This sets the lambda (wavelength) number for the second preferred ring, mirroring circuitPreferredEP1OptVport but for the second ring segment of a circuit that spans two DWDM rings. This lets an admin fully specify a two-ring circuit's exact optical path down to the wavelength level on both legs, which matters for consistent latency and protection characteristics across the whole route. For example, pinning both EP1 and EP2 to lambda 3 on their respective rings would keep the circuit on matching wavelength channels across both ring segments if that's operationally preferred.