Abstract: Apparatus and method are disclosed that utilize a particular delay modulation technique (i.e., Miller coding) to encode 25 Gb/s data for inclusion with the 50 Gb/s NRZ data in a downstream broadcast transmission from an optical line terminal (OLT) to a plurality of optical network units (ONUs) through an optical distribution network (ODN). The specific Miller coding technique allows for a secondary data stream, operating at half the rate of the NRZ data) to supplement the primary 50 Gb/s NRZ transmission, since both signals are recovered using the same clocking circuitry at the ONU.

Abstract: An optical line terminal (OLT) operating within a multi-rate PON is configured to perform downstream timeslot scheduling among an associated number of ONUs so as to minimize the change in information rate from one scheduled ONU timeslot to the next. In this manner, the clock recovery component at each ONU is best able to follow the change in information rates, remaining locked on the system clock regardless of the specific implementation of the clock and data recovery (CDR) functionality at a given ONU. The OLT may schedule timeslot assignments that span a pair of adjacent parts (referred to as a two-part cycle), with the first part having timeslots assigned from the lowest information rate (e.g., NRZ) to the highest (e.g., PAM4) and the second part's timeslots assigned in the reverse order; that is, from the highest to the lowest information rate.

Abstract: A method and apparatus is proposed for accurately evaluating the performance of optical transmitters under test conditions (such as high bit-rate modulation formats) that compromise the operability of standard test equipment used for this purpose. The proposed apparatus and method are similar to the elements associated with existing testing standards based on an optical eye diagram, with an important distinction that allows for accurate measurements of the transmitter's performance to be made. In particular, the sampling point for collecting eye diagram data samples in the inventive arrangement is shifted by half a period with respect to the conventional mid-eye sampling point, eliminating the need to include representative reference equalizer in the test equipment and providing an evaluation not influenced by the test equipment, resulting in a more accurate measurement of transmitter-related distortions.

Abstract: An optical line terminal (OLT) in flexible passive optical network (PON) transmits a downstream signal with two or more modulation formats, wherein at least one of the modulation formats is a modified PAMx modulation format and wherein x is greater than 2. The modified PAMx modulation encodes data bits such that the probability of at least one predetermined transition between amplitude levels is modified. Furthermore, an optical network unit (ONU) in the flexible PON is assigned to one of the plurality of modulation formats based on one or more parameters, such as configuration of the ONU and line conditions.

Abstract: Various example embodiments for supporting forward error correction (FEC) in a communication system are presented. Various example embodiments for supporting FEC in a communication system may include the selection of a FEC setting for a communication channel from a transmitter to a receiver, e.g., the selection of a FEC setting for a communication channel, the selection of a FEC setting for a data burst sent over a communication channel, the selection of a FEC setting for a portion of a data burst sent over a communication channel, switching between FEC settings for different portions of a data burst over a communication channel, or the like, as well as various combinations thereof.

Abstract: Apparatus and method are disclosed that utilize a particular delay modulation technique (i.e., Miller coding) to encode 25 Gb/s data for inclusion with the 50 Gb/s NRZ data in a downstream broadcast transmission from an optical line terminal (OLT) to a plurality of optical network units (ONUs) through an optical distribution network (ODN). The specific Miller coding technique allows for a secondary data stream, operating at half the rate of the NRZ data) to supplement the primary 50 Gb/s NRZ transmission, since both signals are recovered using the same clocking circuitry at the ONU.

Abstract: An optical line terminal (OLT) operating within a multi-rate PON is configured to perform downstream timeslot scheduling among an associated number of ONUs so as to minimize the change in information rate from one scheduled ONU timeslot to the next. In this manner, the clock recovery component at each ONU is best able to follow the change in information rates, remaining locked on the system clock regardless of the specific implementation of the clock and data recovery (CDR) functionality at a given ONU. The OLT may schedule timeslot assignments that span a pair of adjacent parts (referred to as a two-part cycle), with the first part having timeslots assigned from the lowest information rate (e.g., NRZ) to the highest (e.g., PAM4) and the second part's timeslots assigned in the reverse order; that is, from the highest to the lowest information rate.

Abstract: Various embodiments of the disclosed PON system enable approximate leveling of the optical-modulation amplitudes in a sequence of optical bursts received by a system's OLT from a plurality of ONUs. Some embodiments additionally enable approximate leveling of the average optical power, received at the OLT from different ONUs, in such a sequence. Some embodiments may rely on control messaging between the OLT and ONUs to perform one or both types of leveling. The disclosed leveling may advantageously provide an effective tool for optimizing upstream transmission for high-speed TDM-PONs.

Abstract: The method includes receiving, at a first optical communication device, feedback information on training of a neural network from at least one second optical communication device, the neural network configured to process a signal received from the first optical communication device, the feedback information at least including a training performance indication for training of the neural network conducted at the at least one second optical communication device; updating, based on the feedback information, a first initial parameter value set for the neural network maintained at the first optical communication device, to obtain a second initial parameter value set for the neural network; and transmitting the second initial parameter value set to at least one further second optical communication device, for training of the neural network to be conducted at the at least one further second optical communication device based on the second initial parameter value set.

Abstract: Various example embodiments for supporting forward error correction (FEC) in a communication system are presented. Various example embodiments for supporting FEC in a communication system may include the selection of a FEC setting for a communication channel from a transmitter to a receiver, e.g., the selection of a FEC setting for a communication channel, the selection of a FEC setting for a data burst sent over a communication channel, the selection of a FEC setting for a portion of a data burst sent over a communication channel, switching between FEC settings for different portions of a data burst over a communication channel, or the like, as well as various combinations thereof.

Abstract: A passive optical network having an optical-signal monitor configured to monitor carrier-wavelength drifts during optical bursts transmitted between the optical line terminal and optical network units thereof. In an example embodiment, the optical-signal monitor uses heterodyne beating between two differently delayed portions of an optical burst to generate an estimate of the carrier-wavelength drift during that optical burst. The passive optical network may also include an electronic controller configured to use the estimates generated by the optical-signal monitor to make configuration changes at the optical network units and/or implement other control measures directed at reducing to an acceptable level the amounts of carrier-wavelength drift during the optical bursts and/or mitigating some adverse effects thereof.

Abstract: Various example embodiments for supporting forward error correction (FEC) in a communication system are presented. Various example embodiments for supporting FEC in a communication system may include selection of a FEC setting (e.g., an amount of puncturing and/or shortening of a FEC code, a FEC code, or the like) for a communication channel from a transmitter to a receiver based on channel characteristic information of the communication channel from the transmitter to the receiver (e.g., transfer function information, channel loss information, noise characteristic information, error information (e.g., bit error rate, error modeling, or the like), or the like). Various example embodiments for supporting FEC in a communication system, based on selection of a FEC setting for a communication channel based on channel characteristic information of the communication channel, may be applied within various types of communication systems, including various types of wired and/or wireless communication systems.

Abstract: A PON having an OLT configured to send downlink transmissions to ONUs using amplitude modulation and two symbol rates. An example ONU includes a clock-recovery circuit capable of continuous clock extraction from the received variable-rate modulated optical signal. The continuous clock extraction can be achieved, e.g., by (i) configuring the photodetector to convert the higher-rate portions of the received optical signal into transformed electrical waveforms while converting the lower-rate portions thereof into similar electrical waveforms and (ii) configuring the clock-recovery circuit to phase-align the clock signal with signal transitions in the resulting sequence of transformed and similar electrical waveforms. An ONU configured to operate in this manner can advantageously stay locked to the received data signal during transmissions at both symbol rates, without the need to reacquire the clock signal at each rate change and/or at the beginning of each packet intended for the host ONU.

Abstract: A passive optical network having an optical-signal monitor configured to monitor carrier-wavelength drifts during optical bursts transmitted between the optical line terminal and optical network units thereof. In an example embodiment, the optical-signal monitor uses heterodyne beating between two differently delayed portions of an optical burst to generate an estimate of the carrier-wavelength drift during that optical burst. The passive optical network may also include an electronic controller configured to use the estimates generated by the optical-signal monitor to make configuration changes at the optical network units and/or implement other control measures directed at reducing to an acceptable level the amounts of carrier-wavelength drift during the optical bursts and/or mitigating some adverse effects thereof.

Abstract: A coherent optical receiver capable of receiving data encoded in optical bursts whose optical power can vary significantly from burst to burst. In an example embodiment, the coherent optical receiver comprises a variable optical attenuator connected between an optical local oscillator and an optical hybrid and configured to controllably vary the intensity of the local-oscillator signal in response to a control signal generated by a control circuit. In an example embodiment, the control circuit is configured to generate the control signal for the variable optical attenuator using power-control settings read from a memory and further using a transmission schedule according to which different remote optical transmitters are scheduled to transmit their respective optical bursts. The power-control settings can be loaded into the memory, e.g., using a suitable calibration method configured to determine a respective nearly optimal coherent gain for receiving data from each of the remote optical transmitters.

Abstract: A coherent optical receiver having an analog electrical circuit connected to combine the outputs of multiple photodetectors to generate an electrical output signal from which the data encoded in a received modulated optical signal can be recovered in a robust and straightforward manner. In an example embodiment, the analog electrical circuit includes one or more transimpedance amplifiers connected between the photodetectors and the receiver's output port. The coherent optical receiver may include a dual-polarization optical hybrid coupled to eight photodiodes to enable polarization-insensitive detection of the received modulated optical signal. The signal processing implemented in the analog electrical circuit advantageously enables the use of relatively inexpensive local-oscillator sources that may have relaxed specifications with respect to linewidth and wavelength stability.

Abstract: An optical device includes a waveguide slab, first and second input port couplers, and first and second output port couplers located over a planar optical substrate. The waveguide slab has a plane of symmetry. The first and second input port couplers extend from the waveguide slab and have an input coupler pair axis located about midway between the first and second input port couplers. The input coupler pair axis is offset at a nonzero first distance from the plane of symmetry. The first and second output port couplers extend from the waveguide slab and have an output coupler pair axis located about midway between the first and second output port couplers. The output coupler pair axis is offset at a different nonzero second distance from the plane of symmetry.

Abstract: An optical device includes a waveguide slab, first and second input port couplers, and first and second output port couplers located over a planar optical substrate. The waveguide slab has a plane of symmetry. The first and second input port couplers extend from the waveguide slab and have an input coupler pair axis located about midway between the first and second input port couplers. The input coupler pair axis is offset at a nonzero first distance from the plane of symmetry. The first and second output port couplers extend from the waveguide slab and have an output coupler pair axis located about midway between the first and second output port couplers. The output coupler pair axis is offset at a different nonzero second distance from the plane of symmetry.

Abstract: An optoelectronic receiver and associated method of operation.

Abstract: An optoelectronic receiver and associated method of operation.