Optical signal detection method and system

Abstract

The invention provides an optical signal detection method and system. The method comprises the following steps: distinguishing a signal from a non-signal according to kurtosis; the signals comprise a PAM4 signal and an NRZ signal; the PAM4 signal is realized through a multi-stage amplitude modulation technology and represents four different digital states, and each digital state represents two bits of data; the NRZ signal uses a fixed level to represent a bit 0 and a bit 1, and only one bit is transmitted in unit time; the no-signal is an AC OFF signal, which means that no useful information is carried on the optical signal, and the optical signal is divided into a large optical no-signal and a small optical no-signal according to the optical power. According to the method, the implementation complexity is low, the LOS reporting accuracy can be improved, and particularly, the error detection probability can be effectively reduced in the detection of no signal of large light and signal of small light.

Description

Technical Field

[0001] The present invention relates to the technical field of optical signal detection, and in particular to an optical signal detection method and system. Background Art

[0002] Our DSP chips are used in optical modules, and LOS detection of optical modules is a basic function.

[0003] The requirement of DC LOS means that the input optical power cannot be lower than the set value within a given time, otherwise it will be judged as signal loss.

[0004] The AC LOS requirement refers to the useful signal (differential input signal that carries information). Even if there is optical power, it does not mean that the useful signal is carried. The algorithm needs to determine whether the signal carries the useful signal when the optical power meets the requirement, otherwise the signal is lost.

[0005] The IPEC SFP56 standard stipulates that the LOS detection time must be within 100μs. However, current detection technology cannot fully achieve this, and there is a problem of false detection for large light without signal and small light with signal.

[0006] Patent document CN114938248A discloses a construction and demodulation method of an underwater wireless optical communication demodulation model: the construction method includes the following steps: first, obtaining a data set; using an experimental device to generate a data set of several common modulation signals, and dividing them into a training set and a test set; then, extracting the relevant features of the communication signal in the data set through an algorithm, including time domain features, frequency domain features, and instantaneous features; then, building a machine learning demodulator algorithm model and training it, and selecting the Boosting algorithm or the Bagging algorithm in machine learning as the demodulator algorithm model; finally, testing the trained demodulator algorithm model. However, this patent cannot completely solve the current technical problems, nor can it meet the needs of the present invention. Summary of the invention

[0007] In view of the defects in the prior art, an object of the present invention is to provide an optical signal detection method and system.

[0008] The optical signal detection method provided by the present invention includes:

[0009] Distinguish between signal and no signal based on kurtosis;

[0010] The signal includes a PAM4 signal and an NRZ signal; the PAM4 signal is implemented by a multi-level amplitude modulation technology, indicating four different digital states, each digital state representing two bits of data; the NRZ signal uses a fixed level to indicate bit 0 and bit 1, and only transmits one bit per unit time;

[0011] The no signal is an AC OFF signal, which means that the optical signal carries no useful information, and is divided into a large optical no signal and a small optical no signal according to the optical power.

[0012] Preferably, an ASIC algorithm is used to accelerate the detection speed of the loss of signal LOS.

[0013] Preferably, the optical power of the large light without signal exceeds 0 dBm, and the optical power of the small light without signal is below -10 dBm.

[0014] Preferably, a hardware accelerator is used to calculate m1-m4, and the expression is:

[0015]

[0016] Among them, m1~m4 are the center distances of the first to fourth order samples respectively; x i is the i-th value; N is the number of samples;

[0017] Using m1 and m2 to calculate the variance, the expression is:

[0018]

[0019] The kurtosis is calculated using m1~m4, and the expression is:

[0020] Numerator of Kurtosis

[0021] Denominator of kurtosis: kurt_den = std 2 ;

[0022] Kurtosis:

[0023] The current LOS status determination value los_status is determined based on the mean of the variance and kurtosis;

[0024] If the variance mean value std_avg < the variance threshold value STD_THR, then los_status = 1, indicating no signal; otherwise, go to the next step;

[0025] If the kurtosis mean kurt_avg<kurtosis threshold KURT_THR, then los_status=0, indicating that there is a signal; otherwise los_status=1.

[0026] Preferably, if los_status is the same for a preset number of consecutive times and is different from the currently output LOS decision result los_assert, the output los_assert is changed to make los_assert=los_status, thereby improving the stability of the decision.

[0027] The optical signal detection system provided by the present invention comprises:

[0028] Distinguish between signal and no signal based on kurtosis;

[0029] The signal includes a PAM4 signal and an NRZ signal; the PAM4 signal is implemented by a multi-level amplitude modulation technology, indicating four different digital states, each digital state representing two bits of data; the NRZ signal uses a fixed level to indicate bit 0 and bit 1, and only transmits one bit per unit time;

[0030] The no signal is an AC OFF signal, which means that the optical signal carries no useful information, and is divided into a large optical no signal and a small optical no signal according to the optical power.

[0031] Preferably, an ASIC algorithm is used to accelerate the detection speed of the loss of signal LOS.

[0032] Preferably, the optical power of the large light without signal exceeds 0 dBm, and the optical power of the small light without signal is below -10 dBm.

[0033] Preferably, a hardware accelerator is used to calculate m1-m4, and the expression is:

[0034]

[0035] Among them, m1~m4 are the center distances of the first to fourth order samples respectively; x i is the i-th value; N is the number of samples;

[0036] Using m1 and m2 to calculate the variance, the expression is:

[0037]

[0038] The kurtosis is calculated using m1~m4, and the expression is:

[0039] Numerator of Kurtosis:

[0040] Denominator of kurtosis: kurt_den = std 2 ;

[0041] Kurtosis:

[0042] The current LOS status determination value los_status is determined based on the mean of the variance and kurtosis;

[0043] If the variance mean value std_avg < the variance threshold value STD_THR, then los_status = 1, indicating no signal; otherwise, go to the next step;

[0044] If the kurtosis mean kurt_avg<kurtosis threshold KURT_THR, then los_status=0, indicating that there is a signal; otherwise los_status=1.

[0045] Preferably, if los_status is the same for a preset number of consecutive times and is different from the currently output LOS decision result los_assert, the output los_assert is changed to make los_assert=los_status, thereby improving the stability of the decision.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention provides an optical signal detection method, which distinguishes between signal presence and signal absence according to kurtosis, has low implementation complexity and can improve the accuracy of LOS reporting, especially for the detection of large light without signal and small light with signal, which can effectively reduce the probability of false detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0049] Figure 1a to Figure 1d There is no signal and variance for large light, and there is signal and variance for small light;

[0050] Figure 2 To reduce the kurtosis value by 3, so that the kurtosis of the normal distribution is 0;

[0051] Figure 3a and Figure 3b is the kurtosis of PAM4 and NRZ signals;

[0052] Figure 4 This is a flow chart for judging whether there is a signal. DETAILED DESCRIPTION

[0053] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0054] Example 1

[0055] Generally speaking, the variance of large light without information is smaller than the variance of small light with signal. However, sometimes the AGC gain is relatively large, which may also cause the power of large light without signal to increase, such as Figure 1a to Figure 1dAs shown, the large light has no signal and the variance is 540; the small light has a signal (NRZ) and the variance is 131.

[0056] The present invention considers distinguishing whether there is a signal from the flatness (ie, kurtosis) of the signal statistical histogram.

[0057] Kurtosis, also known as the peak coefficient, is a characteristic number that characterizes the height of the peak of the probability density distribution curve at the mean value. Intuitively, kurtosis reflects the sharpness of the peak. Kurtosis is generally based on the normal distribution and can describe the steepness of the distribution shape. The kurtosis of the normal distribution is a constant of 3, and the kurtosis of the uniform distribution is a constant of 1.8. If the kurtosis is less than 3, the distribution is said to have insufficient kurtosis; if the kurtosis is greater than 3, the distribution is said to have excessive kurtosis.

[0058] In practical applications, the kurtosis value is usually reduced by 3 to make the kurtosis of the normal distribution 0, such as Figure 2 shown.

[0059] Comparing the kurtosis of AC_OFF, PAM4 and NRZ signals, the results are as follows Figure 3a and Figure 3b .

[0060] It can be seen that the kurtosis can distinguish between AC OFF signal and PAM4 signal, AC OFF signal and NRZ signal. In order to speed up the detection speed, LOS detection can be implemented in hardware.

[0061] In statistics, the following eigenvalues ​​are used to measure the probability distribution of a real random variable.

[0062] 1) First-order moment: The mean and first-order moment are the expected values ​​of random variables, indicating the average value or central position of the random variable.

[0063]

[0064] 2) Second moment: variance, the second moment is the expected value of the square of the deviation of the random variable from its expected value, which indicates the degree of discreteness of the random variable.

[0065]

[0066] 3) Third-order moment: skewness. The third-order moment is the expected value of the cube of the deviation of the random variable from its expected value, which indicates the degree of skewness of the distribution of the random variable.

[0067]

[0068] 4) Fourth-order moment: Kurtosis, the fourth-order moment is a characteristic number that characterizes the height of the peak of the probability density distribution curve at the mean value, reflecting the sharpness of the peak.

[0069] For a sample with n values, the sample kurtosis is:

[0070]

[0071] Among them, m4 is the fourth-order sample central moment, m2 is the second-order central moment, x i is the i-th value, and is the sample mean.

[0072] Such as Figure 4 , the detection process is as follows:

[0073] 1. Calculate m1 to m4 using a hardware accelerator;

[0074]

[0075] 2. Calculate the variance using m1 and m2;

[0076]

[0077] 3. Calculate the kurtosis using m1 to m4;

[0078] The numerator of the kurtosis:

[0079] The denominator of the kurtosis: kurt_den = std 2 ;

[0080] The kurtosis: Multiplying by 100 here is to convert the decimal to an integer, so that the kurtosis of the normal distribution is 300.

[0081] 4. Judge los_status according to the means of the variance and kurtosis;

[0082] 1) If std_avg < STD_THR, then los_status = 1 (no signal), otherwise go to the next step;

[0083] 2) If kurt_avg < KURT_THR, then los_status = 0 (signal present), otherwise los_status = 1 (no signal);

[0084] 5. If los_status is the same for T consecutive times and is different from the current los_assert, then change the output los_assert to make los_assert = los_status. This step is to improve the stability of the decision.

[0085] Embodiment 2

[0086] The present invention also provides an optical signal detection system, which can be implemented by executing the process steps of the optical signal detection method, that is, those skilled in the art can understand the optical signal detection method as a preferred implementation of the optical signal detection system.

[0087] The optical signal detection system provided by the present invention includes: distinguishing between signal and no signal according to kurtosis; the signal includes PAM4 signal and NRZ signal; the PAM4 signal is implemented by multi-level amplitude modulation technology, representing four different digital states, each digital state represents two bits of data; the NRZ signal uses a fixed level to represent bit 0 and bit 1, and only transmits one bit per unit time; the no signal is an AC OFF signal, which means that the optical signal does not carry useful information, and is divided into large light no signal and small light no signal according to the optical power.

[0088] Use ASIC algorithm to speed up the detection of signal loss LOS.

[0089] The optical power of the large light without a signal exceeds 0 dBm, and the optical power of the small light without a signal is below -10 dBm.

[0090] Using the hardware accelerator to calculate m1~m4, the expression is:

[0091]

[0092] Among them, m1~m4 are the center distances of the first to fourth order samples respectively; x i is the i-th value; N is the number of samples;

[0093] Using m1 and m2 to calculate the variance, the expression is:

[0094]

[0095] The kurtosis is calculated using m1~m4, and the expression is:

[0096] Numerator of Kurtosis:

[0097] Denominator of kurtosis: kurt_den = std 2 ;

[0098] Kurtosis:

[0099] The current LOS status determination value los_status is determined based on the mean of the variance and kurtosis;

[0100] If the variance mean value std_avg < the variance threshold value STD_THR, then los_status = 1, indicating no signal; otherwise, go to the next step;

[0101] If the kurtosis mean kurt_avg<kurtosis threshold KURT_THR, then los_status=0, indicating that there is a signal; otherwise los_status=1.

[0102] If los_status is the same for a preset number of consecutive times and is different from the currently output LOS decision result los_assert, the output los_assert is changed to make los_assert=los_status, thereby improving the stability of the decision.

[0103] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0104] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for detecting an optical signal, characterized in that: include: Distinguish between signal and no signal based on kurtosis; The signal includes a PAM4 signal and an NRZ signal; the PAM4 signal is implemented by a multi-level amplitude modulation technology, indicating four different digital states, each digital state representing two bits of data; the NRZ signal uses a fixed level to indicate bit 0 and bit 1, and only transmits one bit per unit time; The no signal is an AC OFF signal, which means that the optical signal carries no useful information, and is divided into a large optical no signal and a small optical no signal according to the optical power.

2. The optical signal detection method according to claim 1, characterized in that: Use ASIC algorithm to speed up the detection of signal loss LOS.

3. The optical signal detection method according to claim 1, characterized in that: The optical power of the large light without a signal exceeds 0 dBm, and the optical power of the small light without a signal is below -10 dBm.

4. The optical signal detection method according to claim 1, characterized in that: Using the hardware accelerator to calculate m1~m4, the expression is: Among them, m1~m4 are the center distances of the first to fourth order samples respectively; x i is the i-th value; N is the number of samples; Using m1 and m2 to calculate the variance, the expression is: The kurtosis is calculated using m1~m4, and the expression is: Numerator of Kurtosis: Denominator of kurtosis: kurt_den = std 2 ; Kurtosis: The current LOS status determination value los_status is determined based on the mean of the variance and kurtosis; If the variance mean value std_avg < the variance threshold value STD_THR, then los_status = 1, indicating no signal; otherwise, go to the next step; If the kurtosis mean kurt_avg<kurtosis threshold KURT_THR, then los_status=0, indicating that there is a signal; otherwise los_status=1.

5. The optical signal detection method according to claim 4, characterized in that: If los_status is the same for a preset number of consecutive times and is different from the currently output LOS decision result los_assert, the output los_assert is changed to make los_assert=los_status, thereby improving the stability of the decision.

6. An optical signal detection system, characterized in that: include: Distinguish between signal and no signal based on kurtosis; The signal includes a PAM4 signal and an NRZ signal; the PAM4 signal is implemented by a multi-level amplitude modulation technology, indicating four different digital states, each digital state representing two bits of data; the NRZ signal uses a fixed level to indicate bit 0 and bit 1, and only transmits one bit per unit time; The no signal is an AC OFF signal, which means that the optical signal carries no useful information, and is divided into a large optical no signal and a small optical no signal according to the optical power.

7. The optical signal detection system according to claim 6, characterized in that: Use ASIC algorithm to speed up the detection of signal loss LOS.

8. The optical signal detection system according to claim 6, characterized in that: The optical power of the large light without a signal exceeds 0 dBm, and the optical power of the small light without a signal is below -10 dBm.

9. The optical signal detection system according to claim 6, characterized in that: Using the hardware accelerator to calculate m1~m4, the expression is: Among them, m1~m4 are the center distances of the first to fourth order samples respectively; x i is the i-th value; N is the number of samples; Using m1 and m2 to calculate the variance, the expression is: The kurtosis is calculated using m1~m4, and the expression is: Numerator of Kurtosis: Denominator of kurtosis: kurt_den = std 2 ; Kurtosis: The current LOS status determination value los_status is determined based on the mean of the variance and kurtosis; If the variance mean value std_avg < the variance threshold value STD_THR, then los_status = 1, indicating no signal; otherwise, go to the next step; If the kurtosis mean kurt_avg<kurtosis threshold KURT_THR, then los_status=0, indicating that there is a signal; otherwise los_status=1.

10. The optical signal detection system according to claim 9, characterized in that: If los_status is the same for a preset number of consecutive times and is different from the currently output LOS decision result los_assert, the output los_assert is changed to make los_assert=los_status, thereby improving the stability of the decision.

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