Anyone who does optical cable construction will often come into contact with optical power meter and OTDR (optical time domain reflectometer). Multi-users do not understand why it is necessary to use an optical power meter to test the optical loss after testing the OTDR. Doesn't OTDR have the function of testing fiber loss? And there are some differences in the main functions of the two devices? One is event analysis; the other is distance test and length data, which is different in function. Let's take a closer look at it.

The principle of its use is also different.

The optical power meter can determine the total amount of loss or attenuation in the tested optical fiber link: at one end of the optical fiber, the stable light source emits a signal formed by continuous light waves at a specific wavelength; at the other end, the optical power meter detects and measures the power level of the signal.

On the other hand, OTDR detects and analyzes the signals returned by Fresnel reflection and Rayleigh scattering.

So there is a very vivid analogy, the optical power meter test loss is like this: I sent 100 photons at the beginning of the link, received only 20 photons at the terminal, of which 80 were lost, which is very real. OTDR, on the other hand, is not tested in this way. It also sends 100 photons at the beginning of the link, but it does not test at the opposite end, but by testing the photons scattered or reflected back to get the results.

This involves a problem: the blind spot of OTDR. Those who do this all know that the length of the optical fiber is too short, for example, less than 100m, the OTDR is impossible to measure. This is because when OTDR detects the optical fiber link, due to the influence of reflection, it can not detect or accurately locate the event point and fault point in the optical fiber link within a certain distance (or time). The distance here is what we call a blind spot. When testing with OTDR, the inevitable OTDR blind area will not only affect the test accuracy at the starting point and non-end, but also be limited by its loss measurement accuracy and measurement range.

Therefore, it is recommended to use the light source optical power meter to test the optical link loss in the international standard, which can provide the precision of the tested optical fiber link. It is true that the total loss is the only one. One way.