為保證光傳輸信號距離遠、低損耗的應用特性，一條光纜線(xiàn)路必須滿(mǎn)足一定的物理環(huán)境條件。任何輕微的光纜彎曲形變或者輕度污染都會(huì )造成光信號的衰耗，甚至中斷通信。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. Due to the physical characteristics of the optical cable itself and the unevenness in the production process, the optical signals propagating through it 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 is too large, and the bending attenuation and compression attenuation of the optical cable are essentially caused by the deformation of the optical cable, which cannot meet the total reflection generation 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 compression or breakage is the most common fault in fiber optic cable failures. Due to external forces or natural disasters, the fiber optic cable may experience slight irregular bending or even breakage. When the breakage occurs inside the splice box or fiber optic cable, it cannot be detected from the outside. However, at the point of fiber optic cable 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 optic cable. 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: During the process of laying optical cables, fiber optic 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 optic cables with different core diameters are often laid using various flexible 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 joint contamination, tail fiber joint contamination, and fiber skipping moisture are the main causes of fiber optic 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 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.
