Of an optical fiber, the Transmission Window at which the Attenuation coefficient is at or near the theoretical (quantum-limited) minimum.

Note 1: IF the losses from various mechanisms are plotted on a single graph as a function of wavelength, the minimum-loss window occurs in the vicinity of the Wavelength at which the Rayleigh-scattering attenuation curve and the infrared-phonon-absorption curve intersect. Note 2: For silica-based fibers, the minimum-loss window occurs at approximately 1.55 m.