| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical fiber filter in which a spectral waveform of transmitted light is strictly controlled by using a long period fiber diffraction grating. SOLUTION: This optical fiber filter 1 has such a characteristic that a diffraction grating group, where three or more long period diffraction gratings are formed at constant intervals L, is installed on a core part 23 of a single mode optical fiber. Preferably, the first diffraction grating 2, by counting from the incident end of the light, satisfies the condition,κ0×d0=π/2 (where,κ0 is a coupling constant of a diffraction grating and d0 is a diffraction grating length), and diffraction gratings on and after the second position, by counting from the incident end of the light, satisfy the condition,κ0×d0<π/2. |
