In optical fiber transmission, improper operation can easily lead to transmission loss. This article will analyze five common causes of loss, providing a reference before optical fiber connection operations.
1. Excessive bending of optical fiber
Optical fibers possess a certain degree of flexibility, but when bent to a certain extent, they can alter the propagation path of light, allowing a portion of the light energy to penetrate into the cladding or pass through it as radiation modes, resulting in leakage and loss, thereby generating bending loss. When the bending radius is too small, the loss caused by bending becomes notably pronounced. Generally, it is recommended that the dynamic bending radius should not be less than 20 times the outer diameter of the optical cable, and the static bending radius should not be less than 15 times the outer diameter of the optical cable.
2. Poor optical cable splicing
In optical fiber cabling, fusion splicing technology is a crucial step in merging two optical fibers into one. Since it involves splicing the glass fibers at the core layer, it is necessary to strip the outer layer and filler of the optical fibers to be fused during the splicing process. Improper operation or harsh construction environments can easily cause contamination of the glass fibers, leading to impurities, density changes, and even bubbles during the splicing process, which can affect communication quality.
3. Optical cable is pressed or broken
When optical fibers are subjected to uneven stress, such as pressure or temperature changes in coated fibers, small irregular bends or even fractures may occur along the fiber axis. This results in the transformation of guided modes into radiative modes, leading to optical energy loss. Especially when the fracture occurs inside the optical cable, the fault cannot be detected from the outside. However, due to the sudden change in refractive index at the fiber fracture, reflection loss may even occur, significantly compromising the signal quality of the fiber.
4. Connector contamination
Contamination of fiber optic connectors and moisture on pigtails are among the primary causes of optical cable communication failures. Studies have found that 80% of users and 98% of suppliers have experienced failures due to unclean fiber optic termination surfaces, while another 72% of users and 88% of suppliers have encountered issues caused by poor polishing. This statistic is significantly higher than fiber optic failures caused by other reasons. Dust falling, finger contact, and wear and tear from insertion and extraction can easily contaminate fiber optic connectors, and such contamination can affect optical transmission.
5. Mismatch in core diameter
Movable connections are also a commonly used cabling method in fiber optic cabling, such as flange connections. This method is flexible, simple, convenient, and reliable, and is often used in computer network cabling within buildings. The loss of a movable connection is generally around 1dB, but if the fiber end faces are not clean, the joint is not tight, or the core diameters do not match when making a movable connection, the joint loss will increase significantly. Core diameter mismatch not only refers to the mixed use of single-mode and multimode fibers, but also includes the mixed use of multimode fibers with diameters of 62.5 and 50.
