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I am very confused with understand how is possible to have a lot of losses in decibels.

Let´s suppose we have two arbitrary point A and B. Transmition trhought these points are about optical-fiber. We don´t care the wavelenght, distance and and other stuffs.

Let´s suppose we have total atenuation of 16 dB. According to formula of decibels:

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Let´s solve the formula and the relationship between Power Out and Power in would be :

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It means to the custumer, just only arrives 0.025 of the power sent from de source (ISP, and so on). That means If we want to the custumers arrive 1 watts, We need to sent at least 40 watts:

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My question is:

Really this happen ? Companies spent thousands of watts so that only a few watts reach customers ? (because atenuation ). Does It make sense ?

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It means to the custumer, just only arrives 0.025 of the power sent from de source (ISP, and so on). That means If we want to the custumers arrive 1 watts, We need to sent at least 40 watts

While that attenuation is technically accurate, power levels in fiber communications are several orders of magnitude lower.

E.g. 1000BASE-LX10 has a nominal launch power of -11 dBm ≈ .08 mW with a receiver sensitivity of -19 dBm, sufficient for 10 km reach. For more reach, the overall power budget needs to be increased.

With passive fiber distribution (PON), a 1:32 split causes additional attenuation of -15 dB, requiring a more generous power budget. E.g. 1000BASE-PX10 launches between -1 and +4 dBm (2.5 mW max), with the receiver detecting down to -24 dBm ≈ 4 µW.

So, we're not really burning "thousands of watts" here.

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