A system and method for monitoring all the characteristic parameters of a DWDM communication system is implemented with two variants. Firstly, this is achieved by means of a specific grating spectrometer displaying a high resolution and a high-speed sampling of the measured values, and secondly by the application of an opto-electronic cross correlator as a purely electronic solution. The grating spectrometer is expediently a particular system in a mixed array according to Ebert and Fastie, wherein the light to be measured passes four times through the grating in a specific manner. The opto-electronic cross correlator can mix the working light with a reference light tunable in terms of its frequency to form an electrical low-frequency signal that is analyzed in a high-impedance operation.
RELATED APPLICATION
This application claims benefit of International Aplication No. PCT/EP99/097340, filed Oct. 5, 1990 having a priority date of Oct. 5, 1998 based on DE 198 45 701.4. This application has not been published in English.
A wavelength beam splitter (WBS) is combined with a conventional tunable filter to sequentially select different channels in a multi-channel communication system. The WBS is characterized by a periodic spectral response with period equal to the channel spacing of the ITU grid. Preferably, the WBS consists of an optical cavity with an optical path length that produces a free-spectral range substantially equal to the channel spacing of the ITU grid. The WBS is used to separate the signal in each channel passband from the noise in the corresponding channel stopband. This provides a signal and a noise output for each channel. A tunable filter is used to scan the channels of the ITU grid sequentially and provide output signals for a single channel at a time. Therefore, a much smaller frequency bandwidth needs to be measured at a time and a less expensive detector may be used.
A fiber polarimeter has one or more oblique fiber Bragg gratings disposed one behind the other in a fiber. The fiber Bragg gratings couple out portions of a light wave input to the fiber depending on its polarization. For more than one fiber Bragg grating a wave plate is disposed in the fiber between consecutive fiber Bragg gratings. The portions of the light wave from the fiber Bragg grating(s) are detected to produce measurement data that is used to calculate four Stokes parameters for determining polarization, degree of polarization and/or power of the light wave.
