A light pulse that travels at different velocities causes spreading of the pulse or pulses to overlap (Figure 1 Part 1) with one another, resulting in bit errors and dB loss. The velocity of a wavelength and the color of light is directly related to the refractive index of a fiber, where longer wavelengths or lower frequencies travel slightly faster. This type of dispersion with multiple wavelength components and different colors of light, causes light pulses to travel at a slower velocity than in a vacuum (c = 299,792 km/s). Single mode fiber (SMF) with one mode of light has no issues with modal dispersion.Ī second type of dispersion that is important to our access networks is chromatic dispersion (CD), measured in picoseconds (ps) per wavelength (nm) x distance (km). Modal dispersion occurs in multimode optics, where the pulse will spread in time and distance due to multiple modes of light. The first type of dispersion is known as modal dispersion, allowing a light pulse to break up into different modes or different paths. There are several types of dispersion to be aware of in our networks: In networks like 10G and beyond, dispersion may be more of an issue as the light pulses become smaller. The effect of dispersion will reduce the overall capacity of a fiber link, thus lowering the bit rate. The pulses reach a destination using different timing or at a different velocity. Dispersion may change from one measurement to another, impacting the ability for a receiver to distinguish a discrete light pulse properly. Optical signal transmission has always been limited by optical dispersion, an area that is important to understand and characterize in our optical networks.ĭispersion is the spreading or smearing (Figure 1 Part 1) of a light pulse over time (picoseconds/ps) and distance (kilometers/km), or as it travels over an optical link. Operators are evolving networks that use analog intensity modulation (AIM) data, as well as new distributed access architectures (DAA) and passive optical networks (PON) that leverage digital binary encoded data. Optical networks and the performance management of their signals are a key foundation in the telecommunications industry achieving the goals of the 10G platform.
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