G.652 optical fiber is the most widely used optical fiber. At present, in addition to the optical fiber to the home (FTTH) optical fiber into the home, the long-distance, urban optical fiber is almost all of the g. 652 optical fiber.

According to the energy distribution of light, the optical signal in single-mode fiber is not only transmitted in the core, but also in the cladding.In order to describe the concentration of light energy in single-mode optical fiber, the maximum distance between two points in each point of the optical intensity reduced to 1/(e^2) of the maximum light intensity at the axis is defined as the mode field diameter, as shown in the picture.

Obviously, the diameter of the mode field can better reflect the transmission characteristics of the single-mode fiber, so the single-mode fiber does not mention the core diameter at all.The diameter of the mode field is an important parameter of the single-mode fiber.

One of the most important factors affecting the transmission distance of optical fiber is attenuation.The decay coefficient of conventional single-mode fiber is shown in figure 5.As can be seen from the figure, the decline loss of optical fiber at 1310nm and 1550nm is small, and 1310nm and 1550nm have also become the most commonly used two wavelength Windows of single-mode optical fiber.

G. 654 optical fiber

G.654 optical fiber is mainly used in sea-cable communication system. In order to meet the needs of long-distance and large capacity of sea-cable communication, g. 654 optical fiber is mainly improved in two aspects.

(1) reduce the loss of optical fiber;From 0.22dB/km of G.652 to 0.19dB/km (standard value).

(2) increase the mode field diameter of the optical fiber;The larger the diameter of the optical fiber's mode field is, the smaller the energy density of the cross section of the optical fiber will be, so as to improve the nonlinear effect of the optical fiber and improve the signal-to-noise ratio of the optical fiber communication system.

The easiest way to increase the diameter of the fiber field is to increase the diameter of the fiber core.It is not difficult to understand the name of g. 654 fiber: cut-off wavelength shift fiber (the cut-off wavelength of g. 654 fiber is about 1530nm, other single-mode fiber is generally 1260nm).Of course, the core diameter should not be increased too much, otherwise even the wavelength range of 1550nm can not be used, a multimode fiber.

It is reported that the low-loss g.654 optical fiber has been mainly used in the sea cable communication system, divided into four subclasses of ABCD. In July 2013, the industry began to discuss the g.654.e class applicable to the land, and started the standard formulation.At the itu-tsg15 plenary meeting in September 2016, the revision of the g.654 standard was completed and adopted, marking the formal completion of the standardization of the g.654.e optical fiber used in land-speed transmission systems.