In a light attenuator or its attenuating method, a nonlinear optical
material and an aperture section are placed respectively on a same optical
axis, between a receiving optical finder and a sending optical fiber. The
nonlinear optical material receives and refracts an input light outputted
from the receiving optical fiber. The aperture section has an aperture,
receives the light having passed through the nonlinear optical material,
and outputs constant output light to the sending optical fiber by only
allowing only a part of the light to be outputted from the aperture.
