The integrated radar jamming and secure communication system providing both false target and high physical layer transmission security will play an important role in future electronic warfare systems. In this letter, we present and experimentally validate a novel photonics-based integrated system that combines radar jamming with secure communication. The system incorporates velocity and range false targets generation for effective radar deception jamming, along with a secure communication function boasting a remarkable key space of 10 ¹⁵⁶ with the help of Li's hyperchaotic model. The Ka-band radar deception jamming and chaotic encrypted communication signals are simultaneously generated by a photonic frequency upconverter, which consists of a Mach–Zehnder modulator (MZM), an optical filter, an in-phase/quadrature (I/Q) modulator, and dual-drive Mach–Zehnder modulator (DDMZM), and a photodetector (PD). In a proof-of-concept experiment, the generated velocity deception jamming signal extended beyond 40 GHz, achieving a remarkable spurious suppression ratio of over 30 dB. The range deception jamming is also investigated. Meanwhile, the chaotic encrypted 4 Gbaud 16 quadrature amplitude modulation (16QAM) and 32 quadrature amplitude modulation (32QAM) orthogonal frequency division multiplexing (OFDM) signals over a distance of 1 m are successfully demonstrated. The proposed scheme can reduce enemy radar detection capabilities and enhance communication security ability, which is required by future electronic warfare systems.

In this article, we propose a novel photonic-based integrated scheme that simultaneously achieves radar jamming signal generation and chaotic encrypted wireless communication. The velocity deception jamming signals are generated with a high spurious suppression ratio of 31.9–33.2 dB. Additionally, the range deception jamming has been efficiently executed. Simultaneously, an encrypted 64-quadrature amplitude modulation (64QAM) OFDM signal with a key space of 10 $^{50}$ is transmitted over a 1.5-m wireless link, meeting the hard decision forward error correction (HD-FEC) threshold of 3.8 $\times$ 10 $^{-3}$ , corresponding to a net rate of 9.9 Gbit/s. In addition, a maximum modulation error ratio (MER) of 21.4 dB is achieved below the error vector magnitude (EVM) threshold of 9%. The proposed scheme effectively combines the capabilities of degrading enemy radar detection and enhancing one’s wireless communication security, which may be a potential application for electronic countermeasures in the future.

An improved neural network-based equalization method is proposed and experimentally demonstrated. The up-to-137 Gb/s transmission of four level pulse amplitude modulation (PAM-4) signals with 25 G class 850 nm optical devices is achieved over an in-house fabricated 40 cm optical backplane. An in-depth investigation is conducted regarding the impact of delayed taps and spans on equalization performance. A performance comparison of the proposed method with the traditional maximum likelihood sequence estimation (MLSE) and decision feedback equalization (DFE) is also undertaken. For the bit rate from 80 to 100 Gb/s, the proposed method achieves an adopted hard-decision forward error correction (HD-FEC) requirement at a received optical power (RoP) of −9 and −8 dBm, while DFE and MLSE cannot meet the HD-FEC requirement. When the bit rate increases from 120 to 137 Gb/s, the proposed equalization method still successfully maintains the acceptable system performance at an RoP of −4 and −2.5 dBm. Furthermore, the specific bit error rate (BER) performances for varied maximum achievable bit rate under different RoPs by applying MLSE and the proposed method are also analyzed. This provides an important potential solution to realize the future data centers.

In this study, a joint modulation format identification and optical signal-to-noise ratio (OSNR) monitoring algorithm is proposed and experimentally demonstrated using the k-nearest neighbor algorithm for intensity modulation and direct detection (IMDD) orthogonal frequency division multiplexing (OFDM) systems. A modified amplitude histogram of received signal is employed to serve as the classification feature to simplify the computation. Experimental results show that five common quadrature amplitude modulation (QAM) modulation formats, including 4-QAM, 16-QAM, 32-QAM, 64-QAM and 128-QAM, can be identified under 100% accurate estimation at the received optical power of −11 dBm. Robustness of the proposed scheme to constellation rotation is also experimentally assessed. At the same time, system OSNR monitoring also can be achieved and the average prediction mean square error (MSE) is 0.69 dB², which is similar to that using an artificial neural network. Computational complexity assessment demonstrated that similar performance but less computing resource consumption can be achieved by using the proposed scheme rather than the artificial neural network-based scheme.

A high-throughput layered decoder for quasi-cyclic (QC) low-density parity-check (LDPC) codes is required for communication systems. The preferred way to improve the throughput is to insert pipeline stages and increase the operating frequency, which suffers from pipeline conflicts at the same time. A priority-based layered schedule is proposed to keep the updates of log-likelihood ratios (LLRs) as frequent as possible when pipeline conflicts happen. To reduce pipeline conflicts, we also propose double update queues for layered decoders. The proposed double update queues improve the percentage of updated LLRs per iteration. Benefitting from these, the performance loss of the proposed decoder for the fifth generation (5G) new radio (NR) is reduced from 0.6 dB to 0.2 dB using the same quantization compared with the state-of-the-art work. As a result, the throughput of the proposed decoder improved up to 2.85 times when the signal-to-noise ratio (SNR) was equal to 5.9 dB.

A clock-gating-based energy-efficient scheme is proposed, for the first time, for applications in optical network units (ONUs) accommodated by orthogonal frequency division multiplexing passive optical networks (OFDM-PONs) based on intensity modulation and direct detection (IMDD). In the operation of a conventional downlink OFDM-PON, each ONU has to perform the demodulation in the physical layer for all the received OFDM frames, regardless the received frames belong to the ONU or not. To improve the ONU's energy consumption efficiency, in this paper, frame identification and clock control modules are introduced into each ONU, where the former is to distinguish whether a received frame belongs to the ONU or not, and the latter is to control the operating clock of the OFDM demodulation module according to the frame identification output. As a result, when non-local frames arrive, the operating clock is set to a low value by the clock control module to deactivate the OFDM demodulation module in order to avoid unnecessary power consumption of the module. Experiments are undertaken in a real-time IMDD OFDM-PON platform, and measured results show that 51% energy consumption of a FPGA chip embedded in the ONU can be saved compared with its conventional counterpart for downlink unicast scenarios.