40 Gb/s transmission over the existing 10 Gb/s based DWDM network infrastructure

The capacity upgrading techniques to 40 Gb/s channel rate using the existing N times 10 Gb/s based DWDM infrastructure were studied. The super-FEC, carrier- suppressed return-to-zero and pre-emphasis were applied to 40 Gb/s channels for improvement in optical signal to noise ratio sensitivity.