An ultra-flat and broadband optical frequency comb (OFC) generator is proposed and experimentally demonstrated by directly modulating a dual-driven Mach-Zehnder Modulator (MZM) with only one RF signal. The proposed scheme can generate two forms of OFCs by simply adjusting the bias voltages of the MZM and the power of the RF signal. One form is a 20-line OFC with a frequency spacing equals the frequency of the RF signal, the other form is a 16-line OFC with a frequency spacing of two times the frequency of the RF signal. The generated OFCs have low power variation and broad bandwidth. The proposed scheme is verified by an experiment. A 20-line OFC with a frequency spacing of 10 GHz and flatness of 0.7 dB, and a 16-line OFC with a frequency spacing of 20 GHz and flatness of 0.3 dB are experimentally demonstrated.

A photonic approach to generate a frequency and bandwidth multiplying dual-chirp microwave waveform using a single dual-polarization quadrature phase shift keying (DP-QPSK) modulator is proposed and demonstrated. In the proposed scheme, an RF carrier is applied to one QPSK modulator and a baseband single-chirp waveform is applied to another. By setting the driving signals applied to the modulator and adjusting the dc bias phases in the modulator, high-order optical sidebands can be obtained with the optical carrier suppressed. After optical to electrical conversion, a frequency-doubling and bandwidth-quadrupling, or frequency-quadrupling and bandwidth-octupling dual-chirp microwave can be generated. The approach is verified by simulation. Dual-chirp microwave waveforms with 16-GHz central frequency, 2048-MHz bandwidth and 32-GHz central frequency, 4096-MHz bandwidth are generated through an 8-GHz RF carrier and 512-MHz bandwidth baseband signal. The generated dual-chirp microwave waveform can be used in a radar system to improve its range-Doppler resolution.

A novel filterless optical millimeter-wave signal generation scheme is proposed. In the scheme, the undesired sidebands are suppressed using two parallel dual-parallel Mach–Zehnder modulators (MZMs) with different modulation indexes and polarization multiplexing, and frequency multiplication factor as high as 16 can be achieved. Simulation results show that 80, 120, and 160 GHz signals are generated through a 10 GHz RF signal using the proposed method, and the performance of the generated signals is good when commercially available MZMs with extinction ratio of 20–30 dB are used. The scheme has large tunability of modulation index for frequency octupling and 12-tupling signals generation and high stability against the RF driving voltage deviation for frequency 16-tupling generation.

Photonic generation of a bandwidth multiplied linearly chirped signal with phase modulation capability is proposed and its applications in communication and radar systems are demonstrated. In the generator, a dual-polarization quadrature phase shift keying modulator is used to simultaneously perform bandwidth multiplication and phase modulation. The generator can be functionally expanded to a transceiver for wireless communication, which can be used to perform optical generation and coherent demodulation of a phase modulated linearly chirped signal. Meanwhile, the generator can be used to increase the radar detection distance by improving the signal time bandwidth product. The signal generation and application are verified by simulation. A linearly chirped signal with an instantaneous frequency of 8-12 GHz or 16-24 GHz is obtained by using a 4-6 GHz electrical driving signal. The proposed transceiver is demonstrated to perform 156.25-bit/s wireless communication. When the emitting power is 11 dBm and the communication distance is 1 km, the bit error rate can be better than 10-4. While for radar detection, the peak to sidelobe ratio of the compressed pulse is increased from 1.1 dB to 9.2 dB, through which the distance improvement can be verified.

Self-interference (SI) influenced the recovery of the signal of interest (SOI) in In Band Full Duplex (IBFD) radio-over-fiber (ROF) links. The multipath effect and nonlinear distortion aggravate the difficulty of the SI signal elimination. A fiber-transmission-assisted digital self-interference cancellation (DSIC) scheme is proposed to solve the problem at a low time complexity. The key to removing the impact of harmful factors is combined with the advantages of photonics architecture and digital filter algorithm. A fiber-transmission-assisted scheme achieves the transmission of reference signals with all the linear and nonlinear features which transform the nonlinear problem into a linear question for DSIC subsequently. In DSIC, a fast transversal recursive least-squares (FTRLS) algorithm realizes a fast-channel estimating process when the SOI is involved. For 10km fiber transmission, exceeding 38 dB and 34 dB cancellation depth over 50 MHz bandwidth in the X band and Ku band are experimentally demonstrated, and 25 Mbaud 16-quadrature amplitude modulation (16-QAM) SOI is successfully recovered after SIC. In addition, FTRLS merely consumed 7N+14 multiplication times at each iteration (filter order N) in the channel estimating process, which saves multiplications amount above 86% than RLS, DNN, Volterra-RLS algorithm, when N is equal to 80.

A photonic-assisted approach for instantaneous frequency measurement (IFM) based on a 1×4 Mach–Zehnder interferometer (MZI) structure is proposed and experimentally demonstrated. In this IFM method, a Mach–Zehnder modulator (MZM) in conjunction with an optical filter play the role of CS-SSB signal generator, mapping the unknown microwave into a tunable optical sideband. Due to the property of the subsequent 1×4 MZI structure, two amplitude comparison function (ACF) that convert the frequency information into optical power ratio can be established. A detailed theoretical analysis illustrates the realization of frequency measurement with a range of full free spectral range (FSR) and optimized estimation error by using these two ACFs. Simulation has been carried out to verify the mechanism, and the discussion about the merits of CS-SSB modulation and the applicable scenarios is also given. A proof-of-concept experiment is performed, in which the microwave frequency measurement from 7.5 to 20 GHz is demonstrated with an estimation error of less than 100 MHz.