Data sheets of optical transceivers often specify the receiver maximum input power. In addition, non-volatile memory of transceivers often seem to hold this data:

root@MX240> show interfaces diagnostics optics xe-11/3/0 | match "laser rx"
    Laser rx power                            :  0.7614 mW / -1.18 dBm
    Laser rx power high alarm                 :  Off
    Laser rx power low alarm                  :  Off
    Laser rx power high warning               :  Off
    Laser rx power low warning                :  Off
    Laser rx power high alarm threshold       :  1.2589 mW / 1.00 dBm
    Laser rx power low alarm threshold        :  0.0050 mW / -23.01 dBm
    Laser rx power high warning threshold     :  1.1220 mW / 0.50 dBm
    Laser rx power low warning threshold      :  0.0063 mW / -22.01 dBm


I am aware that too strong Rx signal can saturate it for photodiode and as a result cause bit errors, but has anyone permanently damaged an optical transceiver(GBIC, SFP, XFP, SFP+) because of too strong Rx signal?

2 Answers 2


Your biggest risk comes from Single Mode ER (40 Km) and ZX (80 Km) optics, which can overdrive and even burn inputs without sufficient attenuation.

There is no risk of burning Multi Mode optics, as long as you're connecting MM to MM.

  • Have you ever permanently damaged ER or ZX optics that way?
    – Martin
    Jun 10, 2015 at 13:38
  • 7
    No because I don't intentionally destroy things like that. I also don't stick my fingers on live high voltage terminals Jun 10, 2015 at 13:50

For any receiver there is a threshold above which the system will stop receiving correctly and a further threshold above which the receiver will actually be damaged.

According to https://youtu.be/_KFpXuHqHQg?t=4612 10km optics will normally work fine even with a very short fiber. 40km optics will not work correctly but are unlikely to be damaged. 80km optics may suffer actual damage.

So basically it's a potential issue for people playing the long distance WDM or dark fiber game. It shouldn't be an issue for links within a site or links to other nearby sites.

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