In this paper, a parallel coupled optical ring resonator filter is studied and the transfer function is derived using the signal flow graph (SFG) approach to identify the filter performance in terms of crosstalk suppression bandwidth and signal integrity. This paper proposes the use of the SFG (Mason's rule) approach to determine the filtering characteristics of parallel coupled ring resonators. A commercial electromagnetic simulator is used to validate the analytical model. The modeling of the parallel coupled ring resonator covers the analysis of the out-of-band rejection ratio, crosstalk suppression, loss effect, and the effect of coupling coefficients on the crosstalk bandwidth. The good agreement between analytical model results and simulation results suggests that using the derived analytical model provides an accurate starting point for design and analysis and, in doing this, provides a better insight into the signal integrity performance of the filter.