An approach to generating periodic spiking and spiking cluster in a broadband nonlinear opto-electronic oscillator (OEO) is proposed and demonstrated. Through injecting a long-duration square-wave pulse train with a repetition frequency equal to an integral multiple of the free spectral range into the OEO with a high net gain, controllable spiking and spiking cluster oscillation can be achieved when the dual-drive Mach-Zehnder modulator (DDMZM) in the OEO is biased far away from its quadrature point. The proposed scheme is verified by both numerical simulation and experiment. The results indicate that, when the DDMZM in the OEO cavity is biased near its minimum transmission point, positive spiking train with nanosecond-level pulse width is excited by the rising edge of the injected square-wave pulse train. Through further enhancing the injection strength, uniformly-spaced positive spiking fills the high-level voltage duration of each injected square-wave pulse. Hence, spiking cluster oscillation is achieved. Benefiting from its controllability, this approach can be applied in ultra-wideband (UWB) communications, electronic countermeasures, spiking coding and high-speed neuromorphic computing.

A photonic technique for microwave frequency measurement with flexible range and high resolution is proposed based on frequency-configurable pilot tones. The method extracts the remote unknown microwave frequency by measuring electrical power at two known pilot frequencies, avoiding dual-channel photodetection and broadband microwave power measurement over the whole interested frequency range. Moreover, it enables flexible measurement range by configuring two pilot frequencies. A proof-of-concept experiment is successfully demonstrated with the frequency range of 6-18.9 GHz and the resolution of 0.1 GHz.

We propose and demonstrate an approach to generating wide-range tunable coherent dual-frequency microwave signals with high side-mode suppression ratios (SMSRs), ultra-low phase noise and high stability, based on a dual-passband optoelectronic oscillator (OEO). The narrowband passband with a relatively high gain is used to generate the initial oscillation at a fixed frequency. Through injecting a single-tone signal into the OEO cavity via a microwave mixer, frequency-tunable oscillation in the other broadband passband with a relatively low gain is initiated through frequency mixing injection locking. Then, the two oscillation signals are phase-locked through frequency mixing mutual injection locking. In addition, a dual-loop configuration with the assistance of balanced photodetection is utilized to suppress the side modes and improve the phase noise performance, which also enhances the stability of the generated signal. In the experiment, coherent dual-frequency microwave signals with a fixed frequency at 20.0056 GHz and a tunable frequency in the range of 13.9705 GHz to 18.0075 GHz are generated, where the frequency tuning step is 625.6 kHz. The power fluctuation during frequency tuning is smaller than 1.5 dB, and the SMSRs are larger than 77 dB. In addition, the Allan deviation and the phase noise are in the order of 10–11@1 s and better than –138 dBc/Hz@10 kHz, respectively.

An electrical probing test method is proposed based on serial or parallel modulation mixing scheme for characterizing wideband optical transceiving devices including high-speed semiconductor laser diodes, electro-absorption modulators, photodetectors, and Mach-Zehnder modulators. The method enables self-referenced frequency responses measurement, such as modulation index of semiconductor laser diodes, modulation index of electro-absorption modulators, responsivity of photodetectors, and modulation index and half-wave voltage of dual-parallel Mach-Zehnder modulators, dual-drive Mach-Zehnder modulators, and push-pull Mach-Zehnder modulators. In the demonstration, the experimental results are compared to those obtained with the conventional optical or electrical methods for accuracy. The full-electrical test nature is promising for microwave characterization of wafer level devices and circuits with fully integrated transceiving components on chip.

Frequency responses of optoelectronic devices are essential to obtain the precise performance of electrical-to-optical-to-electrical signal conversion or optical signal processing. We reviewed the development of optical or electrical measurement methods proposed for characterizing electrical/optical (E/O) devices, optical/electrical (O/E) devices and optical/optical (O/O) devices in the frequency domain from the perspective of accurate calibration standard. It is found that full calibrated E/O or O/E measurement requires at least an optoelectronic thru standard for the conversion between optical and electrical domains, and an electrical port extension for de-embedding the error or adapter network of microwave source or detector. The indetermination problem still exists in most O/E and E/O device characterization, which appears in different forms for different measurement techniques. Nevertheless, it should be noticed that obtaining an optoelectronic thru standard can be transferred to characterizing a microwave source or detector in the electrical domain, and a precise electrical calibration standard is much easier to be obtained as compared with an optoelectronic calibration standard. Therefore, the calibration standard transfer from optical to electrical domain is a prominent approach to solve the indetermination problem.