The pulse, an aggregate of different modes, begins to spread out, losing its well-defined shape. The need to leave spacing between pulses to prevent overlapping limits bandwidth that is, the amount of information that can be sent. Consequently, this type of fiber is best suited for transmission over short distances, in an endoscope, for instance. The higher refractive index at the center makes the light rays moving down the axis advance more slowly than those near the cladding. The shortened path and the higher speed allow light at the periphery to arrive at a receiver at about the same time as the slow but straight rays in the core axis.
Light thus travels parallel to the axis, creating little pulse dispersion.
Telephone and cable television networks install millions of kilometers of this fiber every year. The modular design of loose-tube cables typically holds up to 12 fibers per buffer tube with a maximum per cable fiber count of more than 200 fibers. The loose-tube design also helps in the identification and administration of fibers in the system. A gel filling compound impedes water penetration. Buffer tubes are stranded around a dielectric or steel central member, which serves as an anti-buckling element.