Technology for simultaneous demultiplexing of subrate tributaries is described and applied to 320-Gb/s return-tozero input. The parametric architecture is scalable with respect to processed input rate and relies on cascaded all-optical multicasting and subrate sampling. Processing of 320-Gb/s input was achieved by creating eight channel copies, followed by a 20-THzwide parametric gate. Multicasting was based on a self-seeded twopump broadband fiber-optic parametric amplifier. The architecture was used to demonstrate error-free parallel demultiplexing of eight 320-Gb/s tributary channels at 40 Gb/s.