I'm currently looking at 40Gbase-LR and am curious about the advertised power budget. Here are the specifications:
Transmit max 2.30dBm Transmit min -7.00dBm Receive max 2.30dBm Receive min -11.50dBm Power Budget 4.50dB
The attenuation test on the cable I want to use indicates a ~6dB drop, mostly due to insertion loss. The indicated power budget is not enough to manage that. This appears to be calculated based on Transmit min and Receive Min (-7 - -11.5=4.5), but I'm wondering if I have more flex here since the maximum transmit power is 2.3dBm (2.3 - -11.5 = 13.8).
What I don't get is why the power budget is listed as 4.5dB when the specs appear to indicate it can go to 11.8dB.