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.

Inspec keywords: amplifiers; quantum noise; laser noise; thermal noise; spontaneous emission; semiconductor lasers; laser beams; photodetectors

Other keywords: spontaneous emission; optical field detection; optical amplifier; quantum noise; numerical noise; thermal noise; photodetector; signal-to-noise power ratio

Subjects: Laser beam characteristics and interactions