Convert miliWatts to dBM

[wojciech.wojcik]

Hello,

I want to grab RX/TX power of optic transceiver off Arista/Cisco. The problem is that Arista reports that in miliWatts and I would like to see it in dBm. Obviously dBm is a logarithmic function of power but I have no idea how to make a conversion.

Many thanks in advance

Wojtek

[jvgenderen]

mw 2 dBm

http://www.rapidtables.com/convert/power/mW_to_dBm.htm#table

possible done with external script ..

grt Joost

[davidalain]

Old but important question!!

I also need to monitoring signal of TX/RX optical transceivers, but in my case was from EPON ONU devices.

I did not found any solution about this, so I have needed to create by my own.

Using following link, I could to implement a JavaScript function to make conversion.

mw 2 dBm

http://www.rapidtables.com/convert/power/mW_to_dBm.htm#table

grt Joost

So, I wrote this JavaScript function in Zabbix 4.2.8 as a pre-processing of the item of type SNMPv2 Agent:

function(value)
return 10*Math.log10(value*0.0001);
}

Running snmpwalk against my EPON OLT device I have got this result:

iso.3.6.1.4.1.34592.1.3.4.1.1.36.1.1.2 = INTEGER: 1958
iso.3.6.1.4.1.34592.1.3.4.1.1.36.1.1.3 = INTEGER: 110
iso.3.6.1.4.1.34592.1.3.4.1.1.36.1.1.4 = INTEGER: 60
iso.3.6.1.4.1.34592.1.3.4.1.1.36.1.1.7 = INTEGER: 907

Note: these values above are with precision of 0.1 micro-watt per unit, because of this I have needed to multiply the read value by 0.0001 to get values in mW.

Those values are respectively (in dBm):

-7.08187312532881
-19.58607314841775
-22.21848749616356
-10.423927129399047

[geysonpls]

Old but important question!!

I also need to monitoring signal of TX/RX optical transceivers, but in my case was from EPON ONU devices.

I did not found any solution about this, so I have needed to create by my own.

Using following link, I could to implement a JavaScript function to make conversion.



So, I wrote this JavaScript function in Zabbix 4.2.8 as a pre-processing of the item of type SNMPv2 Agent:

function(value)
return 10*Math.log10(value*0.0001);
}

Running snmpwalk against my EPON OLT device I have got this result:

iso.3.6.1.4.1.34592.1.3.4.1.1.36.1.1.2 = INTEGER: 1958
iso.3.6.1.4.1.34592.1.3.4.1.1.36.1.1.3 = INTEGER: 110
iso.3.6.1.4.1.34592.1.3.4.1.1.36.1.1.4 = INTEGER: 60
iso.3.6.1.4.1.34592.1.3.4.1.1.36.1.1.7 = INTEGER: 907

Note: these values above are with precision of 0.1 micro-watt per unit, because of this I have needed to multiply the read value by 0.0001 to get values in mW.

Those values are respectively (in dBm):

-7.08187312532881
-19.58607314841775
-22.21848749616356
-10.423927129399047

When you added the item to Grafana it does not show the result in dBm -7.08187312532881, show only a number of 3 decimal places