Modulation-dependent limits to intensity-noise suppression in microwave-photonic links

Highly reconfigurable microwave photonic single-bandpass filter with complex continuous-time impulse responses

“…, by replacing the BOS with a single-wavelength laser. It has been investigated that the modulation-induced noise increment forms a basic limit to the performance of balanced detection [14]. The RF output spectra with balanced detection or with only one single input of the BPD are shown in Fig.…”

Noise Reduction in Class-AB Microwave-Photonic Links

“…However, our modulators have only one output fiber. For a BQB link, intensity noise would be suppressed by some factor dependent on the modulation index [13]. Signal power would have been increased by 6 dB relative to the single QB link, with a 3 dB increase in shot noise (same as doubling optical power in a single QB link).…”

“…where G is the amplifier power gain, F the noise figure, hf the photon energy, and ai P is the optical power at the input to the amplifier [13]. It can be shown that the rms noise current from RIN* in a single detector, averaged over multiple RF cycles, is then …”

“…S is a suppression factor that accounts for the combination of common-mode suppression and impact of modulation [13]. Note that both two-fiber QB and our CAB links can benefit from RIN suppression.…”

Class-B Microwave-Photonic Link Using Optical Frequency Modulation and Linear Frequency Discriminators

“…However, the degree of intensity noise suppression is limited as the modulation index increases [7], the shot noise (uncorrelated in the two detectors) is not reduced, and the intensity noise added after the modulator (e.g., signal-spontaneous beat noise from an optical amplifier) is not suppressed. It was shown [8] that balanced low-biased operation could reduce the second-order distortion associated with low-biased operation.…”