Noise spectrum characterization of optoelectronic oscillators in the presence of laser frequency noise.

Abstract

Frequency domain formulation for computing the noise spectrum of a single loop optoelectronic oscillator (OEO) under the effect of laser frequency noise (LFN) based on the conversion matrix approach is presented. The validity of this approach is verified by comparing its results regarding the phase noise of the OEO with the measurements and simulations of two references in the literature. By performing various simulations, it is observed that the LFN-induced phase noise is approximately independent of the length of the fiber delay line at offset frequencies less than the free spectral range, i.e., the inverse of the time delay of the fiber, and, at larger offset frequencies, the phase noise grows even with increasing the fiber length. Furthermore, it is observed that this phase noise is approximately independent of the distance between the oscillation frequency and the center frequency of the RF filter as well as the value of the small signal loop gain of the OEO. However, the LFN-induced amplitude noise is affected by the distance between the oscillation frequency and the center frequency of the RF filter.