I want to ask about OTDR.
1. How can OTDR measure the length of the fiber optic cable?
2. Can someone tell me specifically about OTDR, especially how can it makes the graphic? What kind of process that it does inside OTDR, after receiving backscatter from the fiber optic cable?
3. For the question number 2, I mean, OTDR receives backscatter from the fiber optic cable and it shows them to a graphic, how can it shows the graphic? What kind of process that it does?
You can think of an OTDR as sonar for optical networks. It sends a pulse of light out at a specific wavelength, portions of which reflect back to the source at varying power levels. The graph that the OTDR produces is a plot of Power Level (Y Axis) and Distance (X Axis). Distance is a function of power, wavelength, optical fiber type, mode size, etc.
At it's core an OTDR is a laser with timed output and a optical transducer that measures power levels.
It correlates time with travelling distance by considering the speed of light inside the silica fiber
OTDR is essentially a one dimensional LIDAR and access is only needed to one end of fiber. OTDR sends a short pulse of signal at specific wavelength along the Fiber, then measure the backscratching light as a function of time after initial launch. The distance between two Fresnel reflection (end reflection) will be your length of fiber, and other losses can be identified as a function of time such as splice, couplers, defects or other losses..
@Joshua & Muhammad : I want to know the process inside the OTDR, if you say that OTDR receives the backscatter of lights, the power of the lights should be reduce twice as it travels 2 ways, go and back, and the OTDR should show the graphic for that 2 ways. I want to know the process inside the OTDR so that it can only show 1 graphic. If it uses microcontroller, microchip, microprocessor, or any kind of processing device, what does that processing device do? Sampling? Filtering? Or what kind of process? :(
@Alexandros : Thx for your answer.. :)
The OTDR sends multiple pulses inside the fiber and performs statistical processing. At the receiver side you have an avalanche photodiode (APD), an amplifier, an Analog-to-Digital converter and the microprocessor which is actually an integrator (averaging) and the crt. A propagating pulse that is back-scattered will not arrive at the same time as the part that travelled all the way and back. If you are reffering to the actual continuous loss than that is simply calculated by being half than that measured
I thought that OTDR only sends 1 pulse to calculate the fiber characteristics.
(www.anritsu.com/en-GB/Media.../Anritsu-understanding-otdrs.pdf)
What does the Microprocessor do inside the OTDR? If you say that it's an integrator, what does it do?
Can you please tell me how does the coupler/splitter inside the OTDR works?
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