By using auto-correlation of signal power waveform (ACSPW) for coherent systems, an improved method for chromatic dispersion (CD) estimation is proposed. In order to overcome the limitation of ACSPW, the ACSPW scheme is extended by artificially adding CD to the received signal using a finite impulse response filter in the estimation phase, moving the pulse to the range that can be measured, and finally subtracting the known added value after the estimation. This method will be essentially unaffected by amplified spontaneous emission noise, pulse shapes and polarization mode dispersion. Mean error of monitoring results is 127 ps/nm.