A tunable optoelectronic oscillator (OEO), which employs an all-optical microwave photonic filter (MPF) consisting of two laser sources (LD1 and LD2), an optical coupler (OC, 50:50), a Mach-Zehnder modulator (MZM), and a chirped fiber Bragg grating, is proposed. Because the central frequency of the all-optical MPF can be shifted by changing the wavelength spacing between the two laser sources, the frequency tunability of the OEO can be realized by incorporating such an all-optical MPF into an optical domain dual-loop OEO without any electronic microwave filters. A detailed theoretical analysis is presented and the results are confirmed by an experiment. A microwave signal with a frequency-tuning range from 4.057 to 8.595 GHz is generated. The phase noise, the long-term stability, and the side-mode suppression performance of the generated microwave signal are also investigated.
A lithium niobate optical waveguide-based integrated electro-optic (EO) electric field (E-field) sensor dedicated to the measurement of intense nanosecond transient electromagnetic pulse (EMP) signals has been developed and calibrated. The time domain calibration system for measurement of intense nanosecond EMP signals has been established. A pure optical bias phase angle control system based on wavelength tuning has been developed and implemented to ensure that the sensor has a linear transfer function. The fluctuations of the sensor static output optical power are <0.1 dB with the proposed bias control system while >3 dB without bias control. The time domain characteristics of the detected pulsed E-fields have been compared with those of the input EMP signals. For the first type nanosecond level (ns-level) EMP signal, the relative errors of the detected E-fields on rise time, fall time, and pulse width are 0.38%, 0.69%, and 0.79%, respectively. Also, for the second type ns-level EMP signal, the relative errors of the measured E-fields on rise time, fall time, and pulse width are 0.40%, 0.31%, and 0.01%, respectively. All these results demonstrate that the developed integrated EO E-field sensing system has the potential to be used to accurately extract the information of transient E-fields.
A reconfigurable optoelectronic oscillator (OEO) based on a double-coupling recirculating delay line (DC-RDL) is analyzed and experimentally demonstrated. In the proposed OEO, an incoherent two-tap microwave photonic filter is formed by an amplified spontaneous emission (ASE) source, a Mach–Zehnder modulator, a DC-RDL, and a polarization beam splitter (PBS) to realize selection of the oscillation mode. Specifically, the incoherence is implemented using an ASE broadband laser source and a DC-RDL, and the high sidemode suppression performance can be achieved by employing the dual-loops system between the dual output of the DC-RDL and the PBS. A detailed theoretical analysis is provided and is verified by the experiment. The single-sideband phase noise, the frequency tunability, and the long-term stability of the generated microwave signal are investigated. In addition, the frequency independent of the phase noise is also experimentally observed.