Noise analysis of optoelectronic oscillators in the presence of the relative intensity noise of the laser

Abstract

Optoelectronic oscillators (OEOs) have recently been considered very good candidates for producing ultra-low phase noise radio frequency (RF) oscillations. One of the most important noise sources of any OEO is the relative intensity noise (RIN) of the optical field in the optical part of this system. It is the dominant noise source in some OEO cases. The initial source of the RIN is the laser; however, it may be largely enhanced in the fiber by some phenomena such as the guided entropy mode Rayleigh scattering. Here a frequency domain analysis approach is introduced to separately analyze the effect of both the low-frequency RIN (LFRIN) and the high-frequency RIN (HFRIN), i.e., the RIN around the RF harmonics, on both the phase and amplitude noises of the delay-based single-loop/dual-loop OEOs. The presented approach can take into account the RIN at both the input and the output of the optical fibers. The measured or analytical nonlinear gain function of the photodetector and the RF amplifier can be taken into account to accurately characterize the important effect of the amplitude noise to phase noise (AN-PN) conversion. It is shown that the AN-PN conversion can largely enhance the LFRIN-induced phase noise. Also, to a much lesser degree, it can enhance the HFRIN-induced phase noise. Furthermore, it is shown that the AN-PN conversion reduces the HFRIN- and LFRIN-induced amplitude noise. It is also shown that the fibers’ dispersion has a small effect on the phase/amplitude noise power induced by either LFRIN or the HFRIN, especially for smaller fiber lengths. The validity of the new analysis approach is verified by comparing its results with those of the previously published works in the literature.