| 摘要 |
PURPOSE:To enable to measure the mode dispersion transmission characteristic of an optical fiber undergoing little effect of wavelength dispersion by using a particular laser beam aplit into that of an extremely narrow wavelength width. CONSTITUTION:A laser pulse beam generated by a tracking generator 1, a laser driver 2, a semiconductor laser 3, etc., passes a lens 4 and is split by a grating spectrograph 5 into a longitudinal mode pulse beam of extremely narrow wavelength width. Using this pulse beam as a light source, the laser beam enters an optical fiber 7 via an immersion cell 6, and the longitudinal mode beam that was propagated through the fiber 7 without undergoing the effect of wavelength dispersion because of the extremely narrow wavelength width of the beam is detected by an APD8 and applied to a spectrum analyzer 10. By comparing with the received light detection signal of the APD8 when the fiber 7 is cut at a position 1-2m from the end of incidence and the same light source is used, the mode dispersion transmission characteristic of the optical fiber can be measured with high accuracy unaffected by wavelength dispersion. |
