G.652 optical fiber is the most widely used optical fiber. At present, except for fiber-to-the-home (FTTH) home optical cables, almost all optical fibers used in long-distance and metropolitan areas are G.652 optical fibers.
From the perspective of light energy distribution, the optical signal in the 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 a single-mode fiber, the maximum distance between two points in each point where the light intensity in the fiber is reduced to 1/(e^2) of the maximum light intensity at the axis is defined as the mode field diameter.
Obviously, the mode field diameter can better reflect the transmission characteristics of the single-mode fiber, so the single-mode fiber simply does not mention the core diameter. Mode field diameter is an important parameter of single-mode fiber, and its size increases with wavelength.
One of the most important factors affecting the transmission distance of optical fibers is attenuation, and the attenuation coefficient of optical fibers is wavelength-dependent. The attenuation of optical fiber at 1310nm and 1550nm is small, and 1310nm and 1550nm have also become the two most commonly used wavelength windows for single-mode fiber.
G.654 optical fiber is mainly used in submarine cable communication systems. In order to meet the needs of long-distance and large-capacity submarine cable communication, G.654 optical fiber has mainly been 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 mode field diameter of the optical fiber, the smaller the energy density through the optical fiber cross-section, thereby improving the nonlinear effect of the optical fiber and improving the signal-to-noise ratio of the optical fiber communication system.
The easiest way to increase the fiber mode field diameter is to increase the core diameter. After the core diameter increases, the cutoff wavelength of the fiber will not increase. It is not difficult to understand that the name of G.654 fiber is: cut-off wavelength shifted fiber (the cut-off wavelength of G.654 fiber is about 1530nm, and other single-mode fibers are generally 1260nm). Of course, the core diameter cannot be increased too much, otherwise, even the wavelength range of 1550nm cannot be used, and it becomes a multimode fiber.
Post time: Apr-27-2022