The 400G era is coming, and new optical fibers may be the best partner

With the continuous emergence of high-definition and ultra-high-definition services such as big video and 4k/8K, the demand for traffic has also exploded. To this end, operators and equipment manufacturers began to consider higher bandwidth and introduced the concept of 400G. At the same time, industry experts also said that my country's transmission network will usher in the 400G era. However, problems also arise. How to meet the technical conditions of 400G is the key. After continuous research by experts, it was finally decided to use new optical fibers.

At present, increasing the effective area of ​​optical fiber and reducing the optical fiber attenuation coefficient are the main means to improve system transmission performance and extend system transmission distance, and are also an important direction for the development of new optical fiber technology.

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The ITU-T G.654E optical fiber standard for terrestrial transmission systems was released in September 2016. After that, G.654E optical fiber attracted the attention of operators and optical communication equipment manufacturers. The CCSA industry standard led by China Unicom has been developed and is about to be released. The industry standard points out that there are two types of optical fiber attenuation coefficients. One is low loss, which is below 0.190dB/Km, close to the low-loss G.652D optical fiber; the other is ultra-low loss, using pure silicon fiber core or reducing the amount of germanium doping in the fiber core, and the attenuation coefficient can be below 0.1700dB/Km. At present, suppliers who can provide G.654 optical fiber include Corning, Changfei, Fiberhome, Zhongtian, Hengtong, Sumitomo, etc.

China Unicom has been testing the 400G transmission capacity of new optical fibers, and has carried out pilot projects in the eastern region, mainly conducting multi-vendor 400G system tests to verify the improvement of 400G transmission capacity of new optical fibers. At the same time, pilot projects in the western region have been carried out to verify the long-term performance stability in complex environments.

At the "New Optical Fiber and 400G Technology and Application Forum" held on June 7, Shen Shikui from China Unicom Network Technology Research Institute said that the same optical cable G.652D and G.654 optical fibers were in different loose tubes, using the same cabling and construction laying process. After a large number of test data comparisons by China Unicom, it was verified that the verification work of the aerial and pipeline optical cable test sections ensured that the new optical fiber could meet the laying and working environment requirements in most parts of China and had environmental universality. At the same time, the existing network splicing performance of G.654E optical fiber was also detected, which was basically the same as G.652, but it was recommended to use G.652 pigtails and jumpers to terminate G.654 optical cables on the ODF rack.

The improvement of optical power is also extremely critical. China Unicom data shows that the larger effective area of ​​G.654 optical fiber will also increase the improvement of optical power. The larger the effective area, the higher the maximum optical power entering the fiber; compared with G.652 optical fiber, the maximum optical power entering the fiber of G.654 optical fiber has at least 1.5-2.0 dB optical power improvement.

In Shen Shikui's opinion, G.654E optical fiber can be applied to complex terrestrial working environments, including overhead and pipeline radiation, under the existing commonly used optical cable structure.

For G.654 optical fiber, Shen Shikui suggested that the maximum effective area should be from 110μm2 to 130μm2, which needs to be further normalized and is recommended to be 125μm2 to 130μm2; based on the same optical cable manufacturing process as G.652, the attenuation and macrobending performance of G.654 optical fiber remains good. In addition, up to now, the long-term operation performance of G.654 optical fiber in winter is good. At the same time, the self-splicing performance of G.654 optical fiber is similar to that of G.652D optical fiber. Shen Shikui also said that after a lot of data, it has been proved that G.654E/G.652D hybrid optical cable is a more suitable optical cable structure choice for trunk applications.

Compared with 400G system, Shen Shikui concluded that its best fiber input is G.654 fiber, because the optical power of G.654 fiber is at least 1.5-2.0 dB higher than that of G.652D fiber, which can significantly improve the transmission capacity of 400G system. At the same time, he also made suggestions to manufacturers, saying that the adaptability of 400G systems of different manufacturers to new optical fibers is different, and some manufacturers need to improve.

400G is an important stage in the era beyond 100G. It plays a role of connecting the past and the future. How to build a high-speed optical fiber and cable network for the future is not only to meet 400G, but also to focus on the future of Tbit/s, because the optical fiber and cable network has a long life span.