High capacity channel for high speed passive optical networks

Abstract

According to one aspect of an embodiment, an optical line terminal (OLT) configured for downlink transmission in a passive optical network (PON) may include a processing device and a transceiver. The processing device may be configured to generate a first downlink signal for transmission on a first channel at a first signal level, and generate a second downlink signal for transmission on a second channel at a second signal level. The first signal level may be greater than the second signal level. The PMD transmitter may be configured to transmit a combined downlink signal including a first downlink signal and a second downlink signal. A first transmit power of the first downlink signal may be selected based on a comparison with a second transmit power of the second downlink signal in order to receive the first downlink signal from the combined downlink signal at an optical network unit (ONU).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 364,412, filed on May 9, 2022, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Embodiments discussed in this disclosure relate to passive optical networks and, in some embodiments, to high capacity channels for higher speed passive optical networks. Background Art

[0004] Unless otherwise indicated herein, the materials described herein are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.

[0005] A passive optical network (PON) may include an optical line terminal (OLT) that may be connected to one or more optical network units (ONUs). Transmissions from the OLT to the one or more ONUs may include broadcasts that may be received by all ONUs included in the PON.

[0006] The subject matter claimed in this disclosure is not limited to embodiments that solve any disadvantages or that operate only in environments such as described above. Rather, this background is merely provided to illustrate one example technology area where some embodiments described in this disclosure may be practiced. Summary of the invention

[0007] In some embodiments, an optical line terminal (OLT) for downstream transmission in a passive optical network (PON) may include a processing device and a physical medium dependent (PMD) transmitter. The processing device may be configured to generate a first downstream signal for transmission on a first channel at a first signal level. The processing device may be configured to generate a second downstream signal for transmission on a second channel at a second signal level. The first signal level may be greater than the second signal level. The PMD transmitter may be configured to transmit a combined downstream signal including the first downstream signal and the second downstream signal. A first transmit power of the first downstream signal may be selected based on a comparison with a second transmit power of the second downstream signal so as to receive the first downstream signal from the combined downstream signal at an optical network unit (ONU).

[0008] In some embodiments, an OLT for upstream reception in a PON may include a PMD receiver and a processing device. The PMD receiver may be configured to receive a combined upstream signal including a first upstream signal and a second upstream signal at the OLT. The first upstream signal may be received from a first ONU, and the second upstream signal may be received from a second ONU. The first upstream signal may have a greater received power than the second upstream signal. The processing device may be configured to decode the first upstream signal at the OLT, and decode the second upstream signal at the ONU by eliminating the first upstream signal from the combined upstream signal.

[0009] In some embodiments, an ONU for downstream reception in a PON may include a PMD receiver and a processing device. The PMD receiver may be configured to receive a combined downstream signal including a first downstream signal and a second downstream signal from an OLT at the ONU. The first downstream signal may have a greater received power than the second downstream signal. The processing device may be configured to decode the first downstream signal at the ONU, and decode the second downstream signal at the ONU by eliminating the first downstream signal from the combined downstream signal.

[0010] The objects and advantages of the embodiments will be realized and attained by at least the elements, features, and combinations particularly pointed out in the claims.

[0011] Both the foregoing general description and the following detailed description are presented by way of example and are explanatory rather than restrictive of the invention, as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Example embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

[0013] Figure 1 An exemplary passive optical network is shown.

[0014] Figure 2 An exemplary passive optical network transmission model for the downstream direction is shown.

[0015] Figure 3A An exemplary non-orthogonal multiple access (NOMA) receiver structure is shown.

[0016] Figure 3B An exemplary NOMA receiver structure is shown.

[0017] Figure 4 An exemplary non-return-to-zero (NRZ) transmission eye diagram is shown.

[0018] Figure 5 An exemplary pulse amplitude modulation 4 (PAM-4) transmission eye diagram is shown.

[0019] Figure 6An exemplary NOMA transmission eye diagram with NRZ main channel and NRZ high capacity is shown.

[0020] Figure 7 An exemplary NOMA transmission with different modulation levels at the transmitter is shown.

[0021] Figure 8 Exemplary transmitters for the main channel and the high capacity channel for a non-linear modulation scheme are shown.

[0022] Fig. 9 Passive optical network transmission with different setups of high capacity channels is shown.

[0023] Fig.10 Passive optical network transmission with different setups of high capacity channels is shown.

[0024] Fig.11 Passive optical network transmission with different setups of high capacity channels is shown.

[0025] Fig.12 An exemplary uplink NOMA transmission is shown.

[0026] Fig.13 The operation of uplink NOMA transmission is shown.

[0027] Fig.14 The operation of establishing a high capacity channel when the ONU is synchronized with the OLT is shown.

[0028] Fig.15 An exemplary downstream transmission process flow in an optical line terminal is shown.

[0029] Fig.16 An exemplary upstream transmission process flow in an optical line terminal is shown.

[0030] Fig.17 An exemplary downstream transmission processing flow in an optical network unit is shown.

[0031] Fig.18 An exemplary communication system for a passive optical network is shown.

[0032] Fig.19 A diagrammatic representation of a machine in the exemplary form of a computing device is shown within which a set of instructions may be executed, for causing the machine to perform any one or more of the methodologies discussed herein.

[0033] Fig. 20 An exemplary network topology used for simulation is shown.

[0034] Fig.21The relationship between the bit error rate (BER) and the optical received power for PAM-4 and NRZ transmission at a fiber length of 10 km is shown.

[0035] Fig. 22 The relationship between the bit error rate (BER) and the optical received power for PAM-4 and NRZ transmission at a fiber length of 20 km is shown.

[0036] Fig.23 The relationship between the mutual information and channel attenuation for NRZ and PAM-4 transmission is shown.

[0037] Fig.24 The relationship between the mutual information and channel attenuation of NOMA transmission is shown.

[0038] Fig.25 The attenuation versus data rate for NOMA transmission versus time-interleaved PAM-4 and NRZ transmission is shown.

[0039] Fig.26 The attenuation versus data rate is shown for different rates and FEC settings. DETAILED DESCRIPTION

[0040] An exemplary passive optical network (PON) may include a point-to-multipoint network. An optical line terminal (OLT) may be connected to multiple optical network units (ONUs) via optical fiber and passive optical splitters. There may be a mix of different generations of ONUs connected to the same OLT, for example, some traditional ONUs and some enhanced ONUs that support additional features.

[0041] As the transmission speed increases, it is no longer appropriate to determine the maximum transmission speed relative to the weakest link in the PON. Depending on the channel quality, for example, by different forward error correction (FEC) and / or modulation settings, a transmission scheme that allows different transmission rates for different ONUs may be more effective. ONUs with high channel quality can be served with higher data rates and reduced delays. All ONUs can benefit from the increase in data rates and the reduction in delays, because extra transmission time can be used for ONUs with lower channel quality and served at lower data rates.

[0042] In the upstream, each ONU may be assigned a transmission time slot based on service requirements. Each ONU may transmit its burst with different modulation and FEC settings. In the downstream, data may be transmitted as a broadcast, and all connected ONUs may receive the same data stream. Therefore, different modulation and FEC settings may not be assigned to different ONUs, since multiple ONUs may receive the transmitted symbols. Therefore, determining when different ONUs may receive different modulation or FEC settings in the downstream direction may facilitate differences in transmission parameters (e.g., modulation settings, FEC settings).

[0043] A possible solution for downstream adaptive transmission settings may include using ONU groups with the same transmission parameters (e.g., modulation and FEC settings) that can be served together at the same time. In the downstream broadcast direction, different ONU groups may have dedicated transmission time so that ONUs with low channel quality receiving the nominal data rate cannot receive higher data rate signals with different modulation and FEC settings. However, this transmission scheme may be incompatible with other PON transmission schemes that use fixed modulation settings (non-return-to-zero (NRZ) modulation with 2 optical power levels) and a fixed FEC code in the downstream.

[0044] In some embodiments, non-orthogonal multiple access (NOMA) can be used to provide a second channel (e.g., a high-capacity channel) on top of a nominal rate channel in a 50G passive optical network. The nominal rate channel can use: (i) nominal modulation, (ii) nominal FEC settings, and (iii) a traditional frame structure. The nominal rate channel can be broadcast to multiple ONUs. A high-capacity channel can be added to the nominal rate channel. The transmit power and FEC settings of the high-capacity channel can be adjusted to be received by ONUs with high channel quality. The high-capacity channel can be configured based on the receiving ONU group (i.e., using different transmit power and FEC settings). In some examples, transmission of the high-capacity channel can be disabled.

[0045] In some embodiments, the ONU that does not support high-capacity channels can decode the nominal rate channel by identifying the high-capacity channel as noise. For the ONU that supports high-capacity channels, the ONU can receive the nominal rate channel and the high-capacity channel. The nominal rate channel can be decoded and subtracted from the combined channel to obtain the high-capacity channel. Due to the existence of the additional channel, the total capacity of the PON may increase. Therefore, adaptive modulation and adaptive FEC settings can promote the increase of network capacity while maintaining the compatibility of the ONUs that use fixed modulation or fixed FEC settings.

[0046] In some embodiments, an optical line terminal (OLT) for downstream transmission in a passive optical network (PON) may include a processing device and a physical medium dependent (PMD) transmitter. The processing device may be configured to generate: (i) a first downstream signal for transmission at a first signal level on a first channel, and (ii) a second downstream signal for transmission at a second signal level on a second channel. The first signal level may be greater than the second signal level. The PMD transmitter may be configured to transmit a combined downstream signal including the first downstream signal and the second downstream signal. The first transmit power of the first downstream signal may be selected based on a comparison with the second transmit power of the second downstream signal so as to receive the first downstream signal from the combined downstream signal at an optical network unit (ONU).

[0047] In some embodiments, an ONU for downstream reception in a PON may include a PMD receiver and a processing device. The PMD receiver may be configured to receive a combined downstream signal including a first downstream signal and a second downstream signal from an OLT. The first downstream signal may have a greater received power than the second downstream signal. The processing device may be configured to decode the first downstream signal and decode the second downstream signal by eliminating the first downstream signal from the combined downstream signal.

[0048] In some embodiments, an OLT for upstream reception in a PON may include a PMD receiver and a processing device. The PMD receiver may be configured to receive a combined upstream signal including a first upstream signal and a second upstream signal. The first upstream signal may be received from a first ONU, and the second upstream signal may be received from a second ONU. The first upstream signal may have a greater received power than the second upstream signal. The processing device may be configured to decode the first upstream signal and the second upstream signal. The second upstream signal may be decoded by eliminating the first upstream signal from the combined upstream signal.

[0049] Embodiments of the present disclosure will be explained with reference to the drawings.

[0050] In some embodiments, Figure 1 A passive optical network (PON) including an optical line terminal (OLT) 110 is shown, and the optical line terminal (OLT) 110 includes optical network units (ONUs) 122a, 122b connected to high-quality channels that may have higher data rates (high data rate ONUs 122a, 122b), and ONUs 120a using nominal (lower) data rates. Transmission schemes that allow different transmission bit rates for different ONUs can be used for upstream and downstream directions. The present disclosure describes a transmission method that allows increased data rates for ONUs (e.g., 122a, 122b) with high channel quality. High data rate ONUs 122a, 122b can be fully backward compatible with ONUs 120a connected to the OLT 110 using nominal data rates.

[0051] In some embodiments, Figure 2 As shown, an exemplary PON transmission model for NOMA in the downstream direction may include an OLT 210 providing two data channels: (i) a first channel (e.g., a nominal data rate channel) having a bit sequence u1, and (ii) a first channel (e.g., a nominal data rate channel) having a transmission bit sequence u2. hThe PON 200 may include an OLT 210 for downstream transmission. The OLT 210 may include a processing device configured to: generate a first downstream signal (e.g., u1) for transmission on a first channel at a first signal level, and generate a second downstream signal (e.g., u2) for transmission on a second channel at a second signal level. h ), wherein the first signal level is greater than the second signal level.

[0052] In some embodiments, the OLT 210 may include an encoder 202a configured to encode the second downstream signal (eg, using forward error correction (FEC) encoding) to output the second downstream signal (eg, u h ) is used for transmission on the second channel. The second downlink signal (eg, u h ) may be directed to the modulation block 204a to be modulated and received by the combiner 206.

[0053] In some embodiments, OLT 210 may include an encoder 202b configured to encode the second downstream signal (e.g., using FEC encoding) to output a first downstream signal (e.g., u1) for transmission on a first channel. The first downstream signal (e.g., u1) may be output to modulation block 204b to be modulated and received by combiner 206.

[0054] In some embodiments, the first downlink signal (eg, u1 which may be modulated) and the second downlink signal (eg, u2 which may be modulated) may be h ) may be combined at combiner 206. The combined downstream signal X may be directed to a physical medium dependent (PMD) transmitter 208. The PMD transmitter 208 may be configured to transmit the combined downstream signal X using the optical fiber connection 212, the downstream signal X including the first downstream signal (e.g., u1) and the second downstream signal (e.g., u h ).

[0055] In some embodiments, the second downstream channel (e.g., a high capacity channel) may use a different (e.g., lower) signal level than the first downstream channel (e.g., a nominal data rate channel). Although the first downstream channel signal level and transmit power may have a relatively low level of variation, the second downstream channel (e.g., a high capacity channel) signal level and transmit power may have a higher level of variability than the variability of the transmit power of the first downstream channel, depending on the channel quality of the receiving ONU. In one example, as the channel quality of a particular ONU improves, the transmit power of that channel may be reduced.

[0056] In some embodiments, the second downlink signal (eg, u h ) to select a first transmit power of the first downstream signal (e.g., u1) by comparing the first transmit power of the first downstream signal (e.g., u1) with the second transmit power of the first downstream signal (e.g., u1) to facilitate receiving the first downstream signal (e.g., u1) from the combined downstream signal X at the optical network unit (ONU) 220, 230. In an example, the combined downstream signal X can be used to receive the first downstream signal (e.g., u1) at one or more of the ONU 220 configured to operate using a nominal (lower) data rate or the high data rate ONU 230 configured to operate using a high data rate.

[0057] In some embodiments, the processing device may be configured to calculate a transmit power scaling factor for the second downlink signal, wherein the transmit power scaling factor is selected to facilitate receiving the first downlink signal from the combined downlink signal.

[0058] In some embodiments, for a time instance t, the combined signal x may be calculated using the following formula:

[0059] x t =mod(u l,t )+α h mod(u h,t )

[0060] where u l,t is the first downlink signal at time instance t, and u h,t is the second downstream signal at time instance t, with a scaling factor α for the high capacity channel h <1.

[0061] In some embodiments, without the second downlink signal u h The first downlink signal u is sent in the case of l Compared with the case of the second downlink signal u h When combined, the first downlink signal u l Therefore, when the first downlink signal u l and the second downlink signal u h When combined, the first downlink signal u can be adjusted l In one example, compared to the case where there is no second downlink signal u h The first downlink signal u is transmitted l In the case of l The transmit power is increased to compensate for the increase in distortion in the combined downlink signal.

[0062] In some embodiments, the first downlink signal u l Or the second downlink signal u hThe transmission power of the first downlink signal u may be reduced based on the distortion caused by excessive transmission power. l Or the second downlink signal u h The transmission power of the first downlink signal u may be calculated based on an industry standard (eg, the Telecommunication Standardization Sector of the International Telecommunication Union (ITU)). Alternatively or additionally, the transmission power of the first downlink signal u may be calculated based on reducing power consumption or energy consumption. l Or the second downlink signal u h of transmission power.

[0063] In some embodiments, the combined electrical signal (e.g., combined downstream signal) can be converted into an optical signal and transmitted to ONUs 220 and 230 via optical fiber 212 and splitter 214. In some embodiments, the first downstream signal and the second downstream signal can be converted from electrical to optical as separate signals and combined in the optical domain to generate a combined downstream signal. Thus, the combined downstream signal can be an electrical signal or an optical signal. When combined in the electrical domain, digital conversion can be used to generate the combined downstream signal.

[0064] In some embodiments, the ONU 220 for downstream reception in the PON 200 may include an optical fiber 218b configured to provide a first downstream signal to a PMD receiver 222b. The PMD receiver may be configured to convert the first downstream signal from an optical signal into an electrical signal y. The received electrical signal y may be converted into a digital signal using an analog-to-digital converter (ADC) 224b. The digital signal may be directed to an equalizer 226b, which may be configured to mitigate inter-symbol interference, and be restored to a signal For using N eqmain Superscript The linear equalizer can be used to calculate the signal at time instance t using the following formula

[0065]

[0066] In some embodiments, the signal may be demodulated in block 228b to generate a signal The signal The signal may be decoded using a decoder 230b (eg, a FEC decoder) to generate an output signal.

[0067] In some embodiments, the receiver of ONU 220 may accept the second downstream signal (e.g., high capacity channel) present on the combined downstream signal as additional noise. When the transmit power of the first channel is selected accordingly, the presence of the second channel (e.g., high capacity channel) may not affect the reception of the first channel (e.g., nominal data rate channel).

[0068] In some embodiments, the ONU 230 for downstream reception in the PON 200 may include a PMD receiver 222a configured to receive a combined downstream signal including a first downstream signal and a second downstream signal from the OLT 210 at the ONU 230. In some examples, the first downstream signal may have a greater received power than the second downstream signal. In some embodiments, the ONU 230 may include a processing device configured to: decode the first downstream signal, and decode the second downstream signal by eliminating the first downstream signal from the combined downstream signal.

[0069] In some embodiments, in an ONU supporting a high capacity channel (e.g., 230), after the received signal is converted to an electrical signal, digitized, and equalized, demodulation and decoding can be performed in two parallel channels (e.g., a nominal rate channel and a high data channel). For a first downstream signal (e.g., a nominal rate channel), the operation can be as described with respect to 220. For a second downstream signal (e.g., a high capacity channel), the operation can use a different signal path than the first downstream signal (e.g., a nominal rate channel).

[0070] In some embodiments, the PMD receiver 222a may be configured to convert the combined downstream signal received at the PMD receiver as an optical signal (via the optical fiber 218a) into an electrical signal. The electrical signal may be converted into a digital signal y using an ADC 224a. The digital signal y may be directed to an equalizer 226a, which may be configured to mitigate intersymbol interference and output a recovered signal Recovered signal may be directed to demodulation block 228a for demodulation and to decoding block 230a for use as the recovered signal The first downlink signal is decoded based on the combined downlink signal present in the decoder.

[0071] In some embodiments, the output from decoder 230a (e.g., a decoded bit sequence calculated based on the first downlink signal) can be directed to encoder 232a to be re-encoded and provided to channel canceller filter 234a (e.g., a nominal rate channel canceller filter). Channel canceller filter 234a can be configured to filter and subtract the output signal of ADC 224a to obtain a high capacity channel, which can be calculated using the following formula:

[0072]

[0073] in is the cancellation signal at time instance t, and is the output of equalizer 226a at time instance t.

[0074] In some embodiments, this signal path (i.e., from decoder 230a to encoder 232a to channel canceller filter 234a) may be denoted as a "high rate path." This high rate path minimizes error propagation from the "nominal rate path" (i.e., from equalizer 226a to demodulation block 228a to decoder 230a) to the high rate path.

[0075] In another embodiment, denoted as "low delay path", a hard decision may be performed on the output of the demodulation block 228a for the first downstream channel to generate the input to the channel canceller filter 234a using the following equation:

[0076]

[0077] in is the cancellation signal at time instance t, and is the output of equalizer 226a at time instance t. For this low-delay path, No pre-decoding and encoding may be required, as the low-latency path may omit the decoder 230a and encoder 232a when input to the channel canceller filter 234a.

[0078] In some embodiments, the output from the channel canceller filter 234a can be used to cancel the first downlink signal from the combined downlink signal received by the combiner. The first downlink signal can be eliminated from the combined downlink signal by using one or more of: (i) the limiter output; or (ii) the re-encoded decoder output. In some examples, reconstructing the first downlink channel can result in decoding a high-capacity channel so that errors do not accumulate.

[0079] In some embodiments, the hard decision output signal can be filtered at combiner 236a and subtracted from the ADC output signal. The signal after the subtraction may be:

[0080]

[0081] In some embodiments, after the first downlink signal has been removed from the combined downlink signal using channel cancellation, the second equalizer 238a may be used to recover the second downlink signal (e.g., carried on the high capacity channel). The linear equalizer can be used to calculate the recovered second downstream signal using the following formula:

[0082]

[0083] In some embodiments, the output of equalizer 238a may be demodulated using demodulation block 240a to generate signal The decoder 242a may be used to decode the signal The two recovered data streams u1 and u h Forwarded to, for example, a user network for further processing.

[0084] In some embodiments, channel canceller filter 234a may be configured to generate a cancellation signal based on one or more of an analog-to-digital (ADC) (eg, 224a) output signal or an equalizer output signal (eg, 226a) to cancel the first downlink signal from the combined downlink signal.

[0085] In some embodiments, Figure 3A As shown, the receiver 300 (eg, for an ONU) may be configured to generate a cancellation signal to subtract the first downstream signal from the combined downstream signal. The signal for canceling the second downstream signal may be taken from the input of the equalizer (eg, Figure 2 as shown) or the output of the equalizer (as Figure 3A and Figure 3B shown).

[0086] In some embodiments, when one equalizer is used for the first downlink signal and the second downlink signal, noise may not be mitigated compared to a case where a different equalizer is used for the second downlink signal. Using different equalizers can provide reduced noise because each equalizer can be designed to reduce noise for a specific downlink signal.

[0087] In some embodiments, the first downlink signal may be decoded using the first equalizer 306, and the second downlink signal may be decoded using the second equalizer 318. In some embodiments, when the cancellation signal is taken from the output of the equalizer 306, the high capacity channel may use the second equalizer 318, which may be coupled to the output of the equalizer 306 and the summing point. The second equalizer may be optimized for the characteristics of the high capacity channel. In one example, Figure 3B As shown, the second equalizer can be omitted. In some embodiments, Figure 3A or Figure 3B The receiver in may include a non-linear filter (not shown).

[0088] In some embodiments, respectively Figure 3A and Figure 3B The receivers 300, 350 shown in FIG. 3 may include a Figure 2Receivers 300, 350 may include PMD receivers 302, 352, ADCs 304, 354, equalizers 306, 356, demodulation blocks 308, 358, decoders 310, 360, encoders 312, 362, channel canceller filters 314, 364, combiners 316, 366, second equalizers 318 (in Figure 3A In, but in Figure 3B ), demodulation blocks 320, 368 and decoders 322, 370. These components may have the same Figure 2 Functionality similar to the one described.

[0089] In some embodiments, the processing device can be configured to combine the second downlink signal with the first downlink signal using non-orthogonal multiple access (NOMA). That is, the disclosed scheme combines two data channels on a single optical fiber established at the same wavelength and time (i.e., using NOMA). The two channels, the nominal rate channel and the high capacity channel, are separated in the transmit power domain.

[0090] In some embodiments, the nominal rate channel can be transmitted with higher power so that it can be decoded by multiple ONUs. In order to receive high-capacity channels, the nominal rate channel can be decoded and eliminated from the received signal. The high-capacity channel can be transmitted with lower power, and only ONUs with sufficient channel quality (i.e., those with sufficiently low signal attenuation or noise) can decode it.

[0091] In some embodiments, as an example, a NOMA transmission scheme 400 with an NRZ nominal rate channel (eg, Figure 4 ) and the transmission eye diagram of the NOMA transmission scheme 500 with a PAM-4 nominal rate channel. Figure 4 and Figure 5 , using the independent variable in time / unit interval and the dependent variable in amplitude (using arbitrary units). Figure 4 The eye opening (410a, 410b) of the NRZ transmission shown or Figure 5 Compared to the eye openings (510a, 510b, 510c, 510d, 510e, 510f) of the PAM-4 transmission shown, Figure 6 The NOMA transmission scheme 600 shown may be selected to have an eye opening (610a, 610b) that is larger than the eye opening (i.e., the upper eye opening 620a, 620c or the lower eye opening 620b, 610b) in a nominal rate channel ( Figure 6Independent variables in time / unit interval and dependent variables in amplitude (using arbitrary units) are used. It should be noted that the NOMA scheme may not be limited to using NRZ modulation, but other modulation schemes may be used for different channels, e.g., NRZ for nominal rate channels and PAM-4 for high capacity channels.

[0092] In some embodiments, the symbol rate of the nominal rate channel and the symbol rate of the high capacity channel may also be different, for example, the high capacity channel may use half the symbol rate of the nominal rate channel or twice the symbol rate of the nominal rate channel. In one example, the receive clock may be derived from the nominal rate channel and used to receive the nominal rate channel and the high capacity channel.

[0093] In some embodiments, the error correction settings (e.g., FEC settings) of the nominal rate channel and the high capacity channel can be different. The high capacity channel can use an error correction code (e.g., FEC code) that allows one or more of a higher raw BER, a lower input SNR, etc.

[0094] In some embodiments, the PON optical receiver may be implemented with an avalanche photodiode for highly nonlinear photoelectric conversion. Therefore, nonlinear equalization and nonlinear precompensation may be used to enhance performance, particularly for reception of high capacity channels. In one example, the processing device may be configured to use one or more of nonlinear equalization or nonlinear precompensation to improve the signal quality of the second downlink signal compared to the signal quality of the first downlink signal.

[0095] In some embodiments, to cope with nonlinear effects, the transmit amplitude of the high capacity channel may be selected differently for different signal levels on the nominal rate channel. Figure 7 As shown, for the NOMA transmission scheme with time / unit interval as the independent variable and amplitude in arbitrary units as the dependent variable, NRZ transmission on the nominal rate channel and the high capacity channel is provided.

[0096] In some embodiments, the processing device can be configured to calculate a first offset compensation for the second downlink signal when a first bit value from the first channel is identified, or to calculate a second offset compensation for the second downlink signal when a second bit value from the first downlink signal is identified. In one example, the first bit value can be different from the second bit value.

[0097] In some embodiments, for a logic 1 transmitted on a nominal rate channel, the signal amplitude may be 5 / 3 of the signal amplitude for a logic 0 transmitted on a nominal rate channel. As a result, the eye openings (720a, 720b, 720c, 720d) of the high capacity channel during transmission of 1s (720a, 720c) and 0s (720b, 720d) on the nominal rate channel may be the same at the receiver side, which is consistent with Figure 6 Different from the scenarios provided in Figure 6 , the eye opening of the high capacity channel during transmission 1 (620a, 620c) is smaller than the eye opening of the high capacity channel during transmission 0 (620b, 620d).

[0098] In some embodiments, Figure 8 As shown, for nonlinear modulation at the transmitter 800, transmitter processing can be adjusted based on the transmission of a logic 1 or logic 0. The transmitter 800 may include an encoder 802, which may be configured to direct a nominal rate signal (e.g., a bit sequence u1) to one or more modulation blocks 840 or modulation blocks 808. The transmitter 800 may also include an encoder 806, which may be configured to direct a high capacity signal (e.g., a bit sequence u1) to one or more modulation blocks 840 or 808. h ) is directed to the modulation block 808. The modulator block 804 can be configured to direct the modulated signal based on the nominal rate signal (e.g., the bit sequence u1) to the combiner 810, and the modulator block 808 can be configured to direct the modulated signal based on the high capacity signal (e.g., the bit sequence u h ) is directed to a combiner 810. The combiner 810 may be configured to combine a nominal rate signal (eg, bit sequence u1) and a high capacity signal (eg, bit sequence u h ) to generate a combined transmit signal x. The combined transmit signal x may be directed to a PMD transmitter 812 to be sent to one or more ONUs using one or more optical fibers, splitters, etc.

[0099] In some embodiments, for a time instance t, the combined transmit signal x may be calculated using the following formula:

[0100]

[0101] With different scaling factors α h,0 <1 and α h,1 <1, depending on the nominal rate channel transmitting 1 or 0. For multi-level modulation on a nominal rate channel, each modulation level of the nominal rate channel may use a different scaling factor.

[0102] In some embodiments, at the receiver side, a nonlinear equalizer may be used. Using a nonlinear equalizer, the offset compensation of the high-capacity channel equalizer may use different coefficients depending on the received symbol of the primary channel, for example, g is used when 0 is received on the primary channel. dcblock,0 and g is used when 1 is received on a nominal rate channel dcnlock,1 .

[0103] In some embodiments, there may be different coefficient sets for different transmission symbols of the high capacity channel equalizer. as well as The overall receive equalization for a given received bit may include a combination of coefficients from the two equalizers calculated using the following equation:

[0104]

[0105] In some embodiments, other types of non-linear equalizer structures may be used (eg, Maximum Likelihood Sequence Estimation (MLSE) or Bahl-Cocke-Jelinek-Raviv (BCJR)). As a result, nominal rate channel bits may be input to a high capacity channel equalizer.

[0106] In some embodiments, in the downstream direction, in order to maintain sufficient sensitivity for ONUs experiencing high attenuation, the opening of the eye diagram of the nominal rate channel can be unaffected by the power transmitted by the high capacity channel. In one example, when the nominal rate channel is intended to be received by these remote ONUs, additional transmit power can be used to carry the NRZ symbols of the two channels.

[0107] In some embodiments, the high capacity channel may not be continuously transmitted, and even with an active high capacity channel, transmission parameters (e.g., signal amplitude, modulation, and FEC settings) may change. In one example, the processing device may be configured to calculate a transmission parameter value for a first downlink signal that is different from a transmission parameter value for a second downlink signal. The transmission parameters may include one or more of a modulation setting, a forward error correction (FEC) setting, a symbol rate, a frame structure, a communication protocol, a burst setting, and the like.

[0108] In some embodiments, the frame structure of the high capacity channel may be different from the frame structure of the nominal rate channel. In some embodiments, FEC may be selected to achieve a threshold channel quality for one or more ONUs. In some embodiments, modulation settings may be selected to achieve a threshold channel quality for one or more ONUs.

[0109] In some embodiments, the downstream transmission can use bursts for high-capacity channels. In one example, when bursts are used for high-capacity channels on the downstream transmission, one or more bits can be used to indicate to the ONU that the burst transmission is coming. This situation may be different from other situations, in which the ONU can monitor all incoming transmissions to determine whether the incoming transmission is for a specific ONU or for different ONUs. Therefore, the one or more bits used to indicate to the ONU that the burst transmission is coming can be used to direct the burst transmission to a specific ONU. In some examples, burst transmission can be used for the downstream of high-capacity channels, and broadcast transmission can be used for the downstream of nominal rate channels. In some examples, the upstream transmission from the ONU to the OLT can use one or more of burst transmission or broadcast transmission.

[0110] In some embodiments, Fig. 9 As shown, a PON transmission 900 has different settings for high capacity channels. The high capacity channel can be disabled 902, or use lower power 904, or use higher power 906. The inner eye (910a, 910b, 910c, 910d, 910e, 910f, 910g, 910h, 910i, 910j) of the channel quality corresponding to the nominal rate channel can be constant.

[0111] In some embodiments, Fig.10 As shown, different settings of high-capacity channels are provided for PON transmission 1000, and the average logic 0 level and logic 1 level of the nominal rate channel can be constant. The high-capacity channel can be disabled 1002, or use a lower power 1004, or use a higher power 1006. The inner eye of the nominal rate channel can have different sizes in the following situations: (i) the high-capacity channel is disabled (1010a, 1010b, 1010c, 1010d), (ii) the high-capacity channel uses a lower power (1010e, 1010f, 1010g, 1010h) and (iii) the high-capacity channel uses a higher power (1010i, 1010j). Nevertheless, the average logic 0 level and the average logic 1 level of the nominal rate channel can be constant.

[0112] In some embodiments, Fig.11 As shown, PON transmission 1100 provides different settings for high-capacity channels and provides average logic 0 levels and logic 1 levels that may be constant for nominal rate channels. In addition, the maximum extinction ratio can be constant. The high-capacity channel can be disabled 1002, or use lower power 1004, or use higher power 1006. The inner eye of the nominal rate channel can have different sizes in the following cases: (i) the high-capacity channel is disabled (1110a, 1110b, 1110c, 1110d) (ii) the high-capacity channel uses lower power (1110e, 1110f, 1110g, 1110h) and (iii) the high-capacity channel uses higher power (1110i, 1110j). However, the average logic 0 level and average logic 1 level of the nominal rate channel can be constant, and the maximum extinction ratio can be constant.

[0113] In some embodiments, the channel conditions of the ONUs receiving the high capacity channels and the channel conditions of the ONUs receiving the nominal rate channels can be used to select the transmission settings for the high capacity channels. In some embodiments, the processing device can be configured to calculate the transmit power increase or extinction ratio increase at the OLT when transmitting the combined downstream signal.

[0114] In some embodiments, the channel quality of the nominal rate channel may be slightly degraded when the high capacity channel is added, because the high capacity channel may appear as additional noise in the nominal rate channel. In one embodiment, the OLT transmitter supporting the high capacity channel may have a higher transmit power and / or a higher extinction ratio than an OLT transmitter that is intended to transmit the nominal rate channel, or that is intended to transmit the high capacity channel without loss relative to the nominal rate channel (see, e.g., Fig. 9 ).

[0115] In some embodiments, the OLT transmitter may not use higher transmit power or higher extinction ratio (see, e.g., Fig.10 and Fig.11 ), but may be able to support ONUs on nominal rate channels without margin for signal quality. In this case, when transmitting the high capacity channel, the ONU receiving the nominal rate channel may experience a reduced eye opening, which is detrimental to signal quality. In some examples, when data packets on the nominal rate channel are sent to a specific ONU (which may not have sufficient margin on the transmission channel), the high capacity channel may be suspended (or sent at a negligibly low power to avoid errors in the nominal rate channel). In some examples, in order to avoid reception errors in the nominal rate channel, the loss of signal quality of the nominal rate channel may be lower than the tolerance of the nominal rate channel of the ONU receiving the nominal rate channel.

[0116] In some embodiments, the high capacity channel can be used to serve some specific ONUs, while other ONUs can be served on the nominal rate channel. In other embodiments, the same ONU can be served simultaneously by the nominal rate channel and the high capacity channel, sending short bursts at very high data rates.

[0117] In some embodiments, the processing device can be configured to transmit duplicate data on a second channel (e.g., a high-capacity channel) to enhance forward error correction (FEC) protection. In some examples, the high-capacity channel can be used to provide higher FEC protection rather than a higher data rate by: (i) transmitting duplicate data on the high-capacity channel, or (ii) sending additional parity bytes on the high-capacity channel to increase FEC decoding in the nominal rate channel.

[0118] In some embodiments, the processing device can be configured to transmit data on a second channel (e.g., a high-capacity channel) to reduce latency. In some examples, transmitting data on the high-capacity channel can be 1.5 times, 2.0 times, 2.5 times, 3.0 times, etc. faster than transmitting data on the nominal rate channel.

[0119] In some examples, when the nominal rate channel is congested by large transmission bursts, the high capacity channel may be used to transmit high latency signals.Alternatively or additionally, when the high capacity channel is congested by large transmission bursts, the nominal rate channel may be used to transmit high latency signals.

[0120] In some embodiments, a high capacity channel may be available at any time, even though its capacity may vary. This availability of a high capacity channel may be used for services that use very low latency, which may not accept longer interruptions that may be caused by transmissions to other ONUs over nominal rate channels or overhead channels established within nominal rate channels. The high capacity channel may be used as a low latency channel in these scenarios, providing low latency services.

[0121] In some embodiments, the processing device can be configured to transmit data on a second channel (e.g., a high-capacity channel) to reduce power usage. When broadcast transmission is used to transmit data, each receiving ONU can process the entire encryption chain for the nominal rate channel. When high-capacity channels are used to transmit data, the ONU can be configured to monitor a specific high-capacity channel instead of multiple broadcast channels.

[0122] In some embodiments, even though high capacity channels may use additional operations and therefore add additional computations, in the receiver, high capacity channels can be used to save power and complexity. In some PON systems, the ONU receiver may not know the arrival time of data packets addressed to the ONU. Therefore, each ONU may perform FEC decoding, packet processing (and decryption) on the complete data stream, while only a small portion of the data may be relevant to the ONU.

[0123] In some embodiments, the high capacity channel can be transmitted to a specific ONU or a specific ONU group. The ONU that can be served by the high capacity channel can save power because the ONU may not always receive all the data on the main channel. This power reduction scheme can be used to transmit overhead channels on the nominal rate channel, and during the reception of data on the high capacity channel. The corresponding transmission time can be known in advance.

[0124] This ability to direct specific downstream transmissions to specific ONUs to reduce power usage can be used for nominal rate channels. The high capacity channel can be configured to provide location information or other configuration information related to the nominal rate channel using a protocol associated with the high capacity channel. Thus, the high capacity channel can provide reduced power usage by: (i) locating the high capacity channel to a specific ONU, or (ii) providing information about the nominal rate channel that can be used to reduce the power usage of the nominal rate channel.

[0125] like Fig.12As shown, the NOMA scheme can also be used for the upstream. Therefore, the OLT 1215 can allow two ONUs 1201a, 1201b with appropriate received power levels at the OLT 1215 to transmit simultaneously, for example, one ONU 1201a has low channel attenuation and the other ONU 1201b has high channel attenuation.

[0126] In some embodiments, the OLT 1215 for upstream reception in the PON 1200 may include a PMD receiver 1214 configured to receive a combined upstream signal including a first upstream signal and a second upstream signal at the OLT 1215. The upstream signal may be received from the first ONU 1201a, and the second upstream signal may be received from the second ONU 1201b. In some examples, the first upstream signal may have a greater received power than the second upstream signal.

[0127] In some embodiments, the OLT 1215 may include a processing device configured to decode the first upstream signal at the OLT 1215, and to decode the second upstream signal by eliminating the first upstream signal from the combined upstream signal at the OLT 1215. In one example, the processing device may be configured to cause a hard decision to be performed on the first upstream signal to generate a first channel canceller filter, thereby eliminating the first upstream signal from the combined upstream signal to generate the second upstream signal.

[0128] In some embodiments, the upstream signal received from the ONU (e.g., 1201a) with a higher receive power may be decoded before the upstream signal is received from the ONU 1201b with a lower receive power. The recovered signal from, for example, ONU 1201a may be re-encoded, filtered, and eliminated from the combined upstream signal to recover the second upstream signal from the second ONU (e.g., 1201b).

[0129] In some embodiments, the processing device may be configured to calculate a minimum received power difference between a first received power of a first ONU (e.g., 1201a) and a second received power of a second ONU (e.g., 1201b). In order to decode messages from multiple ONUs 1201a, 1201b that are transmitting simultaneously, the received power of overlapping signals at the OLT 1215 may be within a certain power limit. In one example, there may be a minimum difference in power levels for distinguishing between different modulation levels.

[0130] In some embodiments, the desired power level can be achieved in various ways. In one example, OLT 1215 can select ONUs (e.g., 1201a, 1201b, etc.) that are allowed to transmit simultaneously so that the received power level at OLT 1215 reaches the minimum power level difference. That is, the processing device can be configured to select the first ONU 1201a and the second ONU 1201b based on the predicted received power difference. The predicted received power difference can contribute to the minimum power difference between the first received power of the first ONU 1201a at OLT 1215 and the second received power of the second ONU 1201b at OLT 1215.

[0131] In some embodiments, the processing device can be configured to select a first transmit power for the first ONU 1201a and a second transmit power for the second ONU 1201b. The first transmit power and the second transmit power can be selected to facilitate a minimum receive power difference between a first receive power of the first ONU 1201a and a second receive power of the second ONU 1201b. In other words, the OLT 1215 can adjust the transmit power of the ONUs 1201a and 1201b that transmit simultaneously so as to reach a minimum receive power level.

[0132] In some embodiments, the minimum receive power difference may be achieved by using one or more of the following: (i) selecting the first ONU and the second ONU to achieve the minimum receive power difference, or (ii) adjusting the transmit power of the first ONU or the second ONU to achieve the minimum receive power difference.

[0133] In some embodiments, adjusting the transmit power of one or more of the first ONU or the second ONU to achieve a minimum receive power difference may provide enhanced performance compared to selecting the first ONU or the second ONU based on a predicted or historical receive power difference.

[0134] In some embodiments, OLT 1215 can be configured to receive a first upstream signal from a first ONU 1201a and a second upstream signal from a second ONU 1201b, wherein both the first ONU 1201a and the second ONU 1201b operate using a nominal rate channel rather than a high capacity channel. In this example, one or more of the first ONU 1201a or the second ONU 1201b can be selected to achieve a minimum receive power difference, or one or more of the transmit power of the first ONU 1201a or the transmit power of the second ONU 1201b can be adjusted to achieve a minimum receive power difference.

[0135] In some embodiments, the processing device may be configured to calculate a first sampling point of the first ONU 1201a and a second sampling point of the second ONU 1201b to align the first ONU 1201a and the second ONU 1201b in time. That is, in contrast to the downstream NOMA channel, upstream transmissions from different ONUs 1201a, 1201b may not be completely aligned in time. Therefore, the sampling point may be adjusted, for example in an equalizer, for decoding the first ONU 1201a or the second ONU 1201b.

[0136] In some embodiments, control of ONU transmit power can be used for upstream NOMA because it is not possible to select ONUs with appropriate channel attenuation to combine for simultaneous transmission. When this happens, the received power measurement at the OLT can be used to control the optical transmit power of one or more of the first ONU or the second ONU to achieve the minimum received power difference.

[0137] In some embodiments, OLT 1215 may include one or more of the following: PMD receiver 1214, ADC 1216, equalizer 1218, demodulation block 1220, decoder 1222, encoder 1224, filter 1226, combiner 1227, equalizer 1228, demodulation block 1230, or decoder 1232. PMD receiver 1214 may be configured to receive an optical uplink signal and convert the optical uplink signal into an uplink electrical signal. ADC 1216 may be configured to receive an upstream electrical signal and convert the upstream electrical signal into an upstream digital signal. Equalizer 1218 may be configured to mitigate inter-symbol interference of an uplink digital signal received from ADC 1216. Demodulation block 1220 may be configured to demodulate a signal received from equalizer 1218. Decoder may be configured to decode a demodulated signal received from demodulation block 1220. The signal output from the decoder may be the recovered first upstream signal (eg, a bit sequence corresponding to the bit sequence transmitted from the first ONU 1201a on the combined upstream signal).

[0138] In some embodiments, the recovered first uplink signal output from the decoder block 1222 may be directed to the encoder 1224 for re-encoding. The re-encoded signal from the encoder 1224 may be directed to the filter 1226 to generate a cancellation signal. The filter 1226 may be configured to cancel the first uplink signal from the combined uplink signal received from the ADC 1216 output at the combiner. The combiner may be configured to direct the eliminated signal to the equalizer 1228 to mitigate inter-symbol interference. The equalizer 1228 may be configured to output the signal to the demodulation block 1230 to output a demodulated signal to be directed to the decoder block 1232. The decoder block may decode the signal to recover the second uplink signal (e.g., a bit sequence corresponding to a bit sequence sent from the second ONU 1201b on the combined uplink signal).

[0139] In some embodiments, the first ONU 1201a may include an encoder 1202, a modulation block 1204, and a PMD transmitter 1206. The encoder 1202 may be configured to encode a first upstream signal (e.g., a bit sequence). The modulation block 1204 may be configured to receive the encoded first upstream signal from the encoder 1202 and modulate the signal. The PMD transmitter 1206 may be configured to receive the modulated signal from the modulation block 1204 and convert the modulated signal into an optical signal for transmission to a splitter 1208 via an optical fiber 1207 for combination with upstream signals from other ONUs (e.g., 1201b) and transmission to an OLT 1215 using an optical fiber 1213.

[0140] In some embodiments, the second ONU 1201b may include an encoder 1208, a modulation block 1210, and a PMD transmitter 1212. The encoder 1208 may be configured to encode a first upstream signal (e.g., a bit sequence). The modulation block 1210 may be configured to receive the encoded first upstream signal from the encoder 1208 and modulate the signal. The PMD transmitter 1212 may be configured to receive the modulated signal from the modulation block 1210 and convert the modulated signal into an optical signal for transmission to the splitter 1208 via an optical fiber 1211 for combination with an upstream signal from other ONUs (e.g., 1201a) and transmission to the OLT 1215 using an optical fiber 1213.

[0141] In some embodiments, Fig.13As shown, a process 1300 for upstream NOMA transmission is provided. As shown in box 1305, the OLT can request an upstream transmission burst from each interested ONU (e.g., using full TX power). As shown in box 1310, the OLT can measure the received (RX) power and signal quality (e.g., BER, SNR, SNR margin, etc.). The received power level can be stored in a database. As shown in box 1315, the OLT can be configured to identify ONUs that can transmit simultaneously. As shown in box 1320, the OLT can be configured to calculate the transmit power level of the ONUs transmitting simultaneously. As shown in box 1325, the OLT can be configured to transmit a burst configuration and transmit power to the ONU for transmission. As shown in box 1330, the OLT can be used to receive and decode a first ONU message. As shown in box 1335, the OLT can be configured to eliminate the first ONU message from the received signal. As shown in box 1340, the OLT can be used to receive and decode a second ONU message.

[0142] In some embodiments, when selecting ONU to transmit simultaneously, ONU can be selected so that the transmit power of the second ONU received can be reduced while the signal quality is maintained at a threshold value sufficient to receive the packet. In one example, the symbol rate of the first ONU transmission and the second ONU transmission can be selected differently. The highest rate can be used for the first ONU transmission, and the same rate or a lower rate can be used for the second ONU signal. Therefore, the receiving path can run at the highest rate.

[0143] In some embodiments, the processing device may be configured to send non-orthogonal multiple access (NOMA) downstream receiving capability from the ONU to the OLT. The processing device may be configured to send diagnostic parameters of the ONU from the ONU to the OLT. The processing device may be configured to send channel quality information from the ONU to the OLT.

[0144] In some embodiments, to establish a high capacity channel for an ONU configured to synchronize with an OLT, several operations 1400 may be performed, such as: Fig.14As shown. In one example, as shown in box 1405, the ONU can be configured to synchronize using a nominal rate channel. In one example, as shown in box 1410, the OLT can be configured to request capabilities from the synchronized ONU using a nominal rate channel. In one example, the OLT can be configured to determine that the synchronized ONU supports NOMA downstream reception and request diagnostic parameters (e.g., BER, SNR, SNR margin, received optical power, etc.), as shown in box 1415. In one example, as shown in box 1420, the OLT can be configured to determine the capacity of the high-capacity channel of the synchronized ONU. In one example, as shown in box 1425, the OLT can be configured to determine the modulation, rate, and FEC settings of the high-capacity channel. In one example, as shown in box 1430, the OLT can be configured to start transmission on the high-capacity channel of the synchronized ONU.

[0145] In some embodiments, synchronization may be performed on a nominal rate channel because it may not be possible to determine in advance whether the ONU supports high-capacity channels. After the ONU has been synchronized for upstream and downstream transmissions, the capabilities of the ONU may be requested to identify the ONU's support for high-capacity channels. In some examples, when a first upstream signal is received from a first ONU and a second upstream signal is received from a second ONU, the first ONU and the second ONU may be synchronized using one or more of: a digital sampling filter, a sampling rate filter, a sampling rate converter, a polyphase filter including a plurality of linear filters that may be switched based on phase alignment between the first upstream signal and the second upstream signal, linear interpolation, etc., or a combination thereof. In one example, the signal used for synchronization may be taken from before the equalizer and before the summing point (e.g., Fig.12 between 1216 and 1227 in), after the summing point (for example, Fig.12 ), or any other suitable point.

[0146] In some embodiments, when the nominal rate channel is used for synchronization and the high capacity channel has been established, the high capacity channel can be used for low latency traffic. Synchronization on the nominal rate channel may take a significant amount of time, which may cause the nominal rate channel to be blocked for a long period of time. In this case, the high capacity channel can be configured to carry low latency traffic.

[0147] Fig.15 The process flow of an example method 1500 for downstream transmission in a PON according to at least one embodiment described in the present disclosure is shown. The method 1500 may be arranged according to at least one embodiment described in the present disclosure.

[0148] Method 1500 may be performed by processing logic that may include hardware (circuitry, dedicated logic, etc.), software (e.g., software running on a computer system or dedicated machine), or a combination of both. Fig.19 Processing device 1902, Fig.18 In the communication system 1800 or another device, combination of devices, or system.

[0149] Method 1500 may begin at block 1505, where processing logic may generate a first downstream signal for transmission on a first channel at a first signal level.

[0150] At block 1510, processing logic may generate a second downstream signal for transmission on a second channel at a second signal level, wherein the first signal level is greater than the second signal level.

[0151] Without departing from the scope of the present disclosure, modifications, additions, or omissions may be made to the method 1500. For example, in some embodiments, the method 1500 may include any number of other components that may not be explicitly shown or described.

[0152] Fig.16 A process flow of an example method 1600 that may be used for upstream reception in a PON according to at least one embodiment described in the present disclosure is shown. The method 1600 may be arranged according to at least one embodiment described in the present disclosure.

[0153] Method 1600 may be performed by processing logic that may include hardware (circuitry, dedicated logic, etc.), software (such as software running on a computer system or a dedicated machine), or a combination of both. Fig.19 Processing device 1902, Fig.18 In the communication system 1800 or another device, combination of devices, or system.

[0154] Method 1600 may begin at block 1605 where processing logic may decode a first upstream signal at an OLT.

[0155] At block 1610 , processing logic may decode the second upstream signal at the OLT by eliminating the first upstream signal from the combined upstream signal.

[0156] Without departing from the scope of the present disclosure, modifications, additions, or omissions may be made to the method 1600. For example, in some embodiments, the method 1600 may include any number of other components that may not be explicitly shown or described.

[0157] Fig.17A process flow of an example method 1700 that may be used for downstream reception in a PON according to at least one embodiment described in the present disclosure is shown. The method 1700 may be arranged according to at least one embodiment described in the present disclosure.

[0158] Method 1700 may be performed by processing logic that may include hardware (circuitry, dedicated logic, etc.), software (e.g., software running on a computer system or dedicated machine), or a combination of both. Fig.19 Processing device 1902, Fig.18 In the communication system 1800 or another device, combination of devices, or system.

[0159] Method 1700 may begin at block 1705 , where processing logic may decode a first downstream signal at an ONU.

[0160] At block 1710, processing logic may decode the second downstream signal at the ONU by eliminating the first downstream signal from the combined downstream signal.

[0161] Without departing from the scope of the present disclosure, modifications, additions, or omissions may be made to the method 1700. For example, in some embodiments, the method 1700 may include any number of other components that may not be explicitly shown or described.

[0162] In some embodiments, a transmitter for NOMA downstream transmission may include: a non-orthogonal multiplexing transmitter for PON downstream transmission, wherein: (i) a first PON signal can be generated according to a PON protocol; and (ii) a second PON transmission with a different (e.g., lower) transmit signal level can be generated and combined with the first PON signal. In some examples, the second signal can use one or more of the following: (a) a different protocol from the first signal, (b) a different modulation from the first signal, (c) a different error correction code from the first signal, (d) a different protocol from the first signal, (e) a different burst setting (e.g., the second signal can be sent in bursts, while the first signal can be continuous).

[0163] In some embodiments, a receiver for NOMA downlink transmission may include a first PON signal that can be received according to a PON protocol. The first PON signal can be demodulated and decoded by hard decision and eliminated from the received signal with a signal elimination filter. Alternatively or additionally, the first PON signal can be demodulated, decoded, re-encoded, re-modulated, and eliminated from the received signal with a signal elimination filter.

[0164] In some embodiments, the signal for nominal rate channel elimination can be taken from: (i) ADC output (nominal rate channel equalizer input) and nominal rate channel FEC decoder output (using re-encoding and filtering of the signal), where the high capacity channel can have a separate equalizer; (ii) ADC output (nominal rate channel equalizer input) and nominal rate channel hard decision (limiter) output for low latency (using filtering), where the high capacity channel can have a separate equalizer; (iii) nominal rate channel equalizer output and nominal rate channel FEC decoder output (using re-encoding and filtering of the signal) (iv) a nominal rate equalizer output and a nominal rate channel hard decision (limiter) output for low delay (using filtering), where the high capacity channel may have a separate equalizer; (v) a nominal rate equalizer output and a nominal rate channel FEC decoder output (using re-encoding and filtering of the signal), where the high capacity channel does not include a separate equalizer; (vi) a nominal rate equalizer output and a nominal rate channel hard decision (limiter) output for low delay (using filtering), where the high capacity channel does not include a separate equalizer.

[0165] In some embodiments, a second PON transmission (e.g., a high capacity channel) may be received. The high capacity channel may use a different protocol than the nominal rate channel. The high capacity channel may use a different modulation than the nominal rate channel. The high capacity channel may use a different error correction code than the nominal rate channel. The high capacity channel may use a different protocol than the nominal rate channel. The high capacity channel may transmit in bursts, while the nominal rate channel may be continuous.

[0166] In some embodiments, to establish a high capacity channel, the OLT transmitter may request channel quality information from the ONU receiver, for example, via a nominal rate channel. Based on the channel quality information and the requested data rate, modulation, FEC, and rate settings may be calculated. Burst information may be provided to the ONU receiver, and bursts on the high capacity channel may be transmitted.

[0167] In some embodiments, one or more delays may be reduced, robustness may be increased, or coverage may be increased. To reduce delays in the downlink direction, a high capacity channel may be present during times when a nominal rate channel may be occupied, such as for transmission of a control channel. To increase robustness and coverage, a high capacity channel may be used to transmit additional FEC parity bytes for the nominal rate channel.

[0168] In some embodiments, a system for NOMA upstream transmission may include: a non-orthogonal multiplexing receiver for PON upstream transmission, wherein a first PON signal can be received from a first ONU transmitter and a second PON signal can be received from a second ONU transmitter. In one example, signals from different ONUs can be transmitted so that the received power at the OLT can be different and the signals can be separated by different power levels. In one embodiment, ONUs with different channel attenuations can be selected for simultaneous reception. In another embodiment, different transmit powers can be selected for ONUs receiving simultaneously. In another embodiment, a combination of different channel attenuations and transmit powers for ONUs receiving simultaneously can be used.

[0169] For simplicity of explanation, the methods and / or process flows described herein are depicted and described as a series of actions. However, actions according to the present disclosure may occur in various orders and / or simultaneously, and may occur together with other actions not presented and described herein. In addition, not all actions shown may be used to implement methods according to the disclosed subject matter. In addition, those skilled in the art will understand and appreciate that these methods may be represented as a series of related states alternatively by state diagrams or events. In addition, the methods disclosed in this specification can be stored on articles such as non-transitory computer-readable media to facilitate the transmission and transfer of these methods to computing devices. The term "article" used herein is intended to include a computer program accessible from any computer-readable device or storage medium. Although illustrated as discrete blocks, various blocks may be divided into additional blocks, combined into fewer blocks or eliminated according to the desired implementation.

[0170] Fig.18 A block diagram of an example communication system 1800 configured for wireless communication according to at least one embodiment described in the present disclosure is shown. The communication system 1800 may include a digital transmitter 1802, a radio frequency circuit 1804, a device 1814, a digital receiver 1806, and a processing device 1808. The digital transmitter 1802 and the processing device may be configured to receive a baseband signal via a connection 1810. A transceiver 1816 may include the digital transmitter 1802 and the radio frequency circuit 1804.

[0171] In some embodiments, the communication system 1800 may include a system of devices that can be configured to communicate with each other via a wired or wired connection. For example, the wired connection in the communication system 1800 may include one or more Ethernet cables, one or more fiber optic cables, and / or other similar wired communication media. Alternatively or additionally, the communication system 1800 may include a system of devices that can be configured to communicate via one or more wireless connections. For example, the communication system 1800 may include one or more devices configured to send and / or receive radio waves, microwaves, ultrasound waves, light waves, electromagnetic induction, and / or similar wireless communications. Alternatively or additionally, the communication system 1800 may include a combination of wireless and / or wired connections. In these and other embodiments, the communication system 1800 may include one or more devices that can be configured to obtain a baseband signal, perform one or more operations on the baseband signal to generate a modified baseband signal, and send the modified baseband signal to, for example, one or more loads.

[0172] In some embodiments, communication system 1800 may include one or more communication channels that may communicatively couple systems and / or devices included in communication system 1800. For example, transceiver 1816 may be communicatively coupled to device 1814.

[0173] In some embodiments, the transceiver 1816 may be configured to obtain a baseband signal. For example, as described herein, the transceiver 1816 may be configured to generate a baseband signal and / or receive a baseband signal from another device. In some embodiments, the transceiver 1816 may be configured to transmit a baseband signal. For example, after obtaining the baseband signal, the transceiver 1816 may be configured to transmit the baseband signal to a separate device, such as device 1814. Alternatively or additionally, the transceiver 1816 may be configured to modify, adjust and / or transform the baseband signal before transmitting the baseband signal. For example, the transceiver 1816 may include an orthogonal upconverter and / or a digital-to-analog converter (DAC), which may be configured to modify the baseband signal. Alternatively or additionally, the transceiver 1816 may include a direct radio frequency (RF) sampling converter, which may be configured to modify the baseband signal.

[0174] In some embodiments, the digital transmitter 1802 may be configured to obtain a baseband signal via connection 1810. In some embodiments, the digital transmitter 1802 may be configured to up-convert the baseband signal. For example, the digital transmitter 1802 may include an orthogonal up-converter applied to the baseband signal. In some embodiments, the digital transmitter 1802 may include an integrated digital-to-analog converter (DAC). The DAC may convert the baseband signal into an analog signal or a continuous time signal. In some embodiments, the DAC architecture may include a direct RF sampling DAC. In some embodiments, the DAC may be a separate component from the digital transmitter 1802.

[0175] In some embodiments, the transceiver 1816 may include one or more subcomponents that may be used to prepare baseband signals and / or transmit baseband signals. For example, the transceiver 1816 may include an RF front end (e.g., in a wireless environment) that may include a power amplifier (PA), a digital transmitter (e.g., 1802), a digital front end, an Institute of Electrical and Electronics Engineers (IEEE) 1588v2 device, a long-term evolution (LTE) physical layer (L-PHY), (S-plane) device, a management plane (M-plane) device, an Ethernet media access control (MAC) / personal communication service (PCS), a resource controller / scheduler, and the like. In some embodiments, the radio (e.g., the RF circuit 1804) of the transceiver 1816 may be synchronized with the resource controller via the S-plane device, which may facilitate high-precision timing relative to a reference clock.

[0176] In some embodiments, transceiver 1816 can be configured to obtain a baseband signal for transmission. For example, transceiver 1816 can receive a baseband signal from a separate device (e.g., a signal generator). For example, the baseband signal can come from a transducer configured to convert a variable into an electrical signal, such as an audio signal output of a microphone that picks up a speaker's voice. Alternatively or additionally, transceiver 1816 can be configured to generate a baseband signal for transmission. In these and other embodiments, transceiver 1816 can be configured to send a baseband signal to another device (e.g., device 1814).

[0177] In some embodiments, device 1814 may be configured to receive transmissions from transceiver 1816. For example, transceiver 1816 may be configured to transmit a baseband signal to device 1814.

[0178] In some embodiments, RF circuit 1804 may be configured to transmit digital signals received from digital transmitter 1802. In some embodiments, RF circuit 1804 may be configured to transmit digital signals to device 1814 and / or digital receiver 1806. In some embodiments, digital receiver 1806 may be configured to receive digital signals from RF circuit and / or send digital signals to processing device 1808.

[0179] In some embodiments, as shown, processing device 1808 may be a stand-alone device or system. Alternatively or additionally, processing device 1808 may be a component of another device and / or system. For example, in some embodiments, processing device 1808 may be included in transceiver 1816. In the case where processing device 1808 is a stand-alone device or system, processing device 1808 may be configured to communicate with additional devices and / or systems remote from processing device 1808, such as transceiver 1816 and / or device 1814. For example, processing device 1808 may be configured to send and / or receive transmissions from transceiver 1816 and / or device 1814. In some embodiments, processing device 1808 may be combined with other elements of communication system 1800.

[0180] Fig.19 A diagram of a machine in the example form of a computing device 1900 is shown, in which a set of instructions can be executed to cause the machine to perform any one or more methods discussed herein. The computing device 1900 may include a rack server, a router computer, a server computer, a mainframe computer, a laptop computer, a tablet computer, a desktop computer, or any computing device with at least one processor, etc., in which a set of instructions can be executed to cause the machine to perform any one or more methods discussed herein. In an alternative embodiment, the machine can be connected (e.g., networked) to other machines in a LAN, an intranet, an extranet, or the Internet. The machine can run with the capacity of a server machine in a client-server network environment. In addition, although only a single machine is shown, the term "machine" may also include any machine collection that executes a set (or multiple sets) of instructions individually or jointly to perform any one or more methods discussed herein.

[0181] The example computing device 1900 includes a processing device (e.g., a processor) 1902, a main memory 1904 (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM)), a static memory 1906 (e.g., flash memory, static random access memory (SRAM)), and a data storage device 1916, which communicate with each other via a bus 1908.

[0182] Processing device 1902 represents one or more general processing devices, such as a microprocessor, a central processing unit, etc. More specifically, processing device 1902 may include a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, or a processor that implements other instruction sets or a processor that implements a combination of instruction sets. Processing device 1902 may also include one or more special-purpose processing devices, such as an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), a network processor, etc. Processing device 1902 is configured to execute instructions 1926 for performing the operations and steps discussed herein.

[0183] The computing device 1900 may also include a network interface device 1922 that may communicate with the network 1918. The computing device 1900 may also include a display device 1910 (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), an alphanumeric input device 1912 (e.g., a keyboard), a cursor control device 1914 (e.g., a mouse), and a signal generating device 1920 (e.g., a speaker). In at least one embodiment, the display device 1910, the alphanumeric input device 1912, and the cursor control device 1914 may be combined into a single component or device (e.g., an LCD touch screen).

[0184] The data storage device 1916 may include a computer-readable storage medium 1924 on which is stored one or more sets of instructions 1926 that embody any one or more of the methods or functions described herein. The instructions 1926 may also reside completely or at least partially in the main memory 1904 and / or the processing device 1902 during execution by the computing device 1900, and the main memory 1904 and the processing device 1902 also constitute computer-readable media. These instructions may also be transmitted or received over the network 1918 via the network interface device 1922.

[0185] Although computer-readable storage medium 1924 is shown as a single medium in the example embodiment, the term "computer-readable storage medium" may include a single medium or multiple media (e.g., a centralized or distributed database and / or associated cache memory and servers) that store one or more sets of instructions. The term "computer-readable storage medium" may also include any medium that is capable of storing, encoding, or carrying a set of instructions executed by a machine and causing the machine to perform any one or more methods of the present disclosure. Therefore, the term "computer-readable storage medium" may include, but is not limited to, solid-state memory, optical media, and magnetic media.

[0186] example

[0187] Examples of performance characteristics according to embodiments of the present disclosure are provided below.

[0188] Example 1: Network topology for simulation

[0189] Performance characteristics of a PON including nominal rate channels and high capacity channels are presented in some examples. Fig. 20 A network topology 2000 is provided for: (i) ONUs connected to OLT 2002 via short fiber branches 2005 (e.g., high data rate ONUs 2010 and ONUs 2012) of 10 km length, and (ii) ONUs connected to OLT 2002 via long fiber 2015 (e.g., ONUs 2014 and high data rate ONUs 2016) of 20 km length. The end-to-end attenuation of the ONUs may be different, for example, due to different splitters (2004, 2008, 2006) and connector losses.

[0190] In some examples, the nominal rate channel is a 50Gbit / s PON using NRZ modulation, and the high capacity channel uses 25Gbit / s or 50Gbit / s NRZ modulation. In some examples, ONUs with higher quality channels can be served using PAM-4 transmission, while ONUs with lower quality channels (or no PAM-4 support) can be served using NRZ transmission.

[0191] Example 2: BER vs. RX power for NPZ and PAM-4 transmission at 10km and 20km

[0192] like Fig.21 and Fig. 22 As shown, the received optical power versus BER (raw BER and post-FEC BER) for transmissions using NRZ and PAM-4 is provided for fiber lengths of 10km and 20km. A 50G PON LDPC code with a code rate of 0.844 is used for the simulation.

[0193] like Fig.21 As shown in Figure 2, the BER of the original NRZ and coded NRZ signals transmitted over a fiber length of 10 km is less than 10 when the RX power is greater than about -22 dB. -5 , below about 10 when RX power is greater than about -27dB -6 . Similarly, Fig. 22 As shown in Figure 2, the BER of the original NRZ and coded NRZ signals transmitted over a fiber length of 20 km is less than 10 when the RX power is greater than about -18 dB. -5 , below about 10 when RX power is greater than about -26dB -6 Therefore, as the dispersion increases in the 20 km fiber, the NRZ transmission is stable for both the 10 km fiber length and the 20 km fiber length.

[0194] In contrast, the original PAM-4 and coded PAM-4 signal transmissions are stable for 10 km fiber length, but unstable for 20 km fiber length. Fig.21 As shown in Figure 2, the BER of the original PAM-4 and coded PAM-4 signals transmitted over a fiber length of 10 km is less than 10 when the RX power is greater than about -10 dB. -5 , below about 10 when RX power is greater than about -21dB -6 .like Fig. 22 As shown in Figure 2, the BER of the original PAM-4 and coded PAM-4 signals transmitted over a fiber length of 20 km is higher than 10 when the RX power is greater than about -5 dB. -1 , above about 10 when the RX power is greater than about -5dB -1 .

[0195] Therefore, PAM-4 transmission is unstable as the dispersion increases over 20 km of fiber, while NRZ transmission is stable for both 10 km and 20 km of fiber.

[0196] Example 3: Relationship between mutual information and channel attenuation for NRZ and PAM-4 transmission

[0197] like Fig.23 As shown, the relationship between channel mutual information (bit / s) and channel attenuation (dB) is provided when 7dBm transmit power is used for NRZ transmission (10km fiber length and 20km fiber length) and 10dBm transmit power is used for PAM-4 transmission.

[0198] For NRZ transmission over a 10 km fiber length, the mutual information per symbol bit is about 1 for channel attenuation from about 15 dB to about 32 dB. As the channel attenuation increases from about 32 dB to about 40 dB, the mutual information per symbol bit decreases from about 1 to about 0.5.

[0199] Similarly, for NRZ transmission over a 20 km fiber length, for channel attenuation from about 15 dB to about 32 dB, the mutual information per symbol bit is about 1. As the channel attenuation increases from about 32 dB to about 37 dB, the mutual information per symbol bit decreases from about 1 to about 0.5.

[0200] Therefore, for example, for 50G-PON, the maximum channel attenuation of the PON network can be 29dB or 32dB, and when using NRZ transmission, the maximum fiber length can be 20km. Therefore, NRZ-based transmission at a transmission speed of 50Gbit / s and a transmission power of 7dBm is reliable for the maximum fiber length and attenuation budget.

[0201] For PAM-4 transmission over a 10 km fiber length, the mutual information in units of per symbol bit is approximately 2 for channel attenuation from approximately 15 dB to approximately 27 dB. As the channel attenuation increases from approximately 27 dB to approximately 35 dB, the mutual information in units of per symbol bit decreases from approximately 2 to approximately 0.5. Therefore, for slightly lower maximum attenuation, stable PAM-4 transmission is possible at shorter fiber lengths.

[0202] Example 4: Relationship between mutual information and channel attenuation in NOMA transmission

[0203] like Fig.24 As shown, NRZ transmission over 10km and 20km fiber lengths and PAM-4 transmission over 10km fiber length as provided in the previous example are compared to NOMA transmission using mutual information (in bit / s) versus channel attenuation (in dB).

[0204] For NOMA transmission, a high-capacity channel is added to the NRZ channel, where the modulation amplitude of the high-capacity channel can vary. Therefore, a scaling parameter α is introduced, where α=0 does not provide a NOMA channel, while α=1 provides 4 equidistant levels for PAM-4 transmission. In order to expand the coverage of the NOMA channel, the NOMA channel is transmitted at a line rate of 50G bit / s or 25G bit / s by repeating each bit. For NOMA transmission and PAM-4 transmission, the transmission power is 10dBm. The relationship between mutual information and channel attenuation is simulated.

[0205] For NOMA transmission using an α of 0.4 and a 50 G bit / s line over a 10 km fiber length, the mutual information in bits per symbol is: approximately 1.9 for a channel attenuation of approximately 13 dB; approximately 1.8 for a channel attenuation of approximately 22; approximately 1.6 for a channel attenuation of approximately 27; approximately 1.4 for a channel attenuation of approximately 31; and approximately 1.2 for a channel attenuation of approximately 34.

[0206] For NOMA transmission using an α of 0.4 and a 50 G bit / s line over a 20 km fiber length, the mutual information in bits per symbol is: approximately 1.6 for a channel attenuation of approximately 18 dB, approximately 1.4 for a channel attenuation of approximately 28, approximately 1.2 for a channel attenuation of approximately 23, and approximately 1.0 for a channel attenuation of approximately 35.

[0207] For NOMA transmission over 10 km fiber length using α of 0.4 and a 25 G bit / s line, the mutual information in bits per symbol is: approximately 1.5 for channel attenuation from approximately 13 dB to approximately 25 dB; approximately 1.4 for channel attenuation of approximately 30; and approximately 1.2 for channel attenuation of approximately 34.

[0208] For NOMA transmission over 20 km fiber length using α of 0.4 and a 25 G bit / s line, the mutual information in bits per symbol is: approximately 1.5 for channel attenuation from approximately 13 dB to approximately 25 dB; approximately 1.4 for channel attenuation of approximately 27; and approximately 1.2 for channel attenuation of approximately 33.

[0209] Therefore, while PAM-4 transmission is unstable at 20km fiber length, the high-capacity channel of NOMA transmission using 10km and 20km fiber is stable. When the capacity of NOMA transmission is lower than that of PAM-4, PAM-4 and NRZ transmission are separated in time, while the NOMA nominal rate channel and the high-capacity channel are provided simultaneously.

[0210] Example 5: Channel attenuation vs. data rate for NOMA transmission compared to time-interleaved PAM-4 and NRZ transmission Tie

[0211] like Fig.25 As shown, for two NRZ data streams, the total rate of time-interleaved NRZ and PAM-4 transmission is lower than that of NOMA transmission. Assume that the lines are: (i) 25% of the lines are 10 km; (ii) 25% of the lines are 20 km, (iii) 25% of the lines support PAM-4 / NOMA at 10 km length; and (iv) 25% of the lines support PAM-4 / NOMA at 20 km length.

[0212] For NRZ transmission over a 10 km fiber length, the data rate in Gbits / s is approximately 42 for channel attenuation from about 18 dB to about 34 dB. For NRZ transmission over a 20 km fiber length, the data rate in Gbits / s is approximately 42 for channel attenuation from about 18 dB to about 32 dB, and approximately 0 for channel attenuation of about 32 or greater. For PAM-4 transmission over a 10 km fiber length, the data rate in Gbits / s is approximately 83 for channel attenuation from about 12 dB to about 31 dB, and approximately 0 dB for channel attenuation of about 32 or greater.

[0213] For time-interleaved NRZ and PAM-4 signals, the rate in Gbits / s does not drop rapidly as the channel attenuation increases beyond a certain threshold. For NRZ transmission over a 10 km fiber length, the data rate in Gbits / s is approximately 50 for channel attenuation from about 18 dB to about 34 dB. For NRZ transmission over a 20 km fiber length, the data rate in Gbits / s is: approximately 50 for channel attenuation from about 18 dB to about 32 dB; approximately 40 for channel attenuation of about 34 dB. For PAM-4 transmission over a 10 km fiber length, the data rate in Gbits / s is: approximately 100 for channel attenuation from about 12 dB to about 28 dB; approximately 90 for channel attenuation of about 31 dB; approximately 80 for channel attenuation of about 33 dB; and approximately 70 for channel attenuation of about 34 dB.

[0214] For combined NRZ and PAM-4 transmission, the data rate in Gbits / s is approximately 52 for channel attenuation from approximately 12 dB to approximately 31 dB.

[0215] For the combined nominal rate channel plus NOMA transmission, the data rate in Gbits / s is: approximately 70 for channel attenuation from about 12 dB to about 20 dB; approximately 65 for channel attenuation from about 21 dB to about 25 dB; approximately 62 for channel attenuation from about 25 dB to about 27 dB; approximately 50 for channel attenuation of about 30; and approximately 20 for channel attenuation from about 32 to about 34.

[0216] Therefore, for NOMA transmission of a high-capacity channel and a nominal-rate channel, the data rate of the high-capacity channel is added to the rate of the nominal-rate channel, which helps to double the data rate to obtain sufficiently low channel attenuation.

[0217] Example 6: Relationship between channel attenuation and data rate at different rates and FEC settings

[0218] like Fig.26 As shown, for high capacity channels, modulation, symbol rate and FEC code rate are adjusted relative to the channel quality. Three different low density parity check (LDPC) code rates (0.844, 0.75, 0.5) and two symbol rates (50 Gbit / s, 25 Gbit / s) are used.

[0219] For NRZ transmission over a 10 km fiber length, the data rate in Gbits / s is approximately 42 for channel attenuation from about 18 dB to about 34 dB. For NRZ transmission over a 20 km fiber length, the data rate in Gbits / s is approximately 42 for channel attenuation from about 18 dB to about 32 dB, and approximately 0 for channel attenuation of about 32 or greater.

[0220] For NOMA transmission using a high-capacity channel over a 10 km fiber length, the data rates in Gbits / s are: approximately 37 for channel attenuation from about 12 dB to about 20 dB (using an LDPC code rate of 0.5 and a symbol rate of 50 G); approximately 25 for channel attenuation from about 21 dB to about 25 dB (using an LDPC code rate of 0.5 and a symbol rate of 50 G); approximately 21 for channel attenuation from about 25 dB to about 27 dB (using an LDPC code rate of 0.844 and a symbol rate of 25 G); approximately 19 for channel attenuation from about 27 dB to about 29 dB (using an LDPC code rate of 0.75 and a symbol rate of 25 G); approximately 13 for channel attenuation from about 29 to about 31 (using an LDPC code rate of 0.5 and a symbol rate of 25 G); and approximately 0 for channel attenuation greater than about 32 dB.

[0221] For NOMA transmission using a high-capacity channel over a 20 km fiber length, the data rates in Gbits / s are: approximately 21 for channel attenuation from about 12 dB to about 24 dB (using an LDPC code rate of 0.844 and a symbol rate of 25 G); approximately 19 for channel attenuation from about 25 dB to about 27 dB (using an LDPC code rate of 0.75 and a symbol rate of 25 G); approximately 13 for channel attenuation from about 28 dB to about 30 dB (using an LDPC code rate of 0.5 and a symbol rate of 25 G); and approximately 0 for channel attenuation greater than about 32 dB. Thus, different rate and FEC settings provide different data rates for specific channel attenuation values.

[0222] In some embodiments, the various components, modules, engines, and services described herein may be implemented as objects or processes executed on a computing system (e.g., as separate threads). Although some of the systems and methods described herein are generally described as being implemented in software (stored on hardware and / or executed by hardware), specific hardware implementations or combinations of software and specific hardware implementations are possible and contemplated.

[0223] The terms used herein, especially in the appended claims (e.g., the bodies of the appended claims), are generally intended to be “open-ended” terms (e.g., the term “including” should be interpreted as “including, but not limited to,” the term “having” should be interpreted as “having at least,” the term “comprising” should be interpreted as “including, but not limited to,” etc.).

[0224] Furthermore, if a specific number of claim recitations is intended to be introduced, such intent will be expressly stated in the claim, and if no such statement is made, such intent is not present. For example, to aid understanding, the following appended claims may contain the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be interpreted as implying that a claim recitation introduced by the indefinite article "a" or "an" will limit any particular claim containing such introduced claim recitation to an embodiment containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should be interpreted to mean "at least one" or "one or more"); the same applies to the use of definite articles used to introduce claim recitations.

[0225] Furthermore, even if a specific number of an introduced claim recitation is explicitly recited, it should be understood that such recitation should be interpreted to mean at least the recited number (e.g., a simple recitation of "two recitations" without other modifiers means at least two recitations, or two or more recitations). Furthermore, where a convention similar to "at least one of A, B, and C, etc." or "one or more of A, B, and C, etc." is used, generally such interpretation is intended to include A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, C together, etc. For example, use of the term "and / or" is intended to be interpreted in this manner.

[0226] In addition, any disjunctive word or phrase indicating two or more optional terms, whether in the specification, claims or drawings, should be understood to include the possibility of one term, one term or both terms. For example, the phrase "A or B" should be understood to include the possibility of "A" or "B" or "A and B".

[0227] Additionally, the use of the terms "first," "second," "third," etc., are not necessarily intended herein to imply a particular order or number of elements. Often, the terms "first," "second," "third," etc., are used to distinguish between different elements as generic identifiers. The terms "first," "second," "third," etc., are not shown to imply a particular order, and these terms should not be construed to imply a particular order. Additionally, the terms "first," "second," "third," etc., are not shown to imply a particular number of elements, and these terms should not be construed to imply a particular number of elements. For example, a first widget may be described as having a first side, and a second widget may be described as having a second side. The use of the term "second side" with respect to the second widget may be intended to distinguish this side of the second widget from the "first side" of the first widget, rather than implying that the second widget has two sides.

[0228] All examples and conditional language cited herein are intended for teaching purposes to help readers understand the present invention and the concepts contributed by the inventors to promote the art, and should be interpreted as not being limited to these specifically cited examples and conditions. Although the embodiments of the present disclosure have been described in detail, it should be understood that various changes, substitutions and modifications may be made thereto without departing from the spirit and scope of the present disclosure.

Claims

1. An optical line terminal OLT for downstream transmission in a passive optical network PON, comprising: A processing device, the processing device being configured to: generating a first downstream signal for transmission on a first channel at a first signal level; and generating a second downlink signal for transmission on a second channel at a second signal level, wherein the first signal level is greater than the second signal level; and a physical medium dependent PMD transmitter, the PMD transmitter being configured to transmit a combined downlink signal comprising the first downlink signal and the second downlink signal, The first transmission power of the first downstream signal is selected based on a comparison with the second transmission power of the second downstream signal, so as to receive the first downstream signal from the combined downstream signal at an optical network unit ONU.

2. The OLT according to claim 1, wherein: The second channel has a greater data capacity than the first channel.

3. The OLT according to claim 1, wherein: The processing device is also configured to: A transmit power scaling factor for the second downlink signal is calculated, wherein the transmit power scaling factor is selected to facilitate receiving the first downlink signal from the combined downlink signal.

4. The OLT according to claim 1, wherein: The processing device is also configured to: The second downlink signal is combined with the first downlink signal using non-orthogonal multiple access (NOMA).

5. The OLT according to claim 1, wherein: The processing device is also configured to: Calculate a transmission parameter value of the first downlink signal that is different from a transmission parameter value of the second downlink signal, wherein the transmission parameter comprises one or more of the following: modulation setting, forward error correction FEC setting, symbol rate, frame structure, communication protocol or burst setting.

6. The OLT according to claim 1, wherein: The processing device is also configured to: Compared with the signal quality of the first downlink signal, the signal quality of the second downlink signal is improved by using nonlinear equalization and nonlinear pre-compensation.

7. The OLT according to claim 1, wherein: The processing device is also configured to: calculating a first offset compensation for the second downlink signal when a first bit value from the first channel is identified; and A second offset compensation for the second downlink signal is calculated when a second bit value from the first downlink signal is identified, wherein the first bit value is different from the second bit value.

8. The OLT according to claim 1, wherein: The processing device is also configured to: At the OLT, when the combined downstream signal is transmitted, a transmit power increase and an extinction ratio increase are calculated.

9. The OLT according to claim 1, wherein: The processing device is also configured to: transmitting repeated data on the second channel to enhance forward error correction (FEC) protection, or transmitting data on said second channel to reduce delay, or Data is transmitted on the second channel to reduce power usage.

10. An optical line terminal OLT for upstream reception in a passive optical network PON, comprising: Physical medium dependent PMD receiver, configured as: receiving, at the OLT, a combined uplink signal including a first uplink signal and a second uplink signal, wherein the first uplink signal is received from a first optical network unit ONU, and the second uplink signal is received from a second ONU, and wherein the first uplink signal has a greater received power than the second uplink signal; and Processing equipment, configured to: Decoding the first upstream signal at the OLT; and At the OLT, the second upstream signal is decoded by eliminating the first upstream signal from the combined upstream signal.

11. The OLT according to claim 10, wherein: The processing device is also configured to: A first sampling point of the first ONU and a second sampling point of the second ONU are calculated to align the first ONU and the second ONU in time.

12. The OLT according to claim 10, wherein: The processing device is also configured to: Calculate a minimum received power difference between a first received power of the first ONU and a second received power of the second ONU; The first ONU and the second ONU are selected based on a predicted received power difference, wherein the predicted received power difference facilitates achieving a minimum power difference between a first received power of the first ONU and a second received power of the second ONU.

13. The OLT according to claim 10, wherein: The processing device is also configured to: Selecting a first transmit power for the first ONU; selecting a second transmit power for the second ONU, The first transmit power and the second transmit power are selected to facilitate a minimum receive power difference between a first receive power of the first ONU and a second receive power of the second ONU.

14. The OLT according to claim 10, wherein: The processing device is also configured to: Performing hard decision on the first uplink signal to generate a first channel cancellation filter, thereby canceling the first uplink signal from the combined uplink signal to generate the second uplink signal; or.

15. An optical network unit ONU for downstream reception in a passive optical network PON, comprising: Physical medium dependent PMD receiver, configured as: Receiving, at the ONU, a combined downstream signal including a first downstream signal and a second downstream signal from an optical line terminal OLT, wherein the first downstream signal has a greater receiving power than the second downstream signal; and Processing equipment, configured to: Decoding the first downstream signal at the ONU; and At the ONU, the second downstream signal is decoded by eliminating the first downstream signal from the combined downstream signal.

16. The optical network unit according to claim 15, wherein: The processing device is also configured to: Based on one or more of the analog-to-digital ADC output signal or the equalizer output signal, a cancellation signal is generated to cancel the first downlink signal from the combined downlink signal.

17. The optical network unit according to claim 15, wherein: The processing device is also configured to: The first downstream signal is eliminated from the combined downstream signal using one or more of: a slicer output; or a re-encoded decoder output.

18. The optical network unit according to claim 15, wherein: The first downlink signal is decoded using a first equalizer, and the second downlink signal is decoded using a second equalizer.

19. The optical network unit according to claim 15, wherein: The processing device is also configured to: Sending a non-orthogonal multiple access (NOMA) downlink receiving capability from the ONU to the OLT; and A diagnostic parameter of the ONU is sent from the ONU to the OLT.

20. The optical network unit according to claim 15, wherein: The processing device is also configured to: Channel quality information is sent from the ONU to the OLT.

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