A novel microwave photonic true-time-delay (TTD) system using carrier compensation technology is proposed and experimentally demonstrated. Wavelength division multiplexing combines ten lasers into a single beam. We separate one channel from the laser as a compensating carrier, and the compensation carrier is combined with the time-delayed optical signals to be detected. Meanwhile, sideband signals are amplified effectively thanks to carrier-suppressed double-sideband (CS-DSB) modulation. Therefore, the power of both the central optical carriers and sidebands is guaranteed, which produces a better beat frequency result than the TTD system without carrier compensation. The simulation results confirm that the signal amplitude has an order of magnitude improvement due to the compensation. With employing the delay fibers based on multiple-fiber Bragg gratings (MFBGs), the experimental delay and response time reach 90.160 μs and 160.80 ns. The proposed technique can find applications in time-delay beamforming of phased array antennas (PAAs).

This study focuses on a 4FSK-modulated ultraviolet (UV) communication system, introducing an innovative symbol-level maximum likelihood decoding approach based on Poisson statistics. A forward error correction (FEC) coding mechanism is integrated to enhance system robustness. Through Monte Carlo simulations, the proposed decoding scheme and the error correction performances of Reed–Solomon (RS) and Low-Density Parity-Check (LDPC) codes are evaluated in UV channels. Both RS and LDPC codes significantly improve the Bit Error Rate (BER), with LDPC codes achieving superior gains under low SNR conditions. Hardware implementation and field tests validate the decoding algorithm and LDPC-optimized 4FSK system. Under non-line-of-sight (NLOS) conditions (10–45° transmit elevation angle), stable 60 m communication with BER < 10⁻³ is achieved. In line-of-sight (LOS) scenarios, the system demonstrates 900 m range with BER < 10⁻³, highlighting practical applicability in challenging atmospheric environments.

A microwave photonic converter based on microwave pre-upconversion is proposed and experimentally demonstrated. Only a single Mach–Zehnder modulator (MZM) is used in the converter system so that the complexity and bandwidth limiting of the link can be reduced. The transmitted and received signals before entering the MZM are firstly upconverted to high frequency (HF) by a microwave upconverter. The HF and local oscillator (LO) signals are combined to drive the MZM. Carrier-suppressed double-sideband (CS-DSB) modulation is introduced to the MZM for effective spectrum utilization. Then, the target signals can be obtained by photoelectric conversion and beating. Experimental results confirm that the mixing spurs including harmonics and intermodulation as well as original signals are all out of system frequency band from 0.8–18 GHz, and the in-band spurious suppression of at least 40 dBc is achieved. In addition, the spurious-free dynamic range (SFDR) reaches 86.23 dB·HZ^2/3 for upconversion and 80.95 dB·HZ^2/3 for downconversion. The proposed microwave photonic converter provides a wideband and high-purity alternative for the applications of radars and signal processing.

In this paper, a photonics-assisted multi-path interference (MI) cancellation system based on the combination of the digital domain and analog domain is proposed and demonstrated. The cancellation in the photonics-assisted analog domain avoids oversaturation of the analog-to-digital converter (ADC) signal at the input while the adaptive feedback control in the digital domain can also compensate for the optical path’s undesirable factors, thus making MI cancellation in the best state all the time. Initially, the differences in MI cancellation between small-signal and large-signal modulations are analyzed. Subsequently, the MI residual power of the multi-tap photonics-assisted cancellation system is derived theoretically by modifying the Wiener solution. Finally, the adaptive feedback control algorithm based on the received signal strength indicator (RSSI) is evaluated by simulation, and the simulated multi-path interference cancellation depth (MICD) reaches 48.4 dB when the convergence condition is satisfied. In addition, the compensation effect of the digital domain on the modulator bias point drift is analyzed.

In this paper, a broadband photoelectric fusion transceiver-multiplexed system is proposed to realize a frequency converter. The system achieves a high spurious suppression ratio through two frequency conversions that utilize the advantages of microwave and photonics technology simultaneously to reduce the complexity of the system and improve the effective spectrum utilization. In addition, the core components, such as the Mach–Zehnder modulator (MZM), are multiplexed in the up and down frequency conversion link. High-frequency local oscillator (LO) signals are used to keep image frequency signals and various kinds of spurious signals obtained by beating frequency outside the system bandwidth. Experimental results demonstrate that the operating frequency ranges from 2 to 18 GHz with high performance for both transmitter and receiver. The image rejection is 57.35 dB for up-conversion and 46.56 dB for down-conversion, and the in-band spurious suppression achieves at least 55.02 dB. At the same time, the spurious-free dynamic range (SFDR) can reach at least 89.11dB⋅Hz^2/3.