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What is Backscatter coefficient K?

What is  Backscatter coefficient K? : You must have read about the scattering of optical fiber cable, but in this article specially I shall discuss about the backscatter coefficient. Some friends have also sent me a request to provide information about backscatter coefficient. First of all, know what is backscatter? Amount of some  light is scattered back in the opposite direction of the pulse and is called a backscattered signal.

Scattering loss in optical fiber cables depends on the wavelength. Scattering loss is the main mechanism of fibers operating in three windows (850/1310/1550 nm). Typically, a single fiber transmitting light at 1550 nm with a scattered coefficient 0.20 dB / km. It can be consider approx. 5% lose of the transmitted power over 1 km of fiber. Now I will discuss a little bit about the backscattering factor here.
What is Backscatter coefficient K?

What is Backscattering factor?

The backscattering factor is a ratio that can be said as that backscattering factor (S) is the ratio between the backscatter power and scattered power. S is usually proportional to the square of Numerical aperture.

Depending on the fiber scattering coefficient and the fiber backscattering factor (S), the backscatter coefficient (K) is the ratio of the backscattered power to the energy launched into the fiber.

It can be explain the value of the backscatter coefficient, normalized to a 1 ns
pulse duration, is mentioned as:
Backscattering formula

Backscattering depends on the launched power Po (Watt), the pulse-width
used △t (seconds), the backscattering coefficient K(s-1), the distance
D (meters) and the fiber attenuation (∝) in dB/km:
Now I am going to discuss Backscatter coefficient K. Friends using the OTDR device can understand that what is the importance of  Backscatter coefficient K.

Backscatter coefficient K

Keep in your mind that this value could not change by the user. The backscatter coefficient K denotes the OTDR the relative backscatter level of a given fiber. This is the coefficient entered the factory and usually the user will not change this parameter.

If you change the value of Backscatter Coefficient K this change will affect the reported value of reflectance and optical return loss. Although the assumption is made that the backscattered coefficient is consistent for the entire span, it is possible that there will be very slight variations from one fiber span to another.

This variation or this type of change can raise some other problems. It can cause measurement anomalies such as splices with negative loss values (or gainers).

Typical backscatter coefficients at 1 ns are:

For single mode fiber:  - 79 dB at1310 nm
                                      - 81 dB at 1550 nm
For multimode fiber:    - 70 dB at 850 nm
                                      - 75 dB at 1300 nm

Last Word

Friends, the Backscatter coefficient K can also be defined in the manner of science. But you all know that is dedicated only for telecom so according to the telecom itself, Backscatter coefficient K have been explained. This article " What is  Backscatter coefficient K? "  how you liked this tell me by commenting.

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