172_1_Last lecture photodetection

172_1_Last lecture photodetection - The equivalent input...

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The equivalent input noise power of optical amplifiers in ASE SE in in in GN N N GS N S SNR output SNR input NF 1 G, NF noisy GS in N in S in GN in +N ASE (1) ASE in N GN Amplification increases the NF of the optical link ow let’s replace the amp with an ideal noiseless amp but with an equivalent . N in =P shot ASE = P ASE in our old notation G oiseless S in GS in Now let s replace the amp with an ideal noiseless amp but with an equivalent input noise source; called Noise Equivalent Power for Amplifier (NEP Amp ) Noiseless (NF=1) + NEP Amp G (N in + NEP Amp ) N in G N NEP N GN G NEP N ASE AMP ASE in AMP in / ) ( (2) (3) AMP AMP in in in AMP NEP NEP N S N NF NEP ) 1 ( (4) (5) When input is shot noise limited Using (1) Minimum signal required for detection
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When is pre-amplification advantageous? ase 1: no preamp ase 2: with preamp G, NF Case 1: no preamp Case 2: with preamp EP in ASE DET in GN N NEP GS NEP DET NEP
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172_1_Last lecture photodetection - The equivalent input...

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