Optical filter

摘要

In an optical filter formed with a grating whose refractive index fluctuates along an optical axis of an optical waveguide so as to reflect light in a predetermined wavelength band, assuming that a position in the grating area is defined by a positional coordinate value z which is standardized by - pi to pi in a light propagating direction, an amplitude DELTA n of refractive index changing width in z satisfies: <MATH> by use of predetermined parameters x1 and x2 and proportional constants k1 and k2, DELTA n monotonously increasing or decreasing depending on whether the expression - pi ≤ z ≤ 0 or 0 ≤ z ≤ pi is satisfied, respectively. <IMAGE>