| 摘要 |
PROBLEM TO BE SOLVED: To obtain a method capable of monitoring a multiple wavelength optical system without using costly elements, such as detector arrays and an apparatus therefor. SOLUTION: The physical parameters of the intra-fiber gratings for coupling the light used in the wavelength division multiplex(WDM) optical fiber system between the spatially different mode are scanned, i.e., changed. The space modes are separated by using a mode discrimination device(MDD) 47 and the spectral components separated by the conventional or other suitable detectors 48 are monitored, i.e., detected. The peak wavelength of the coupling the two different modes to each other is changed and the coupling in the fiber optical system is controlled by scanning the intra-fiber gratings. This system uses the long- period gratings for coupling the spatially different modes for propagating the light in the two same direction to each other or the short-period gratings for coupling the mode for propagating the light in a forward direction and the mode for propagating the light in the opposite direction spatially different therefrom to each other. |
