Suppose we have two arbitrary points A and B. Transmission between these points is over optical-fiber. We don´t care the wavelength, distance  and other stuff. 

Now suppose we have total attenuation of 16 dB in average between these 2 points. According to general decibel formula:

$$ 10\log_{10}\left(\frac{P_\text{out}}{P_\text{in}}\right) = 16\,\text{dB}$$

When we solve the formula and the relationship between power out and power in:

$$10^{-1.6}=\frac{P_\text{out}}{P_\text{in}}=0.025$$


It means to the customer, only 0.025 of the power sent from the source (ISP, and so on) arrives. That means if we want to the customers to receive 1 watt, we need to sent at least 40 watts:

$$P_\text{in} = \frac{1\,\text{W}}{0.025}=40\,\text{W}$$


Does this really happen?  Do companies spend hundreds of watts so that only a few watts reach customers because of attenuation? Does that make sense?

  [1]: https://i.sstatic.net/VeShG.png
  [2]: https://i.sstatic.net/c6mKl.png
  [3]: https://i.sstatic.net/6Aqd4.png