Parity-time symmetric tunable OEO based on dual-wavelength and cascaded PS-FBGs in a single-loop

Abstract

The ability to achieve low phase noise single-mode oscillation within an optoelectronic oscillator (OEO) is of fundamental importance. In the frequency-tunable OEO, the wide microwave photonic filter (MPF) bandwidth is detrimental to select single-mode among the large number of cavity modes, thus leading to low signal quality and spectral purity. Stable single–mode oscillation can be achieved in a large time delay OEO system by harnessing the mechanism from parity-time (PT) symmetry. Here, a PT-symmetric tunable OEO based on dual-wavelength and cascaded phase-shifted fiber gratings (PS-FBGs) in a single-loop is proposed and experimentally demonstrated. Combining the merits of wide frequency tuning of PS-FBG-based MPF and single mode selection completed by the PT-symmetric architecture of the OEO, where the gain and loss modes carried by dual-wavelengths to form two mutually coupled resonators in a single-loop, signals range from 1 GHz to 22 GHz with the low phase noise distributed in −122∼ −130 dBc/Hz at 10 kHz offset frequency are obtained in the experiment.

On-chip tunable parity‐time symmetric optoelectronic oscillator

“…As can be seen, the corresponding SSB phase noises at 10-kHz offset frequency are −83.42 and −80.96 dBc/Hz, respectively. A slight degradation of the phase noise at 13.67 GHz can be observed, which can be blamed on the performance degradation of the electrical devices at high frequency 24 , 25 . The parasitic noise peaks at the 84-kHz offset frequency and its harmonics are induced by cascaded EAs 24 , 26 .…”

“…24,25 The parasitic noise peaks at the 84-kHz offset frequency and its harmonics are induced by cascaded EAs. 24,26 Additionally, the stability of the oscillation frequency is measured by using the Maxhold function of the ESA, as shown in Fig. 4(c).…”

“…A slight degradation of the phase noise at 13.67 GHz can be observed, which can be blamed on the performance degradation of the electrical devices at high frequency 24 , 25 . The parasitic noise peaks at the 84-kHz offset frequency and its harmonics are induced by cascaded EAs 24 , 26 . Additionally, the stability of the oscillation frequency is measured by using the Maxhold function of the ESA, as shown in Fig.…”