TECHNICAL FIELD

The present invention relates to an error rate measuring apparatus that transmits a known pattern (pulse amplitude modulation 4 (PAM4) signal) as a test signal to a device under test in a state in which the device under test has transited to a state of a signal pattern return and measures a bit error rate of input data returned and received from the device under test in compliance with the transmission of the test signal, and in particular, measures whether or not a forward error correction (FEC) operation of the device under test is possible, and an error counting method.

BACKGROUND ART

For example, as disclosed in Patent Document 1 described below, an error rate measuring apparatus is hitherto known as an apparatus that transmits a test signal of a known pattern including fixed data to a device under test and compares a signal under test returned and received from the device under test in compliance with the transmission of the test signal with a reference signal to be a reference in units of bits to measure a bit error rate (BER)

Incidentally, in a case where a PAM is particularly used as the test signal, while a large amount of transmission can be realized compared to a non return to zero (NRZ) signal, an Eye opening is small, and thus, a signal to noise ratio (SNR) is damaged compared to the NRZ. For this reason, as the number of symbols increases, the influence of noise also becomes large, and it is extremely difficult to make errors zero. Therefore, it is desirable to count FEC Symbol Errors that occur in a region according to a communication standard according to the device under test to be measured and to measure whether or not error correction based on forward error correction (FEC) is possible.

RELATED ART DOCUMENT

[Patent Document]

[Patent Document 1] JP-A-2007-274474

DISCLOSURE OF THE INVENTION

Problem that the Invention is to Solve

However, the error rate measuring apparatus of the related art counts error for each physical Eye from captured symbol string data, and has no function of counting errors with a delimiter of data designated by the user based on the communication standard of the device under test in measuring the propriety of the error correction based on the FEC described above. Thus, there is a problem in that a lot of time is needed to investigate a cause of defect of the device under test, and it is not possible to perform efficient debugging. Furthermore, in the error rate measuring apparatus of the related art, in measuring whether or not the FEC operation of the device under test is possible, it is not possible to detect most significant bit errors and least significant bit errors of each one Codeword length in most significant bit string data and least significant bit string data of the symbol string data, respectively, and to display count values.

Accordingly, the invention has been accomplished in view of the above-described problems, and an object of the invention is to provide an error rate measuring apparatus and an error counting method capable of counting errors in a region set by a user based on a communication standard of a device under test.

Means for Solving the Problem

To achieve the above-described object, there is provided an error rate measuring apparatus1according to a first aspect of the invention that inputs a pulse amplitude modulation 4 (PAM4) signal of a known pattern as a test signal to a device under test W, receives a signal from the device under test W compliant with the input of the test signal, and measures whether or not a forward error correction (FEC) operation of the device under test is possible based on a comparison result of the signal received from the device under test and the test signal, the error rate measuring apparatus including:

an operation unit4that sets a setting parameter to the signal received from the device under test; and

a storage unit5that stores symbol string data obtained by converting the signal received from the device under test.

The operation unit4sets one Codeword length and one FEC Symbol length of the FEC according to a communication standard of the device under test.

The error rate measuring apparatus further includes data division means3dafor dividing the symbol string data stored in the storage unit into most significant bit (MSB) string data and least significant bit (LSB) string data;

a data comparison unit3dthat compares each of the most significant bit string data and the least significant bit string data divided by the data division means with error data to detect each of most significant bit errors and least significant bit errors of each one Codeword length set by the operation unit, and detects FEC Symbol Errors of each of the most significant bit string data and the least significant bit string data at an interval of the one FEC Symbol length set by the operation unit; and

error counting means7afor counting the number of most significant bit errors and the number of least significant bit errors, and the number of FEC Symbol Errors detected by the data comparison unit.

According to a second aspect of the invention, the error rate measuring apparatus of the first aspect further includes

a display unit6that displays a count value of at least one of the number of most significant bit errors and the number of least significant bit errors and the number of FEC Symbol Errors based on a result of the counting.

According to a third aspect of the invention, there is provided an error counting method for an error rate measuring apparatus1that inputs a pulse amplitude modulation 4 (PAM4) signal of a known pattern as a test signal to a device under test W, receives a signal from the device under test compliant with the input of the test signal, measures whether or not a forward error correction (FEC) operation of the device under test is possible based on a comparison result of the signal received from the device under test and the test signal, sets a setting parameter to the signal received from the device under test, and stores symbol string data obtained by converting the signal received from the device under test. The error counting method for an error rate measuring apparatus includes

a step of setting one Codeword length and one FEC Symbol length of the FEC according to a communication standard of the device under test,

a step of dividing the stored symbol string data into most significant bit (MSB) string data and least significant bit (LSB) string data,

a step of comparing each of the divided most significant bit string data and least significant bit string data with error data to detect each of most significant bit errors and least significant bit errors of each set one Codeword length, and detecting FEC Symbol Errors of each of the most significant bit string data and the least significant bit string data at an interval of the set one FEC Symbol length, and

a step of counting the number of detected most significant bit errors and the number of detected least significant bit errors, and the number of detected FEC Symbol Errors.

According to a fourth aspect of the invention, the error counting method for an error rate measuring apparatus according to the third aspect further includes a step of displaying a count value of at least one of the number of most significant bit errors and the number of least significant bit errors, and the number of FEC Symbol Errors based on a result of the counting.

Advantage of the Invention

According to the invention, it is possible to detect and count FEC Symbol Errors in captured data with a delimiter set by the user based on a communication standard of a device under test. In addition, it is possible to detect and count most significant bit errors and least significant bit errors of each one Codeword length in most significant bit string data and least significant bit string data of symbol string data, respectively. Furthermore, in a case where the count values of the most significant bit errors, the least significant bit errors, and the FEC Symbol Errors are displayed, the number of errors can be confirmed with a numerical value, and deviation of errors can be recognized.

