A novel approach is used to implement optical carrier suppression and separation (OCSS) labeling. Then, the performance of 10/40-Gb/s duobinary payload with 2.5-Gb/s amplitude shift keying (ASK) or duobinary label by numerical simulations is studied. Influencing factors, such as demultiplexer bandwidth and fiber Bragg grating (FBG) filter bandwidth, are investigated. Simulation result shows that the received sensitivity of ASK label is higher than that of the duobinary label, while the received sensitivity of duobinary payload with duobinary label is higher than that with ASK label.