Error rate measuring apparatus and uncorrectable codeword search method

An error rate measuring apparatus 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 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 received signal and the test signal, the error rate measuring apparatus comprising:

• an operation unit that sets a codeword length of the FEC, an FEC symbol length, and an FEC symbol error threshold in accordance with a communication standard of the device under test;
• error counting means for counting an FEC symbol error detected at one FEC symbol interval between most significant bit string data and least significant bit string data of symbol string data obtained by receiving and converting the signal from the device under test based on a comparison result of error data and each of the most significant bit string data and the least significant bit string data of the symbol string data, and for counting the FEC symbol error as an uncorrectable codeword that is not capable of being forward error corrected when the number of the FEC symbol errors in one codeword exceeds the FEC symbol error threshold;
• and
• a display unit,
• wherein the display unit performs display by setting one zone of a display area of identification display of the display unit as one FEC symbol length, matching a length of a horizontal axis of the display area with one codeword length, and performing line feed in codeword length units so that a head of one codeword of the identification display according to presence or absence of the FEC symbol error in FEC symbol length units based on a counting result of the error counting means is located at a left end of the display area and a tail of one codeword of the identification display is located at a right end of the display area, and
• the error rate measuring apparatus includes search means for searching for a codeword of the identification display, which is an uncorrectable codeword at any of one ahead, one previous, a first, and a last of the codeword starting from a cursor on the identification display, and display control means for performing display control of the cursor at a position of a head error of the codeword, which is the uncorrectable codeword searched for by the search means.

An uncorrectable codeword search method for an error rate measuring apparatus that inputs a non return to zero (NRZ) signal of a known pattern as a test signal to a device under test (W), receives a signal from the device under test 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 received signal and the test signal, the uncorrectable codeword search method comprising:

• a step of setting, by an operation unit, a codeword length of the FEC, an FEC symbol length, and an FEC symbol error threshold in accordance with a communication standard of the device under test;
• a step of counting, by error counting means, an FEC symbol error detected at one FEC symbol interval based on a comparison result of error data and each bit of bit string data obtained by receiving and converting the signal from the device under test;
• a step of counting, by the error counting means, the FEC symbol error as an uncorrectable codeword that is not capable of being forward error corrected when the number of the FEC symbol errors in one codeword exceeds the FEC symbol error threshold;
• a step of performing, on a display unit, display by setting one zone of a display area of identification display of the display unit as one FEC symbol length, matching a length of a horizontal axis of the display area with one codeword length, and performing line feed in codeword length units so that a head of one codeword of the identification display according to presence or absence of the FEC symbol error in FEC symbol length units based on a counting result of the error counting means is located at a left end of the display area and a tail of one codeword of the identification display is located at a right end of the display area;
• a step of searching, by search means, a codeword of the identification display, which is an uncorrectable codeword at any of one ahead, one previous, a first, and a last of the codeword starting from a cursor on the identification display;
• and
• a step of performing, by display control means, display control of the cursor at a position of a head error of the codeword, which is the uncorrectable codeword searched for by the search means.

An uncorrectable codeword search method for an error rate measuring apparatus 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 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 received signal and the test signal, the uncorrectable codeword search method comprising:

• a step of setting, by an operation unit, a codeword length of the FEC, an FEC symbol length, and an FEC symbol error threshold in accordance with a communication standard of the device under test;
• a step of counting, by error counting means, an FEC symbol error detected at one FEC symbol interval between most significant bit string data and least significant bit string data of symbol string data obtained by receiving and converting the signal from the device under test based on a comparison result of error data and each of the most significant bit string data and the least significant bit string data of the symbol string data;
• a step of counting, by the error counting means, the FEC symbol error as an uncorrectable codeword that is not capable of being forward error corrected when the number of the FEC symbol errors in one codeword exceeds the FEC symbol error threshold;
• a step of performing, on a display unit, display by setting one zone of a display area of identification display of the display unit as one FEC symbol length, matching a length of a horizontal axis of the display area with one codeword length, and performing line feed in codeword length units so that a head of one codeword of the identification display according to presence or absence of the FEC symbol error in FEC symbol length units based on a counting result of the error counting means is located at a left end of the display area and a tail of one codeword of the identification display is located at a right end of the display area;
• a step of searching, by search means, a codeword of the identification display, which is an uncorrectable codeword at any of one ahead, one previous, a first, and a last of the codeword starting from a cursor on the identification display;
• and
• a step of performing, by display control means, display control of the cursor at a position of a head error of the codeword, which is the uncorrectable codeword searched for by the search means.