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Chapter 5: 3 Sources of Noise (Signal noise ratio (SNR) (Definition (Ratio…
Chapter 5: 3 Sources of Noise
Signal Short Noise
Definition
Quantum noise arising from discrete nature of incident signal
Photon absorption is discrete process. Thus, number of absorption fluctuates statistically.
Mean square noise current
Dark Current Shot Noise
Definition
Arising from discrete nature of incident nature of photodiode dark current
Dark current, Id
Current with no incident light
Bulk dark current, Ib + surface leakage current, Ii
Mean square DCSN
Thermal noise
Arises from random thermal motion of carries in resistive circuits element
Mean square thermal currrent noise
Fluctuation due to random motion of electrons
Signal noise ratio (SNR)
Definition
Ratio of signal current squared to total mean square noise current
Total mean square noise current
SNR formula
SNR for an APD
Gain factor of M
