What is the expected attenuation for typical single-mode fiber?

The expected attenuation for typical single-mode fiber is approximately 0.2 dB/km. This value represents the loss of signal strength as light travels through the fiber, which can be influenced by several factors, such as the fiber's material, wavelength of the light being used, and manufacturing quality.

Single-mode fibers are designed to allow light to travel straight down the fiber without bouncing around, which minimizes losses and allows for longer transmission distances. The 0.2 dB/km figure reflects a typical performance range for high-quality single-mode fibers operating at wavelengths like 1310 nm and 1550 nm, where the attenuation is at its lowest.

In contrast, other values mentioned, such as 0.1 dB/km, are generally associated with the very best fibers available under ideal conditions, but not typical for standard use. The values of 0.3 dB/km and 0.4 dB/km may indicate fibers that are either less ideal or operating at wavelengths where attenuation is higher, such as in the presence of impurities or additional factors affecting performance. The 0.2 dB/km is thus a benchmark that reflects common practice and performance in the industry for efficient data transmission.