COOLERLESS PHOTONIC INTEGRATED CIRCUITS (PICs) FOR WDM TRANSMISSION NETWORKS AND PICs OPERABLE WITH A FLOATING SIGNAL CHANNEL GRID CHANGING WITH TEMPERATURE BUT WITH FIXED CHANNEL SPACING IN THE FLOATING GRID

A transmitter photonic integrated circuit comprising:

• a plurality of modulated sources, each of the plurality of modulated sources configured to output a corresponding one of a plurality of optical signals, each of the plurality of modulated optical signals having a corresponding one of a plurality of first wavelengths, the plurality of wavelengths forming a laser source wavelength grid;
• an optical combiner having a plurality of inputs and an output, each of the plurality of inputs of the optical combiner configured to receive a corresponding one of the modulated optical signals and combine them into a wavelength division multiplexed signal provided at the output of the optical combiner, the optical combiner having a passband wavelength grid;
• a heater configured to maintain the operation of the photonic integrated circuit at an operating temperature above a room temperature;
• and
• a circuit coupled to the plurality of modulated sources, the circuit configured to control the wavelengths of each of the plurality of modulated optical signals and maintain the laser source wavelength grid in substantial alignment with the passband wavelength grid of the optical combiner and for optimizing the operation of the modulators with changes resulting from said grid alignment.

A transmitter photonic integrated circuit comprising:

• a plurality of modulated sources, each of the plurality of modulated sources being configured to output a corresponding one of a plurality of optical signals at a respective one of a plurality of wavelengths;
• a plurality of photodetectors, each of the photodetectors configured to receive a portion of a respective one of the plurality of optical signals and provide a corresponding one of a plurality of electrical signals,
• a heater to heat a corresponding one of the plurality of modulated sources to an operating temperature above a surrounding room temperature;
• and
• a controller, the controller configured to receive the plurality of electrical signals and change a corresponding one of the plurality of wavelengths of one or more of the plurality of modulated sources so that a spectral spacing between adjacent ones of the plurality of wavelengths is maintained at a predetermined one of a plurality of spectral spacings.

A photonic integrated circuit (PIC) comprising:

• a substrate;
• a plurality of modulated sources provided on the substrate, each of the plurality of modulated sources having an aluminum-containing active region;
• each of the modulated sources providing a corresponding one of a plurality of optical signals having a respective one of a plurality of wavelengths, the plurality of wavelengths forming a signal channel wavelength grid channels with, a corresponding one of a plurality of spectral spacings provided between adjacent ones of the plurality of wavelengths within the signal channel wavelength grid;
• the plurality of optical signals combined into a WDM signal provided at an output of the photonic integrated circuit for,
• the photonic integrated circuit not temperature controlled so that the wavelength grid is thermally floating with a changing surrounding temperature resulting in individual ones of the plurality of wavelengths changing with temperature;
• the plurality of spectral spacings between adjacent ones of the plurality of wavelengths within the signal channel wavelength grid maintained fixed relative to remaining ones of the plurality of spectral spacings.