| 摘要 |
PURPOSE:To simply constitute an external modulation mechanism without use of an optical active element and to reduce the cost of the device by realizing the modulation by a user signal onto a light supplied from a center equipment with an absolute single polarized wave optical fiber, an optical passive element such as a reflector and a piezoelectric element. CONSTITUTION:A continuous stimulated light from a stabilizing light source 13 is made incident in an optical multiplexer demultiplexer 15 via an optical fiber 23, a photocoupler 14 and an optical fiber 24, in which the light is multiplexed with a center signal from an electrooptic conversion circuit 11 and the result is sent to an optical fiber 25 in a center equipment. An optical multiplexer demultiplexer 31 of a user equipment demultiplexes the center signal from the continuous stimulated light, which is fed to a modulation section 41. A reflector 411 is fitted to a piezoelectric element 412 in the modulation section 41 and the reflector is moved in parallel with a radiation end face of an optical fiber 27, that is, in a direction to cross a radiation light attended with the elongation and contraction of the piezoelectric element 412 under the control of a modulation control circuit 413. That is, the modulated light is sent from the user equipment to the center equipment in terms of the presence of a light returned to a photoelectric conversion circuit 12 at the center equipment in response to the user signal. |
