Generation of flat-spectrum wideband chaos by fiber ring resonator

We present a simple method to generate spectrally uniform wideband chaos by injecting chaotic laser into a fiber ring resonator. The resonator is a single-coupler ring equipped with an optical filter and amplifier, which adjust the optical field circulating in the ring. The incoherent interference of the circulating fields produces wideband chaos with uniform power spectrum density distribution. We experimentally achieved a chaotic spectrum that extends over 26.5 GHz (limited by measurement bandwidth) and fluctuates within ±1.5 dB. In addition, tuning the filter frequency can control the spectral profile so as to meet different application needs.