Method for configuring equalization resources for the equalizer of a transceiver optical device.

Abstract

1. A method for configuring equalization resources of an equalizer of a transceiver optical device, the equalization resources being used by the equalizer to perform equalization on optical signals received over channels of an optical line, the method comprising: acquiring environmental parameter values, the environmental parameter values ​​being values ​​of environmental data on physical parameters or derivatives affecting channels of the optical line; acquiring channel depth estimates from past experience in view of the environmental parameter values; and selectively enabling the equalization resources to perform equalization on optical signals received over channels of the optical line according to the acquired channel depth estimates.

Description

Technical Field

[0001] The present invention relates generally to optical communication, and more specifically to setting equalization resources of an equalizer in a transceiver optical device. Priority is claimed to European Patent Application No. 23305866.8, filed on June 1, 2023, the contents of which are incorporated herein by reference.

Background Art

[0002] Within the scope of FTTH ("Fiber To The Home") technology deployment, optical communication is increasingly being used to provide network access (usually Internet access) to residential or office gateways, or data centers. Optical communication can also be used to ensure mobile infrastructure backhaul, for example, within the scope of deployment of 3G (third generation) or 4G (fourth generation) mobile technologies that typically use point-to-point configurations.

[0003] Emerging 5G (fifth-generation) mobile technologies are seeing the emergence of fronthaul, significantly increasing the need for data rate capabilities. The International Mobile Communications (IMT) Recommendation ITU-R M.2083, "IMT Vision: Framework and overall objectives of the future development of IMT for 2020 and beyond," published in September 2015, can be referenced. Within such a framework, fronthaul is achieved by moving mobile infrastructure processing functions, previously performed at or near base stations of 3G or 4G mobile technologies, upstream. This is referred to as the "split option" in the specification 3GPP® TR 38.801 V 14.0.0, "Study on new radio access technology: Radio access architecture and interfaces," published in March 2017 (see Section 11 and Table A-1 for more details).

[0004] Therefore, 5G mobile technology has a broader set of requirements compared to the FTTH requirements that have driven the evolution of optical access technologies to date. Consequently, 5G mobile technology will, among other things, move towards higher nominal data rates, lower latency, and higher-density deployments.

[0005] Furthermore, the Internet of Things, edge computing, artificial intelligence, robotics, and augmented reality are highly demanding technological trends in terms of communication infrastructure. However, these technological trends also have widely different requirements regarding data throughput or quality of service that must be supported by optical access networks.

[0006] Therefore, optical access systems should be able to carry extremely high data rate throughput (exceeding 50 Gbit / s, or even several hundred Gbit / s in the near future) for carrying IoT flows, for example, as well as very low data rates. Optical access networks should support low latency, such as sub-millisecond fractions, for applications like virtual reality or industrial use. This requires a highly flexible and efficient optical infrastructure.

[0007] Due to these diverse applications and corresponding requirements, the term here may refer not simply to "optical access networks," but rather to "optical access and aggregation networks."

[0008] Furthermore, it must be considered that fiber optic cables often have to deal with very different length constraints, typically ranging from a few hundred meters to 40 kilometers.

[0009] Such a wide variety of requirements and constraints make it difficult to manage the time and frequency spread of optical signals.

[0010] First, chromatic dispersion varies with the length of the optical line and further depends on the modulation signal bandwidth and optical signal wavelength. For example, considering wavelengths around 1550 nm, the time expansion due to chromatic dispersion can vary from a portion of one symbol period to up to 20 symbol periods, as the optical line length varies from 1 km to 40 km at @3 dB and 100 GHz. Furthermore, fluctuations in ambient temperature have a significant impact on chromatic dispersion in high-bitrate optical communication systems. It should also be noted that optical access and aggregation networks are typically deployed under outdoor conditions, i.e., in environments without temperature control.

[0011] Since optical fiber circuits are typically deployed under outdoor conditions, they are subjected to vibrations from wind and potentially passing vehicles, in addition to the aforementioned temperature fluctuations. These vibrations and temperature fluctuations affect polarization mode dispersion (PMD). PMD arises from the relative delay between both polarization axes when anisotropy constraints are applied to the optical fiber. This relative delay depends on the square of the optical fiber's length.

[0012] 10 -7 For a failure probability of 3 seconds per year, the channel can be demonstrated to be 6 times larger than the mean differential group delay (DGD). In optical access and aggregation networks, the mean differential group delay is 0.05 picoseconds / km, which is commonly encountered in core networks. 0,5 Therefore, under harsh conditions, it is hundreds of times higher than the normal value of the core network, reaching tens of picoseconds / km. 0.5 It can vary in size over a wide range. Therefore, 10 -7 In the case of a stopping probability of 0.05 ps / km, 0.5 From 10ps / km 0.5 Considering the mean differential group delay difference, which can vary up to a certain point, the variation in time diffusion associated with polarization mode dispersion can range from a portion of the symbol period to nearly 20 symbol periods for a 30 Gbaud system, or up to 45 symbol periods for a 100 Gbaud system.

[0013] Another aspect is that in uncontrolled environments such as those encountered by optical access and aggregation networks, the nominal wavelength of a laser source preventing inter-channel crosstalk or the center wavelength of an optical bandpass filter may shift. Because such devices are located in different geographical locations within the deployment of optical access and aggregation networks, they are exposed to different environmental conditions that induce relative wavelength shifts. For example, considering a 100 GHz optical bandpass filter at 3 dB based on a Bragg grating, its time response can span over 200 picoseconds as the carrier wavelength shifts across the passband of the optical bandpass filter. This can correspond to a time variation of approximately 10 symbol periods for a 30 Gbaud system, or even 30 symbol periods for a 100 Gbaud system.

[0014] Optical access and aggregation networks can also be further enhanced by the use of various transceivers (multiple vendors, variable working points), which implies various types of pulse distortion and results in different symbol spread behaviors.

[0015] As can be understood from the above, many physical phenomena affect the diffusion of optical signals in optical access and aggregation networks. Such physical phenomena may have been considered unimportant in the past, as high data rate capability needs were only considered for core networks with controlled environments, while optical access networks in uncontrolled environments targeted much lower data rate capability needs.

[0016] Currently, optical access and aggregation networks must address these physical phenomena. Therefore, equalization should be performed. Equalization is a signal processing procedure aimed at mitigating intersymbol interference (ISI) on communication channels.

[0017] For illustrative purposes, when considering linear equalization in the time domain, consecutive received symbol samples [Mathematical Expression] a transmitted optical signal obtained from equalization spanning [Mathematical Expression] the k-th symbol of [Mathematical Expression] the estimation of [Mathematical Expression] can be expressed as follows. [Mathematical Expression] In the formula, j is an integer varying from -K to K, which means that 2K+1 equalization coefficients [Mathematical Expression] are used together with 2K+1 symbol samples [Mathematical Expression] Symbols before j=-K and beyond j=K are not significant for obtaining the estimation [Mathematical Expression] , and therefore 2K+1 represents the channel depth.

[0018] Equalization coefficients [Mathematical Expression] Different techniques can be used to determine and update these equalization coefficients in accordance with the temporal evolution of the communication channel. Dedicated exchange sequence analysis, or data-assisted schemes based on blind equalization techniques such as LMS (Least Mean Square) or CMA (Constant Modulus algorithm), do not require prior knowledge of the channel response to find appropriate equalization coefficient values ​​(often called "taps" in time-domain equalization).

[0019] As for the dimensionalization of the optical link, the dimensionalization of the equalization resource must be defined according to the worst-case diffusion case. In light of the above, a large amount of information must be retrieved from the channel, a large number of symbols must be processed to perform equalization in the worst-case diffusion case, which means that a large number of equalization coefficients must be calculated, and furthermore, once the equalization coefficients are properly determined, a large number of computational resources must be dedicated to optical signal equalization.

[0020] However, relying on the worst-case diffusion scenario to make equalization resources work is inefficient in terms of equalization signaling overhead, and therefore computational resource usage, and energy consumption, particularly in terms of hardware block allocation. Therefore, it is desirable to provide an energy-efficient solution suitable for optical access and aggregation networks. Ideally, the solution should be as simple as possible. [Prior art documents] [Non-patent literature]

[0021] [Non-Patent Document 1] International Mobile Communications (IMT) Recommendation ITU-R M.2083 "IMT Vision: Framework and overall objectives of the future development of IMT for 2020 and beyond" [Non-Patent Document 2] Specification 3GPP® TR 38.801 V 14.0.0 "Study on new radio access technology: Radio access architecture and interfaces" [Overview of the project] [Means for solving the problem]

[0022] For that purpose, the Specified provides a method for configuring an equalization resource of an equalizer for a transceiver optical device, wherein the equalization resource is used by the equalizer to perform equalization on an optical signal received over a channel of an optical line, the method comprising: obtaining environmental parameter values, where the environmental parameter values ​​are values ​​of environmental data for a physical parameter or derivative affecting the channel of the optical line; obtaining a channel depth estimate from past experience in consideration of the environmental parameter values; and selectively activating the equalization resource to perform equalization on an optical signal received over a channel of an optical line according to the obtained channel depth estimate.

[0023] Therefore, the operation of the equalization resource is improved in terms of the use of the equalization resource, particularly in terms of hardware block allocation, equalization signaling overhead, and thus in terms of the use of computational resources, and energy consumption.

[0024] In a particular embodiment, in order to obtain a channel depth estimate from past experience, the method includes the steps of: searching within the lookup table to determine whether the lookup table contains channel-related information associated with environmental parameter values; if the lookup table contains channel-related information associated with environmental parameter values, using the channel depth estimate contained in the channel-related information contained in the lookup table; and if the lookup table does not contain channel-related information associated with environmental parameter values, using the channel depth estimate as the worst-case scenario.

[0025] Therefore, improvements in the operation of the equalization resource can be easily achieved.

[0026] In certain embodiments, the lookup table is populated at least partially by monitoring the equalization performance of the equalizer to determine the channel learning data, timestamping the channel learning data, acquiring environmental learning data that reflects the actual environmental conditions of the optical line, timestamping the environmental learning data, and associating the environmental learning data with the channel learning data using the timestamp information.

[0027] Therefore, by inputting data into the lookup tables, their contents are improved in accordance with the experience gained by the transceiver optical device.

[0028] In certain embodiments, the lookup table is populated at least partially by acquiring training data from another channel having similar deployment conditions for the optical line.

[0029] Therefore, once the lookup table is populated, its contents are improved using experience obtained from another optical fiber line.

[0030] In certain embodiments, the method further includes the step of adding a predetermined depth margin to the channel depth estimate.

[0031] Therefore, channel fluctuations and estimation errors can be easily compensated for.

[0032] In certain embodiments, a predetermined depth margin depends on the time elapsed since the last update of the channel coherence time and / or the actual equalization performance and / or the actual knowledge of the channel characteristics.

[0033] Therefore, the depth margin can be optimized according to the situation.

[0034] In certain embodiments, the equalization resource includes a hardware block used to perform equalization on optical signals received over a channel of an optical line.

[0035] Therefore, improvements in power consumption for hardware resources can be achieved.

[0036] In certain embodiments, the equalization resource includes equalization overhead in an optical signal received over a channel of an optical line, and the method includes the step of sending equalization-related information indicating the size of the equalization overhead used to transmit the optical signal to another transceiver optical device that transmits the optical signal over the channel of the optical line.

[0037] Therefore, improvements in computational resources and latency can be achieved to handle the equalization overhead, such as preambles.

[0038] In certain embodiments, the method further includes the step of defining the size of the equalization overhead of other optical signals transmitted from one transceiver optical device to another transceiver optical device, according to the acquired channel depth estimate.

[0039] Therefore, the aforementioned other transceiver optical device can also benefit from this improvement, taking into account the interconnected channels.

[0040] In certain embodiments, the environmental data is predicted environmental data for a future point in time, and the use of equalization resources is scheduled to be activated when the relevant future point in time is reached.

[0041] Therefore, the use of equalization resources can be scheduled, and improvements can be expected.

[0042] This specification further proposes a transceiver optical device including an equalizer for performing equalization on an optical signal received over a channel of an optical line, wherein the transceiver optical device is configured to set up equalization resources for the equalizer, which are used by the equalizer to perform equalization on an optical signal received over a channel of an optical line, and the transceiver optical device further includes an electronic circuit configured to acquire environmental parameter values, which are values ​​of environmental data about physical parameters or derivatives affecting the channel of the optical line, acquire a channel depth estimate from past experience in light of the environmental parameter values, and selectively enable the equalization resources to perform equalization on an optical signal received over a channel of an optical line according to the acquired channel depth estimate. [Brief explanation of the drawing]

[0043] The features of the present invention will become clearer by reading the following description of at least one example of the embodiments, which is derived from reference to the accompanying drawings. [Figure 1] This diagram schematically shows the arrangement of an optical communication system in which the present invention can be implemented. [Figure 2] This diagram schematically shows the arrangement of transceiver optical devices in an optical communication system. [Figure 3] This diagram schematically shows the arrangement of the equalization preset devices. [Figure 4] This figure schematically represents an algorithm for selectively enabling equalization resources in one embodiment of the present invention. [Figure 5]This figure schematically represents an algorithm for selectively activating equalization resources in a particular embodiment of the present invention. [Figure 6] This figure schematically illustrates an algorithm for supplying data to a lookup table in a particular embodiment of the present invention. [Modes for carrying out the invention]

[0044] Since wavelength and frequency are related to each other through a direct inverse relationship, it should be noted that these two terms are used interchangeably by those skilled in the art, as they refer to the same concept.

[0045] Figure 1 schematically shows the arrangement of an optical communication system 100 in which the present invention may be implemented.

[0046] The optical communication system 100 is part of an optical access and aggregation network.

[0047] The optical communication system 100 includes at least a first transceiver optical device T1 111 and a second transceiver optical device T2 112 that communicate with each other using an optical line 121.

[0048] As illustrated in the optical communication system 100 of Figure 1, the first transceiver optical device T1 111 may communicate with other transceiver optical devices T3 113 and T4 114 using their respective optical lines 122 and 123.

[0049] An optical circuit is an optical path between transceiver optical devices. While an optical circuit includes optical fibers, it may also include power splitters, spectral splitter devices for performing WDM (Wavelength Division Multiplexing), optical termination outputs, optical termination connectors, and the like.

[0050] For example, the first transceiver optical device T1 111 is an OLT (Optical Line Terminal) device, while the second transceiver optical device T2 112, as well as the other transceiver optical devices T3 113 and T4 114, are ONU (Optical Network Unit) devices.

[0051] Figure 2 schematically shows the arrangement of the transceiver optical devices in the optical communication system 100. Figure 2 is considered to schematically show the arrangement of the second transceiver optical device T2 112.

[0052] The second transceiver optical device T2 112 comprises a receive chain and a transmit chain.

[0053] The receive chain comprises a receive analog stage 211 including a photodiode for capturing an optical signal transmitted by a first transceiver optical device T1 111 via an optical line 121. The receive chain further comprises a receive digital stage RDS212 for performing digital processing on the captured optical signal. Digital processing in the receive chain typically includes demodulation, equalization, and removal of equalization overhead. The equalization overhead shall be understood as a cyclic prefix and / or cyclic suffix in the frequency domain, or a preamble in the time domain, depending on the modulation / demodulation in use. The receive chain further comprises a receive data processing stage RDPS213 for unpacking data to be processed by application APP230.

[0054] The transmit chain comprises a transmit data processing stage TDPS223 for packing data provided by application APP230. The transmit chain further comprises a transmit digital stage TDS222 for performing digital processing on the packed data. Digital processing in the transmit chain typically includes modulation and equalization overhead insertion. The transmit chain further comprises a transmit analog stage 221 including a laser for transmitting an optical signal over optical line 121 to a first transceiver optical device T1 111.

[0055] As illustrated by the dotted line in Figure 2, the receiving digital stage RDS212 may communicate equalization-related information to the transmitting digital stage TDS222 in order to set the size of the equalization overhead for inserting equalization overhead into the transmitting chain of the second transceiver optical device T2 112, and / or to provide feedback information to the first transceiver optical device T1 111 so that the first transceiver optical device T1 111 can perform its own equalization configuration accordingly, and / or to provide feedback information to the first transceiver optical device T1 111 so that the first transceiver optical device T1 111 adjusts the size of the equalization overhead of the optical signal transmitted to the second transceiver optical device T2 112 accordingly. In a modified example, this communication of equalization-related information from the receiving chain to the transmitting chain may be performed via the receiving data processing stage RDPS213 and the transmitting data processing stage TDPS223 to facilitate information packing to the first transceiver optical device T1 111.

[0056] Figure 3 schematically shows the configuration of the equalization presetter 300. The equalization presetter 300 is part of the receiving digital stage RDS212 in the arrangement shown in Figure 2 and is connected to the equalizer 360.

[0057] The equalization preconfigurator 300 comprises a learning agent 310 configured to supply a lookup table (LUT) 320, which is later used by the resource manager 330 to estimate the channel depth. The estimated channel depth is used to configure appropriate equalization resources via a hardware (HW) block selector 351 and an overhead preconfigurator 352.

[0058] The hardware block selector 351 is configured to selectively enable / disable hardware blocks (logical cells, registers, multipliers, memory devices) used to perform equalization, and to indicate to the equalizer 360 which hardware blocks are available to perform equalization. This reduces energy consumption by disabling hardware blocks that are not needed to perform equalization in light of the estimated channel depth.

[0059] The overhead pre-configurator 352 is configured to tell the equalization overhead agent 380 of the receiving digital stage RDS212 what the appropriate size of the equalization resources should be, which means how many equalization resources should be processed to perform equalization. As a result, the equalization overhead agent 380 configures the equalizer 360. The equalization overhead agent 380 may also be configured to tell the feedback agent 390 what the appropriate size of the equalization resources should be. This allows the feedback agent 390 to inform the transmitting digital stage TDS222 about the appropriate size of the equalization resources, and as a result, the transmitting digital stage TDS222 can adjust the size of the equalization overhead (preamble, cyclic prefix, cyclic suffix) when transmitting an optical signal to the first transceiver optical device T1 111 over the optical line 121. This is particularly applicable when the channels are reciprocal (substantially identical channels in both directions on the optical line 121). This limits the equalization overhead in the direction from the second transceiver optical device T2 112 to the first transceiver optical device T1 111, and consequently, this limits the use of computing resources and energy consumption. From the perspective of the first transceiver optical device T1 111, it can be further noted that the delay time is improved (e.g., a shortened preamble compared to the worst case). This allows the transmission chain to inform the first transceiver optical device T1 111 about an appropriate size of equalization resources, and consequently, the first transceiver optical device T1 111 can adjust the size of the equalization overhead (preamble, cyclic prefix, cyclic suffix) when transmitting optical signals to the second transceiver optical device T2 112 over the optical line 121. This limits the equalization overhead in the direction from the first transceiver optical device T1 111 to the second transceiver optical device T2 112, and consequently, this limits the use of computing resources and energy consumption.From the perspective of the second transceiver optical device T2 112, it can be further noted that the delay time is improved (e.g., a shortened preamble compared to the worst case).

[0060] In the receiving digital stage RDS212, the equalizer 360 includes or is connected to a channel estimator 370. The channel estimator 370 is configured to estimate the response of the optical line 121 so that the equalizer 360 can determine appropriate values ​​for the equalization coefficients (taps in the time domain). Channel estimation can be non-data-assisted or data-assisted. The channel estimator 370 is further configured to monitor equalization performance, the rate of change of the channel, and the coherence time of the channel. The coherence time of the channel is defined as the duration during which the channel exhibits constant or monotonic behavior. The channel estimator 370 may be further configured to monitor the signal-to-noise ratio (SNR), which is an indicator of equalization performance.

[0061] The learning agent 310 is configured to receive environmental learning data Env_Ld. Environmental learning data Env_Ld is data relating to the environmental conditions of the optical line 121. Environmental data such as environmental learning data Env_Ld is environmental information about physical parameters or derivatives that affect the channels of the optical line 121 and thus cause variations in the channels of the optical line 121, and may include temperature information (such as that provided by temperature sensors along the optical line 121 at the locations of the first transceiver optical device T1 111 and the second transceiver optical device T2 112), the rate of temperature change (e.g., due to the passage of clouds), wind strength information, etc. The environmental learning data Env_Ld is timestamped so that it can be processed by the learning agent 310 to be properly fed into the lookup table 320.

[0062] The learning agent 310 is also configured to receive channel learning data Ch_Ld. The channel learning data Ch_Ld is data relating to the channel depth, the rate of change of the channel, and the coherence time of the channel. If several channels are available (for example, in the case of the first transceiver optical device T1 111 in Figure 1 for communicating with various transceiver optical devices T2 111, T3 113, and T4 114), the channel learning data Ch_Ld is associated with a channel identifier ChID. The channel learning data Ch_Ld is timestamped so that it can be processed by the learning agent 310 to be properly fed into the lookup table 320. The channel learning data Ch_Ld may also be provided by the channel estimator 370, as already described.

[0063] The learning agent 310 is configured to associate channel learning data Ch_Ld and environment learning data Env_Ld by relying on timestamp information where the timestamp information of the channel learning data Ch_Ld matches the timestamp information of the environment learning data Env_Ld. The associated learning data Ch_Ld and environment learning data Env_Ld are placed into the lookup table 320. Thus, from the environment data, which is considered to be Env_tbc, the resource manager 330 can obtain corresponding channel data, such as channel depth information.

[0064] Channel learning data Ch_Ld and environment learning data Env_Ld may be provided by setup. In this case, the channel learning data Ch_Ld and environment learning data Env_Ld are timestamped identically so that they can be associated by the learning agent 310. In the first embodiment, the channel learning data Ch_Ld and environment learning data Env_Ld are the results of a simulation. In the second embodiment, the channel learning data Ch_Ld and environment learning data Env_Ld are data acquired for other channels having similar deployment conditions for the optical line. For example, if transceiver optical device T3 113 is located near a second transceiver optical device T2 112, the channel learning data Ch_Ld acquired by transceiver optical device T3 113 can be used as setup data for the second transceiver optical device T2 112 under the same environmental conditions (i.e., the same environment learning data Env_Ld).

[0065] Channel learning data Ch_Ld may be provided by the channel estimator 370 by monitoring the operation of the receiving chain, and more specifically by monitoring the channel response. Thus, once the channel data is determined by the channel estimator 370 under actual conditions, this channel data can be used later when similar environmental conditions are met. Corresponding environmental learning data Env_Ld may be provided in real time, for example, by receiving measurements from sensors or from an environmental data server responsible for collecting environmental measurements of the optical communication system 100.

[0066] Thanks to the input of the lookup table 320 by the learning agent 310, the resource manager 330 can obtain an estimate of the channel depth and potentially other channel-related information from the environmental data, presumably Env_tbc. This allows the resource manager 330 to determine (and potentially anticipate) the needs of the equalization resources in light of the provided environmental data Env_tbc. From the channel depth information contained in the lookup table 320, the resource manager 330 may apply a predetermined depth margin to address potential time variations in channel characteristics. The depth margin may be fixed or vary according to a predetermined criterion. Such a predetermined criterion may be the time elapsed since the last update of the channel coherence time and / or the actual equalization performance (e.g., as indicated by the signal-to-noise ratio (SNR)) and / or the actual knowledge of the channel characteristics. In the latter case, a larger margin is used when the channel coherence time is short and / or the signal-to-noise ratio is poor and / or a time greater than a predetermined threshold has elapsed since the last update of the actual knowledge of the channel characteristics.

[0067] The resource manager 330 may include, or be connected to, a scheduler 340 configured to schedule the subsequent configuration of the equalization resources via a hardware block selector 351 and an overhead preconfigurator 352. This allows for the anticipation of changes in predicted channel characteristics. For example, the resource manager 330 receives environment data, which may be Env_tbc, which is predicted environment data (e.g., a storm is coming in the near future) with time data Time_d (a future point in time). The resource manager 330 can program the scheduler 340 with a predicted channel depth corresponding to the time data. When the scheduler 340 detects that the future point in question has been reached, the scheduler 340 is configured to instruct the resource manager 330 to configure the hardware block selector 351 and the overhead preconfigurator 352 according to the predicted channel depth. As already mentioned, a depth margin can be applied, for example, as a function of the time elapsed since the scheduler 340 was programmed.

[0068] Figure 4 schematically illustrates an algorithm for selectively activating equalization resources in one embodiment of the present invention. The algorithm in Figure 4 is performed by the receiving chain of the transceiver optical device shown in Figure 2, more specifically by its receiving digital stage RDS212. Referring to Figure 3, the algorithm in Figure 4 is performed by the equalization presetter 300.

[0069] In step S401, the transceiver optical device acquires environmental parameter values. These environmental parameter values ​​are environmental information about physical parameters or derivatives, which affect the channel and thus generate channel fluctuations (temperature, vibration, etc.).

[0070] In step S402, the transceiver optical device obtains channel depth information from past experience, taking into account the environmental parameter values. The past experience is preferably the channel depth encountered by the transceiver optical device under the same environmental conditions as reflected by the environmental parameter values. The past experience may be obtained by simulation or for another channel with similar deployment conditions for the optical line.

[0071] In step S403, the transceiver optical device selectively enables equalization resources according to the acquired channel depth. Equalization resources are hardware blocks (logical cells, registers, multipliers, memory devices) used to perform equalization. Equalization resources may also include equalization overhead (i.e., cyclic prefixes and / or cyclic suffixes in the frequency domain, or preambles in the time domain).

[0072] Figure 5 schematically illustrates an algorithm for selectively activating equalization resources in a particular embodiment of the present invention. The algorithm in Figure 5 is performed by the receiving chain of the transceiver optical device shown in Figure 2, more specifically by its receiving digital stage RDS212. Referring to Figure 3, the algorithm in Figure 5 is performed by the equalization presetter 300.

[0073] In step S501, the transceiver optical device acquires environmental parameter values ​​(environmental data that can be considered as Env_tbc within the range shown in Figure 3). Environmental parameter values ​​are environmental information about physical parameters or derivatives that affect the channel and therefore generate channel variations (temperature, vibration, etc.).

[0074] In step S502, the transceiver optical device searches within the lookup table 320 to determine whether the lookup table 320 contains channel-related information associated with environmental parameter values. The transceiver optical device may also search for a specific channel associated with the channel identifier ChID.

[0075] In step S503, the transceiver optical device determines whether such channel-related information is found in the lookup table 320 (for the potentially problematic channel identifier ChID). If it is found, it means that the equalization resource can be pre-configured using past experience, and step S506 is performed. Otherwise, it means that the default setting for the equalization resource should be used, and step S504 is performed.

[0076] In step S504, the transceiver optical device defines the channel depth as the worst-case scenario. The worst-case scenario may differ for each optical line, i.e., for each channel identifier (ChID). In fact, the worst-case scenario is more severe, for example, if an optical line contains longer optical fibers compared to another optical line.

[0077] In step S505, the transceiver optical device may optionally begin learning to supply channel-related data corresponding to the environmental parameter values ​​(environmental conditions) in question to the lookup table 320. This is particularly true when the environmental parameter values ​​reflect the current environmental conditions (not for later scheduling). Specific embodiments are disclosed hereafter with respect to Figure 6. Step S508 is then performed.

[0078] In step S506, the transceiver optical device defines the channel depth as shown in the lookup table 320 in relation to the environmental parameter values ​​obtained in step S501. Thus, past experience is used to estimate the channel depth.

[0079] In step S507, the transceiver optical device preferably adds a depth margin to the channel depth obtained from the lookup table 320 in step S506. Then, step S508 is performed. The depth margin allows for potential time variations in channel characteristics and also allows for some inaccuracy in the channel depth estimation.

[0080] In step S508, the transceiver optical device determines the amount of equalization resources to be used as a function of channel depth. Equalization resources are hardware blocks (logical cells, registers, multipliers, memory devices) used to perform equalization. Equalization resources may also include equalization overhead (i.e., cyclic prefixes and / or cyclic suffixes in the frequency domain, or preambles in the time domain).

[0081] As already mentioned, various equalization techniques may be used by transceiver optical devices. For each equalization technique, a deterministic correspondence is known between the channel depth and the amount of equalization resources (hardware blocks, equalization overhead).

[0082] In step S509, the transceiver optical device uses the determined amount of equalization resources for equalization (for the optical signal received via the optical line 121 for the second transceiver optical device T2 112). In other words, the transceiver optical device selectively enables the equalization resources according to the acquired channel depth (potentially for transmission over the channel associated with the channel identifier ChID in question). Thus, the equalization resources in use are defined according to the worst-case scenario only if no past experience is recorded in the lookup table 320; otherwise, the equalization resources in use are defined according to the said past experience, and therefore energy consumption is reduced compared to the worst-case scenario.

[0083] It should be noted that the use of the equalization resource in step S509 can refer to immediate use when the environmental parameter value (environmental data, which can be considered as Env_tbc within the range of Figure 3) reflects current environmental conditions, or to future use (via scheduler 340 in Figure 3) when the environmental parameter value reflects future environmental conditions (associated with time data Time_d within the range of Figure 3). In the latter case, the environmental data is predicted environmental data for a future point in time, and the use of the equalization resource is scheduled to be activated when the future point in question is reached.

[0084] Figure 6 schematically illustrates an algorithm for supplying data to the lookup table 320 in a particular embodiment of the present invention. The algorithm in Figure 6 is performed by the receiving chain of the transceiver optical device shown in Figure 2, more specifically by its receiving digital stage RDS212. Referring to Figure 3, the algorithm in Figure 6 is performed by the equalization presetter 300.

[0085] In step S601, the transceiver optical device receives an optical signal (for example, via the optical line 121 for the second transceiver optical device T2 112). The optical signal may be received via a channel associated with the channel identifier ChID.

[0086] In step S602, the transceiver optical device determines the equalization coefficient using the effectively available equalization resources. Thus, the channel estimator 370 can monitor the performance of the equalization.

[0087] In step S603, the transceiver optical device determines the highest-order equalization coefficient and obtains the convergence time for finding the equalization coefficient. The highest-order equalization coefficient is set to a coefficient that exceeds a predetermined threshold. The convergence time is the time thereafter during which the refinement of the equalization coefficient does not change beyond a predetermined threshold ratio of the coefficient's magnitude.

[0088] In step S604, the transceiver optical device determines the actual channel depth and time (number of symbols) required to set up channel equalization, respectively (from the top-level equalization coefficient and convergence time). In fact, the top-level equalization coefficient directly provides the optical signal spreading that should be considered so that the symbols of the optical signal can be reconstructed from the consecutive symbols. The time required to set up channel equalization directly provides the size of the equalization overhead (size of the preamble / cycle prefix / cyclic suffix).

[0089] In step S605, the transceiver optical device records the channel-related information (channel learning data Ch_Ld within the range shown in Figure 3) obtained in step S604 in the lookup table 320. The channel-related information may be associated with the channel identifier ChID. The transceiver optical device times-stamps the channel-related information to record the moment when the channel-related information was acquired.

[0090] In the independent process, in step S611, the transceiver optical device acquires environmental parameter values ​​(environmental learning data Env_Ld in the scope of Figure 3). The environmental parameter values ​​reflect the actual environmental conditions.

[0091] Next, in step S612, the transceiver optical device records the environmental parameter values ​​acquired in step S611 in the lookup table 320. The transceiver optical device times the environmental parameter values ​​to record the moment when the environmental parameter values ​​were acquired.

[0092] Steps S605 and S612 are part of the learning phase that enables the data to be supplied to the lookup table 320. In step S621, by associating the channel learning data Ch_Ld and the environment learning data Env_Ld with the timestamp information associated with them, the transceiver optical device can determine which channel depth and other channel-related information can be estimated for which environmental conditions.

Claims

1. A method for configuring an equalization resource for an equalizer of a transceiver optical device, wherein the equalization resource is used by the equalizer to perform equalization on optical signals received over a channel of an optical line, and the method is A step of obtaining environmental parameter values, wherein the environmental parameter values ​​are values ​​of environmental data for physical parameters or derivatives affecting the channel of the optical line, The steps include obtaining a channel depth estimate from past experience, taking into account the aforementioned environmental parameter values, A method comprising the step of selectively enabling the equalization resource to perform equalization on the optical signal received through the channel of the optical line in accordance with the acquired channel depth estimation.

2. To obtain channel depth estimation from past experience, the method described above is: The steps include: searching within the lookup table to determine whether the lookup table contains channel-related information associated with the environmental parameter value; If the lookup table includes channel-related information associated with the environmental parameter values, the step is to use the channel depth estimate included in the channel-related information included in the lookup table. The method according to claim 1, further comprising the step of using a channel depth estimate as the worst case if the lookup table does not contain channel-related information associated with the environmental parameter values.

3. The aforementioned lookup table is To determine the channel learning data, monitor the equalization performance of the equalizer, The channel learning data is timestamped, Environmental learning data reflecting the actual environmental conditions of the aforementioned optical fiber line is acquired. The aforementioned environmental learning data is timestamped, The method according to claim 2, wherein the environmental learning data and the channel learning data are input by associating them using timestamp information.

4. The method according to claim 2, wherein the lookup table is populated by acquiring training data for another channel having similar deployment conditions for an optical fiber line.

5. The step of adding a predetermined depth margin to the channel depth estimation. The method according to claim 1, further comprising:

6. The method according to claim 5, wherein the predetermined depth margin depends at least on the time of coherence of the channel, the actual equalization performance, or the time elapsed since the last update of actual knowledge of the channel's characteristics.

7. The method according to claim 1, wherein the equalization resource includes a hardware block used to perform the equalization on the optical signals received through the channel of the optical line.

8. The method according to claim 1, wherein the equalization resource includes an equalization overhead in the optical signal received over the channel of the optical line, and the method includes the step of transmitting equalization-related information indicating the size of the equalization overhead used to transmit the optical signal to another transceiver optical device that transmits the optical signal over the channel of the optical line.

9. The method according to claim 8, further comprising the step of defining the size of the equalization overhead of other optical signals transmitted from the transceiver optical device to the other transceiver optical device according to the channel depth estimation obtained.

10. The method according to claim 1, wherein the environmental data is predicted environmental data for a future point in time, and the use of the equalization resources is scheduled to be activated when the future point in question is reached.

11. A transceiver optical device including an equalizer for performing equalization on an optical signal received via a channel of an optical line, wherein the transceiver optical device is configured to set up equalization resources for the equalizer, the equalization resources are used by the equalizer to perform equalization on the optical signal received via the channel of the optical line, and the transceiver optical device is an electronic circuit, Obtain environmental parameter values, which are values ​​of environmental data for physical parameters or derivatives affecting the channel of the optical line, Taking into account the aforementioned environmental parameter values, channel depth estimation is obtained from past experience. A transceiver optical device comprising an electronic circuit configured to selectively activate the equalization resource to perform equalization on the optical signal received through the channel of the optical line, in accordance with the acquired channel depth estimation.

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