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Introduction to G.654E Optical Fiber

At present, the optical fiber network of the “East Counting West” project carries out large-span transmission and transfer in the spatial dimension, which undoubtedly puts forward higher requirements for the security, reliability, networking, bandwidth and other performance of the optical fiber network.

There are three main sources of optical fiber loss: absorption loss, bending loss, and scattering loss. Absorption loss is divided into intrinsic absorption and impurity absorption. Thanks to the continuous improvement of optical fiber manufacturing technology, absorption loss has been reduced to an extremely low level, close to the theoretical limit, and there is little room for optimization. Bending loss is the additional loss caused by the bending of the fiber. It can be divided into macrobending loss and microbending loss. Macrobending loss is related to the excess length of the cabled fiber, which can be improved through design and process. Microbending loss can be improved by coating. Scattering loss is caused by Rayleigh scattering caused by the fluctuation of density factor and concentration factor of silica fiber, which accounts for 50%~85% of the existing fiber loss. Therefore, reducing Rayleigh scattering is the most important way to reduce fiber loss. Effective ways, the main methods include reducing the concentration of doping particles, improving viscosity matching and optimizing drawing tension. Pure silica core fiber can effectively reduce the concentration of doped particles and Rayleigh scattering without doping germanium dioxide (GeO2) in the core layer, thereby reducing fiber loss, and is currently the preferred technical path for preparing ultra-low loss fibers.

In addition to the influence of Rayleigh scattering on optical fiber transmission, the nonlinear effect will also affect the capacity and relay distance of the transmission system. In order to realize ultra-long-distance optical transmission, higher optical power needs to be injected into the optical fiber. However, increasing the injected optical power will strengthen the nonlinear effect without increasing the effective area of the optical fiber to guide the light, thereby affecting the transmission performance of the optical fiber. Therefore, while reducing fiber loss, it is also necessary to consider reducing the impact of fiber nonlinear effects on transmission performance, which requires increasing the effective area of the fiber, that is, preparing a large effective area fiber. Increasing the diameter of the core part is the most direct way to increase the effective area of the fiber, but the increase in the core diameter will deteriorate the bending loss performance of the fiber. In order to overcome this shortcoming, the researchers proposed a solution of depressed cladding, through the ingenious design of the refractive index profile of each core layer of the optical fiber, the bending loss of the optical fiber can be effectively reduced. According to the current standard classification, the optical fiber with both ultra-low loss characteristics and large effective area is called ultra-low loss large effective area G.654 optical fiber.