A clock recovery apparatus being configured to recover clock information from an input signal, wherein the input signal is a digitalized version of an optical signal having a first optical signal portion being associated with a first optical polarization and a second optical signal portion being associated with a second optical polarization, the apparatus comprising: Fourier transforming means being configured to transform the input signal into a first frequency domain signal upon the basis of a Fourier transform by a first Fourier transformer and into a second frequency domain signal upon the basis of a Fourier transform by a second Fourier transformer , wherein the first frequency domain signal portion being associated with the first optical polarization and the second frequency domain signal portion being associated with the second optical polarization; correlating means being configured to correlate the first frequency domain signal to obtain a first correlation value associated with a first certain frequency and to correlate the second frequency domain signal to obtain a second correlation value associated with a second certain frequency, and further to auto-correlate the first or the second frequency domain signal portion or to cross-correlate the first frequency domain signal portion and the second frequency domain signal portion to obtain a correlation value; and clock recovery means being configured to determine whether the first or second certain frequency corresponds to a clock frequency in order to recover the clock information, and further to decide that the first certain frequency corresponds to the clock frequency if the first correlation value is greater than the second correlation value or to decide that the first certain frequency corresponds to the clock frequency if the correlation value is greater than or equal to a certain threshold. Fourier transforming means being configured to transform the input signal into a first frequency domain signal upon the basis of a Fourier transform by a first Fourier transformer and into a second frequency domain signal upon the basis of a Fourier transform by a second Fourier transformer , wherein the first frequency domain signal portion being associated with the first optical polarization and the second frequency domain signal portion being associated with the second optical polarization; correlating means being configured to correlate the first frequency domain signal to obtain a first correlation value associated with a first certain frequency and to correlate the second frequency domain signal to obtain a second correlation value associated with a second certain frequency, and further to auto-correlate the first or the second frequency domain signal portion or to cross-correlate the first frequency domain signal portion and the second frequency domain signal portion to obtain a correlation value; and clock recovery means being configured to determine whether the first or second certain frequency corresponds to a clock frequency in order to recover the clock information, and further to decide that the first certain frequency corresponds to the clock frequency if the first correlation value is greater than the second correlation value or to decide that the first certain frequency corresponds to the clock frequency if the correlation value is greater than or equal to a certain threshold. <EOS>