| 摘要 |
PURPOSE:To allow one wavelength multiplex demultiplexer to perform demultiplexing covering plural wavelengths, and to reduce its size and cost, by sticking an amorphous semiconductor film to one end surface of a convergent rod lens which varies in refractive index radially from the center part almost with a square distribution. CONSTITUTION:The amorphous semiconductor 7 vapor-deposited on one end surface 6 of the convergent rod lens 5 varies in refractive index when irradiated with light having wavelength close to absorption edge, forming a diffraction grating 8 of interference fringes. An incident wave 10 having wavelengths lambda1, lambda2, and lambda3 enters the rod lens 5 from an end surface 9 through a fiber 11 and is reflected by the diffraction grating 8. Its angle of reflection is different depending upon the wavelengths, and the light is focused on different positions on the end surface 9, thereby demultiplexing light signals with the wavelengths lambda1, lambda2, and lambda3 from fibers 21, 31, and 41 couled with the positions. |
