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dBc/Hz: This is used for noise and means dBc in a 1-Hz bandwidth.For example, −30 dBc means that the sideband is 30 dB below the carrier, i.e., it has a 1000 times lower power. to specify the power of a sideband in a modulated signal relative to the carrier. Some frequently used related specifications are: Therefore, 3 dB more optical input power leads to 6 dB more signal power. When the optical input power is doubled while the modulation remains unchanged, the signal power (modulation power) will be increased by a factor of 4. in cases with intensity (power) modulation the signal power is then again related to the square of the signal amplitude and can thus have units of W 2 (watts squared). However, one may also take the signal to be an optical power, e.g. If the signal is an electrical voltage or current, the signal power corresponds to an electrical power delivered to a given impedance (e.g. The modulation power is proportional to the square of the signal amplitude.with modulation of the optical phase, the optical power is not directly relevant for the signal.
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In the case of direct detection with a photodetector, this is translated into an electrical photocurrent or voltage.
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