| 摘要 |
PURPOSE:To offer a high-gain, low-noise device which can reduce the intensity of ASE light generated in an optical fiber by inserting a fiber coupler type optical filter or Mach-Zehnder type optical filter which transmits only signal light and exciting light. CONSTITUTION:The signal light S and the exciting light P from an exciting light source 2 are multiplexed by an optical multiplexer 3 and made incident on one end of a rare-earth-element added optical fiber 1a. The exciting light P of the incident multiplexed light excites rare earth element erbium in the optical fiber 1a to form an inverted distribution and the optical fiber 1a functions as an amplifying medium to amplify the signal light S with a specific gain. At this time, the ASE light is generated simultaneously with the amplification of the signal light S. The ASE light, signal light S, and exciting light P are made incident on the fiber coupler type optical filter 4, which transmits only the signal light S of 1.552mu in wavelength and the exciting light P of 1.484mu, but interrupts the ASE light whose wavelength is 1.535mu or nearly equal to the wavelength. Only the signal light S and exciting light P are therefore guided to an optical fiber 1b. |
