10-29-2019 09:36 PM - edited 10-30-2019 12:24 AM
Hello
Hope everything is working fine with you.
Could you please do me a favor on below questions?
We shut down the local SFP, and monitor the received power on opposite SFP. The received power is always -40dBM when we using below modules. I think its the value when the port is shutdown.
GLC-LH-SMD
SFP-10G-LR
SFP-25G-SR-S
QSFP-100G-LR4-S
But when we try on GLC-SX-MMD, the received power is -25.2dBM.
Could you please tell me why there is such difference? -25.2 is specific to GLC-SX-MMD when it is down?
The value of Rx dBm when the SFP is shutdown,(-25dBM on GLC-SX-MMD, and -40dBM on other four)is the minimum dBM that the SFP can received? Or it’s just a fake value we use when the connection is down on each SFP.
Attach the log for your reference.
Thanks in advance.
Br/Neil
Solved! Go to Solution.
10-29-2019 09:59 PM
The longer reach and/or single mode optics will have a lower "noise floor". That's what we call the level below which no usable signal can be extracted. That's one reason why they cost more - more sensitive receivers that are able to work over a longer distance are a higher precision component.
The "entry level" GLC-SX-MMD won't distinguish any signal below approximately -25 dBm; so even a receive link with no light on it will register as having that level.
10-29-2019 09:59 PM
The longer reach and/or single mode optics will have a lower "noise floor". That's what we call the level below which no usable signal can be extracted. That's one reason why they cost more - more sensitive receivers that are able to work over a longer distance are a higher precision component.
The "entry level" GLC-SX-MMD won't distinguish any signal below approximately -25 dBm; so even a receive link with no light on it will register as having that level.
10-29-2019 10:25 PM
Thanks Marvin,
So can I think when GLC-SX-MMD is shutdown, the Rx dBm will shown as -25.2?
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