System and method for coherent detection with digital signal procession

A method of generating a wide bandwidth multiplexed optical signal and transmitting it over an optical fiber, the method comprising:

• generating, by a laser, a continuous lightwave;
• generating, from the continuous lightwave, a multicarrier signal having a fixed channel spacing of f GHz;
• separating the multicarrier signal into a plurality of optical subcarriers;
• routing each of the optical subcarriers to a respective I/Q modulator and modulating each of the subcarriers to carry f Gbaud of data as a QPSK signal by the corresponding I/Q modulator;
• combining, in an optical multiplexer, the modulated optical subcarriers into a multiplexed optical signal, wherein the optical multiplexer has a 3 dB bandwidth of −f GHz;
• and
• transmitting the multiplexed optical signal with no synchronization information over an optical fiber.