Jilin Zheng

The frequency-sweep nonlinearity of the light source in frequency-modulated continuous-wave (FMCW) LiDAR degrades the signal-to-noise ratio, thereby affecting the ranging accuracy and effective detection range of the LiDAR. Meanwhile, the maximum detection range of FMCW LiDAR is restricted by the coherence length of the light source. The inherent frequency modulation nonlinearity of a linear frequency-modulated (LFM) laser has to be corrected by complex predistortion compensation circuits or digital post-processing algorithms, which increases hardware cost and system integration difficulty. In addition, the ultra-narrow linewidth required for long-distance detection also raises the fabrication difficulty of LiDAR light sources. To solve the above-mentioned problems, this paper proposes an innovative FMCW LiDAR scheme without nonlinearity correction. Based on monolithically integrated sideband injection-locking technology, low-distortion LFM laser output can be realized without additional correction systems. Experimental results show that the proposed scheme achieves a frequency modulation nonlinearity of approximately 0.025% and a relative ranging error of less than 0.6%. Clear scanning imaging of the target is obtained. Moreover, the proposed scheme overcomes the light source's coherence length limitation, achieving a detection range exceeding seven times its intrinsic coherence length.

The escalating demands for spectral resources and information security have propelled significant interest in frequency-hopping (FH) communication. However, conventional electronic-based FH techniques face inherent limitations, such as restricted bandwidth, poor tunability, complex systems, and susceptibility to electromagnetic interference, making them increasingly inadequate for future applications. In this paper, we propose a photonic-assisted approach to generate wideband multichannel FH signals. This scheme eliminates the need for optical amplifiers and optical filters conventionally used in microwave photonic links, instead achieving amplification and filtering functions within semiconductor lasers. An optical frequency comb (OFC) is generated through optical injection of a gain-switched laser. This OFC then serves as a multi-wavelength seed to injection-lock (IL) a semiconductor laser, enabling selective amplification and filtering of individual comb lines. This method significantly improves frequency agility and signal purity while substantially reducing system complexity and power consumption. Experimentally, we demonstrate the generation of FH signals over 21 GHz with 7 channels and over 20 GHz with 20 channels. Furthermore, by pre-compensating the FH control signal, we achieve a hopping rate of $\sim$10 $\mu$s and explore the potential for 50 ns switching. Finally, the successful up-conversion of 3Gbps and 1Gbps QPSK signals, while maintaining error vector magnitude (EVM) below 9%, validates the practical viability of the proposed architecture. This work offers a promising pathway toward highly integrated, low-noise, and interference-resistant FH systems for next-generation wireless communication.

A photonics-assisted system for joint radar ranging, wireless communications and spectrum sensing is proposed and experimentally demonstrated. The carrier-suppressed single-sideband (CS-SSB) modulation and polarization multiplexing enable multi-function signal generation on the X-polarization state, concurrently enabling radar ranging and spectrum sensing on the Y-polarization state. Communication signals and radar signals are merged optically using a shared system architecture and hardware to achieve signal level sharing, with de-chirping and spectrum sensing also performed in the optical domain, utilizing the same hardware platform. A filtering structure is employed to differentiate between de-chirping and spectral sensing on the Y-polarization state. The joint system achieves radar ranging with a measurement error of ±3.2 cm, wireless communications at 1 Gbit/s over 1.8 m free space transmission, and precise spectrum sensing with a measurement error within ±3.2 MHz, simultaneously. This study provides a viable technical approach for future integrated sensing and communication scenarios.

This paper introduces an optical frequency comb (OFC) source. It is constructed using a monolithically integrated gain-switched semiconductor laser with the optical injection technique. The theoretical analysis of the working principle of this integrated OFC source based on optical injection is carried out. Fabricated via micro–nano processing technology, the proposed OFC source has been experimentally investigated. The results clearly show that the optical injection method can notably increase the number of comb teeth with a higher carrier-to-noise ratio. The measured phase noise of the beat-frequency signal between comb teeth is less than −102 dBc Hz⁻¹ @ 10 kHz. Moreover, a Doppler velocity-measuring LIDAR system is designed based on this OFC source, and the velocity of a moving target is measured. Compared with single-frequency speed measurement, using multi-comb teeth for speed measurement can significantly reduce the error.

A frequency-hopping optical stealth communication scheme based on a supercontinuum spectrum laser source is proposed and demonstrated in a proof-of-principle experiment. In this system, the frequency bands of the wavelength selective switch (WSS) turn off in the public channel and the WSS select in the stealth channel are consistent. Hence, the supercontinuum spectrum signal light can be embedded in the spectral gap of different wavelength-division multiplexed (WDM) signals to achieve the effect of concealment. By selecting different frequency bands to access the public channel at different times based on a WSS, providing huge flexibility and additional security. Attributing to the narrower frequency band occupied by the public signal, the colossal convenience of the frequency hopping of the stealth signal carrier can be guaranteed. In order to measure the security of the proposed scheme, the physical layer security of the system using the interception probability as an index is investigated

Photonic microwave harmonic down-converters (PMHDCs) based on self-oscillation optical frequency combs (OFCs) are interesting because of their broad bandwidth compared with plain optoelectronic oscillators. In this paper, a high-efficiency and flexible PMHDC is proposed and demonstrated. The properties of the OFC, such as the carrier-to-noise ratio (CNR), bandwidth and free spectral range (FSR), and the influence of optical injection, are investigated. The broadband OFC provides a frequency tunable and high-quality local oscillation (LO), which guarantees flexible down-conversion for the radio frequency (RF) signal. The sideband selective amplification (SSA) effect not only improves the conversion efficiency but also promotes single-sideband modulation. The conversion range can reach 100 GHz. The 12–40 GHz RF signal can be down-converted to intermediate frequency (IF) signals with a high conversion efficiency of 14.9 dB. The fixed 40-GHz RF signal is flexibly down-converted to an IF signal with the frequency from 55.4 to 2129.4 MHz. The phase noise of an IF signal at a frequency offset of 10 kHz is the same as that of the input RF signal. The PMHDC shows great performance and will find applications in radio-over-fiber (RoF) networks, electronic warfare receivers, avionics, and wireless communication systems.

A novel photonic method of linearly frequency-modulated (LFM) signal generation with high purity based on the monolithically integrated semiconductor laser (MISL) subject to the dynamical optoelectrical feedback is proposed and demonstrated in this paper. In this approach, the MISL is firstly operated in period-one state. By introducing the dynamical optoelectrical feedback to modulate the MISL, the generated LFM signals would be constantly optimized as long as the delay of the feedback loop is matched with the repetition period of the LFM signal. In this system, no additional high-speed external modulator, high-frequency electrical LFM oscillator are required, highly simplifying the framework and reducing the power consumption. In the current proof-of-concept experiment, one LFM signal with the bandwidth as large as 5.6 GHz is generated and the corresponding frequency comb contrast can be drastically improved by 51 dB. Furthermore, the effect of the delay mismatch is also discussed in this paper.

In this paper, the simple multi-band triangular frequency modulation (TFM) signals generation with multiplying bandwidth and center frequency using photon-photon resonance (PPR) effect in three-section monolithic integrated directly-modulated laser (TS_MIDML) has been experimentally demonstrated. The traditional optical-injection system replaced by the TS_MIDML, and the high-speed external modulator, polarization controller and filter are eliminated in this paper. A three-band TFM signals with carrier frequencies ranging from X-band to K-band are given as an example, and the time bandwidth product (TBWP) up to 20000. The numbers of bands and TBWP of generated signals could be easily adjusted by tuning the reference signal from arbitrary waveform generator (AWG). The results of auto-correlations of the generated waveforms are also given.