WDM Add-Drop Multiplexer (2D)

Four wavelength channels travel down a single photonic-chip bus waveguide, each destined for its own micro-ring resonator drop port. This 2D schematic renders the ring-resonator add-drop filter that makes wavelength-division multiplexing possible side-by-side with its live transmission spectrum: pick a channel, drive its ring's thermo-optic heater, and watch the resonance shift away from — or back onto — that channel's wavelength in both the chip diagram and the Lorentzian curve. Live readouts track the ring's resonant wavelength, its linewidth, the insertion loss on its own channel, and the isolation from its nearest neighbour, so the loss/cross-talk trade-off that governs real WDM filter design is visible rather than abstract. The Q-factor and channel-spacing controls reproduce the same selectivity-versus-tolerance balance that photonic foundries manage with coupling-gap process control.