At present, domestic and foreign operators have carried out corresponding 400G technology research and testing. However, mainstream 400G technology has the problem of limited powerless relay distance. In order to solve this problem, it has both large effective area and low loss characteristics. New optical fiber technology has become a hot spot for research and application in the industry.
ITU-T has been discussing this G.654 optical fiber (G.654.E) suitable for terrestrial transmission systems since July 2013, because it can maintain the same characteristics as existing single-mode optical fiber for terrestrial applications. Under the premise of consistent basic performance, the effective area of the optical fiber is increased and the attenuation coefficient of the optical fiber is reduced, thereby improving the 400G transmission performance.
The previous version of the ITU-TG.654 standard was released in 2012 and included four subcategories: A, B, C and D. The main difference lies in the MFD range and macro-bending performance.
In the latest revision of G.654, subcategory E has been added for land high-speed coherent transmission system applications.
At the ITU-TSG15 plenary meeting in September 2016, the G.654 standard revision was completed and approved, marking the formal completion of the standardization work for G.654.E optical fiber used in land high-speed transmission systems.
This meeting mainly stipulated the mode field diameter (MFD) and effective area, macrobending loss characteristics, dispersion parameters and attenuation coefficient of G.654.E optical fiber.
The MFD range of G.654.E optical fiber in the 1550nm area is 11.5um~12.5um, and the corresponding effective area range is from 110um2 to 130um2. Compared with the existing G.654.B subcategory ( 9.5um ~ 13um), narrowing the MFD nominal value range, but the tolerance remains ±0.7um.
At present, the G.654 optical fiber indicators provided by major optical fiber manufacturers are distributed within the scope of this standard. However, starting from the deployment of existing network applications, the MFD nominal value and tolerance range are too broad, which may cause problems in the connection. Problems such as large losses are not conducive to application promotion. In the future, it is necessary to further reduce the standard indicators after the G.654.E optical fiber production and manufacturing process gradually matures and improves.
The working environment of terrestrial applications is complex, with complex and changeable temperatures and climates, and the external environment has a greater impact on optical fiber performance.
Therefore, the bending performance of G.654.E optical fiber is particularly important, and G.654 optical fiber that is far superior to submarine applications is required.
Therefore, for the G.654.E subcategory, the standard requires that when making 100 turns of a 30mm radius ring, the maximum additional attenuation at 1625nm should not exceed 0.1dB, which is far better.For G.654.B subcategory (0.5dB) and G.654.D subcategory (2dB), it achieves exactly the same bending performance as G.652.D to eliminate the possible degradation of bending performance in land applications caused by the increase in effective area. concerns.
In the pilot test of China Unicom's live network, based on the test method of ITU specifications, the macro-bend loss at 1550nm and 1625nm was tested respectively, and it was found that the additional attenuation was basically less than 0.1dB, of which 81.8% was less than 0.05dB. .
Since the main operating wavelength range of G.654 optical fiber is between 1530nm and 1625nm, the range of dispersion and dispersion slope is standardized for this wavelength range.
At 1550nm, the maximum value of dispersion Dmax is 23ps/(nm·km), the minimum value of Dmin is 18ps/(nm·km), and the maximum value of dispersion slope Smax is 0.07ps/(nm2·km) ), the minimum Smin is 0.05ps/(nm2·km).
The standard does not specify the optical fiber attenuation coefficient, but only provides the optical cable attenuation parameter, which is required to be no higher than 0.23dB/km at 1550nm.
In the standard Appendix I terrestrial transmission system optical fiber link indicators, the link attenuation coefficient is not given.
However, the text clearly states that in the 1550nm region, an optical fiber attenuation coefficient of 0.15dB/km to 0.19dB/km can be achieved, with the lowest attenuation coefficient depending on the manufacturing process, optical fiber materials and design, and optical cable design.
According to the current test results of relevant operators, the maximum attenuation coefficient of the optical cable disk after being cabled is 0.202dB/km, of which 97.7% are less than 0.19dB/km, and some can reach 0.16dB/km.
G.654.E has the same macrobending and polarization mode dispersion indicators, the dispersion is slightly larger than G.652.D, the effective area increases by 40% to 60%, and the attenuation coefficient trend is the same, both in Gradually reduce.
By increasing the effective area, the nonlinear effect of the optical fiber is further reduced, the optimal optical power entering the fiber is increased, and the transmission distance is extended.
The increase in dispersion parameters will not increase the system burden in high dispersion tolerance coherent optical communication transmission systems.
