  We analyze optical spectroscopy data of the electron-doped superconductor
(Pr$_{2-x}$Ce$_x$)CuO$_4$ (PCCO) to investigate the coupling of the charge
carriers to bosonic modes. The method of analysis is the inversion of the
optical scattering rate $\tau^{-1}_{\rm op}(\omega,T)$ at different
temperatures $T$ by means of maximum entropy technique combined with Eliashberg
theory. We find that in the superconducting state the charge carriers couple to
two dominant modes one at $\sim 10 $meV and a second one at $\sim 45 $meV. The
low energy mode shows a strong temperature dependence and disappears at or
slightly above the critical temperature $T_c$. The high energy mode exists
above $T_c$ and moves towards higher energies with increasing temperatures. It
also becomes less prominent at temperatures $> 100 $K above which it evolves
into a typical spin-fluctuation background. In contrast to the hole-doped
High-$T_c$ superconductors PCCO proves to be a superconductor close to the
dirty limit.
