WO2023142846A1 - Compliance test method, device, and system. - Google Patents

Abstract

The present application provides a compliance test method, a device, and a system. The method comprises: first, an optical receiver obtains a test eye pattern, wherein the test eye pattern is obtained after equalization and compensation of a first test sequence in an optical signal transmitted by an optical transmitter to be tested, and equalization and compensation comprises first equalization and compensation and second equalization and compensation. Then, the optical receiver calculates the value of a first parameter according to the test eye pattern, a noise enhancement coefficient corresponding to first equalization and compensation, and the absolute value of a tap coefficient corresponding to second equalization and compensation, the first parameter being used for determining the degree of transmitter and dispersion eye pattern closure of the optical transmitter to be tested. The method provided by the present application can effectively improve the accuracy of a performance evaluation of a transmitting end device, improves the yield of transmitting end devices, and reduces system costs.

Description

A method, device and system for consistency testing

This application claims the priority of the Chinese patent application filed with the State Intellectual Property Office of China on January 27, 2022, with the application number 202210100981.1 and the application name "A Method, Device and System for Conformance Testing", the entire content of which is passed References are incorporated in this application.

technical field

The present application relates to the technical field of optical communication, and, more specifically, to a method, device and system for conformance testing.

Background technique

With the evolution of the access network system, the single-wavelength transmission rate has been increased from 10G to 50G. In order to ensure that the power budget meets the standard and provide a low-cost solution, the 50G passive optical network (PON) introduces Optical digital signal processing (ODSP) equalization mechanism to compensate for the limited bandwidth of transceiver devices and intersymbol interference caused by fiber dispersion.

Generally speaking, physical layer devices in a data communication network include components such as optical transmitters, channels (cables or optical fibers), and optical receivers. In order to ensure that various devices provided by different manufacturers are compatible and interoperable, it is usually necessary to define the conformance test parameters and methods of the above devices in the standard, so as to maximize the integration of industry chain resources and allow different manufacturers to participate in the testing of different components as much as possible. from the supply.

When the receiving device adopts the balanced receiving method to receive the optical signal, the transmitter and dispersion eye closure (TDEC) can be used as the conformance test parameters in 50G PON at present, but this solution is only applicable to the evaluation before Feedforward equalizer (FFE) is the transmitter performance of the receiver equalizer benchmark. However, there are at least two hidden dangers when using the equalization mechanism of FFE. On the one hand, compared with the actual equalization algorithm, FFE has a large gap in sensitivity performance. The budget is at risk, and chirp is not tolerated enough. On the other hand, from a system perspective, when FFE is used as a reference equalizer, the performance margin of the receiving end is not fully released, but the pressure is concentrated on the output optical power of the transmitting end, which is not conducive to the allocation of headroom at the receiving end.

Contents of the invention

The present application provides a method, device and system for consistency testing. It can effectively improve the accuracy of the performance evaluation of the sending device, improve the yield of the sending device, and reduce the system cost.

In the first aspect, the embodiment of the present application provides a testing method. The method may be executed by the receiving device, or may also be executed by a component (such as a chip or a chip system, etc.) configured in the receiving device, which is not limited in the present application. The method includes: including: obtaining a test eye diagram, the test eye diagram is obtained after equalization compensation based on the first test sequence in the optical signal emitted by the optical transmitter to be tested, and the equalization compensation includes the first equalization compensation and the second equalization compensation Two equalization compensation, according to the test eye diagram, the noise enhancement coefficient corresponding to the first equalization compensation and the absolute value of the tap coefficient corresponding to the second equalization compensation, calculate the value of the first parameter, the first parameter It is used to determine the closure degree of the transmitter and dispersion eye diagram of the optical transmitter to be tested.

It should be noted that the receiving device may be a receiver, or may be combined with a processing module in the receiver. The acquired test eye diagram may be directly obtained by the receiving device, or may be provided to the receiving device by other devices after obtaining the test eye diagram, which is not limited in this application.

For non-return to zero pulse amplitude modulation 2 (NRZ-PAM2), the first parameter can be expressed as transmitter and dispersion eye closure (transmitter and dispersion eye closure, TDEC ), for four-level pulse amplitude modulation (PAM4), the first parameter can be expressed as transmitter and dispersion eye closure quaternary (TDECQ), and for the transmitter The definition of the degree of closure of the dispersion eye diagram is the same as that in the current prior art, and will not be repeated here.

Based on the above-mentioned scheme, the embodiment of the present application is based on the equalization architecture of the first equalization compensation and the second equalization compensation to obtain the test eye diagram of the optical transmitter to be tested, and define the transmitter and The calculation method of the degree of closure of the dispersion eye diagram makes the performance evaluation of the transmitting device more accurate.

With reference to the first aspect, in some implementation manners of the first aspect, the obtaining the test eye diagram includes: obtaining a first test sequence in the optical signal, the first test sequence being the test sequence of the optical transmitter to be tested Generate a second test sequence, the second test sequence is a test sequence preset by the optical transmitter to be tested, and obtain a third test sequence, the third test sequence is the combination of the second test sequence and the first test sequence A test sequence generated after bit alignment, using the third test sequence to perform the equalization compensation on the first test sequence to generate a fourth test sequence, and using the fourth test sequence to synthesize the test eye diagram.

Based on the above solution, in the embodiment of the present application, based on the equalization framework of the first equalization compensation and the second equalization compensation, the first test sequence is used for equalization compensation by using the third test sequence, since the third test sequence does not carry any noise , therefore, in the process of equalization compensation, the noise introduced in the equalization compensation of the first test sequence will not be affected, the noise characteristics of the original signal can be preserved, and the consistency test parameters can be continued to be used without redefining the consistency test parameters. The performance of the transmitter device is evaluated by the degree of transmitter and dispersion eye closure.

With reference to the first aspect, in some implementation manners of the first aspect, the first test sequence is generated by using a second test sequence for the optical transmitter under test, including: the first test sequence is the The optical transmitter modulates the second test sequence by using the first modulation format to generate it.

With reference to the first aspect, in some implementations of the first aspect, the absolute value of the noise enhancement coefficient corresponding to the first equalization compensation and the tap coefficient corresponding to the second equalization compensation according to the test eye diagram, , calculate the value of the first parameter, including:

The first parameter according to

Sure,

Among them, σ _{0, ideal} is the standard deviation of the maximum additive noise that the ideal transmitter can support when the target bit error rate is reached, and σ _{estimated DUT} is the maximum that the optical transmitter under test can support when the target bit error rate is reached. The standard deviation of additive noise, K _eq is used to correct the sensitivity cost corresponding to the equalization compensation, the K _eq is calculated according to the absolute value of the tap coefficient of the second equalization compensation, and the first modulation format is non-return-to-zero Code two-level pulse amplitude modulation or four-level pulse amplitude modulation.

With reference to the first aspect, in some implementation manners of the first aspect, the K _eq is calculated according to the absolute value of the second equalization compensation tap coefficient, including: the K _eq is calculated according to K _eq =k|10log ₁₀ (1 -C)|calculation, wherein k is an empirical parameter, the value range of k is (0,1], and C is the absolute value of the tap coefficient corresponding to the second equalization compensation.

With reference to the first aspect, in some implementation manners of the first aspect, the first test sequence is an input of the first equalization compensation, and the third test sequence is an input of the second equalization compensation.

Based on the above scheme, in the equalization framework of the embodiment of the present application, the input of the second equalization compensation is the test sequence after bit-aligning the preset test sequence of the optical transmitter to be tested with the first test sequence transmitted by the transmitter. The sequence will not have any influence on the noise in the output sequence of the first equalization compensation, and the noise characteristics of the original signal can be preserved, so that the embodiments provided by this application can continue to use the transmitter and the degree of closure of the dispersion eye diagram in the prior art. The performance of the transmitting device is evaluated.

With reference to the first aspect, in some implementations of the first aspect, the method further includes: when the value of the first parameter is less than or equal to a preset threshold, determining the consistency of the optical transmitter under test The test passes.

In the second aspect, the embodiment of the present application provides a testing device. The device includes: a transceiver module, configured to receive an optical signal transmitted by the optical transmitter to be tested, and a processing module, configured to obtain a test eye diagram, the test eye diagram is based on the first optical signal of the optical transmitter to be tested. The equalization compensation is obtained after the test sequence performs equalization compensation. The equalization compensation includes the first equalization compensation and the second equalization compensation, and is also used for the noise enhancement coefficient corresponding to the test eye diagram, the first equalization compensation, and the second The absolute value of the corresponding tap coefficient is equalized and compensated, and the value of the first parameter is calculated, and the first parameter is used to determine the transmitter and dispersion eye closure degree of the optical transmitter to be tested.

With reference to the second aspect, in some implementation manners of the second aspect, the processing module is specifically configured to acquire a first test sequence in the optical signal, acquire a third test sequence, and use the third test sequence performing the equalization compensation on the first test sequence, generating a fourth test sequence, and using the fourth test sequence to synthesize the test eye diagram, wherein the first test sequence is the optical transmitter to be tested Generated by using a second test sequence, the second test sequence is a test sequence preset by the optical transmitter to be tested, and the third test sequence is after the bit alignment of the second test sequence and the first test sequence Generated.

With reference to the second aspect, in some implementation manners of the second aspect, the first test sequence is generated by modulating the second test sequence by the optical transmitter under test using a first modulation format.

With reference to the second aspect, in some implementations of the second aspect, the first parameter is based on

Determine, wherein, σ _{0, ideal} is the standard deviation of the maximum additive noise that the ideal transmitter can support when reaching the target bit error rate, and σ _{estimated DUT} is that the optical transmitter to be tested can support when reaching the target bit error rate The standard deviation of the maximum additive noise, K _eq is used to correct the sensitivity cost corresponding to the equalization compensation, the K _eq is calculated according to the absolute value of the tap coefficient of the second equalization compensation, and the first modulation format is not Return-to-zero code two-level pulse amplitude modulation or four-level pulse amplitude modulation.

With reference to the second aspect, in some implementation manners of the second aspect, the K _eq is calculated according to K _eq =k|10log ₁₀ (1-C)|, where k is an empirical parameter, and the value range of k is is (0,1], and C is the absolute value of the tap coefficient of the second equalization compensation.

With reference to the second aspect, in some implementation manners of the second aspect, the first test sequence is an input of the first equalization compensation, and the third test sequence is an input of the second equalization compensation.

With reference to the second aspect, in some implementation manners of the second aspect, the device further includes: a display module, configured to display the value of the first parameter, when the value of the first parameter is less than or equal to the preset When the threshold is set, it is determined that the conformance test of the optical transmitter under test passes.

In a third aspect, the embodiment of the present application provides a testing system. The system includes: an optical transmitter, used for transmitting a test optical signal, an optical receiver, used for receiving the test optical signal, and using the test optical signal for testing, and the optical receiver includes the above-mentioned second aspect and the first A testing device in any possible implementation manner in the second aspect.

In a fourth aspect, the embodiment of the present application provides a chip. The chip is connected to a memory, and is configured to read and execute program codes stored in the memory, so as to implement the above first aspect and the method in any possible implementation manner of the first aspect.

In a fifth aspect, the embodiment of the present application provides a computer-readable storage medium. The computer-readable storage medium is used to store a computer program, and when the computer program is run on a computer, the computer is made to execute the method in the above-mentioned first aspect and any possible implementation manner of the first aspect.

In a sixth aspect, the embodiment of the present application provides a computer program product. The computer program product includes: computer program code, when the computer program code is executed, implement the method in the above first aspect and any possible implementation manner of the first aspect.

For the beneficial effects brought about by the above-mentioned second aspect to the sixth aspect, reference may be made to the description of the beneficial effects in the first aspect, and details are not repeated here.

Description of drawings

FIG. 1 shows a schematic diagram of the composition and structure of a transmitter conformance testing system provided by an embodiment of the present application.

Fig. 2 shows a schematic diagram of a testing system provided by an embodiment of the present application.

Fig. 3 shows a schematic diagram of another test system provided by the embodiment of the present application.

Fig. 4 shows a schematic flowchart of a method for consistency testing provided by an embodiment of the present application.

FIG. 5 shows a schematic diagram of a test eye diagram provided by an embodiment of the present application.

FIG. 6 shows a schematic block diagram of a process for obtaining an eye diagram for testing provided by an embodiment of the present application.

Fig. 7 shows a schematic flowchart of calculating a first parameter provided by an embodiment of the present application.

FIG. 8 shows a schematic flowchart of calculating the first standard deviation provided by the embodiment of the present application.

Fig. 9 shows a schematic diagram of an equalization architecture applicable to the embodiment of the present application.

FIG. 10 shows a schematic structural diagram of a conformance testing device provided by an embodiment of the present application.

FIG. 11 shows a schematic structural diagram of another conformance testing device provided by an embodiment of the present application.

Detailed ways

The technical solution in this application will be described below with reference to the accompanying drawings.

In order to facilitate understanding of the embodiments of the present application, the following descriptions are made.

First, the text descriptions in the embodiments of the present application shown below or the terms in the drawings, "first", "second", etc. and various numerical numbers are only for the convenience of description, and do not have to be used for The description of a specific sequence or sequence is not intended to limit the scope of the embodiments of the present application. For example, it is used to distinguish different test sequences and the like in the embodiment of the present application.

Second, the terms "comprising" and "having" and any variations thereof in the embodiments of the present application shown below are intended to cover non-exclusive inclusion, for example, a process, method, or system that includes a series of steps or units The process, method, product or device are not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to the process, method, product or device.

Third, in the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or illustrations, and the embodiments or designs described as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. The use of words such as "exemplary" or "for example" is intended to present related concepts in a specific manner for easy understanding.

Fourth, in the embodiment of the present application, the optical transmitter adopts the NRZ-PAM2 modulation mode as an example to illustrate the conformance testing method provided in the present application.

The technical solution of the embodiment of the present application can be applied to a transmitter conformance test system, as shown in FIG. 1 , which is a schematic diagram of the composition and structure of the transmitter conformance test system provided by the embodiment of the present application. The transmitter conformance test system may include: a transmitter and a receiver, wherein an optical transmission channel may be configured between the transmitter and the receiver. The transmitter can send an optical signal to the receiver, and the receiver can receive the optical signal and complete the consistency test of the transmitter through the optical signal.

Wherein, the optical transmission channel mentioned here may also be called a transmission medium, for example, a transmission optical fiber or a dispersion medium having the same dispersion value as the optical fiber.

As the transmission rate continues to increase, the impact of inter-symbol interference (ISI) on the quality of transmitted data signals is becoming more and more serious. Therefore, equalization receiving techniques such as feed forward equalization (FFE), decision feedback equalization (DFE), and maximum likelihood sequence estimation (MLSE) are gradually introduced into the Checked optical link. That is, when the optical receiver receives the optical signal transmitted by the optical transmitter, it performs equalization processing on the optical signal.

Currently, the 50G PON standard has adopted TDEC as a conformance test parameter, and the corresponding equalizer is FFE. As a very basic equalization mechanism, FFE has shown some shortcomings with practical application. First of all, in practical applications, manufacturers will use relatively enhanced algorithms to ensure sensitivity performance, and the premise of using FFE as an equalizer is that the system power budget and other indicators need to meet the requirements. In addition, some implicit constraints such as chirp tolerance also need to be controlled within a reasonable range. However, the results of the actual technical verification stage have shown that FFE has a large gap in sensitivity performance compared with the actual equalization algorithm, and there is a risk that the power budget cannot be achieved when evaluating the transmitter performance of the existing power budget level. And chirp tolerance is insufficient. In addition, from a system perspective, using FFE as an equalizer does not fully release the performance margin of the receiving end, but instead concentrates the pressure on the output optical power of the transmitting end, which is not conducive to the allocation of headroom at the receiving end.

To sum up, this application proposes a conformance testing method, which can improve the accuracy of performance evaluation of the transmitting end, improve device yield, reduce system cost, and can be applied to PON systems with higher power budget levels.

Fig. 2 shows a schematic diagram of a testing system provided by an embodiment of the present application. As shown in Figure 2, the test system includes: an optical transmitter to be tested, a test fiber, a photoelectric converter, a clock recovery unit, an oscilloscope, an equalizer, and an analysis software module. Among them, the photoelectric converter, clock recovery unit, reference equalizer and analysis software modules can be integrated in the oscilloscope.

The optical-to-electrical converter, the clock recovery unit and the equalizer are used to simulate the behavior of an optical receiver (that is, an optical receiver that receives optical signals in an equalized manner). Among them, the photoelectric converter is used to convert the received optical signal into an electrical signal. The clock recovery unit is used to extract the clock of the optical signal transmitted by the optical transmitter. The oscilloscope is used to collect the code pattern of the electrical signal processed by the photoelectric converter and the clock recovery unit in the form of sequence. The optical modulation amplitude (OMA), average optical power, extinction ratio and other parameters of the optical signal emitted by the optical transmitter can be calculated through the code pattern of the collected electrical signal. The equalizer is used for equalizing and compensating the collected code patterns.

Optionally, the above-mentioned oscilloscope may be a pattern-triggered oscilloscope, and may also be a real-time acquisition oscilloscope. The pattern triggered oscilloscope means that after the oscilloscope detects the signal of the preset pattern, it triggers the oscilloscope to start acquisition. The real-time acquisition oscilloscope means that the oscilloscope is always in the state of acquiring signals.

It should be noted that the above photoelectric converter, clock recovery unit and equalizer may exist independently of the oscilloscope, or may be integrated in the oscilloscope. For example, FIG. 3 shows a schematic diagram of another testing system provided by an embodiment of the present application. As shown in Figure 3, the equalizer is integrated in the oscilloscope.

FIG. 4 shows a schematic flowchart of a method for consistency testing provided by an embodiment of the present application. As shown in Figure 4, the method includes:

S401. Acquire a test eye diagram.

Specifically, the receiver acquires a test eye diagram, which is obtained after equalization compensation based on the first test sequence in the optical signal emitted by the optical transmitter to be tested, and the equalization compensation includes the first equalization compensation and the second equalization compensation . That is, in the embodiment of the present application, the equalization compensation is a result of the joint action of the first equalization compensation and the second equalization compensation.

It should be noted that, in the embodiment of the present application, the test eye diagram needs to be acquired when the receiver performs the transmitter conformance test. Wherein, the receiver may include a device for obtaining the test eye diagram, that is, the device for obtaining the test eye diagram is a component of the receiver, and the device for obtaining the test eye diagram may perform the method for obtaining the test eye diagram in the embodiment of the present application . Or the device for obtaining the test eye diagram is a device independent of the receiver, the device for obtaining the test eye diagram executes the method for obtaining the test eye diagram, the receiver can obtain the test eye diagram from the device for obtaining the test eye diagram, and then the receiver can Use this test eye diagram for transmitter compliance testing.

S402. Calculate the value of the first parameter.

Specifically, the receiver calculates the value of the first parameter according to the test eye diagram, the noise enhancement coefficient corresponding to the first equalization compensation, and the absolute value of the tap coefficient corresponding to the second equalization compensation, wherein the first parameter is used to determine the Transmitter and dispersion eye closure degree of optical transmitter.

Optionally, the method may also include the following steps:

S403. When the value of the first parameter is less than or equal to the preset threshold, determine that the conformance test of the transmitter-under-test passes.

To sum up, in the embodiment of this application, the degree of closure of the transmitter and dispersion eye diagram of the optical transmitter to be tested is not only related to the noise enhancement coefficient corresponding to the first equalization compensation, but also related to the absolute value of the tap coefficient corresponding to the second equalization compensation. value dependent. That is, when the embodiment of the present application is used for the conformance test of the transmitter under test, two factors need to be considered at the same time, so that the test result is more realistic, thereby improving the accuracy and reliability of the test.

Specifically, the test eye diagram acquired by the receiver may be as shown in FIG. 5 . A schematic flow chart of the method for obtaining a test eye diagram is shown in FIG. 6 .

S601. Acquire a first test sequence.

Specifically, during the test, the optical transmitter to be tested will first load the test sequence of the preset pattern (that is, the above-mentioned second test sequence), and use a certain method to modulate the second test sequence to generate an optical signal, and then the optical signal The signal is sent to the optical link, and after the optical signal is received by the optical receiver, the complete code pattern of the test sequence in the received optical signal can be collected by an oscilloscope, and then the corresponding test sequence (that is, the above-mentioned first test sequence) can be obtained. sequence).

It should be noted that the second test sequence has sufficient randomness to simulate data transmitted in real scenarios. The second test sequence may be a preset test sequence of the optical transmitter to be tested. When the optical transmitter modulates the test sequence to generate an optical signal, it may use NRZ-PAM2 or PAM4, which is not limited in this application. In addition, the optical transmitter may use a rotating polarizer to change the polarization direction of the modulated optical signal according to test requirements, etc., which is not limited in the present application.

In addition, in the embodiment of the present application, the device for obtaining the first test sequence, for example, may be that the optical receiver includes the device for obtaining the first test sequence, that is, the device for obtaining the first test sequence is a component of the receiver, The apparatus for obtaining the first test sequence may execute the method for obtaining the first test sequence in the embodiment of the present application. Or the device for obtaining the first test sequence is a device independent of the receiver, the device for obtaining the first test sequence executes the method for obtaining the transmitter test sequence, and the receiver can obtain the first test sequence from the device for obtaining the first test sequence sequence, and then the receiver can perform a consistency test on the transmitter, which is not limited in this application.

S602. Acquire a third test sequence.

Specifically, the third test sequence is a test sequence generated after bit-aligning the second test sequence and the first test sequence. It should be understood that when the first test sequence is received by the optical receiver, the start position of the first test sequence may be offset relative to the start position of the second test sequence. Therefore, it is necessary to align the bits in the second test sequence with the bits in the first test sequence to generate an aligned third test sequence, so that the third test sequence can be used to compensate the first test sequence.

It should be noted that the manner of bit alignment is not limited in this application.

S603. Use the third test sequence to perform equalization compensation on the first test sequence to generate a fourth test sequence.

Exemplarily, the equalization architecture provided by the present application may be shown in FIG. 9 , as shown in FIG. 9 , x is the first test sequence, and y is the fourth test sequence.

It should be noted that, in the equalization architecture shown in Figure 9, for a certain input signal sequence, its output sequence after passing through the equalization compensation architecture of this application can be obtained, as well as the corresponding tap coefficients of the first equalization compensation and the first equalization compensation. Two tap coefficients for equalization compensation. Since the second equalization compensation can eliminate the backward intersymbol interference, the sensitivity performance can be improved. To a certain extent, the second equalization compensation weakens the effect of the first equalization compensation on noise enhancement.

It should be noted that, in the equalization compensation architecture described in FIG. 9, the first equalization compensation can be regarded as a finite impulse response (finite impulse response, FIR) filter, and the second equalization compensation can be regarded as a test sequence auxiliary balanced. In other words, this application does not limit the specific form of the equalization architecture, as long as the essence of the equalization compensation is the same as that of the equalization architecture provided by this application, or the principle adopted is the same, it should be within the scope of protection of this application, namely FIG. 9 is only an example and not a limitation.

It should be understood that, in FIG. 9 , the number of taps for the second equalization compensation is one. Of course, this application is not limited thereto, and there may be multiple taps. The number of taps of the first equalization compensation can be correspondingly changed according to different requirements, and the changed structure of the equalization compensation should also be within the scope of protection of the present application.

S604. Use the fourth test sequence to synthesize a test eye diagram.

Specifically, after equalization compensation is performed on the first test sequence by using the third test sequence, a test eye pattern is synthesized by using the fourth test sequence after equalization compensation.

Next, in combination with the test eye diagram shown in Figure 5, the optical receiver calculates the first parameter according to the absolute value of the test eye diagram, the noise enhancement coefficient corresponding to the first equalization compensation, and the tap coefficient corresponding to the second equalization compensation The value process is described in detail.

Specifically, the process of calculating the value of the first parameter may be calculated as shown in the flow chart of FIG. 7 .

S701, according to the test eye diagram, construct the histogram of the first sampling window, the histogram of the second sampling window, the histogram of the third sampling window and the histogram of the fourth sampling window, the distribution of the first sampling window and the second sampling window In the left half of the test eye diagram, the third sampling window and the fourth sampling window are distributed in the right half of the test eye diagram.

Specifically, refer to FIG. 5 , where y ₁ and y ₀ are the optical powers of level 1 and level 0 respectively, the difference between the two is the optical modulation amplitude (OMA), and the mean of the two is the average power P _th , the positions of the intersection points of the eye diagram are 0UI and 1UI, respectively.

It should be understood that in different application scenarios, the defined sampling windows may be different. In Figure 5, the histogram sampling window is defined as 0.425UI and 0.575UI, and four histograms of sampling point distribution are constructed, and the sampling window width of each histogram is 0.04UI.

It should be noted that when defining the sampling window, the boundary of each window in the vertical direction that is closer to the P _th schematic line needs to be as close as possible to the P _th schematic line, so as to ensure that when the window boundary is further close to the P _th schematic line , no additional sampling points enter the sampling window. The boundary farther away from P _th in the vertical direction of each window should include the sampling point outside the eye diagram that is farthest from the eye diagram, so as to ensure that when the boundary is further expanded, no additional sampling points will enter the sampling window.

S702, according to the histogram of the first sampling window, the histogram of the second sampling window, the histogram of the third sampling window, the histogram of the fourth sampling window and the noise enhancement coefficient, determine the first standard deviation σ _L satisfied by the first A relationship, the first standard deviation σ _L is expressed as calculating the standard deviation of noise related to optical power introduced by the transmitter when the first sampling window and the second sampling window reach the target bit error rate. And determine the second relationship satisfied by the second standard deviation σ _R , the second standard deviation σ _R is the optical power-related optical power introduced when the transmitter reaches the target bit error rate in the third sampling window and the fourth sampling window Noise standard deviation.

Specifically, the histogram of the first sampling window and the histogram of the second sampling window are respectively multiplied by the Q function to estimate the bit error probability caused by the maximum noise that can be tolerated. The obtained histogram distribution is integrated, and after the integral is divided by the original histogram distribution itself, two bit error probabilities are obtained. Wherein, the first standard deviation σ _L in the Q function can be adjusted so that the mean of the two bit error probabilities is the target bit error rate (BER), as shown in formula (1).

Wherein, f _u (y) and f _l (y) are the histogram distributions of the first sampling window and the second sampling window respectively, and BER _target is the target BER.

Wherein, the noise enhancement coefficient _Ceq corresponding to the first equalization compensation can be calculated by the following formula (2):

In formula (2), f is the rate of the NRZ signal, and N(f) is the normalized noise power spectral density at the entrance of the first equalization compensation, which is equal to white noise passing through a bandwidth equal to a certain given value (for example , can be the result of a 4th order Bessel-Thomson response filter at 18.75GHz). _Heq (f) is the normalized frequency response of the first equalization compensation, and at the same time, ∫ _f N(f)df= _Heq (f=0)=1.

It should be noted that when the optical receiver uses the equalization architecture provided by this application to perform equalization compensation on the first test sequence, it can optimize the tap coefficient corresponding to the first equalization compensation to the best, that is, the tap coefficient corresponding to the first equalization compensation The sum is 1, so that the signal-to-noise ratio of the test sequence after equalization compensation is the best, the bit error rate is the lowest, and the quality of the optical signal is the best, thereby simulating the equalization receiving process of the optical receiver in the actual transmission scene. In this way, the purpose of compensating for ISI can be achieved, thereby ensuring the correctness of the analysis of the maximum tolerable additive noise of the optical transmitter.

Since the above-mentioned histogram distribution function is used to characterize the probability distribution of the sampling point distortion degree in the sampling window, the above-mentioned Q(x) is used to characterize the optical transmitter can support when the first sampling window and the second sampling window reach the target bit error rate Probability distribution for maximum additive noise. Therefore, the result obtained by multiplying and integrating the two is divided by the integral of the histogram function itself, which can be normalized to represent the probability that the optical signal will be wrongly judged by the optical receiver (that is, the bit error rate) when the noise is σ _L . For example, the first term on the left side of the equation in formula (1) is used to calculate the probability of being misjudged as 0 when the optical signal is 1, and the second term on the left side of the equation is used to calculate the probability of being misjudged as 1 when the optical signal is 0. probability. Take one-half of each of the two items and add them together, which is the bit error rate corresponding to the test eye diagram under the σ _L value.

In addition, in the embodiment of the present application, the above-mentioned target bit error rate is a threshold of forward error correction (forward error correction, FEC). That is, the σ _L value corresponding to the target bit error rate BER _target in formula (1) is the standard deviation of the maximum additive noise that the optical transmitter can support when the first sampling window and the second sampling window reach the target bit error rate BER _target . In other words, when the value of σ _L is such that the bit error rate obtained by adding the two terms on the left side of the equation in formula (1) is greater than the target bit error rate BER _target , the optical receiver cannot correctly receive the optical transmission through FEC The optical signal emitted by the machine.

Similarly, for the upper and lower histogram distributions on the right side of the eye diagram, the second relationship satisfied by the second standard deviation σ _R can be obtained, as shown in formula (3).

Wherein, f _u (y) and f _l (y) are the histogram distributions of the third sampling window and the fourth sampling window respectively.

It should be noted that the above BER _target may be preset in advance. In the embodiment of the present application, "preset" may refer to being configured in advance, for example, it may be stipulated in a protocol, which is not limited in this application.

It should be noted that although the above σ _L satisfies the formula (1), the value of σ _L cannot be obtained through the method of analytical formula (1). Therefore, the optical transmitter in the first sampling window can be and the standard deviation σ _L of the maximum additive noise that can be supported when the second sampling window reaches the target bit error rate BER _target is estimated.

FIG. 8 shows a schematic flow chart of determining the first standard deviation σ _L by means of numerical simulation.

S801, giving an initial value of the first standard deviation.

S802. Put the initial value into formula (1) to calculate BER.

S803. Compare the BER with the size of the BER _target .

Specifically, when the value of the BER calculated in S802 is greater than the BER _target , execute S804. When the value of the BER calculated in S802 is smaller than the BER _target , execute S805. When the value of the BER calculated in S802 is equal to the BER _target , execute S806.

S804. Decrease the first standard deviation, and return to execute 802.

S805, increase the first standard deviation, and return to execute 802.

S806. Determine the value of the first standard deviation corresponding to the BER as the first standard deviation.

It should be understood that the process of estimating the standard deviation σ _R of the maximum additive noise that the optical transmitter can support when the third sampling window and the fourth sampling window reach the target bit error rate BER _target is similar to the process shown in Figure 8 Similarly, for simplicity of description, details are not repeated here.

S703. Calculate the third standard deviation and the fourth standard deviation.

Specifically, σ _L also satisfies formula (4):

Among them, M(y) satisfies the following formula (5):

In formula (4),

σ ₀ and σ ₁ are the noise of 0 level and 1 level respectively, since the sampling oscilloscope generally adopts a high-bandwidth PIN optical receiver for photoelectric conversion, its noise has nothing to do with different levels of optical power, and the avalanche photodiode (avalanche photodiode , APD) type optical receiver noise is related to different levels of optical power, therefore, for an actual optical link using an APD receiver, the influence of the power correlation of the noise needs to be considered, and m needs to be set to 1.5.

Therefore, the third standard deviation σ _0,L can be calculated according to the above formula (4) and formula (5). It should be understood that the fourth standard deviation σ 0, _R can also be calculated according to the above ( ₄ ) for σ R.

S704. Based on the third standard deviation and the fourth standard deviation, calculate the standard deviation of the maximum additive noise that the optical transmitter under test can support when reaching the target bit error rate.

Specifically, for the optical transmitter to be tested, the loadable noise is given by the following formula (6):

In the formula, N=min(σ _{0, L} , σ _{0, R} ), and S is the noise floor of the oscilloscope.

S705. Calculate the standard deviation of the maximum additive noise that the ideal transmitter can support when reaching the target bit error rate.

Specifically, the noise σ _{0 that can be loaded by the ideal transmitter, ideal} is given by the following equation (7),

Wherein, OMA=y ₁ −y ₀ .

It should be noted that the loadable noise σ ₀ of the ideal transmitter still has no analytical solution, and it can be obtained by numerical calculation methods. This process is the same as the above-mentioned process for obtaining the loadable noise of the transmitter under test. Here No longer.

S706. According to the absolute value of the tap coefficient corresponding to the second equalization compensation, calculate the sensitivity cost corresponding to the equalization compensation that needs to be corrected.

Specifically, the sensitivity cost corresponding to equalization compensation can be determined by the following formula (8):

K _eq ＝k|10log ₁₀ (1-C)| (8)

Wherein, k is an empirical parameter, the value range of k is (0,1], and C is the absolute value of the tap coefficient corresponding to the second equalization compensation.

It should be noted that the equalization compensation used in the test method of this application is the auxiliary equalization using the preset test sequence of the optical transmitter (that is, the above-mentioned second test sequence), and the preset test sequence is not known when the receiving end equalization compensation is performed in the actual communication service. In the test sequence set, if the equalization compensation includes a judgment step, there will be a possibility of misjudgment near the sensitivity point, which will lead to a corresponding sensitivity penalty. Therefore, when calculating the first parameter, a correction factor related to the second equalization compensation needs to be considered.

S707. Calculate the value of the first parameter.

Specifically, based on the loadable noise of the above-mentioned transmitter to be tested, the loadable noise of the ideal transmitter, and the sensitivity cost corresponding to the equalization compensation, the value of the first parameter can be calculated by the following formula (9):

It should be noted that the first parameter calculated based on the above formula (9) is a specific calculation formula given when the number of taps of the second equalization compensation is 1, and when the second equalization compensation includes a plurality of taps, the above equalization compensation The corresponding sensitivity penalty is still related to the multiple tap coefficients of the second equalization compensation.

In addition, in the embodiment of the present application, the physical meaning of the first parameter T may still be the degree of closure of the transmitter and dispersion eye diagram of the optical transmitter to be tested.

To sum up, the consistency test method provided by this application not only takes into account the noise introduced in the equalization compensation process, but also takes into account the sensitivity cost caused by misjudgment, so that the accuracy of the performance evaluation of the transmitter can be improved.

Above, the method for implementing the conformance test provided by the present application is described in detail with reference to FIG. 4 to FIG. 9 . Below, the conformance test device provided in the embodiment of the present application is described in detail with reference to FIG. 10 and FIG. 11 .

FIG. 10 is a schematic structural diagram of a possible consistency testing device provided by the embodiment of the present application. As shown in FIG. 10 , the conformance testing device 1000 includes a transceiver module 1010 and a processing module 1020 .

Conformance testing device 1000 is used to realize the function or operation module of the optical receiver in the method embodiments shown in Fig. 4, Fig. 6, Fig. 7 and Fig. 8 above. or any combination thereof.

When the conformance test device 1000 is used to realize the function of the optical receiver in the method embodiment shown in FIG. 4 , the transceiver module 1010 is used to receive the optical signal emitted by the optical transmitter to be tested, and the processing module 1020 is used to obtain the test eye diagram . Wherein, the test eye diagram is obtained after performing equalization compensation based on the first test sequence in the optical signal emitted by the optical transmitter to be tested. The equalization compensation includes the first equalization compensation and the second equalization compensation, for example, as shown in FIG. 9 The framework is also used to calculate the value of the first parameter according to the absolute value of the test eye diagram, the noise enhancement coefficient corresponding to the first equalization compensation and the tap coefficient corresponding to the second equalization compensation, and the first parameter is used to determine the Transmitter and dispersion eye closure degree of optical transmitter.

When the conformance testing device 1000 is used to realize the function of the optical receiver in the method embodiment shown in FIG. 6, the processing module 1020 is used to obtain the first test sequence in the optical signal, obtain the third test sequence, and use the The test sequence performs equalization compensation on the first test sequence, generates a fourth test sequence, and uses the fourth test sequence to synthesize a test eye diagram. Wherein, the first test sequence is generated by the optical transmitter to be tested using the second test sequence, the second test sequence is the preset test sequence of the optical transmitter to be tested, and the third test sequence is the combination of the second test sequence and the first test sequence bit Generated after alignment.

When the conformance testing device 1000 is used to realize the function of the optical receiver in the method embodiment shown in FIG. 7 , the processing module 1020 is used to realize S701-S707 in FIG. 7 .

When the conformance testing device 1000 is used to realize the function of the optical receiver in the method embodiment shown in FIG. 8 , the processing module 1020 is used to realize S801-S806 in FIG. 8 .

More detailed descriptions about the above-mentioned transceiver module 1010 and processing module 1020 can be directly obtained by referring to the relevant descriptions in the method embodiments shown in FIG. 4 or FIG. 6 or FIG. 7 or FIG. 8 , and will not be repeated here.

FIG. 11 is a schematic structural diagram of another possible consistency testing device provided by the embodiment of the present application. As shown in FIG. 11 , the conformance testing device 1100 includes a transceiver module 1110 , a processing module 1120 , and a display module 1130 .

For the functions of the transceiver module 1110 and the processing module 1120 in FIG. 11 , reference may be made to the related description in FIG. 10 above, and details will not be repeated here.

The display module 1130 is configured to display the value of the first parameter. When the value of the first parameter is less than or equal to the preset threshold, it is determined that the conformance test of the optical transmitter under test is passed.

For the explanations and beneficial effects of relevant content in any of the conformance testing devices provided above, reference may be made to the corresponding method embodiments provided above, and details are not repeated here.

According to the method provided by the embodiment of the present application, the present application also provides a computer-readable medium, the computer-readable medium stores program codes, and when the program codes are run on the computer, the computer is made to perform the operations shown in Fig. 4, Fig. 6, The method of the embodiment shown in Fig. 7 and Fig. 8 . For example, when the computer program is executed by a computer, the computer can implement the methods performed by the optical receiver in the above method embodiments.

The embodiment of the present application also provides a computer program product including instructions, and when the instructions are executed by a computer, the computer implements the method performed by the optical receiver in the above method embodiments.

In the above embodiments, all or part of them may be implemented by software, hardware, firmware or any combination thereof. When implemented using software, it may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on the computer, the processes or functions according to the embodiments of the present application will be generated in whole or in part. The computer can be a general purpose computer, a special purpose computer, a computer network, or other programmable devices. The computer instructions may be stored in or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be transmitted from a website, computer, server or data center Transmission to another website site, computer, server or data center by wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.). The computer-readable storage medium may be any available medium that can be accessed by a computer, or a data storage device such as a server or a data center integrated with one or more available media. The available medium may be a magnetic medium (for example, a floppy disk, a hard disk, a magnetic tape), an optical medium (for example, a high-density digital video disc (digital video disc, DVD)), or a semiconductor medium (for example, a solid state disk (solid state disc, SSD)) etc.

The terms "component", "module", "system" and the like are used in this specification to refer to a computer-related entity, hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be components. One or more components can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. A component may, for example, be based on a signal having one or more packets of data (e.g., data from two components interacting with another component between a local system, a distributed system, and/or a network, such as the Internet via a signal interacting with other systems). Communicate through local and/or remote processes.

Those skilled in the art can appreciate that the units and algorithm steps of the examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed by hardware or software depends on the specific application and design constraints of the technical solution. Skilled artisans may use different methods to implement the described functions for each specific application, but such implementation should not be regarded as exceeding the scope of the present application.

Claims (18)

1. A method for consistency testing, characterized in that it comprises:

   Obtain a test eye diagram, the test eye diagram is obtained after equalization compensation based on the first test sequence in the optical signal emitted by the optical transmitter to be tested, and the equalization compensation includes a first equalization compensation and a second equalization compensation;

   According to the test eye diagram, the noise enhancement coefficient corresponding to the first equalization compensation and the absolute value of the tap coefficient corresponding to the second equalization compensation, calculate the value of the first parameter, and the first parameter is used to determine the Describe the transmitter and dispersion eye closure degree of the optical transmitter to be tested.
2. The method according to claim 1, wherein said obtaining the test eye diagram comprises:

   Obtain a first test sequence in the optical signal, the first test sequence is generated by the optical transmitter under test using a second test sequence, and the second test sequence is preset by the optical transmitter under test test sequence;

   Obtaining a third test sequence, where the third test sequence is generated after bit-aligning the second test sequence with the first test sequence;

   performing the equalization compensation on the first test sequence by using the third test sequence to generate a fourth test sequence;

   The test eye diagram is synthesized using the fourth test sequence.
3. The method according to claim 2, wherein the first test sequence is generated using a second test sequence for the optical transmitter to be tested, comprising:

   The first test sequence is generated by modulating the second test sequence by the optical transmitter under test using a first modulation format.
4. The method according to claim 3, characterized in that, according to the absolute value of the test eye diagram, the noise enhancement coefficient corresponding to the first equalization compensation, and the tap coefficient corresponding to the second equalization compensation, the second is calculated The value of a parameter, including:

   The first parameter according to

   

   Sure,

   Among them, σ _{0, ideal} is the standard deviation of the maximum additive noise that the ideal transmitter can support when the target bit error rate is reached, and σ _{estimated DUT} is the maximum that the optical transmitter under test can support when the target bit error rate is reached. The standard deviation of additive noise, K _ea is used to correct the sensitivity penalty corresponding to the equalization compensation, the K _ea is calculated according to the absolute value of the tap coefficient of the second equalization compensation, and the first modulation format is non-return-to-zero Code two-level pulse amplitude modulation or four-level pulse amplitude modulation.
5. The method according to claim 4, wherein the K _ea is calculated according to the absolute value of the tap coefficient of the second equalization compensation, comprising:

   The K _{ea is} calculated according to K _ea =k|10log ₁₀ (1-C)|,

   Wherein, k is an empirical parameter, the value range of k is (0,1], and C is the absolute value of the tap coefficient corresponding to the second equalization compensation.
6. A method according to any one of claims 2 to 5, wherein

   The first test sequence is an input of the first equalization compensation, and the third test sequence is an input of the second equalization compensation.
7. The method according to any one of claims 1 to 6, further comprising:

   When the value of the first parameter is less than or equal to the preset threshold, it is determined that the conformance test of the optical transmitter under test is passed.
8. A device for conformance testing, characterized in that it comprises:

   The transceiver module is used to receive the optical signal emitted by the optical transmitter to be tested;

   A processing module, configured to obtain a test eye diagram, the test eye diagram is obtained after performing equalization compensation based on the first test sequence in the optical signal emitted by the optical transmitter to be tested, and the equalization compensation includes the first equalization compensation and the second The second equalization compensation is also used to calculate the value of the first parameter according to the test eye diagram, the noise enhancement coefficient corresponding to the first equalization compensation and the absolute value of the tap coefficient corresponding to the second equalization compensation, the said The first parameter is used to determine the transmitter and dispersion eye closure degree of the optical transmitter to be tested.
9. The device according to claim 8, wherein the processing module is specifically used for:

   acquiring a first test sequence in the optical signal, acquiring a third test sequence, and using the third test sequence to perform the equalization compensation on the first test sequence, generating a fourth test sequence, and using the first test sequence Four test sequences synthesize the test eye diagram, wherein the first test sequence is generated by the optical transmitter under test using a second test sequence, and the second test sequence is preset for the optical transmitter under test A test sequence, the third test sequence is generated after bit alignment of the second test sequence and the first test sequence.
10. The device according to claim 9, characterized in that,

    The first test sequence is generated by modulating the second test sequence by the optical transmitter under test using a first modulation format.
11. The device according to claim 10, characterized in that,

    The first parameter according to

    

    Sure,

    Among them, σ _{0, ideal} is the standard deviation of the maximum additive noise that the ideal transmitter can support when the target bit error rate is reached, and σ _{estimated DUT} is the maximum that the optical transmitter under test can support when the target bit error rate is reached. The standard deviation of additive noise, K _ea is used to correct the sensitivity penalty corresponding to the equalization compensation, the K _ea is calculated according to the absolute value of the tap coefficient of the second equalization compensation, and the first modulation format is non-return-to-zero Code two-level pulse amplitude modulation or four-level pulse amplitude modulation.
12. The device according to claim 11, characterized in that,

    The K _{ea is} calculated according to K _ea =k|10log ₁₀ (1-C)|,

    Wherein, k is an empirical parameter, the value range of k is (0,1], and C is the absolute value of the tap coefficient corresponding to the second equalization compensation.
13. Apparatus according to any one of claims 9 to 12, characterized in that

    The first test sequence is an input of the first equalization compensation, and the third test sequence is an input of the second equalization compensation.
14. The device according to any one of claims 8 to 13, wherein the device further comprises:

    The display module is configured to display the value of the first parameter, and when the value of the first parameter is less than or equal to a preset threshold, it is determined that the conformance test of the optical transmitter under test is passed.
15. A testing system, characterized in that it comprises:

    An optical transmitter, used for transmitting a test optical signal;

    An optical receiver, configured to receive the test optical signal and use the test optical signal to perform a test, the optical receiver comprising the testing device according to any one of claims 8 to 14.
16. A chip, characterized in that the chip is connected to a memory for reading and executing program codes stored in the memory, so as to implement the method as claimed in any one of claims 1 to 7.
17. A computer-readable storage medium, characterized in that the computer-readable storage medium is used to store a computer program, and when the computer program runs on a computer, the computer executes any one of claims 1 to 7. method described in the item.
18. A computer program product, characterized in that the computer program product comprises: computer program code, when the computer program code is executed, the method according to any one of claims 1 to 7 is implemented.

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