Flicker noise in high-speed p-i-n photodiodes

Abstract

The microwave signal at the output of a photodiode that detects a modulated optical beam contains the phase noise ϕ(t) and the amplitude noise α(t) of the detector. Beside the white noise, which is well understood, the spectral densities Sϕ(f ) and Sα(f ) show flicker noise, proportional to 1/f . We report on the measurement of the phase and amplitude noise of high-speed p-i-n photodiodes. The main result is that the flicker coefficient of the samples is ∼ 10 −12 rad 2 /Hz (−120 dBrad 2 /Hz) for phase noise, and ∼ 10 −12 Hz −1 (−120 dB) for amplitude noise. These values could be observed only after solving a number of experimental problems and in a protected environment. By contrast, in ordinary conditions insufficient EMI isolation, and also insufficient mechanical isolation, are responsible for additional noise to be taken in. This suggests that if package and EMC are revisited, applications can take the full benefit from the surprisingly low noise of the p-i-n photodiodes.

Exploiting shot noise correlations in the photodetection of ultrashort optical pulse trains

“…Correlated optical noise has also been observed in harmonically mode-locked lasers, where the supermode noise power has been shown to be sensitive to the optical pulse width [54]. Another possible time-varying noise source is photodetector flicker noise [45]. If this noise source is present only when current is being generated, then it too can produce phase/amplitude imbalance.…”

“…Note that this is not simply one-half the noise-to-signal ratio of the photocurrent (inverse of Eq. (11)) as is commonly assumed [10,11,35,38,[44][45][46][47][48]. Equation (20) contains the additional term in brackets that is a direct result of shot noise correlations that are symmetric about the microwave carrier, described above in Section 2.3.…”

Low-Drift Optoelectronic Oscillator Based on a Phase Modulator in a Sagnac Loop

“…The predicted phase noise is calculated using (27), datasheets of the above discussed components, and measured phase noise of the LO. Below a few kHz offset frequencies, the measured phase noise is poorer than the predicted one, which may be caused due to the flicker noise of the photodetector [64] or AM-to-PM conversion in photodetector [65], and also due to the random-walk and frequency drift induced by environmental factors such as temperature fluctuations and vibration. As shown in this figure, there is a flat noise floor at high offset frequencies (>1 MHz), which is coming from the high frequency noise of the loop components and laser that contains three dominant noise sources, laser RIN, shot noise, and thermal noise.…”

“…Close-to-carrier phase noise of the TF-OEO is limited by the amplifier flicker noise and photodetector AM-to-PM conversion. So, using ultralow phase noise HF/VHF amplifiers (such as API Technologies (formerly SpectrumMicrowave) amplifiers with phase noise of −160 dBc/Hz at an offset of 10 Hz), an ultralow RIN laser (such as Orbits Lightwave Ethernal SlowLight Lasers with −138 dBc/Hz and −165 dBc/Hz at 1 kHz and 100 MHz offset frequencies, respectively) and a photodetector with low powerto-phase conversion factor (such as modified unitraveling carrier (MUTC) photodiodes with α < 0.1 rad [65]- [67]), the close-to-carrier phase noise can be reduced tremendously.…”

Cross-Correlation Measurements of Phase Noise Induced by Relative Intensity Noise in Photodetectors

“…Two of the main sources of noise in the photodetection of optical carrier are the conversion of laser RIN into electronic phase noise, and the fundamental shot noise. Shot noise is related to the randomness of the incident photon stream [8,9], while at higher powers another powerdependent effect, AM-PM conversion, is observed to adversely affect the transition from optical to microwave within the PD [5][6][7][8][9][10][11][12]. That is, the RIN could contribute to the phase noise of the reference signal through such AM-PM conversion, because it produces a change in the RF phase, since the propagation speed of the RF signal (or the PD microwave refractive index) depends on the number of carriers in the semiconductor [5][6][7].…”