An optical fiber with a step-index profile has a core with a diameter of 4 µm. The core and shell indexes are approximately equal (¹~¹₂), and the difference between them, An=n-₂, is such that An/n, = 2%. Find the minimum wavelength inside the core, ^=¹/¹, for which the fiber operates as a single mode.

An optical fiber with a step-index profile has a core with a diameter of 4 µm. The core and shell indexes are approximately equal (¹~¹₂), and the difference between them, An=n-₂, is such that An/n, = 2%. Find the minimum wavelength inside the core, ^=¹/¹, for which the fiber operates as a single mode.