KR-102963472-B1 - Receiver and receiving method for passive optical networks

KR102963472B1KR 102963472 B1KR102963472 B1KR 102963472B1KR-102963472-B1

Abstract

A receiver for a passive optical network is provided. The receiver includes an analog-to-digital converter circuit configured to generate a digital received signal based on an analog received signal. The analog received signal is based on an optical received signal encoded in a binary transmission sequence. The receiver further includes a linear equalizer circuit configured to generate an equalized received signal by linearly equalizing the digital received signal. Additionally, it includes a second-order equalizer circuit configured to generate soft information representing the reliability of each element within the equalized received signal using a Viterbi algorithm. Furthermore, the receiver includes a decoder circuit configured to generate a digital output signal based on the soft information using soft decision forward error correction.

Inventors

스트로벨 라이네르
싱 라빈드라

Assignees

인텔 코포레이션

Dates

Publication Date: 20260512
Application Date: 20200928
Priority Date: 20191025

Claims (20)

As a receiver for passive optical networks, An analog-to-digital converter circuit configured to generate a digital reception signal based on an analog reception signal - said analog reception signal is based on an optical reception signal encoded in a binary transmission sequence - and, A linear equalizer circuit configured to generate an equalized received signal by linearly equalizing the digital received signal, and A second-order equalizer circuit configured to generate soft information indicating the reliability of each element within the equalized received signal using the Viterbi algorithm, and A decoder circuit configured to generate a digital output signal based on the above soft information using soft judgment forward error correction. A receiver including
In Article 1, The above linear equalizer circuit includes a feed-forward equalizer. receiving set.
In Article 2, The transfer function of the above linear equalizer circuit is trained not to cancel out the inter-symbol interference of the digital received signal assumed by the above second-order equalizer circuit, receiving set.
In Article 2 or Article 3, The transfer function of the above linear equalizer circuit is It is given by a coefficient vector g leg proportional to, represents an estimate of the transmission channel of the optical signal of the passive optical network assumed by the second-order equalizer circuit, and represents an element of the above-mentioned digital received signal receiving set.
In any one of paragraphs 1 to 3, The above second equalizer circuit is, A Maximum Likelihood Sequence Estimation (MLSE) equalizer configured to determine the most likely binary transmit sequence based on the equalized received signal, and An inter-symbol interference estimator configured to determine an estimate of inter-symbol interference in the equalized received signal based on the most likely binary transmission sequence determined above, and A combiner configured to combine the above-mentioned equalized received signal and the signal representing the above-mentioned estimate of inter-symbol interference into a modified received signal, and A soft information determination circuit configured to determine the soft information based on the modified received signal. including, receiving set.
In Article 5, The inter-symbol interference estimator is configured to determine the estimate of the inter-symbol interference in the equalized received signal using a non-linear model of the transmission channel of the optical signal of the passive optical network. receiving set.
In any one of paragraphs 1 to 3, The second equalizer circuit comprises a BCJR equalizer configured to receive the equalized received signal and determine the soft information based on the equalized received signal. receiving set.
In Article 7, The above BCJR equalizer is configured to determine the soft information using a nonlinear model of the transmission channel of the optical signal of the above passive optical network, receiving set.
In Article 7, The above decoder circuit is configured to feed back the digital output signal to the BCJR equalizer, and The above BCJR equalizer is configured to adjust a branch metric used to determine the soft information based on the digital output signal, receiving set.
In any one of paragraphs 1 to 3, The above digital output signal represents additional soft information indicating the reliability of each element of the received sequence determined by the decoder circuit based on the soft information using forward error correction, receiving set.
In Article 10, The above additional soft information is a log likelihood ratio representing the reliability of each of the elements of the above receiving sequence, receiving set.
In any one of paragraphs 1 to 3, The above soft information is a log likelihood ratio representing the reliability of each of the elements of the equalized received signal, receiving set.
In any one of paragraphs 1 to 3, The receiver further includes a calibration circuit for training a nonlinear model of a transmission channel for an optical signal of the passive optical network used by the second equalizer circuit, and The above-mentioned optical reception signal is encoded into a binary training sequence containing all possible state transitions in a predefined trellis diagram during the training period, and The above correction circuit is, During the above training period, a binary output sequence is determined based on the software information determined by the above second equalizer circuit, and Configured to adapt the nonlinear model of the transmission channel based on the above-determined binary output sequence, receiving set.
In Article 13, In order to adapt the above nonlinear model of the above transmission channel, The above correction circuit is, For the elements of the above-determined binary output sequence, the most likely state in the above-determined trellis diagram is determined, and Based on the elements of the above-determined binary output sequence, the most likely transmitted element is determined, and Based on the most probable state and the most probable transmitted element in the above trellis diagram, to adapt the nonlinear model of the transmission channel Constituting, receiving set.
In Article 13, The above second equalizer circuit is configured to store a first lookup table and a second lookup table representing a nonlinear model of the transmission channel, and The first lookup table represents the average estimate of the transmission channel, and the second lookup table represents the variance of the average estimate of the transmission channel. receiving set.
In any one of paragraphs 1 to 3, The above decoder circuit includes an LDPC (Low-Density Parity-Check) decoder, receiving set.
In any one of paragraphs 1 to 3, A clock recovery circuit configured to determine information about a transmission clock used to transmit an optical signal based on the above-mentioned equalized received signal, and A clock generation circuit configured to generate a clock signal to the analog-to-digital converter circuit based on information regarding the transmission clock. Includes, The above analog-to-digital converter circuit is configured to generate the digital reception signal using the clock signal, receiving set.
In Article 17, The above clock generation circuit is a phase-locked loop, receiving set.
In any one of paragraphs 1 to 3, It further includes an interface for connecting to the above passive optical network, and The above interface is configured to receive an optical signal from the above passive optical network. receiving set.
In Article 19, A receiver further comprising an optical-electric converter circuit configured to convert the above optical signal into the above analog reception signal. receiving set.

Description

Receiver and receiving method for passive optical networks The present disclosure relates to receiving technology for a Passive Optical Network (PON). In particular, examples relate to a receiver and a receiving method for a PON. The data rate per wavelength of PON is increasing. In PON, to improve error correction (e.g., forward error correction, FEC), low-density parity checking (LDPC) codes capable of processing soft information (i.e., non-binary input) are introduced to increase efficiency. Furthermore, digital equalization becomes more important as the transmission speed increases. In particular, since optical receiver components are inexpensive, PON transmission channels are highly non-linear, so non-linear equalization is required. Some examples of the apparatus and/or method are merely exemplary and will be described below with reference to the attached drawings. FIG. 1 illustrates a first example of a receiver for PON. Figure 2 illustrates a second example of a receiver for PON. Figure 3 illustrates a third example of a receiver for PON. Figure 4 illustrates a fourth example of a receiver for PON. Figure 5 shows an example of a trellis diagram. Figure 6 shows an exemplary comparison of bit error rate (BER) courses for transmission power in various equalization techniques. Figure 7 shows an exemplary comparison of mutual information courses for transmission power in various equalization technologies. Figure 8 illustrates an exemplary comparison of the course of the probability of a continuous output error with respect to the number of continuous error inputs in various equalization techniques. Figure 9 illustrates a flowchart of an example of a method for PON. Some examples are described in more detail below with reference to the attached drawings. However, other possible examples are not limited by the features of these embodiments described in detail. Other examples may include modifications to the function, as well as equivalents and alternatives to the function. Furthermore, the terms used in this specification to describe specific examples are not limited to additional possible examples. Throughout the description of the drawings, identical or similar reference numbers indicate identical or similar elements and/or features, which may be implemented in the same or modified forms while providing the same or similar functions. For illustrative purposes, the thickness of lines, layers, and/or regions in the drawings may be exaggerated. If two elements A and B are combined using 'or', it should be understood that all possible combinations, namely A only, B only, and A and B, are disclosed, unless otherwise explicitly defined in each case. As alternative expressions for the same combination, "at least one of A and B" or "A and/or B" may be used. This applies equally to cases where two or more elements are combined. Where singular forms such as "a," "an," and "the" are used, and where it is not explicitly or implicitly defined to use only a single element, additional examples may use multiple elements to implement the same function. Where a function is described below as being implemented using multiple elements, additional examples may implement the same function using a single element or a single processing object. Where the terms "include," "including," "comprise," and/or "comprising" are used, they refer to a specified function, integer, step, action, process, element, component, and/or group thereof, but do not exclude the existence or addition of one or more other functions, integers, steps, operations, processes, elements, components, and/or groups thereof. FIG. 1 illustrates a receiver (100) for a PON. A PON is not illustrated in FIG. 1. A PON is a fiber optic access network that connects a transmitter (e.g., a service provider's OLT (Optical Line Terminal)) to a receiver (100) and optionally connects additional receivers. A PON consists of fibers and passive splitters. A PON does not include active elements between the endpoints of the network (i.e., there are no power requirements or active electronic components for optical transmission when a signal passes through the network). The receiver (100) includes a (hardware) interface (160) to be connected to the PON. For example, the interface (160) may be connected to the PON's ONT (Optical Network Terminal) or ONU (Optical Network Unit). The interface (160) is configured to receive an optical signal (101) from the PON. For example, on the transmitter side for downstream data, an EML (Externally Modulated Laser) may be used to generate an intensity-modulated signal, for example, at two levels (NRZ (Non-Return-to-Zero) modulation), which is received by the receiver (100) through the PON. The optical reception signal (101) is encoded into a binary transmission sequence to be transmitted from the transmitter side to the receiver (100). The receiver further includes an optical-to-electric converter circuit (150) configured to convert an optical sign