In this paper, we present a method for combined fiber parameter estimation from digital filter coefficients of a polarization diverse coherent receiver. All deterministic linear optical channel parameters like residual chromatic dispersion (CD), polarization-mode dispersion (PMD), and polarization-dependent loss (PDL) are continuously monitored by analysis of the filter impulse response of the adaptive equalizer. After deriving the according equations from the theoretical linear fiber channel model, we demonstrate robust estimation for a joint combination of all impairments.