Fiber Optic Cable Assemblies Bel Fiber Optic Cable Assemblies feature a high-flexibility, tight-buffered design suitable for indoor environments. These single- and multi-mode assemblies offer multiple end configurations, duplex fiber cable construction, and a PVC jacket. The cable diameters are 2mm for single mode and 3mm for multi-mode. Cable lengths range from 1m to 5m. Bel Fiber Optic Cable Assemblies are designed for high-speed, high-bandwidth applications and are backward compatible with legacy LANs.