This, therefore, limits the bit rate or bandwidth of a multimode fiber. Multimode-graded index fibers therefore have the ability to transport pulses closer together without spreading into each other than do the step index fibers. They therefore can support a much higher bit rate or bandwidth. The actual bandwidth depends on how well a particular fiber's index profile minimizes modal dispersion, and on the wavelength of light launched into the fiber. It is decreasing in popularity due to its high cost and poor performance in attenuation and bandwidth.
T here is also a family of all-plastic fibers.
These also have a step index profile with the expected low bandwidth. This limits the light transmission to a single ray or mode of light to propagate down the core of the fiber. T wo slightly different constructions of standard single-mode fibers are in use today. These terms refer to the refractive index profile of the fibers. These fiber designs are generally perceived as interchangeable and compatible.