Optical Signal Phase Reconstruction Based on Temporal Transport-of-Intensity Equation

A non-iterative reconstruction scheme of phase modulated optical signals using dispersive media in direct-detection receiver is described. The phase retrieval is achieved by solving the temporal transport-of-intensity equation (TIE). The TIE is solved by the use of Fast Fourier Transform algorithm. Required carrier power added to the signal is examined and it is shown that carrier power larger by 2 to 3 dB than that needed in the Kramers-Kronig receiver. The carrier can be located inside the signal spectrum, lifting the condition that the signal needs to be single-sideband with tightly confined spectrum. The noise immunity in solving the TIE, which will be an issue in practical usage of the scheme, is also discussed.