To ensure the application characteristics of long-distance and low loss optical transmission signals, a fiber optic cable line must meet certain physical environmental conditions. Any slight bending deformation or contamination of optical cables can cause attenuation of optical signals and even interrupt communication.
1. Fiber optic cable routing line length
Due to the physical characteristics of optical cables and the unevenness in the production process, the optical signals propagated in them are constantly diffusing and being absorbed. When the fiber optic cable link is too long, it will cause the overall attenuation of the optical signal of the entire link to exceed the requirements of network planning. If the attenuation of the optical signal is too large, it will reduce the communication effect.
2. The bending angle of the optical cable placement is too large
The bending attenuation and compression attenuation of optical cables are essentially caused by the deformation of optical cables, which leads to the inability to satisfy total reflection during the optical transmission process. Fiber optic cables have a certain degree of bendability, but when the fiber optic cable is bent to a certain angle, it will cause a change in the propagation direction of the optical signal in the cable, resulting in bending attenuation. This requires special attention to leaving sufficient angles for wiring during construction.
3. Fiber optic cable is compressed or broken
This is the most common fault in optical cable failures. Due to external forces or natural disasters, optical fibers may experience small irregular bends or even breakage. When the breakage occurs inside the splice box or optical cable, it cannot be detected from the outside. However, at the point of fiber breakage, there will be a change in refractive index, and even reflection loss, which will deteriorate the quality of the transmitted signal of the fiber. At this point, use an OTDR optical cable tester to detect the reflection peak and locate the internal bending attenuation or fracture point of the optical fiber.
4. Fiber optic joint construction fusion failure
In the process of laying optical cables, fiber fusion splicers are often used to fuse two sections of optical fibers into one. Due to the fusion splicing of the glass fiber in the core layer of the optical cable, it is necessary to use the fusion splicer correctly according to the type of optical cable during the construction site fusion splicing process. Due to the operation not complying with the construction specifications and changes in the construction environment, it is easy for the optical fiber to be contaminated with dirt, resulting in impurities mixed in during the fusion splicing process and causing a decrease in the communication quality of the entire link.
5. Fiber core wire diameter varies
Fiber optic cable laying often uses various active connection methods, such as flange connections, which are commonly used in computer network laying in buildings. Active connections generally have low losses, but if the end face of the optical fiber or flange is not clean during active connections, the diameter of the core optical fiber is different, and the joint is not tight, it will greatly increase the joint loss. Through OTDR or dual end power testing, core diameter mismatch faults can be detected. It should be noted that single-mode fiber and multi-mode fiber have completely different transmission modes, wavelengths, and attenuation modes except for the diameter of the core fiber, so they cannot be mixed.
6. Fiber optic connector contamination
Tail fiber joint contamination and fiber skipping moisture are the main causes of optical cable failures. Especially in indoor networks, there are many short fibers and various network switching devices, and the insertion and removal of fiber optic connectors, flange replacement, and switching are very frequent. During the operation process, excessive dust, insertion and extraction losses, and finger touch can easily make the fiber optic connector dirty, resulting in the inability to adjust the optical path or excessive light attenuation. Alcohol swabs should be used for cleaning.
7. Poor polishing at the joint
Poor polishing of joints is also one of the main faults in fiber optic links. The ideal fiber optic cross-section does not exist in the real physical environment, and there are some undulations or slopes. When the light in the optical cable link encounters such a cross-section, the irregular joint surface causes diffuse scattering and reflection of light, which greatly increases the attenuation of light. On the curve of the OTDR tester, the attenuation zone of the poorly polished section is much larger than that of the normal end face.
Frequently asked questions
Does the optical port of the switch need to be turned on?
Unconfigured network management switches, except for the optical port of the optical multiplexing port that needs to be turned on, all other switches have plug and play optical ports that do not require configuration to be turned on.
What should I do if the light port doesn’t light up?
1. Check if the device’s optical port and the speed of the optical module used match.
2. Check if the optical modules used at both ends are paired.
3. Check if the fiber used matches the optical module. Single mode optical module uses single-mode fiber, multi-mode optical module uses multi-mode fiber, dual fiber optical module, and the two fibers at one end are swapped left and right.
4. Check if the fiber optic link is OK and use short fibers for testing.
5. The ceramic core of the optical module, tail fiber, or optical module is too dirty.
6. The optical module or tail fiber is damaged, or the fiber fusion is not good.
Fiber optic related faults are the most noticeable and frequent faults during debugging or maintenance. Therefore, an instrument is needed to check whether the fiber optic light emission is normal. This requires the use of fiber optic fault diagnosis tools, such as optical power meters and red light pens. Optical power meters are used to test fiber optic transmission losses and are very user-friendly, simple, and easy to use, making them the best choice for troubleshooting fiber optic faults. The red light pen is used to find which fiber optic disc the fiber optic is on. These two essential tools for troubleshooting fiber optic faults, but now the optical power meter and red light pen are combined into one instrument, which is more convenient.
Post time: May-29-2025