Dispersion shifted fiber
When the operating wavelength of a single-mode fiber is 1.3Pm, the mode field diameter is about 9Pm, and its transmission loss is about 0.3dB/km. At this time, the zero-dispersion wavelength is exactly at 1.3pm. Among the quartz optical fibers, the transmission loss in the 1.55pm section is the smallest (about 0.2dB/km) from the raw material. Since the practical erbium-doped fiber amplifier (EDFA) works in the 1.55pm band, if zero dispersion can be achieved in this band, it will be more conducive to the application of long-distance transmission in the 1.55Pm band. Therefore, clever use of the composite offset characteristics of the dispersion of the quartz material in the fiber material and the dispersion of the core structure can make the original zero dispersion of the 1.3Pm section, and the shift to the 1.55pm section also constitutes the zero dispersion. Therefore, it is named Dispersion Shifted Fiber (DSF: DispersionShifted Fiber). The method of increasing structural dispersion is mainly to improve the refractive index distribution performance of the core. In the long-distance transmission of optical communication, zero fiber dispersion is important, but not the only one. Other properties include low loss, easy connection, cable formation or small changes in characteristics during work (including the effects of bending, stretching and environmental changes). DSF is designed to consider these factors comprehensively.
Dispersion Flat Fiber
Dispersion shifted fiber (DSF) is a single-mode fiber designed to have zero dispersion in the 1.55pm band. The dispersion flattened fiber (DFF: Dispersion Flattened Fiber) has a wide wavelength range from 1.3Pm to 1.55pm, which can be made very low, and the fiber that achieves almost zero dispersion is called DFF. Because DFF has to reduce the dispersion in the range of 1.3pm to 1.55pm. It is necessary to carry out a complicated design for the refractive index distribution of the optical fiber. However, this kind of fiber is very suitable for wavelength division multiplexing (WDM) lines. Because the process of DFF fiber is more complicated, the cost is more expensive. As output increases in the future, prices will also decrease.