Passive optical network with asymmetric modulation scheme

An apparatus for a passive optical network (“PON”), the apparatus comprising:

• a wavelength-division multiplexing (“WDM”) optical network unit (“ONU”) for delivering communication services to customer premise equipment from the PON, the WDM ONU including:
• a tunable optical transmitter to launch upstream WDM signals into the PON, the tunable optical transmitter including a first tunable laser source coupled to generate a selectable upstream carrier wavelength and direct amplitude modulation circuitry coupled to amplitude modulate the first tunable laser source;
• and
• a tunable optical receiver to receive downstream WDM signals from the PON, the tunable optical receiver including coherent detection circuitry to demodulate phase information from the downstream WDM signals and a second tunable laser source operated as a local oscillator and coupled to tune to a selectable downstream carrier wavelength, wherein the tunable optical receiver further includes:
• a polarizing beam splitter (“PBS”) including an upstream port for coupling to the PON;
• a first 90 degree hybrid coupled to a first output of the PBS to receive a first polarization of the downstream WDM signals and coupled to the second tunable laser source to receive a tunable beat signal;
• a second 90 degree hybrid coupled to a second output of the PBS to receive a second polarization of the downstream WDM signals and coupled to the second tunable laser source to receive the tunable beat signal;
• and
• first and second pairs of balanced photo-receivers coupled to outputs of the first and second 90 degree hybrids, respectively, and wherein each of the first and second pair of balanced photo-receivers includes four photodiodes.

A hybrid passive optical network (“PON”), comprising:

• a time-division multiplexing (“TDM”) optical line terminal (“OLT”) for delivering communication services to a first group of customer premises (“CPs”) via TDM signals;
• a wavelength-division multiplexing (“WDM”) OLT for delivering the communication services to a second group of CPs via WDM signals, the WDM OLT including first asymmetric modulation circuitry for upstream and downstream WDM signals, wherein the WDM OLT further includes:
• a plurality of physical photonic integrated circuits (“PIC”) for coupling to the second group of CPs, wherein each physical PIC includes:
• an optical transmitter array including a plurality of coherent transmitters to generate the downstream WDM signals encoded using phase modulation;
• and
• an optical receiver array including a plurality of direct detection photo-detectors to receive the upstream WDM signals encoded with amplitude modulation;
• a remote node power splitter coupled to receive the TDM signals and the WDM signals and to broadcast both the TDM signals and the WDM signals on all ports of the remote node power splitter facing towards the first and second groups of CPs;
• TDM ONUs disposed at the first group of CPs to communicate with the TDM OLT via the TDM signals;
• and
• WDM ONUs disposed at the second group of CPs to communicate with the WDM OLT via the WDM signals, wherein the WDM ONUs are colorless transceivers including second asymmetric modulation circuitry for the upstream and downstream WDM signals.