I have been researching the effect of wavelength on macro-bend losses for my extended essay (a 4000 word paper on a subject of your choice, high school level) on fiber optic cables. I asked this question already about two months ago, and this was the reply:
An intuitive explanation for why this occurs is as follows. If you think of the wavelength of the light as the limiting length scale for it to resolve changes in the guiding structure then as the wavelength increases resolution decreases. Since the resolution has decreased the bend in the guide appears to become more abrupt and causes a larger perturbation in the propagating mode resulting in more radiated power from the optical fiber.
Consider how the radius of curvature (R) would appear to change as the wavelength increases. To do this we can normalize (R) to the resolving ability of the light, the wavelength (λ). Looking at R/λ it is apparent that this normalized version of the radius of curvature becomes smaller at larger wavelengths.
I had trouble understanding the explanation. If anyone would be so kind as to explain it to me further I would greatly appreciate it. Thank you :).