Nonlinear response of light such as bistability, the Ikeda instability and the dynamics of light within InGaAsPInP-modified add-drop resonator (PANDA Vernier resonator) is studied. The signal flow graph method is used to obtain the optical transfer function. Invariant and symmetric coupling coefficients k(R) = k(L) = 0.25 for indirect couplers are applied and the effect of changing symmetric direct couplers (K-1 = K-2) for two different resonant mode numbers is studied. The minimum drop port switching time of 2.83 ps and 2.87 ps for resonant mode numbers of 7;5;5 and 4;3;3 are achieved, respectively. The simulated results introduce the PANDA Vernier system as a proper optical device for future optical communication and signal processing systems.