The pulse delay for the fiber under test as a function of wavelength is PDout. The pulse delay for the reference fiber as a function of wavelength is PDin. The delay for the pulses for both a long test sample fiber and a short reference fiber are measured over a range of wavelengths.
#Reverse dispersio in light Patch
This reference fiber is usually a 2 meter length patch chord which is connected to the input end and output end of the testing equipment. A multi-wavelength source can be a wavelength selectable laser.īefore starting chromatic dispersion measurement, a reference fiber is tested to measure the delay and kept in the memory of the system. Such kind of chromatic dispersion measurements are done by using multi-wavelength sources or multiple sources of different wavelengths.
There are chromatic dispersion measurement methods that use the group delay as a function of wavelength and the chromatic dispersion and dispersion slope are deduced from the derivatives with respect to wavelength of this data.Ĭhromatic dispersion of graded-index multimode and step index single mode fiber is obtained by measuring fiber group delays in the time domain. IEC 6 use differential phase shift method for the measurement of chromatic dispersion. These methods measure the composite optical fiber material and waveguide dispersion. Chromatic dispersion can also be measured in the frequency domain using EIA/TIA-455-169 and EIA/TIA-455-175. Differential group delay is the cause for pulse broadening and pulse broadening is called dispersion.Ĭhromatic dispersion is measured according to EIA/TIA-455-168. This delay difference is called the differential group delay per unit length. Since the different colors of light have different velocities, some colors arrive at the far end of the fiber faster than others. Dispersion happens to the beam of light when different colors of light travel through the fiber at different speeds. Different colors travel with different velocities as they differ in wavelength even though the difference is small. For a beam of light there are always a spectrum starting from violet color to the red color. Chromatic dispersion or intra-modal dispersion happens in both single mode and multimode optical fibers.Ĭhromatic dispersion is a wavelength dependant parameter. Dispersion is the broadening of pulse width after travelling through the fiber. Dispersion is a natural phenomenon which happens to light while it travels through a medium. Dispersion compensation fibers are used to nullify the effect of dispersion in a fiber optic link. Dispersion broadens the signal pulse and it becomes messy after travelling some distance. Dispersion is one of the parameter that decide the span of optical fiber link before the optical signal is required to be recovered to its original form. Chromatic Dispersion in Single Mode Optical Fiber and Test Methodsĭispersion is a villain in Optical transmission.
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