At what wavelength is the attenuation of multimode fiber higher?

The attenuation of multimode fiber is indeed higher at shorter wavelengths, particularly around 850 nm. This wavelength is commonly associated with light sources such as light-emitting diodes (LEDs) that are typically used in multimode systems.

At 850 nm, the intrinsic material properties of multimode fiber, such as scattering and absorption losses due to the fiber's polymer components, are more pronounced, leading to greater signal loss. As the wavelength increases to 1300 nm and 1550 nm, the attenuation tends to decrease significantly in multimode fibers due to improved performance characteristics at those wavelengths. While 1300 nm can also experience some attenuation, it is generally lower compared to 850 nm.

The choice of 500 nm is not typically relevant in standard multimode fiber applications, as this wavelength is outside the common operating ranges for such systems and doesn't reflect the attenuation characteristics generally associated with multimode fibers.