Fig. 4.

Experimental results for 6-BUL ring resonator infinite impulse response and combined finite impulse response and infinite impulse response filters. Waveguide mesh connection diagram, circuit layout and measured modulus, and phase transfer function for a a 6-BUL optical ring resonator (ORR) infinite impulse response (IIR) filter for different values of the coupling constants K ₁ and K ₂; b a 6-BUL ORR finite impulse response (FIR) + IIR filter for different values of the coupling constants K ₁ and K ₂; c a 6-BUL ORR IIR filter along a full spectral period for different values of the optical ring resonator round-trip phase shift. BUL, basic unit length; CS, cross state; BS, bar state; AV, available; TC, tuneable coupler