Wavelength-Space Parity-Time Symmetric Optoelectronic Oscillator Using a Chirped Fiber Bragg Grating

A wavelength-space parity-time (PT) symmetric optoelectronic oscillator (OEO) with the gain/loss balance implemented using a chirped fiber Bragg grating (CFBG) is proposed and experimentally demonstrated. In the proposed OEO, two optical carriers at two different wavelengths are employed to form two coupled wavelength-space OEO loops, with one wavelength reflected from the top of the CFBG refection spectrum and the other from the slope of the refection spectrum, thus making one OEO loop have a gain and the other a loss. Once the gain and loss coefficients are matched and the gain coefficient is greater than the coupling coefficient, PT symmetry is broken, and a single-frequency oscillation is enabled. The operation of the proposed OEO is evaluated by an experiment. A microwave signal at 6.19 GHz is generated. The side mode suppression ratio (SMSR) is measured to be 32 dB and the phase noise is measured to be -118 dBc/Hz at an offset frequency of 10 kHz. The stability of the OEO is also studied.