method one:
In the engineering test environment where accuracy is not high, method 1 is usually used to test the optical fiber link. In order to eliminate the attenuation of the test jumper, reset to zero before the test, and then connect the test jumper to the fiber link under test to test the attenuation value of the fiber link under test.
In the zero setting of method 1, in addition to two test jumpers, it also includes a coupler for connection, so the actual measured attenuation value is equal to the attenuation of the fiber under test itself and another coupler for connection.
To sum up, the first method is only applicable to the case where the distance of the optical fiber link is long. When the distance of the optical fiber link is short, the attenuation of the optical fiber coupler that is deducted in the zero setting is relatively large and cannot be ignored. Therefore, method 1 is not recommended.
Method Two:
Since the accuracy of test method 1 is not high, it has been adjusted and improved. The improved method is referred to as method 2, and the details are as follows:
First set the classification according to method 1, and then connect the tested fiber and the compensation jumper to test according to Figure 3. At this time, the measured attenuation values include ① the attenuation of the tested fiber and ② the attenuation of the two tested connectors , ③ Compensate the attenuation of the optical fiber. Due to the short length of the compensation fiber, the attenuation of the compensation fiber is negligible relative to the attenuation of the entire fiber link. Compared with method 1, method 2 has higher accuracy for the test value of light attenuation.
Method three
In practice, there is a need to only test the optical attenuation of optical fiber jumpers, so we also designed method three, as follows:
First use the short fiber jumper to reset to zero, and then test the fiber jumper under test. This method needs to consider the matching between the connection port of the test equipment and the fiber port under test, and the accuracy is not high when testing short-distance fibers.
Method 4
The choice of method three will lead to excessive loss of the connection port of the test equipment, so the improved test method four is produced. This method is suitable for testing a large number of optical fibers, as follows:
First use the test jumper, return-to-zero coupler, and return-to-zero jumper to set the return-to-zero, and then connect to the fiber under test for testing.
Test Method 4 is also often used for Fibre Channel testing, which includes fibre links and fibre patch cords at both ends.
