# Energy of a signal

I have a graph of "dBm vs Wavelength".
I want the total Power in a certain area of the graph.

Do I convert the graph to:
"Power (Watts) vs Wavelength" then just Integrate within the required wavelength region?
ie.
$$\int_{\lambda_1}^{\lambda_2} Power d\lambda = Total Power$$

The way you described, you'll get some quantity with dimensions "power x length", which is not "power". If you had a graph of "Power per unit wavelength vs Wavelength", then you could integrate and obtain total power in the region of your choice. For example, see Planck's law in Wikipedia or somewhere else.

Gokul43201
Staff Emeritus