An integrated-optics system comprising a first frequency-filter block, the frequency-filter block including: first and second input ports (In1 and In2); first and second output ports (Out1 and Out2); a first Mach-Zehnder Interferometer, MZI, having a first free-spectral range FSR, and a first coupling coefficient; a second MZI having a second FSR and a second coupling coefficient, wherein the first and second FSR have a ratio that is selected from the group consisting of 2:1 and 1:2; first, second, and third tunable couplers; and first, second, third, fourth and fifth phase controllers; wherein the first phase controller configured to control the first coupling coefficient the second phase controller configured to control the second coupling coefficient; the first tunable coupler having a third coupling coefficient; the third phase controller configured to control the third coupling coefficient; the second tunable coupler having a fourth coupling coefficient; the fourth phase controller configured to control the fourth coupling coefficient; the third tunable coupler having a fifth coupling coefficient; and the fifth phase controller configured to control the fifth coupling coefficient; wherein each phase controller is operatively coupled with one arm of an MZI or a tunable coupler, wherein the first MZI, second MZI and the first, second, and third tunable couplers are optically coupled and monolithically integrated on a substrate and arranged such that the first MZI is between the first and second tunable couplers and the second MZI is between the second and third tunable couplers; wherein the first frequency-filter block is a flat-top response for each wavelength signal of the first plurality of wavelength signals; the first, second, third, fourth, and fifth phase controllers being collectively configured to enable independent control of the propagation of each of a first plurality of wavelength signals from the either of the first and second input ports to either of the first and second output ports; and at least one of the first, second, third, fourth, and fifth phase controllers being a low-power phase controller. first and second input ports (In1 and In2); first and second output ports (Out1 and Out2); a first Mach-Zehnder Interferometer, MZI, having a first free-spectral range FSR, and a first coupling coefficient; a second MZI having a second FSR and a second coupling coefficient, wherein the first and second FSR have a ratio that is selected from the group consisting of 2:1 and 1:2; first, second, and third tunable couplers; and first, second, third, fourth and fifth phase controllers; wherein the first phase controller configured to control the first coupling coefficient the second phase controller configured to control the second coupling coefficient; the first tunable coupler having a third coupling coefficient; the third phase controller configured to control the third coupling coefficient; the second tunable coupler having a fourth coupling coefficient; the fourth phase controller configured to control the fourth coupling coefficient; the third tunable coupler having a fifth coupling coefficient; and the fifth phase controller configured to control the fifth coupling coefficient; wherein each phase controller is operatively coupled with one arm of an MZI or a tunable coupler, wherein the first MZI, second MZI and the first, second, and third tunable couplers are optically coupled and monolithically integrated on a substrate and arranged such that the first MZI is between the first and second tunable couplers and the second MZI is between the second and third tunable couplers; wherein the first frequency-filter block is a flat-top response for each wavelength signal of the first plurality of wavelength signals; the first, second, third, fourth, and fifth phase controllers being collectively configured to enable independent control of the propagation of each of a first plurality of wavelength signals from the either of the first and second input ports to either of the first and second output ports; and at least one of the first, second, third, fourth, and fifth phase controllers being a low-power phase controller.