METHOD FOR MANUFACTURING OPTICAL WAVEGUIDE TYPE DIFFRACTION GRATING ELEMENT, THE DIFFRACTION GRATING ELEMENT AND OPTICAL COMMUNICATION SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical waveguide type diffraction grating element capable of sufficiently suppressing influence due to the loss of light of a wavelength shorter than a reflected wavelengthλB. SOLUTION: The value of the reflected wavelengthλB is determined and the value of a backward higher order leakage mode coupling loss wavelengthλL is determined on the basis of respective signal light wavelengths and the wavelengthλB (S1). The ratio (βf(λL)/βh(λL)) of the propagation constantβf(λL) of a forward base mode in the wavelengthλL of an optical fiber to the propagation constantβh(λL) of a backward higher order leakage mode is found out on the basis of the values of respective wavelengthsλB,λL (S2). An optical fiber 110 having the value of the ratio (βf(λL)/βh(λL)) is prepared (S3). Refractive index modulation for Bragg-reflecting light of the reflected wavelengthλB is formed on the fiber 110 to manufacture the optical wavelength type diffraction grating element 100 (S4).