Fiber Optic Wiki

Multifiber Cable Systems

August 24, 2011

Multifiber systems are constructed with strength members that resist crushing during cable pulling and bends. The outer cable jackets are OFNR (riser rated), OFNP (plenum rated), or LSZH (low-smoke, zero-halogen rated).

Inside Plant Ribbon-Cable System

August 24, 2011

Figure 3-6 shows a typical six-fiber, inside-plant cable system. The central core is composed of a dielectric strength member with a dielectric jacket. The individual fibers are positioned around the dielectric strength member.

Cross Section of Inside-Plant Cables

August 24, 2011

Figure 3-7 shows a typical armored outside-plant cable system. The central core is composed of a dielectric with a dielectric jacket or steel strength member. The individual gel-filled subunit buffer tubes are positioned around the central strength member. Within the subunit buffer tube, six fibers are positioned around an optional dielectric strength member.

Propagation Modes Of Propagation

August 24, 2011

Fiber-optic cable has two propagation modes: multimode and single mode. They perform differently with respect to both attenuation and time dispersion. The single-mode fiber-optic cable provides much better performance with lower attenuation. To understand the difference between these types, you must understand what is meant by "mode of propagation."

Optical-Cable Construction

August 23, 2011

The core is the highly refractive central region of an optical fiber through which light is transmitted. The standard telecommunications core diameter in use with SMF is between 8 m and 10 m, whereas the standard core diameter in use with MMF is between 50 m and 62.5 m. Figure 3-4 shows the core diameter for SMF and MMF cable.

Figure 3-4 Optical-Cable Construction

August 23, 2011

Fiber-optic cable sizes are usually expressed by first giving the core size followed by the cladding size. Consequently, 50/125 indicates a core diameter of 50 microns and a cladding diameter of 125 microns, and 8/125 indicates a core diameter of 8 microns and a cladding diameter of 125 microns.

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