Views: 39 Author: Ada Ru Publish Time: 2021-10-28 Origin: Site
Anyone doing fiber optic cable construction will definitely come into contact with such equipment as optical power meter and OTDR (optical time domain reflectometer). Many users do not understand why the optical power meter needs to be used to test the optical loss after testing the OTDR? Does OTDR not have the function of testing fiber loss? And the main functions of these two devices are somewhat different? One is event analysis; the other is distance test and length data, which are different in use function. Let's take a closer look at it together.
The principle of its use is also different.The optical power meter can determine the total amount of loss or attenuation in the measured optical fiber link: at the end A of the fiber, a stable light source emits a signal formed by continuous light waves at a specific wavelength; at the other end B, the optical power meter detects and measures The power level of the signal.
The OTDR detects and analyzes the signals returned by Fresnel reflection and Rayleigh scattering.So there is a vivid analogy. The optical power meter test loss is like this: I sent 100 photons at the beginning of the link, and only received 20 photons at the end, of which 80 were lost, which is very real. The OTDR is not tested in this way. It also sends 100 photons at the beginning of the link, but it does not go to the opposite end to test it.
This involves a problem: the blind zone of OTDR. Anyone who does this knows that the length of the optical fiber is too short, such as less than 100 meters, and the OTDR is inaccurate. This is because the OTDR cannot detect or accurately locate the event points and fault points in the optical fiber link within a certain distance (or time) due to the influence of reflection when detecting the optical fiber link. The distance here is what we call the blind zone. When using OTDR for testing, because the inevitable OTDR blind zone will affect the test accuracy at the beginning and end, it will also be limited by its loss measurement accuracy and measurement range.
Therefore, in the international standard, it is recommended to use a light source optical power meter to test the optical link loss. It is the only method that can provide an accurate and accurate total loss of the optical fiber link under test.
However, OTDR measurement is essential for finding the location of fiber link failures and drawing long-distance link loss charts. When a link fails, it is not enough to know the loss value. We also need to know where the failure occurred. And repair it; in fact, this is also the reason why OTDR is so popular among outside engineering users.