Abstract: A technique for presetting the tap values of the equalizer component of an OLT burst mode receiver is used to eliminate (or at least shorten) the conventional equalizer training period, which is known to delay the ability to transmit useful data from the ONU to the OLT. The disclosed technique is based on a collection of three known frequency responses: (1) the ONU transmitter response FT(f); (2) the OLT receiver response FR(f); and (3) a specific fiber frequency response FF(f) calculated for the span connecting the transmitter and receiver. FT(f) and FR(f) are known quantities measured during component testing prior to installation. The frequency response of the fiber span may be determined by a combination of the known ONU transmitter measurements with a measurement of the separation between the ONU and the OLT (“reach”) created during a previous activation (ranging) process.

Abstract: Various example embodiments for supporting optical communications in an optical communication system may be configured to support dual-polarization based communications within the context of a direct detection based point-to-multipoint optical network (e.g., a passive optical network (PON) based on direction detection). Various example embodiments for supporting optical communications in an optical communication system may be configured to support optical communications based on application of dual polarizations to each of one or more wavelengths within the context of a direct detection based point-to-multipoint optical network to support multiple optical channels within the direct detection based point-to-multipoint optical network (e.g.

Abstract: Various example embodiments for providing a passive optical network (PON), supporting communications between an optical line terminal (OLT) and a set of optical network units (ONUs) of a PON, are presented. The PON may be enabled based on use of an optical frequency comb (OFC), generated at the OLT and reconstructed at the ONUs for locking the OFC at the ONUs to the OFC at the OLT. The OFC may include a set of optical frequency lines used as seed lines for reconstruction of the OFC at the ONUs (e.g., the pair of OFC lines at the center of the OFC which may be used to regenerate locked OFCs at the ONUs), a set of optical frequency lines used to support downstream communications from the OLT to the ONUs, and a set of optical frequency lines used to support upstream communications from the ONUs to the OLT.

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 of a signal analysis capability are presented herein. The signal analysis capability may be configured to support analysis of a signal for determining the signal integrity of the signal, where the signal integrity of the signal corresponds to a set of one or more measures of the quality of an electrical signal (e.g., one or more signal integrity metrics indicative of the signal integrity of the signal). The signal analysis capability may be configured to support analysis of a signal for determining the signal integrity of the signal for various types of signals which may be communicated within various types of communication networks. The signal analysis capability may be configured to support analysis of a signal for determining the signal integrity of the signal where the signal may include various types of data traffic (e.g., live data traffic, user data traffic, test data traffic, or the like).

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: A technique for presetting the tap values of the equalizer component of an OLT burst mode receiver is used to eliminate (or at least shorten) the conventional equalizer training period, which is known to delay the ability to transmit useful data from the ONU to the OLT. The disclosed technique is based on a collection of three known frequency responses: (1) the ONU transmitter response FT(f); (2) the OLT receiver response FR(f); and (3) a specific fiber frequency response FF(f) calculated for the span connecting the transmitter and receiver. FT(f) and FR(f) are known quantities measured during component testing prior to installation. The frequency response of the fiber span may be determined by a combination of the known ONU transmitter measurements with a measurement of the separation between the ONU and the OLT (“reach”) created during a previous activation (ranging) process.

Abstract: A phased approach to training of an upstream burst mode receiver equalizer is disclosed that proceeds incrementally through modulation schemes requiring increasing levels of equalization in a manner where the equalizer maintains the capability to accurately recover data transmitted during each training phase. The phased approach includes an initial training phase (one or more upstream bursts) using a simple modulation format, one or more intermediate phases of different modulation schemes, and a final training phase using the PON-defined (high) line rate upstream modulation format. Equalizer settings generated during the initial phase are used as a starting point for the equalization process in the next training phase, and so on, until the equalizer training reaches the final phase where the ONU uses the PON-defined upstream data rate and the burst mode equalizer is updated accordingly.

Abstract: A phased approach to training of an upstream burst mode receiver equalizer is disclosed that proceeds incrementally through modulation schemes requiring increasing levels of equalization in a manner where the equalizer maintains the capability to accurately recover data transmitted during each training phase. The phased approach includes an initial training phase (one or more upstream bursts) using a simple modulation format, one or more intermediate phases of different modulation schemes, and a final training phase using the PON-defined (high) line rate upstream modulation format. Equalizer settings generated during the initial phase are used as a starting point for the equalization process in the next training phase, and so on, until the equalizer training reaches the final phase where the ONU uses the PON-defined upstream data rate and the burst mode equalizer is updated accordingly.

Abstract: A network element includes at least one processor and at least one memory. The at least one non-transitory memory including computer program code configured to, when executed by the at least one processor, cause the apparatus to determine whether a bit error rate (BER) of a FEC codeword is at or below a correctable BER, wherein the FEC codeword is transmitted between an OLT and ONU, a first percentage of the FEC codeword is at a lower order modulation, and a second percentage of the FEC codeword is at a higher order modulation, establish, based on a determination that the BER is at or below the correctable BER, a connection between the OLT and the ONU at the higher order modulation, and maintain, based on a determination that the BER is greater than the correctable BER, the connection between the OLT and the ONU at the lower order modulation.

Abstract: A method and apparatus is proposed for performing the ONU activation process in a PON having a standard line rate of 50 G or higher. The method and apparatus are based upon having the OLT instruct any activating ONUs to transmit at a line rate that is less than 50 G, which allows for an OLT receiver without any particular equalization configuration to accurately recover the upstream burst-mode transmissions from the activating ONUs. Once the activation process is completed, the OLT may instruct the new ONUs to reset their transmitters to operate at the higher line rate of the PON. Alternatively, at the end of the activation process, the new ONUs may be configured to automatically reset their transmitters to higher line rate.

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: 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: A network element includes at least one processor and at least one memory. The at least one non-transitory memory including computer program code configured to, when executed by the at least one processor, cause the apparatus to determine whether a bit error rate (BER) of a FEC codeword is at or below a correctable BER, wherein the FEC codeword is transmitted between an OLT and ONU, a first percentage of the FEC codeword is at a lower order modulation, and a second percentage of the FEC codeword is at a higher order modulation, establish, based on a determination that the BER is at or below the correctable BER, a connection between the OLT and the ONU at the higher order modulation, and maintain, based on a determination that the BER is greater than the correctable BER, the connection between the OLT and the ONU at the lower order modulation.

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.