<P> Wavelength - division multiplexing (WDM) is the practice of multiplying the available capacity of optical fibers through use of parallel channels, each channel on a dedicated wavelength of light . This requires a wavelength division multiplexer in the transmitting equipment and a demultiplexer (essentially a spectrometer) in the receiving equipment . Arrayed waveguide gratings are commonly used for multiplexing and demultiplexing in WDM . Using WDM technology now commercially available, the bandwidth of a fiber can be divided into as many as 160 channels to support a combined bit rate in the range of 1.6 Tbit / s . </P> <P> Because the effect of dispersion increases with the length of the fiber, a fiber transmission system is often characterized by its bandwidth--distance product, usually expressed in units of MHz km . This value is a product of bandwidth and distance because there is a trade - off between the bandwidth of the signal and the distance over which it can be carried . For example, a common multi-mode fiber with bandwidth--distance product of 500 MHz km could carry a 500 MHz signal for 1 km or a 1000 MHz signal for 0.5 km . </P> <P> Engineers are always looking at current limitations in order to improve fiber - optic communication, and several of these restrictions are currently being researched . </P> <P> Each fiber can carry many independent channels, each using a different wavelength of light (wavelength - division multiplexing). The net data rate (data rate without overhead bytes) per fiber is the per - channel data rate reduced by the FEC overhead, multiplied by the number of channels (usually up to eighty in commercial dense WDM systems as of 2008). </P>

What is the maximum bandwidth that can be supported by fiber optics cable