Patent ID: 8792788

Claim:
A method for optical communications based on wavelength division multiplexing (WDM), comprising: providing tunable laser transmitter modules based on a common tunable laser transmitter module design which includes (1) a plurality of tunable laser modules to produce laser light at different optical wavelengths to carry different WDM signal channels, respectively, each tunable laser module operable to tune a respective optical wavelength, and (2) a beam combiner that includes input ports that are respectively coupled to receive the laser light from the tunable laser modules and an output port that combines the received laser light from the tunable laser modules into a combined optical output carrying light at the different optical wavelengths, the beam combiner structured to exhibit a common transmission spectral profile from each input port to the output port that has periodic repetitive transmission bands that are adjacent to one another in wavelength and extend to cover different WDM sub-bands within a WDM band, wherein each transmission band has a spectral width to cover a predetermined number of WDM wavelengths; operating the tunable laser transmitter modules to produce WDM optical signals at different optical wavelengths in different WDM sub-bands, laser light at a respective optical WDM wavelength from each tunable laser transmitter module being modulated to produce a respective WDM optical signal carrying information of a respective WDM channel, wherein operating the tunable laser transmitter modules includes applying a common control signal to each of a plurality of tunable lasers within the tunable laser transmitter modules to synchronously tune the plurality of tunable laser to the different optical wavelengths, and wherein the common control signal tunes each of a the tunable lasers in the plurality by a coarse tuning step approximately equal to a number of the tunable lasers in the plurality, multiplied by, a channel spacing between the respective optical wavelengths; and combining the WDM signals in the different WDM sub-bands from the tunable laser transmitter modules into a combined WDM optical output for transmission over a fiber link.