Tunable optical filter in coherent optical transmitters

A method implemented in a coherent transmitter comprising steps of:

• receiving an optical signal that was coherent modulated via a coherent modulator;
• measuring, via one or more photodetectors, a signal baud or spectral width of an output signal via one or more photodetectors;
• configuring a plurality of tunable optical filters, integrated within the coherent transmitter, which are connected to an output of the coherent modulator, wherein each of the plurality of tunable optical filters has a fixed width and a tunable center frequency, and wherein the plurality of the tunable optical filters are cascaded and configured such that frequency offsets between their tunable center frequencies create an effective transfer function having a variable width and center frequency, and wherein the plurality of tunable optical filters are adaptively controlled based on tthe measured signal baud or spectral width of the received optical signal;
• and
• outputting a signal from the coherent transmitter such that the effective transfer function suppresses out-of-band noise and the signal has corresponding noise pedestals removed by the plurality of tunable optical filters, prior to any multiplexing.