An apparatus for a passive optical network, PON, the apparatus comprising: a wavelength-division multiplexing, WDM, optical line terminal, OLT, for delivering communication services to customer premises, CPs, via an asymmetric modulation scheme using WDM signals, wherein the WDM OLT includes: a plurality of physical photonic integrated circuits, PIC, for coupling to the PON to provide the communication services to the CPs, wherein each physical PIC includes: an optical transmitter array including a plurality of coherent transmitters to generate downstream WDM signals encoded using phase modulation, and an optical receiver array including a plurality of direct detection photo-detectors to receive upstream WDM signals encoded with amplitude modulation; an interleaver block having an optical diplexer optically coupled to the optical transmitter arrays of the physical PICs via an M:1 interleaver, and the optical receiver arrays of the physical PICs via an M:1 de-interleaver, the optical diplexer for combining wavelengths of the upstream and downstream WDM signals onto a single fiber and coupling the WDM OLT to a remote node power splitter via one or two fiber trunk lines (115, 416, 417) to deliver the downstream WDM signals from the optical transmitter arrays to the PON and to deliver the upstream WDM signals from the PON to the optical receiver arrays; an optical multiplexer coupled between each optical transmitter array and the M:1 interleaver to multiplex the downstream WDM signals each having a different wavelength onto a first optical link; and an optical demultiplexer coupled between the M:1 de-interleaver and each optical receiver array to de-multiplex the upstream WDM signals each having a different wavelength to respective ones of the direct detection photo-detectors. a wavelength-division multiplexing, WDM, optical line terminal, OLT, for delivering communication services to customer premises, CPs, via an asymmetric modulation scheme using WDM signals, wherein the WDM OLT includes: a plurality of physical photonic integrated circuits, PIC, for coupling to the PON to provide the communication services to the CPs, wherein each physical PIC includes: an optical transmitter array including a plurality of coherent transmitters to generate downstream WDM signals encoded using phase modulation, and an optical receiver array including a plurality of direct detection photo-detectors to receive upstream WDM signals encoded with amplitude modulation; an interleaver block having an optical diplexer optically coupled to the optical transmitter arrays of the physical PICs via an M:1 interleaver, and the optical receiver arrays of the physical PICs via an M:1 de-interleaver, the optical diplexer for combining wavelengths of the upstream and downstream WDM signals onto a single fiber and coupling the WDM OLT to a remote node power splitter via one or two fiber trunk lines (115, 416, 417) to deliver the downstream WDM signals from the optical transmitter arrays to the PON and to deliver the upstream WDM signals from the PON to the optical receiver arrays; an optical transmitter array including a plurality of coherent transmitters to generate downstream WDM signals encoded using phase modulation, and an optical receiver array including a plurality of direct detection photo-detectors to receive upstream WDM signals encoded with amplitude modulation; an interleaver block having an optical diplexer optically coupled to the optical transmitter arrays of the physical PICs via an M:1 interleaver, and the optical receiver arrays of the physical PICs via an M:1 de-interleaver, the optical diplexer for combining wavelengths of the upstream and downstream WDM signals onto a single fiber and coupling the WDM OLT to a remote node power splitter via one or two fiber trunk lines (115, 416, 417) to deliver the downstream WDM signals from the optical transmitter arrays to the PON and to deliver the upstream WDM signals from the PON to the optical receiver arrays; an optical multiplexer coupled between each optical transmitter array and the M:1 interleaver to multiplex the downstream WDM signals each having a different wavelength onto a first optical link; and an optical demultiplexer coupled between the M:1 de-interleaver and each optical receiver array to de-multiplex the upstream WDM signals each having a different wavelength to respective ones of the direct detection photo-detectors.