OSNR MONITORING APPARATUS USING POLARIZATION NULLING METHOD AND PMD COMPENSATING METHOD

摘要

An apparatus for monitoring an OSNR(Optical Signal-to-Noise Ratio) by using a polarization nulling method and a polarization mode dispersion compensation method is provided to easily measure an OSNR by implementing the polarization nulling method by moving the wavelength variable band pass optical filter as much as a certain amount. A polarization mode dispersion compensation unit(30) compensates polarization mode dispersion of a wavelength division multiplexed optical signal. A wavelength variable band pass optical filter(26) filters an optical signal of the first central wavelength whose OSNR is to be measured among wavelength division multiplexed optical signals by varying the second central wavelength. The first polarization controller(42) controls a polarization state of the filtered optical signal. A one-to-one directional coupler(44) splits the polarization state-controlled optical signal into the first optical signal and the second optical signal. A linear polarization unit(46) linearly polarizes the second optical signal. An OSNR measuring unit(50) obtains the first power of the first optical signal when the second and first central wavelengths are identical, obtains the second power, namely, the minimum value of the second optical signal after passing through the linear polarization unit(46) by moving the second central wavelength as much as a certain amount from the first central wavelength, and then obtains an OSNR by using the first power and the second power.