The signal-to-noise ratio determines how “usable” a signal is after it passes through the optical device. The general formula used to calculate SNR is written as:

$$ \text{SNR} = \frac{s_{\text{target}}}{\sigma_{\text{noise}}} $$

Where

• $\text{SNR}$: Signal to noise ratio of the optical device.
• $s_{\text{target}}$ [electron]: Signal.
• $\sigma_{\text{noise}}$ [electron]: Noise.