This appendix first considers thermal and quantum noise and the ideal signal-to-noise power ratio that can be measured using a 100%-efficient photodetector. An ideal optical amplifier followed by an ideal detector is then considered. At the output of this ideal amplifier, the signal-to-noise-power ratio depends on the spontaneous emission and it is argued that this ratio has to be the same as the signal to-noise-power ratio for the ideal direct detection of optical fields at the input.
Appendix 9: Thermal, quantum and numerical noise, Page 1 of 2
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