increase the diameter of the cladding so as to increase the tension above which micro-bendings occur; to increase the continuous bending radius due to cabling; to decrease the effects of roughness (μ); to integrate the effects of roughness as much as possible by decreasing the Young modulus of the coating and of the cable material and by increasing the cladding thickness; and to suppress the tension T of the fiber in the cable. The cabling element is made of a V-grooved cylindrical core, in which the fiber with an outside diameter d_e (outside diameter or primary coating) are laid without tension, with a slight excess length. The slots with a depth h are helical or alternated helical, providing the possibility of additional excess length, and the fiber can be “cabled” directly without stresses. A central strength member with a diameter Dp reinforces the cylindrical rod, ensuring the mechanical and thermal qualities.