Coherent signal processing in optical access networks

Abstract

An apparatus for an optical network unit (ONU) in a point-to-multipoint optical access system is disclosed. The apparatus includes front-end circuitry with a local oscillator. The front-end circuitry is configured to receive spectrum assignment information from an optical line terminal (OLT). The circuitry determines a downstream central frequency based on the received information. The local oscillator is adjusted to obtain an updated frequency offset. The apparatus decodes a downstream optical transmission from the OLT using the adjusted frequency offset. The spectrum assignment information may include details about subcarriers and central frequencies for both downstream and upstream directions. The apparatus may receive this information through an extended bandwidth map, a separate spectrum map message, or a physical layer operations, administration, and maintenance (PLOAM) message. The apparatus enables precise tuning for coherent signal processing and improves data recovery in optical access networks.

Description

COHERENT SIGNAL PROCESSING IN OPTICAL ACCESS NETWORKSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 713,502, filed on October 29, 2024, entitled '‘SPECTRUM MAP TO SUPPORT COHERENT SIGNAL PROCESSING IN OPTICAL ACCESS NETWORKS,” which provisional application is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to optical access networks, and specifically to techniques for supporting coherent signal processing using spectrum mapping between optical line terminals and optical network units.BACKGROUND

[0003] Optical access networks, such as passive optical networks (PONs), are widely used to deliver high-capacity broadband services to end users through a central optical line terminal (OLT) and multiple optical network units (ONUs) connected via optical fibers and passive splitters. Traditional PON systems rely on intensity modulation with direct detection (IM-DD) and non- retum-to-zero (NRZ) line coding, which have enabled the deployment of standards like G-PON, XG-PON. XGS-PON, and 50G-PON. However, as network demands increase, these systems face challenges in supporting higher transmission rates over long distances due to fiber dispersion, transceiver nonlinearity7, and electronic speed limitations. For example, sustaining transmission rates beyond 100 Gb / s over distances of 40 kilometers is extremely challenging due to fiber dispersion penalty, transceiver nonlinearity, and electronics speed constraints. These limitations affect the management and transmission of optical signals in passive optical networks, specifically within the domain of optical communication hardware and network protocols.Coherent optical transmission technology has emerged as a promising approach to address these limitations by enabling more precise signal recovery and improved compensation for transmission impairments, but its implementation in point-to-multipoint architectures introduces additional complexity in managing bandwidth and frequency assignments among multiple ONUs.SUMMARY

[0004] Various examples are now described to introduce a selection of concepts in a simplified form that is further described below in the detailed description. The Summary is not intended to identify essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0005] According to a first aspect of the present disclosure, there is provided an apparatus for performing optical communications in a point-to- multipoint (P2MP) access system, the apparatus including front-end circuitry with a local oscillator, where the front-end circuitry' is configured to decode spectrum assignment information received from an optical line terminal (OLT), determine a downstream central frequency based on the spectrum assignment information, adjust a frequency offset of the local oscillator to obtain an adjusted frequency offset, and decode a downstream optical transmission received from the OLT based on the adjusted frequency offset.

[0006] In a first implementation form of the apparatus according to the first aspect as such, the front-end circuitry is further configured to determine a number of downstream subcarriers assigned to the apparatus and decode the downstream optical transmission further based on the number of downstream subcarriers.

[0007] In a second implementation form of the apparatus according to the first aspect as such or any preceding implementation form of the first aspect, the front-end circuitry’ is further configured to decode an extended bandwidth map (BWmap) message received from the OLT and determine the spectrum assignment information based on the extended BWmap message.

[0008] In a third implementation form of the apparatus according to the first aspect as such or any preceding implementation form of the first aspect, the extended BWmap message comprises, for the ONU and one or more additional ONUs in the P2MP access system, a spectrum structure including the downstream central frequency, a downstream subcarrier count, an upstream central frequency, and an upstream subcarrier count.

[0009] In a fourth implementation form of the apparatus according to the first aspect as such or any preceding implementation form of the first aspect, the front-end circuitry is further configured to decode a spectrum map message included in a framing sublayer header or a physical layer frame header received from the OLT and determine the spectrum assignment information based on the spectrum map message.

[0010] In a fifth implementation form of the apparatus according to the first aspect as such or any preceding implementation form of the first aspect, the spectrum map message comprises, for the ONU and one or more additional ONUs in the P2MP access system, a spectrum structure including the downstream central frequency, a downstream subcarrier count, an upstream central frequency, and an upstream subcarrier count.

[0011] In a sixth implementation form of the apparatus according to the first aspect as such or any preceding implementation form of the first aspect, the front-end circuitry is further configured to decode a physical layer operations, administration, and maintenance (PLOAM) message broadcast from the OLT and determine the spectrum assignment information based on the PLOAM message.

[0012] In a seventh implementation form of the apparatus according to the first aspect as such or any preceding implementation form of the first aspect, the front-end circuitry is further configured to verify integrity of the spectrum assignment information based on a message integrity check field in the PLOAM message.

[0013] In an eighth implementation form of the apparatus according to the first aspect as such or any preceding implementation form of the first aspect,the front-end circuitry is further configured to determine an upstream central frequency and an upstream subcarrier count based on the spectrum assignment information and encode upstream data for transmission to the OLT based on the upstream central frequency and the upstream subcarrier count.

[0014] According to a second aspect of the present disclosure, there is provided a computer-implemented method for performing optical communications in a point-to-multipoint (P2MP) access system, the method comprising decoding, at an optical network unit (ONU), spectrum assignment information received from an optical line terminal (OLT) of the P2MP access system, determining a downstream central frequency based on the spectrum assignment information, adjusting a frequency offset of a local oscillator of the ONU to obtain an adj usted frequency offset, and decoding a downstream optical transmission received from the OLT based on the adjusted frequency offset.

[0015] In a first implementation form of the computer-implemented method according to the second aspect as such, the method further comprises determining a number of downstream subcarriers assigned to the ONU and decoding the downstream optical transmission further based on the number of downstream subcarriers.

[0016] In a second implementation form of the computer-implemented method according to the second aspect as such or any preceding implementation form of the second aspect, the method further comprises decoding an extended bandwidth map (BWmap) message received from the OLT and determining the spectrum assignment information based on the extended BWmap message.

[0017] In a third implementation form of the computer-implemented method according to the second aspect as such or any preceding implementation form of the second aspect, the extended BWmap message comprises, for the ONU and one or more additional ONUs in the P2MP access system, a spectrum structure comprising the downstream central frequency, a downstream subcarrier count, an upstream central frequency, and an upstream subcarrier count.

[0018] In a fourth implementation form of the computer-implemented method according to the second aspect as such or any preceding implementationform of the second aspect, the method further comprises decoding a spectrum map message included in a framing sublayer header or a physical layer frame header received from the OLT and determining the spectrum assignment information based on the spectrum map message.

[0019] In a fifth implementation form of the computer-implemented method according to the second aspect as such or any preceding implementation form of the second aspect, the spectrum map message comprises, for the ONU and one or more additional ONUs in the P2MP access system, a spectrum structure comprising the downstream central frequency, a downstream subcarrier count, an upstream central frequency, and an upstream subcarrier count.

[0020] In a sixth implementation form of the computer-implemented method according to the second aspect as such or any preceding implementation form of the second aspect, the method further comprises decoding a physical layer operations, administration, and maintenance (PLOAM) message broadcast from the OLT and determining the spectrum assignment information based on the PLOAM message.

[0021] In a seventh implementation form of the computer-implemented method according to the second aspect as such or any preceding implementation form of the second aspect, the method further comprises verifying integrity of the spectrum assignment information based on a message integrity check field in the PLOAM message.

[0022] In an eighth implementation form of the computer-implemented method according to the second aspect as such or any preceding implementation form of the second aspect, the method further comprises determining an upstream central frequency and an upstream subcarrier count based on the spectrum assignment information and encoding upstream data for transmission to the OLT based on the upstream central frequency and the upstream subcarrier count.

[0023] According to a third aspect of the present disclosure, there is provided a non-transitory computer-readable medium storing computer instructions for performing optical communications in a point-to-multipoint(P2MP) access system, that configure at least one processor, upon execution of the computer instructions, to perform steps comprising decoding, at an optical network unit (ONU), spectrum assignment information received from an optical line terminal (OLT) of the P2MP access system, determining a downstream central frequency based on the spectrum assignment information, adjusting a frequency offset of a local oscillator of the ONU to obtain an adjusted frequency offset, and decoding a downstream optical transmission received from the OLT based on the adjusted frequency offset.

[0024] In a first implementation form of the non-transitory computer- readable medium according to the third aspect as such, the steps further comprise determining a number of downstream subcarriers assigned to the ONU and decoding the downstream optical transmission further based on the number of downstream subcarriers.

[0025] In a second implementation form of the non-transitory computer- readable medium according to the third aspect as such or any preceding implementation form of the third aspect, the steps further comprise decoding an extended bandwidth map (BWmap) message received from the OLT and determining the spectrum assignment information based on the extended BWmap message.

[0026] In a third implementation form of the non-transitory computer- readable medium according to the third aspect as such or any preceding implementation form of the third aspect, the extended BWmap message comprises, for the ONU and one or more additional ONUs in the P2MP access system, a spectrum structure comprising the downstream central frequency, a downstream subcarrier count, an upstream central frequency, and an upstream subcarrier count.

[0027] In a fourth implementation form of the non-transitory computer- readable medium according to the third aspect as such or any preceding implementation form of the third aspect, the steps further comprise decoding a spectrum map message included in a framing sublayer header or a physical layer frame header received from the OLT and determining the spectrum assignment information based on the spectrum map message.

[0028] In a fifth implementation form of the non-transitory computer- readable medium according to the third aspect as such or any preceding implementation form of the third aspect, the spectrum map message comprises, for the ONU and one or more additional ONUs in the P2MP access system, a spectrum structure comprising the downstream central frequency, a downstream subcarrier count, an upstream central frequency, and an upstream subcarrier count.

[0029] In a sixth implementation form of the non-transitory computer- readable medium according to the third aspect as such or any preceding implementation form of the third aspect, the steps further comprise decoding a physical layer operations, administration, and maintenance (PLOAM) message broadcast from the OLT and determining the spectrum assignment information based on the PLOAM message.

[0030] In a seventh implementation form of the non-transitory computer- readable medium according to the third aspect as such or any preceding implementation form of the third aspect, the steps further comprise verifying integrity of the spectrum assignment information based on a message integrity check field in the PLOAM message.

[0031] In an eighth implementation form of the non-transitory computer- readable medium according to the third aspect as such or any preceding implementation form of the third aspect, the steps further comprise determining an upstream central frequency and an upstream subcarrier count based on the spectrum assignment information and encoding upstream data for transmission to the OLT based on the upstream central frequency and the upstream subcarrier count.

[0032] According to a fourth aspect of the present disclosure, there is provided an apparatus for performing optical communications in a point-to- multipoint (P2MP) access system, where the apparatus includes means for decoding spectrum assignment information received from an optical line terminal (OLT) of the P2MP access system, means for determining a downstream central frequency based on the spectrum assignment information, means for adjusting a frequency offset of a local oscillator of the ONU to obtainan adjusted frequency offset, and means for decoding a downstream optical transmission received from the OLT based on the adjusted frequency offset.

[0033] In a first implementation form of the apparatus according to the fourth aspect as such, the apparatus further includes means for determining a number of downstream subcarriers assigned to the apparatus and means for decoding the downstream optical transmission further based on the number of downstream subcarriers.

[0034] Any one of the foregoing examples may be combined with any one or more of the other foregoing examples to create a new embodiment within the scope of the present disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

[0036] FIG. 1 is a block diagram of an optical communication system using coherent signal transmission and reception, according to example embodiments.

[0037] FIG. 2 is a block diagram of a point-to-multipoint (P2MP) communication system using coherent signal transmission via subcarriers, according to example embodiments.

[0038] FIG. 3 illustrates a bandwidth map (BWmap) message used in Passive Optical Network (PON) communications, according to example embodiments.

[0039] FIG. 4 illustrates an extended BWmap message that includes timeslot assignment and optical network unit (ONU) spectrum structures with central frequencies and subcarriers, according to example embodiments.

[0040] FIG. 5 illustrates an example spectrum map message including ONU spectrum structures with central frequencies and subcarriers, according to example embodiments.

[0041] FIG. 6 illustrates an example PON Physical Layer Operations, Administrations and Maintenance (PLOAM) message including an ONU spectrum map, according to example embodiments.

[0042] FIG. 7 is a schematic diagram of an apparatus according to an embodiment of the disclosure.

[0043] FIG. 8 is a flowchart of a method for performing optical communications in a P2MP access system, according to example embodiments.

[0044] FIG. 9 is a diagram of circuitry for a device that implements algorithms and performs methods, according to some example embodiments.DETAILED DESCRIPTION

[0045] The present detailed description provides illustrative examples of the disclosed subject matter, which pertains to advancements in optical access networks, particularly techniques for supporting coherent signal processing through spectrum mapping between optical line terminals (OLTs) and optical network units (ONUs). The disclosed technology addresses challenges in achieving higher transmission rates and efficient bandwidth management in point-to-multipoint (P2MP) architectures, leveraging coherent optical transmission technology to overcome limitations of traditional intensity modulation with direct detection (IM-DD) systems. While specific embodiments and implementations are described herein, these examples are provided for illustrative purposes only and are not intended to limit the scope of the disclosed subject matter.

[0046] Certain details, such as commonly recognized components, processes, or techniques, may be omitted for clarity and conciseness, as they are readily understood by those skilled in the art. Additionally, the disclosed subject matter allows for various modifications, rearrangements, and alternative embodiments that align with the scope of the appended claims and their equivalents. The described technology is designed to accommodate different configurations and implementations, providing adaptability to address the evolving needs of optical access networks.

[0047] It should be understood at the outset that although an illustrative implementation of one or more embodiments is provided below, the disclosed systems and / or methods described with respect to FIGS. 1-9 may be implemented using any number of techniques, whether currently known or not yet in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplars' designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.

[0048] In the following description, reference is made to the accompanying drawings that form a part hereof and are shown, by w ay of illustration, specific embodiments that may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the inventive subject matter, and it is to be understood that other embodiments may be utilized, and that structural, logical, and electrical changes may be made without departing from the scope of the present disclosure. The following description of example embodiments is, therefore, not to be taken in a limiting sense, and the appended claims define the scope of the present disclosure.

[0049] As used herein, the term "OLT indicates an optical line terminal, which is a central device in an optical access network responsible for managing and transmitting optical signals to multiple optical network units (ONUs) and coordinating upstream and downstream communications.

[0050] As used herein, the term “ONU” indicates an optical network unit, which is a device located at the user premises in an optical access network that receives optical signals from the OLT and transmits upstream signals back to the OLT.

[0051] As used herein, the term “PON’’ indicates a passive optical network, which is a point-to-multipoint optical fiber network architecture that uses passive splitters to distribute signals from a single OLT to multiple ONUs without requiring active electronic components in the distribution network.

[0052] As used herein, the term “LO” indicates a local oscillator, which is a tunable optical source used in coherent receivers to mix with incoming optical signals, enabling the recovery of amplitude and phase information for coherent signal processing.

[0053] As used herein, the term “IM-DD” indicates intensity modulation with direct detection, a technique for optical signal transmission in which the intensity of the optical carrier is modulated and detected directly by a photodetector, commonly used in traditional PON systems.

[0054] As used herein, the term "NR.Z" indicates non-retum-to-zero, a line coding scheme used in digital signal transmission where the signal does not return to zero between bits, enabling efficient data encoding in optical networks.

[0055] As used herein, the term “BWmap” indicates a bandwidth map, a data structure or message used in PON protocols to assign upstream transmission timeslots to ONUs, facilitating time-division multiplexing in the network.

[0056] As used herein, the term “subcarrier” indicates a frequency division within the optical spectrum that is used to carry a portion of the data assigned to a specific ONU, enabling frequency-division multiplexing in coherent optical networks.

[0057] As used herein, the term “central frequency” indicates the center wavelength or frequency of an optical sub-band or subcarrier, which is used for tuning the local oscillator or laser transmitter in coherent signal processing.

[0058] As used herein, the term “PLOAM” indicates physical layer operations, administration, and maintenance, which refers to control and management messages exchanged between the OLT and ONUs to configure, monitor, and maintain the physical layer of the optical access network.

[0059] As used herein, the term “point-to-multipoint” or “P2MP” indicates a network architecture in which a single transmitter, such as an OLT, communicates with multiple receivers, such as ONUs, over a shared optical medium.

[0060] As used herein, the term “DSP” indicates digital signal processing or digital signal processor, which refers to hardware or algorithms used toprocess digital signals, compensate for transmission impairments, and recover data in coherent optical receivers.

[0061] As used herein, the term ■'ADC ' indicates an analog-to-digital converter, a device that converts analog electrical signals into digital data for further processing in optical communication systems.

[0062] As used herein, the term “Alloc-ID” indicates an allocation identifier, a unique identifier assigned to an ONU or a transmission burst in PON protocols to manage upstream bandwidth allocation.

[0063] As used herein, the term “HEC” indicates header error control, a field or code used for error detection and correction in protocol headers, such as those found in spectrum map or bandwidth map data structures.

[0064] As used herein, the term ‘THY"’ indicates physical layer, which refers to the lowest layer in the network protocol stack responsible for the transmission and reception of raw optical signals over the fiber medium.

[0065] As used herein, the term “TDMA” indicates time-division multiple access, a multiplexing technique in which multiple ONUs share the same transmission medium by transmitting in assigned time slots.

[0066] As used herein, the term “FDMA” indicates frequency-division multiple access, a multiplexing technique in which multiple ONUs transmit simultaneously over different frequency subcarriers within the optical spectrum. As used herein, the term ‘"broadcast” indicates the transmission of a message or signal from the OLT to all ONUs in the network, as opposed to a direct or unicast message sent to a specific ONU.

[0067] As used herein, the term “spectrum map” indicates a data structure or message that conveys central frequency and subcarrier assignment information for both downstream and upstream directions, enabling ONUs to tune their local oscillators and transmitters for coherent signal processing.

[0068] As used herein, the term “DAC” indicates a digital-to-analog converter, a device that converts digital data into analog electrical signals for use in optical transmitters or other electronic systems.

[0069] As used herein, the term “MZ” indicates a Mach-Zehnder modulator, an optical device used to modulate the intensity, phase, or polarization of an optical signal by interfering two light paths, commonly employed in coherent optical transmission systems.

[0070] As used herein, the term 'PBC ' indicates a polarization beam combiner, an optical component that combines two beams of light with orthogonal polarizations into a single output beam, facilitating polarization multiplexing in optical networks.

[0071] As used herein, the term ‘TBS’" indicates a polarization beam splitter, an optical device that separates an incoming beam of light into two beams with orthogonal polarizations, used in coherent receivers and other optical systems.

[0072] As used herein, the term “TIA” indicates a transimpedance amplifier, an electronic amplifier that converts input current to output voltage, typically used in optical receivers to amplify the electrical signal generated by a photodetector.

[0073] As used herein, the term ‘"spectrum assignment information" indicates information used for adjusting a receiver's local oscillator and correcting a prior frequency offset from the transmitter’s local oscillator. Example spectrum assignment information can include information identifying a central frequency and subcarrier assignment information.

[0074] In existing systems, optical line terminals communicate with multiple optical network units using IM-DD and NRZ coding. As the need for higher performance grows, coherent optical transmission technology becomes crucial for meeting these requirements. Coherent systems require precise tuning of local oscillators and laser sources for effective signal recovery7, but the process of tuning optical carriers is slow and does not match the rapid changes in data traffic and bandwidth allocation. As a result, ONUs may experience degraded data rates, increased noise, and inefficient use of available spectrum. This problem occurs in point-to-multipoint optical access networks, where a central OLT serves multiple ONUs over shared optical fibers and passive splitters.

[0075] The problem addressed in the current document concerns the management and transmission of optical signals in passive optical networks, specifically within the domain of optical communication hardware and network protocols. In existing systems, optical line terminals communicate with multiple optical network units using intensity modulation with direct detection and non- retum-to-zero line coding. These systems are limited in their ability to support higher transmission rates over long distances due to fiber dispersion, transceiver nonlinearity, and electronic speed constraints.

[0076] A specific issue arises in the context of coherent optical transmission, where precise tuning of local oscillators and laser sources is used for effective signal recovery7. The process of tuning these optical carriers is slow and does not match the rapid changes in data traffic and bandwidth allocation. As a result, ONUs may experience degraded data rates, increased noise, and inefficient use of available spectrum. The environment in which this problem occurs is a point-to-multipoint optical access network, where a central OLT serves multiple ONUs over shared optical fibers and passive splitters.

[0077] The impact of this problem is seen in reduced netw ork performance, increased hardware complexity, and higher costs for ONUs. If the problem is not addressed, users may encounter lower data throughput, increased latency, and the need for more expensive receiver and transmitter components. The root causes include the limitations of current PON protocols, which do not provide mechanisms for dynamic and precise frequency assignment, and the inherent slow response of optical tuning hardware.

[0078] The impact of the limitations of existing technology is seen in reduced network performance, increased hardware complexity, and higher costs for ONUs. If not addressed, users may encounter lower data throughput, increased latency, and the need for more expensive receiver and transmitter components. The root causes include the limitations of current PON protocols, which do not provide mechanisms for dynamic and precise frequency assignment, and the inherent slow response of optical tuning hardware. Existing solutions have relied on more complex and costly hardw are at the ONUs or have accepted reduced performance as a trade-off. No protocol-based approach fordynamic spectrum assignment has been widely adopted. Recommendations have included hardware upgrades and manual configuration, but these do not fully resolve the underlying issues.

[0079] The technical solution described in the current document introduces a protocol-level mechanism for spectrum mapping and frequency assignment in passive optical access networks to support coherent signal processing. This solution is designed for point-to-multipoint architectures, such as PONs, where a central optical line terminal (OLT) communicates with multiple optical network units (ONUs) over shared optical fibers and passive splitters. The solution operates by communicating spectrum assignment information, including central frequency and subcarrier assignment information, from the OLT to each ONU via the downstream channel. This information enables each ONU to precisely tune its local oscillator for coherent reception and its laser transmitter for coherent upstream transmission. The disclosed solutions can be implemented through one or more of the following methodologies: extending the existing bandwidth map (BWmap) to include the spectrum assignment information, introducing a separate spectrum map message, or transmitting spectrum assignment information using a control message, such as physical layer operations, administration, and maintenance (PLOAM) messages.

[0080] The rationale behind the solution is based on the principle that precise and dynamic frequency assignment enables efficient use of the optical spectrum, reduces noise, and improves data rates. By providing ONUs with accurate spectrum assignment information (e.g., central frequency and subcarrier information), the solution allows for rapid adaptation to changing data traffic and bandwidth requirements, overcoming the slow response of optical tuning hardware.

[0081] The solution addresses technical challenges related to spectral efficiency, dynamic bandwidth allocation, and hardware complexity. It targets the protocol layer, enabling dynamic and precise frequency assignment without requiring expensive hardware upgrades at the ONUs. The expected outcomes include improved network performance, higher data throughput, reduced latency, and lower hardware costs for ONUs. For example, in a PON system with 32ONUs, the OLT can assign each ONU a specific downstream central frequency and subcarrier count based on current traffic demands. The OLT generates a spectrum map message containing these assignments and transmits it in the downstream frame. Each ONU receives the message, tunes its LO to the assigned frequency, and adjusts its transmitter for upstream communication. This process enables efficient and flexible use of the optical spectrum, minimizes noise, and supports high-capacity transmission rates. Diagrams such as FIG. 4, FIG. 5, and FIG. 6 illustrate the protocol structures and message formats used in the proposed solution. These figures provide detailed examples of how the spectrum assignment information is organized and transmitted within the optical communication system.

[0082] FIG. 1 introduces the fundamental architecture and signal flow of a coherent optical communication system. It provides a detailed view of the hardware components involved in both transmission and reception, highlighting the use of coherent detection and polarization multiplexing.

[0083] FIG. 1 is a block diagram of an optical communication system 100 using coherent signal transmission and reception, according to example embodiments. Referring to FIG. 1, the optical communication system 100 comprises a digital signal processor (DSP) 102, digital -to-analog converters (D ACs) 1 4, a coherent transmitter (Tx) front-end 106, a coherent receiver (Rx) front-end 108, a plurality of analog-to-digital converters (ADCs) 110, and a DSP 112.

[0084] The coherent Tx front-end 106 comprises a laser 114, a plurality of amplifiers 116. a plurality of Mach-Zehnder modulators 118, a plurality of phase shifters 120, and a polarization beam combiner (PBC) 122.

[0085] The coherent Rx front-end 108 comprises a local oscillator 124, polarization beam splitters (PBSs) 126 and 128, phase shifters 130 and 132, a plurality' of photodetectors 134, a plurality of photodetectors 136, and transimpedance amplifiers (TIAs) 138 and 140.

[0086] The DSP 102 generates and processes the electrical signals for transmission. It performs digital modulation, coding, and other signal processing functions required for coherent optical communication.

[0087] The coherent Tx front-end 106 includes the laser 114, which provides the optical carrier signal. Amplifiers 116 increase the strength of the electrical signals before modulation. Mach-Zehnder modulators 118 modulate the optical carrier with the electrical signal, encoding data onto the light. Phase shifters 120 adjust the phase of the optical signal for polarization multiplexing. The PBC 122 combines two orthogonally polarized optical signals into a single output for transmission.

[0088] The coherent Rx front-end 108 includes the local oscillator 124, which generates a reference optical signal for coherent detection. PBSs 126 and 128 separate the incoming optical signal into orthogonal polarization components. Phase shifters 130 and 132 further adjust the phase of the separated signals. Photodetectors 134 and 136 convert the optical signals into electrical currents. TIAs 138 and 140 amplify these electrical currents for further processing.

[0089] ADCs 110 digitize the amplified electrical signals from the receiver front-end, enabling subsequent digital processing. The DSP 112 processes the digitized signals to recover the transmitted data, compensate for transmission impairments, and perform error correction.

[0090] In operation, the DSP 102 generates a digital signal that is converted to an analog electrical signal and sent to the coherent Tx front-end 106. The laser 114 produces an optical carrier, which is modulated by the Mach- Zehnder modulators 118 with the input data. Amplifiers 116 and phase shifters 120 prepare the signal for polarization multiplexing, and the PBC 122 combines the signals for transmission over the optical fiber.

[0091] At the coherent Rx front-end 108. the incoming optical signal is mixed with the reference signal from the local oscillator 124. PBSs 126 and 128 split the signal into polarization components, which are phase-adjusted by phase shifters 130 and 132. Photodetectors 134 and 136 convert the optical signals toelectrical currents, which are amplified by TIAs 138 and 140. The ADCs 110 digitize these signals, and the DSP 112 processes them to recover the transmitted information.

[0092] FIG. 2 illustrates how coherent signal processing is applied in a point-to-multipoint optical access network, with particular emphasis on the allocation of subcarriers among multiple ONUs by a central OLT. This transition from the basic system architecture to the network-level configuration introduces the context for dynamic spectrum management and the challenges addressed by the disclosed solution.

[0093] FIG. 2 is a block diagram of a P2MP communication system 200 using coherent signal transmission via subcarriers, according to example embodiments. Referring to FIG. 2, the P2MP communication system 200 comprises OLT 202 and a plurality of ONUs, such as ONU 204, ONU 206, ONU 208, and ONU 210.

[0094] OLT 202 is the optical line terminal that serves as the central node in the P2MP communication system 200. It is responsible for generating, modulating, and transmitting optical signals to multiple optical network units (e.g., ONUs 204-210) over shared optical fibers.

[0095] OLT 202 includes the coherent Tx front-end 106, which provides the capability7for coherent signal transmission using advanced modulation and polarization techniques.

[0096] ONU 204, ONU 206, ONU 208, and ONU 210 are optical network units located at the user premises. Each ONU is configured to receive optical signals from the OLT and transmit upstream signals back to the OLT. The ONUs include the coherent Rx front-end 108, which enables recovery of amplitude and phase information from the received optical signals using coherent detection.

[0097] The coherent Tx front-end 106 within OLT 202 is responsible for modulating the optical carrier with data and distributing the signal across multiple subcarriers. This front-end supports polarization multiplexing andadvanced modulation formats, enabling the OLT to allocate specific subcarriers to individual ONUs according to network requirements.

[0098] The coherent Rx front-end 108 within each ONU is designed to mix the incoming optical signal with a local oscillator, enabling the recovery of both amplitude and phase information. This front-end supports the tuning of the local oscillator to the assigned central frequency and subcarrier, facilitating coherent signal processing and efficient data extraction.

[0099] Operationally, OLT 202 transmits a composite optical signal containing multiple subcarriers, each carrying data intended for a specific ONU. The coherent Tx front-end 106 modulates the optical carrier and assigns subcarriers to ONUs according to current traffic demands. For example, FIG. 2 illustrates specific subcarriers in the communication bandwidth assigned by the OLT to each ONU.

[0100] Each ONU, equipped with the coherent Rx front-end 108, receives the optical signal and tunes its local oscillator to the assigned central frequency and subcarrier (as illustrated in FIG. 2). This allows the ONU to isolate and recover its designated data from the composite signal, while ignoring subcarriers assigned to other ONUs.

[0101] In some aspects, the ONU receiver bandwidth may be significantly smaller than the OLT transmitter bandwidth, reducing the complexity and cost of the ONU. The OLT may serve multiple ONUs, each with a narrower bandwidth allocation, while maintaining high overall system capacity.

[0102] FIG. 3 introduces the protocol structure, which can be used for upstream bandwidth allocation in PON systems. More specifically, FIG. 3 illustrates a bandwidth map (BWmap) message 300 used in Passive Optical Network (PON) communications, according to example embodiments.

[0103] The BWmap message 300 is a data structure used in PON communications. Its primary function is to assign upstream transmission timeslots to ONUs within the network. The BWmap message 300 facilitatestime-division multiplexing (TDMA) by specifying which ONUs are permitted to transmit data during particular time intervals on the shared upstream channel.

[0104] The BWmap message 300 contains allocation information for each ONU, including identifiers and timing parameters. This information enables the ONUs to coordinate their upstream transmissions and avoid collisions on the optical fiber. The BWmap message is generated by the OLT and transmitted downstream to all ONUs in the network.

[0105] Operationally, the OLT creates the BWmap message 300 based on current network traffic and bandwidth requirements. The message is broadcast to all ONUs, which decode their respective allocation details and schedule their upstream transmissions accordingly. This process ensures efficient use of the shared medium and maintains orderly communication betw een the OLT and multiple ONUs.

[0106] FIG. 4 introduces an enhancement to the BWmap protocol by integrating spectrum assignment information with timeslot allocation. FIG. 4 illustrates an extended BWmap message 400 that includes timeslot assignment and optical network unit (ONU) spectrum structures with central frequencies and subcarriers, according to example embodiments. The extended BWmap message 400 includes ONU spectrum structures and allocation structures. The ONU spectrum structures include ONU-ID, flags, downstream (DS) central frequency, DS subcarrier (SC) count, upstream (US) central frequency, US SC count, and header error control (HEC) information.

[0107] The extended BWmap message 400 is a data structure used in PON communications to facilitate both upstream timeslot assignment and spectrum mapping for ONUs. This message builds upon the BWmap message 300 by adding spectrum assignment information, including fields that specify the downstream and upstream central frequencies, as well as the number of subcarriers assigned to each ONU.

[0108] The timeslot assignment structures within the extended BWmap message 400 define the specific time intervals during which each ONU is permitted to transmit data on the shared upstream channel. These structurescontain allocation identifiers and timing parameters, enabling time-division multiplexing (TDMA) and preventing transmission collisions among ONUs.

[0109] The ONU spectrum structures in the extended BWmap message 400 provide detailed information about the frequency and subcarrier assignments for each ONU. Each spectrum structure includes fields for the ONU identifier (ONU-ID), downstream central frequency, downstream subcarrier count, upstream central frequency, upstream subcarrier count, and header error control (HEC). The HEC field is used for error detection and correction in the spectrum structure header, ensuring reliable communication of spectrum assignment information. In some aspects, the HEC field in the ONU spectrum structure may be implemented as a truncated BCH(63, 12, 2) code operating on the initial bits of the header, combined with a single parity bit.

[0110] Operationally, the OLT generates the extended BWmap message 400 based on cunent network traffic, bandwidth requirements, and spectrum allocation policies. The message is transmitted in the downstream frame to all ONUs, with its total length indicated in the framing sublayer header. Upon receipt, each ONU decodes its timeslot assignment and spectrum structure, enabling it to schedule upstream transmissions and adjust its local oscillator and transmitter to the assigned frequencies and subcarriers for coherent signal processing.

[0111] In some aspects, an ONU may be assigned two downstream subcarriers and a central frequency within a single superframe. At a later time, the ONU may be reassigned to a single subcarrier and a new central frequency, with the updated assignment communicated in the next spectrum map or extended BWmap message.

[0112] In some aspects, allocation structures and BWmap formats may be defined according to protocol standards such as G.987.3, G.9807.1, G.989.3, and G.9804.2.

[0113] In some aspects, spectrum assignment information may be used by the ONU to tune its local oscillator for downstream reception and its lasertransmiter for upstream transmission, enabling coherent signal processing in both directions.

[0114] FIG. 5 introduces a separate protocol structure for communicating spectrum assignment information in PON systems. More specifically, FIG. 5 illustrates an example spectrum map message 500 including ONU spectrum structures with central frequencies and subcarriers, according to example embodiments.

[0115] The spectrum map message 500 is a data structure used in PON communications to convey spectrum assignment information to ONUs. The message includes one or more ONU spectrum structures, each specifying the assigned downstream central frequency, downstream subcarrier count, upstream central frequency, and upstream subcarrier count for a particular ONU.

[0116] In some aspects, each ONU spectrum structure within the spectrum map message 500 provides the necessary' information for each ONU to tune its local oscillator and transmiter for coherent signal processing and efficient data recovery. The downstream central frequency and subcarrier count fields enable the ONU to adjust its receiver for downstream communication, while the upstream central frequency and subcarrier count fields allows the ONU to configure its transmiter for upstream communication.

[0117] The OLT generates the spectrum map message 500 based on current network traffic and spectrum allocation policies. The message is transmitted in the downstream frame and may be included in the framing sublayer header or the physical layer frame header. A spectrum map length field is used to indicate the size of the map, ensuring that ONUs can accurately parse and extract their assigned spectrum information.

[0118] Operationally, upon receipt of the spectrum map message 500, each ONU decodes its assigned spectrum structure and adjusts its local oscillator and transmiter to the specified frequencies and subcarriers. This process enables rapid and precise adaptation to changing network conditions and traffic demands.

[0119] In some aspects, a spectrum map length field may be included in the spectrum map message to indicate the total size of the map, enabling ONUs to accurately parse and extract their assigned spectrum information.

[0120] FIG. 6 introduces a control message-based methodology for distributing spectrum assignment information, demonstrating how spectrum mapping can be integrated into physical layer operations, administration, and maintenance protocols. FIG. 6 illustrates an example PON Physical Layer Operations, Administrations and Maintenance (PLOAM) message 600 including an ONU spectrum map, according to example embodiments.

[0121] The PLOAM message 600 is a control and management message that can be used in PON communications. The message includes an ONU spectrum map, which contains spectrum assignment information for one or more ONUs. Each ONU spectrum map structure within the PLOAM message can include fields for the ONU identifier (ONU-ID), downstream central frequency, downstream subcarrier count, upstream central frequency, upstream subcarrier count, and a message integrity check (MIC).

[0122] In some aspects, the PLOAM message may be limited to a fixed size, such as 48 bytes, which restricts the number of ONU spectrum structures that can be included in a single message. Multiple PLOAM messages may be transmitted sequentially to distribute the full spectrum assignment information.

[0123] The ONU-ID field identifies the specific ONU to which the spectrum assignment information pertains. The downstream central frequency and downstream subcarrier count fields specify the frequency and number of subcarriers allocated to the ONU for downstream communication. The upstream central frequency and upstream subcarrier count fields specify the frequency and number of subcarriers allocated for upstream transmission.

[0124] The message integrity check (MIC) field is used to verify the integrity of the spectrum assignment information, ensuring reliable communication and preventing errors.

[0125] Operationally, the OLT generates the PLOAM message 600 and includes the ONU spectrum map for one or more ONUs. The message can besent as a broadcast to all ONUs or as a direct message to a specific ONU. Due to message size limitations, multiple PLOAM messages may be required to distribute the full spectrum map to all ONUs. The OLT must be equipped with a spectrum assignment module and a spectrum map generator to support this functionality. Upon receipt, each ONU decodes its spectrum assignment information, verifies the integrity using the MIC field, and adjusts its local oscillator and transmitter to the assigned frequencies and subcarriers for coherent signal processing.

[0126] In some aspects, the extended BWmap, spectrum map, and PLOAM messages may be structured with explicit byte and bit fields for each parameter, as specified in the protocol.

[0127] In some aspects, the central frequency fields in the spectrum assignment structures may be expressed as unsigned integers indicating values in units of 0. 1 GHz.

[0128] In some aspects, the PLOAM message may be sent as a broadcast to all ONUs, with the ONU-ID field set to 0x03FF, or as a direct message to a specific ONU using its assigned ONU-ID.

[0129] In some aspects, upon receipt of a PLOAM message, the ONU may verify the integrity of the spectrum assignment information using the message integrity check (MIC) field before applying the frequency and subcarrier assignments.

[0130] FIG. 7 is a schematic diagram of an apparatus 700 according to an embodiment of the disclosure. The apparatus 700 may implement the disclosed embodiments. The apparatus 700 comprises ingress ports 710, receiver (Rx) 720 (or receiving means) to receive data, a processor 704 (also referred to as processing means, a logic unit, baseband unit, or CPU) to process the data, a transmitter (Tx) 706 (also referred to as transmitting means), egress ports 712 to transmit the data, and a memory 708 (also referred to as data storing means) to store the data.

[0131] The Rx 702 is coupled or connected to the ingress ports 710 and the processor 704; the processor 704 is coupled or connected to the Rx 702, thememory 708, and the Tx 706; and the Tx 706 is coupled to or connected to the processor 704 and the egress ports 712. The apparatus 700 may also comprise components coupled to the ingress ports 710, the Rx 702, the Tx 706, and the egress ports 712 to provide ingress or egress of optical signals, electrical signals, or RF signals.

[0132] The processor 704 is any combination of hardware, middleware, firmware, or software. The processor 704 comprises any combination of one or more CPU chips, cores. FPGAs, ASICs, or DSPs. The processor 704 communicates with the ingress ports 710, the Rx 702, the Tx 706, the egress ports 712, and the memory 708. The processor 704 comprises a spectrum mapping component 705, which implements the disclosed embodiments. The inclusion of the spectrum mapping component 705 provides an improvement to the functionality of apparatus 700, resulting in the transformation of apparatus 700 into a different state. Alternatively, the memory 708 stores instructions associated with the spectrum mapping component 705, and the processor 704 executes those instructions.

[0133] The memory' 708 comprises any combination of disks, tape drives, or solid-state drives. The apparatus 700 may utilize the memory 708 as an overflow data storage device to store programs when the apparatus 700 selects those programs for execution, and to store instructions and data that the apparatus 700 reads during the execution of those programs. The memory' 708 may be volatile or non-volatile and may be any combination of ROM, RAM, TCAM. or SRAM, for example. Other memories or memory types are contemplated and fall within the scope of this disclosure.

[0134] A computer program product may’ comprise computer-executable instructions that are stored on a computer-readable medium and that, when executed by a processor, cause an apparatus to perform any of the embodiments. The non-transitory medium may be the memory 708, the processor may be the processor 704, and the apparatus may be the apparatus 700.

[0135] FIG. 8 is a flowchart of a method 800 for performing optical communications in a point-to-multipoint (P2MP) access system, according to example embodiments. Method 800 includes operations 802, 804, 806, and 808.By way of example and not limitation, method 800 is described as being performed by one or more of the disclosed circuits (e.g., the front-end circuits of FIG. 1, the OLT or ONUs of FIG. 2, apparatus 700 of FIG. 7, or the spectrum mapping component 960 associated with computer 900 of FIG. 9). Any of the methods disclosed herein can be configured as computer-implemented methods performed by one or more processors within a computing device (e.g., computer 900) or a communication apparatus / device (e.g.. apparatus 700).

[0136] At operation 802, the optical network unit (e.g., ONU 204 using coherent Rx front-end 108) decodes spectrum assignment information received from the optical line terminal (e.g., OLT 202 using coherent Tx front-end 106) of the P2MP access system. This information may be transmitted in various formats, such as an extended BWmap, a separate spectrum map message, or a PLOAM message, as illustrated in FIGS. 4-6. The decoding process extracts relevant data fields, including central frequency and subcarrier assignments, which are necessary' for subsequent signal processing steps.

[0137] At operation 804, the ONU determines a downstream central frequency based on the decoded spectrum assignment information. The central frequency is identified from the received message and corresponds to the specific sub-band within the optical spectrum allocated to the ONU for downstream communication. This operation ensures that the ONU is aware of the precise frequency at which it should tune its receiver to recover the intended optical signal effectively.

[0138] At operation 806, the ONU adjusts a frequency offset of its local oscillator to obtain an adjusted frequency offset. Using the determined downstream central frequency, the ONU tunes its local oscillator to align with the assigned frequency, compensating for any prior offset or drift. This adjustment is used to achieve coherent signal processing, as it enables the receiver to accurately mix the incoming optical signal with the local oscillator reference, thereby facilitating precise amplitude and phase recovery.

[0139] At operation 808, the ONU decodes a downstream optical transmission received from the OLT based on the adjusted frequency offset. With the local oscillator properly tuned, the ONU processes the incoming opticalsignal, extracting the transmitted data using coherent detection techniques. This operation leverages the hardware components and signal flow described in FIG. 1, ensuring data recovery in the optical access network.

[0140] FIG. 9 is a diagram of circuitry for a device that implements algorithms and performs methods, according to some example embodiments. Not all components need to be used in various embodiments. For example, clients, servers, and cloud-based network devices may each utilize a distinct set of components, or, in the case of servers, larger storage devices.

[0141] One example computing device in the form of a computer 900 (also referred to as computing device 900, computer system 900, or computer 900) may include a processor 905, memory 910, removable storage 915, nonremovable storage 920, input interface 925, output interface 930, and communication interface 935, all connected by a bus 940. Although the example computing device is illustrated and described as computer 900, the computing device may take different forms in different embodiments.

[0142] Memory 910 may include volatile memory 945 and non-volatile memory 950, and may store a program 955. The computer 900 may include, or have access to, a computing environment that includes a variety of computer- readable media, such as the volatile memory 945, the non-volatile memory' 950. the removable storage 915, and the non-removable storage 920. Computer storage includes random-access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM) and electrically erasable programmable read-only memory (EEPROM), flash memory' or other memory' technologies, compact disc read-only memory (CD ROM), digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium capable of storing computer-readable instructions.

[0143] Computer-readable instructions stored on a computer-readable medium (e.g., the program 955 stored in memory' 910) are executable by the processor 905 of the computer 900. A hard drive, CD-ROM, and RAM are some examples of articles that include a non-transitory computer-readable medium such as a storage device. The terms “computer-readable medium” and‘‘storage device” do not include carrier waves to the extent that carrier waves are deemed too transitory. “Computer-readable non-transitory media” includes all types of computer-readable media, including magnetic storage media, optical storage media, flash media, and solid-state storage media. It should be understood that software can be installed and sold on a computer. Alternatively, the software can be obtained and loaded into the computer, either through a physical medium or a distribution system, such as a server owned by the software creator or a server not owned by the creator but used by them. The software can be stored on a server for distribution over the Internet, for example. As used herein, the terms “computer-readable medium” and “machine-readable medium” are interchangeable.

[0144] Processor 905 may utilize one or more circuits discussed herein, such as spectrum mapping component 960 configured according to disclosed techniques (e.g., to perform one or more of the disclosed coherent signal transmission and reception functionalities discussed in connection with FIGS. 1- 8).

[0145] Any one or more of the modules described herein may be implemented using hardware (e.g., a processor of a machine, an applicationspecific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any suitable combination thereof). Moreover, any two or more of these modules may be combined into a single module, and the functions described herein for a single module may be subdivided among multiple modules. Furthermore, according to various example embodiments, modules described herein as being implemented within a single machine, database, or device may be distributed across multiple machines, databases, or devices.

[0146] Although a few embodiments have been described in detail above, other modifications are possible. For example, the logic flow s depicted in the figures do not require the particular order shown or a sequential order to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Other embodiments may be within the scope of the following claims.

[0147] It should be further understood that software, including one or more computer-executable instructions that facilitate processing and operations as described above concerning any one or all of the steps of the disclosure, can be installed in and sold with one or more computing devices consistent with the disclosure. Alternatively, the software can be obtained and loaded into one or more computing devices, including obtaining the software through a physical medium or distribution system, including, for example, from a server owned by the software creator or from a server not owned but used by the software creator. The software can be stored on a server for distribution over the Internet, for example.

[0148] Also, it will be understood by one skilled in the art that this disclosure is not limited in its application to the details of construction and the arrangement of components outlined in the description or illustrated in the drawings. The embodiments herein are capable of other embodiments and capable of being practiced or carried out in various ways. Also, it will be understood that the phraseology and terminology' used herein are for description and should not be regarded as limiting. The use of ‘Including / ’ “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. Also, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings. Further, terms such as up, down, bottom, and top are relative and are employed to aid illustration, but are not limiting.

[0149] The components of the illustrative devices, systems, and methods employed following the illustrated embodiments can be implemented, at least in part, in digital electronic circuitry, analog electronic circuitry, computer hardware, firmware, software, or in combinations of them. These components can be implemented, for example, as a computer program product such as a computer program, program code, or computer instructions tangibly embodied in an information carrier, or a machine-readable storage device, for execution by,or to control the operation of, data processing apparatus such as a programmable processor, a computer, or multiple computers.

[0150] A computer program can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or another unit suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or multiple computers at one site or distributed across multiple sites and interconnected by a communication network. Also, functional programs, codes, and code segments for accomplishing the techniques described herein can be easily construed as within the scope of the claims by programmers skilled in the art to which the techniques described herein pertain. Method steps associated with the illustrative embodiments can be performed by one or more programmable processors executing a computer program, code, or instructions to perform functions (e.g., by operating on input data and / or generating an output). Method steps can also be performed by, and an apparatus for performing the methods can be implemented as special-purpose logic circuitry, e.g., an FPGA (field- programmable gate array) or an ASIC (application-specific integrated circuit), for example.

[0151] The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an ASIC, an FPGA, or other programmable logic devices, discrete gate, or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0152] Processors suitable for the execution of a computer program include, by way of example, both general and special-purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory, a randomaccess memory, or both. The required elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Generally’, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example, semiconductor memory devices, e.g., electrically programmable read-only memory7or ROM (EPROM), electrically erasable programmable ROM (EEPROM), flash memory7devices, and data storage disks (e.g., magnetic disks, internal hard disks, or removable disks, magneto-optical disks, and CD-ROM and DVD-ROM disks). The processor and the memory can be supplemented by or incorporated into special-purpose logic circuitry7.

[0153] Those with skill in the art understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0154] As used herein, ’‘machine-readable medium” (or ’‘computer- readable medium”) means a device able to store instructions and data temporarily or permanently and may include, but is not limited to, randomaccess memory (RAM), read-only memory (ROM), buffer memory, flash memory, optical media, magnetic media, cache memory, other types of storage (e.g., Erasable Programmable Read-Only Memory (EEPROM)), and / or any suitable combination thereof. The term “machine-readable medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, or associated caches and servers) able to store processorinstructions. The term ‘‘machine-readable medium” shall also be taken to include any medium (or a combination of multiple media) that is capable of storing instructions for execution by one or more processors 905, such that the instructions, when executed by one or more processors 905, cause the one or more processors 905 to perform any one or more of the methodologies described herein. Accordingly, a “machine-readable medium” refers to a single storage apparatus or device, as well as “cloud-based” storage systems or storage networks that include multiple storage apparatus or devices. The term “machine-readable medium” as used herein excludes signals per se, including carrier waves.

[0155] In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate maybe combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component, whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the scope disclosed herein.

[0156] Although the present disclosure has been described regarding specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the scope of the disclosure. For example, other components may be added to or removed from the described systems. The specification and drawings are, accordingly, to be regarded simply as an illustration of the disclosure as defined by the appended claims, and are contemplated to cover any modifications, variations, combinations, or equivalents that fall within the scope of the present disclosure. Other aspects may be within the scope of the following claims.

Claims

CLAIMSWhat is claimed is:

1. An apparatus of an optical network unit (ONU) for performing optical communications in a point-to-multipoint (P2MP) access system, the apparatus comprising: front-end circuitry comprising a local oscillator, the front-end circuitry configured to: decode spectrum assignment information received from an optical line terminal (OLT) of the P2MP access system; determine a downstream central frequency based on the spectrum assignment information; adjust a frequency offset of the local oscillator to obtain an adjusted frequency offset; and decode a downstream optical transmission received from the OLT based on the adjusted frequency offset.

2. The apparatus of claim 1, wherein the front-end circuitry' is configured to: determine a number of downstream subcarriers assigned to the apparatus; and decode the downstream optical transmission further based on the number of downstream subcarriers.

3. The apparatus of any of claims 1-2, wherein the front-end circuitry' is configured to: decode an extended bandwidth map (BWmap) message received from the OLT; and determine the spectrum assignment information based on the extended BWmap message.

4. The apparatus of claim 3, wherein the extended BWmap message comprises, for the ONU and one or more additional ONUs in the P2MP access system: a spectrum structure comprising the downstream central frequency; a downstream subcarrier count; an upstream central frequency; and an upstream subcarrier count.

5. The apparatus of claim 1, wherein the front-end circuitry' is configured to: decode a spectrum map message included in a framing sublayer header or a physical layer frame header received from the OLT; and determine the spectrum assignment information based on the spectrum map message.

6. The apparatus of claim 5. wherein the spectrum map message comprises, for the ONU and one or more additional ONUs in the P2MP access system: a spectrum structure comprising the downstream central frequency; a downstream subcarrier count; an upstream central frequency; and an upstream subcarrier count.

7. The apparatus of claim 1, wherein the front-end circuitry is configured to: decode a physical layer operations, administration, and maintenance (PLOAM) message broadcast from the OUT; and determine the spectrum assignment information based on the PUOAM message.

8. The apparatus of claim 7, wherein the front-end circuitry’ is configured to: verily integrity' of the spectrum assignment information based on a message integrity check field in the PUOAM message.

9. The apparatus of any of claims 1-8, wherein the front-end circuitry is configured to: determine an upstream central frequency and an upstream subcarrier count based on the spectrum assignment information; and encode upstream data for transmission to the OLT based on the upstream central frequency and the upstream subcarrier count.

10. A computer-implemented method for performing optical communications in a point-to-multipoint (P2MP) access system, the method comprising: decoding, at an optical network unit (ONU), spectrum assignment information received from an optical line terminal (OLT) of the P2MP access system; determining a downstream central frequency based on the spectrum assignment information; adjusting a frequency offset of a local oscillator of the ONU to obtain an adjusted frequency offset; and decoding a downstream optical transmission received from the OLT based on the adjusted frequency offset.

11. The computer-implemented method of claim 10, the method comprising: determining a number of downstream subcarriers assigned to the ONU; and decoding the downstream optical transmission further based on the number of downstream subcarriers.

12. The computer-implemented method of claim 10, the method comprising: decoding an extended bandwidth map (BWmap) message received from the OLT; and determining the spectrum assignment information based on the extended BWmap message.

13. The computer-implemented method of claim 12, wherein the extended BWmap message comprises, for the ONU and one or more additional ONUs in the P2MP access system: a spectrum structure comprising the downstream central frequency; a downstream subcarrier count; an upstream central frequency; and an upstream subcarrier count.

14. The computer-implemented method of claim 10, the method comprising: decoding a spectrum map message included in a framing sublayer header or a physical layer frame header received from the OLT; and determining the spectrum assignment information based on the spectrum map message.

15. The computer-implemented method of claim 14, wherein the spectrum map message comprises, for the ONU and one or more additional ON s in the P2MP access system: a spectrum structure comprising the downstream central frequency; a downstream subcarrier count; an upstream central frequency; and an upstream subcarrier count.

16. The computer-implemented method of claim 10, the method comprising: decoding a physical layer operations, administration, and maintenance(PLOAM) message broadcast from the OLT; and determining the spectrum assignment information based on the PLOAM message.

17. The computer-implemented method of claim 16, the method comprising: verifying integrity of the spectrum assignment information based on a message integrity check field in the PLOAM message.

18. The computer-implemented method of claim 10, the method comprising: determining an upstream central frequency and an upstream subcarrier count based on the spectrum assignment information; and encoding upstream data for transmission to the OLT based on the upstream central frequency and the upstream subcarrier count.

19. A non-transitory computer-readable medium storing computer instructions for performing optical communications in a point-to-multipoint (P2MP) access system, that configure at least one processor, upon execution of the computer instructions, to perform steps comprising: decoding, at an optical network unit (ONU), spectrum assignment information received from an optical line terminal (OLT) of the P2MP access system; determining a dow nstream central frequency based on the spectrum assignment information; adjusting a frequency offset of a local oscillator of the ONU to obtain an adjusted frequency offset; and decoding a downstream optical transmission received from the OLT based on the adjusted frequency offset.

20. The non-transitory computer-readable medium of claim 19, the steps comprising: determining a number of downstream subcarriers assigned to the ONU; and decoding the downstream optical transmission further based on the number of downstream subcarriers.

21. The non- transitory' computer-readable medium of claim 19, the steps comprising: decoding an extended bandwidth map (BWmap) message received from the OLT; and determining the spectrum assignment information based on the extended BWmap message.

22. The non-transitory computer-readable medium of claim 21, wherein the extended BWmap message comprises, for the ONU and one or more additional ONUs in the P2MP access system: a spectrum structure comprising the downstream central frequency; a downstream subcarrier count; an upstream central frequency; and an upstream subcarrier count.

23. The non-transitory computer-readable medium of claim 19, the steps comprising: decoding a spectrum map message included in a framing sublayer header or a physical layer frame header received from the OLT; and determining the spectrum assignment information based on the spectrum map message.

24. The non-transitory computer-readable medium of claim 23, wherein the spectrum map message comprises, for the ONU and one or more additional ONUs in the P2MP access system: a spectrum structure comprising the downstream central frequency; a downstream subcarrier count; an upstream central frequency; and an upstream subcarrier count.

25. The non-transitory computer-readable medium of claim 19, the steps comprising: decoding a physical layer operations, administration, and maintenance (PUOAM) message broadcast from the OUT; and determining the spectrum assignment information based on the PLOAM message.

26. The non-transitory computer-readable medium of claim 25, the steps comprising: verifying integrity of the spectrum assignment information based on a message integrity check field in the PLOAM message.

27. The non-transitory computer-readable medium of claim 19, the steps comprising: determining an upstream central frequency and an upstream subcarrier count based on the spectrum assignment information; and encoding upstream data for transmission to the OLT based on the upstream central frequency and the upstream subcarrier count.

28. An apparatus of an optical network unit (ONU) for performing optical communications in a point-to-multipoint (P2MP) access system, the apparatus comprising: means for decoding spectrum assignment information received from an optical line terminal (OLT) of the P2MP access system; means for determining a downstream central frequency based on the spectrum assignment information; means for adjusting a frequency offset of a local oscillator of the ONU to obtain an adjusted frequency offset; and means for decoding a downstream optical transmission received from the OLT based on the adjusted frequency offset.

29. The apparatus of claim 28, further comprising: means for determining a number of downstream subcarriers assigned to the apparatus; and means for decoding the dow nstream optical transmission further based on the number of downstream subcarriers.

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