Once I needed to monitor the optical signal level on the Cisco Nexus C3064PQ-10GX to prevent cable sagging, stretching and signal loss, because in this case the signal deteriorates gradually, usually I monitor the signal on the end equipment, but I came across an old BDCOM 3310B model in which there was no support DDM.
You can also see my articles:
BDCOM OLT DDM SNMP OID
Juniper SNMP OIDs DDM for optical signal transceivers
You can use the following SNMP OID to determine the port index:
For example from Linux:
snmpwalk -v2c -c ixnfo.com 192.168.5.5 220.127.116.11.18.104.22.168.22.214.171.124
For example, I displayed the following indexes and their description:
SNMPv2-SMI::mib-126.96.36.199.188.8.131.520052803 = STRING: "Ethernet1/31 Lane 1 Transceiver Voltage Sensor" SNMPv2-SMI::mib-184.108.40.206.220.127.116.110052804 = STRING: "Ethernet1/31 Lane 1 Transceiver Bias Current Sensor" SNMPv2-SMI::mib-18.104.22.168.22.214.171.1240052807 = STRING: "Ethernet1/31 Lane 1 Transceiver Temperature Sensor" SNMPv2-SMI::mib-126.96.36.199.188.8.131.520052813 = STRING: "Ethernet1/31 Lane 1 Transceiver Receive Power Sensor" SNMPv2-SMI::mib-184.108.40.206.220.127.116.110052814 = STRING: "Ethernet1/31 Lane 1 Transceiver Transmit Power Sensor"
Then you need to substitute the index into the following OID:
18.104.22.168.22.214.171.124.126.96.36.199.1.4 snmpwalk -v2c -c ixnfo.com 192.168.5.5 188.8.131.52.184.108.40.206.220.127.116.11.1.4.300052813
The result must be multiplied by 0.001 and the current level of the optical signal will be obtained.