A dispersion-shifted fiber (DSF) refers to a type of optical fiber designed to minimize the effects of chromatic dispersion, which is the phenomenon where different wavelengths of light travel at different speeds, causing them to spread out over long distances. Dispersion-shifted fibers are specifically engineered to mitigate the impact of dispersion in certain wavelength regions, particularly in the vicinity of the third telecommunications window (around 1550 nm).
To address the challenges posed by chromatic dispersion, two types of dispersion-shifted fibers were developed:
Dispersion-shifted single-mode fiber (DSF): This type of fiber is designed to shift the zero-dispersion wavelength (the wavelength where the fiber has zero chromatic dispersion) away from the commonly used 1310 nm wavelength to a longer wavelength, typically around 1550 nm. By doing so, DSF reduces the dispersion in the 1550 nm region, which is advantageous for long-distance telecommunications.
Nonzero dispersion-shifted fiber (NZ-DSF): NZ-DSF is another type of dispersion-shifted fiber that intentionally introduces a small amount of dispersion at the 1550 nm wavelength. This helps balance the trade-off between minimizing dispersion and avoiding nonlinear effects that can occur in fibers with zero dispersion at 1550 nm.
The use of dispersion-shifted fibers, especially in the 1550 nm wavelength range, is crucial for long-haul optical communication systems. This wavelength region is of particular interest because it aligns with the minimum loss window of standard single-mode optical fibers and allows for efficient amplification using erbium-doped fiber amplifiers (EDFAs).