When testing the optical fiber jumper with a light-passing pen, the problem of light leakage of the jumper is often encountered, but the light leakage jumper is re-tested, and its parameters are all qualified. This problem is particularly evident in single-mode fibers.
Single-mode jumper test results comparison
When the single-mode fiber jumper is light, it can be seen that the jumper has some light leakage on the side close to the light-transmitting pen. Light leaks are especially noticeable in darker environments.
Serious light leakage can also occur where the fiber is bent too much. Although there will be losses, the fiber can still pass light.
If the jumper is broken in the middle, the light leakage will be very serious, and the optical fiber will not be able to pass the light.
Comparison of test results of multimode patch cords
When the multimode fiber jumper is light, under normal lighting conditions, the multimode fiber jumper does not see obvious light leakage. Only in a darker environment, you can see that the multimode fiber jumper has insignificant light leakage.
Combined with the official instructions of the optical fiber and cable company, let's analyze the reasons for light leakage:
1. The red light emitted by the light-passing pen is visible light with a wavelength of 650 nm, while the cut-off wavelength of G.652 fiber is generally 1260 nm. Since the wavelength of red light is smaller than the cut-off wavelength of single-mode fiber, red light is multi-mode in the fiber. form transmission.
2. The red light emitted by the light-passing pen is a surface light source. The diameter of the surface light source is larger than the inner diameter of the optical fiber. When the light is clear, a large amount of light will be transmitted in the optical fiber cladding, and the high-order mode part of the red light is easily transmitted from the optical fiber.
3. Where the fiber is bent too much, the distortion of the cross-section may destroy the conditions for total reflection, so refracted light will be transmitted, but the remaining reflected light will continue to propagate in the fiber to the end after passing through the bend .
Therefore, when the optical fiber jumper is tested by the light-passing pen, it is normal for the light-leakage phenomenon of the jumper to light-through, and it is impossible to judge whether the jumper itself has quality problems. In order to accurately judge whether the fiber patch cord has quality problems, insertion loss and return loss tests are required.
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