Transmitter photonic integrated circuits (TxPIC) and optical transport networks employing TxPICs

A monolithic transmitter photonic integrated circuit (TxPIC) chip comprising:

• an array of modulated sources integrated on said chip, each operating at a different wavelength and providing a respective signal output;
• all of said channel signals representative of a wavelength on a standardized wavelength grid;
• a wavelength selective optical multiplexer formed on the PIC chip, said wavelength selective multiplexer having reduced insertion loss compared to multiplexers that are not wavelength selective;
• the signal outputs of the modulated laser sources optically coupled to a plurality of inputs of the optical multiplexer and provided as a multiplexed output from the optical multiplexer.