Optical nyquist superchannel generation using microwave low-pass filtering and optical equalization

1. A method of generating a Nyquist superchannel output signal comprising the steps of:

performing Nyguist shaping in two steps: one in a baseband frequency and one in an optical frequency including:

filtering an electrical baseband signal with finite rise-time symbols by high-order microwave low pass filter (LPF) such that the baseband signal energy is confined to a small fraction above a Nyquist rate, and no digital-to-analog converters are used for signal generation;

upconverting the filtered signal to optical frequencies by applying the filtered signal to and driving an optical modulator substantially in its linear region;

demultiplexing a multi-tone optical signal and applying a demultiplexed output to the optical modulator;

passively coupling an output from the optical modulator to other outputs from other modulators such that multiple subcarriers are multiplexed at a spacing above their Nyquist bandwidth; and

optically equalizing the coupled multiple subcarriers such that the Nyquist superchannel is generated.