Author Affiliations
Abstract
1 Peng Cheng Laboratory, Shenzhen, China
2 Shanghai Jiao Tong University, State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Electronic Engineering, Shanghai, China
3 University of L’Aquila, Department of Physical and Chemical Sciences, L’Aquila, Italy
We propose a joint look-up-table (LUT)-based nonlinear predistortion and digital resolution enhancement scheme to achieve high-speed and low-cost optical interconnects using low-resolution digital-to-analog converters (DACs). The LUT-based predistortion is employed to mitigate the pattern-dependent effect (PDE) of a semiconductor optical amplifier (SOA), while the digital resolution enhancer (DRE) is utilized to shape the quantization noise, lowering the requirement for the resolution of DAC. We experimentally demonstrate O-band intensity modulation and direct detection (IM/DD) transmission of 124-GBd 4 / 6-level pulse-amplitude modulation ( PAM ) -4 / 6 and 112-GBd PAM-8 signals over a 2-km standard single-mode fiber (SSMF) with 3 / 3.5 / 4-bit DACs. In the case of 40-km SSMF transmission with an SOA-based preamplifier, 124-GBd on-off-keying (OOK)/PAM-3/PAM-4 signals are successfully transmitted with 1.5 / 2 / 3-bit DACs. To the best of our knowledge, we have achieved the highest net data rates of 235.3-Gb / s PAM-4, 289.7-Gb / s PAM-6, and 294.7 Gb / s PAM-8 signals over 2-km SSMF, as well as 117.6-Gb / s OOK, 173.8-Gb / s PAM-3, and -231.8 Gb / s PAM-4 signals over 40-km SSMF, employing low-resolution DACs. The experimental results reveal that the joint LUT-based predistortion and DRE effectively mitigate the PDE and improve the signal-to-quantization noise ratio by shaping the noise. The proposed scheme can provide a powerful solution for low-cost IM/DD optical interconnects beyond 200 Gb / s.
look-up-table digital resolution enhancer quantization noise semiconductor optical amplifier pattern-dependent effect pulse-amplitude modulation Advanced Photonics Nexus
2024, 3(3): 036007
强激光与粒子束
2024, 36(4): 043012
强激光与粒子束
2024, 36(4): 043006
强激光与粒子束
2024, 36(4): 043024
强激光与粒子束
2024, 36(4): 043031
提出并演示了一个光子辅助的集成雷达和通信系统,该系统利用光子辅助拍频在W波段产生毫米波信号。通过将正交相移键控(QPSK)信号编码到线性调频连续波(LFMCW)雷达信号上,实现了传感和通信波形的集成。一体化波形可以通过去啁啾分离通信信号与雷达感知信号,并通过脉冲压缩实现高分辨率感知。实验结果表明,在91 GHz频段内可实现单目标和双目标检测,感知精度约为2.0 cm。此外,成功实现了W波段下2 m、10 m和50 m传输距离的20 Gbit/s高质量无线通信。该系统还适用于各种成分的一体化波形,为高速通信和高分辨率雷达感知融合提供了有效参考。
光通信 通信与雷达感知一体化系统 毫米波通信 脉冲压缩 一体化波形
1 中国科学院空间应用工程与技术中心,北京 100094
2 中国科学院大学,北京 100094
激光通信是近年深空探测领域的研究热点之一。深空激光通信采用脉冲位置调制(PPM)提升通信能量效率,并使用单光子探测器以高效地接收信号。其中,超导纳米线单光子探测器(SNSPD)被广泛认可是最优选择之一。本文分析了SNSPD的死时间和抖动特性,以及高速脉冲信号的拖尾现象,对基于PPM-SNSPD调制探测方式的深空激光通信产生的影响,并计算了SNSPD在该体系下的光子计数特性。基于分析,提出一种偏移补偿保护时隙PPM符号同步算法。相较普通的保护时隙同步算法,所提算法能有效减少PPM-SNSPD体系下的同步误差,提升系统误码率。
自由空间光通信 深空激光通信 脉冲位置调制 单光子探测器 激光与光电子学进展
2024, 61(7): 0706012
Author Affiliations
Abstract
1 College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
2 School of Information and Communications, National University of Defense Technology, Wuhan 430035, China
3 Nanhu Laser Laboratory, National University of Defense Technology, Changsha 410073, China
4 Hunan Provincial Key Laboratory of High Energy Laser Technology, National University of Defense Technology, Changsha 410073, China
High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated. The active polarization control technology based on the root-mean-square propagation (RMS-prop) algorithm is employed to guarantee a linearly polarized output from the system. A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio (PER) of > 11.4 dB. In addition, the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser. The M2 factor of the laser beam at the highest output power is measured to be less than 1.15, indicating a diffraction-limited beam quality. Finally, the amplified laser pulse is temporally compressed to 755 fs with a highest average power of 273.8 W. This is the first time, to the best of our knowledge, that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier.
active polarization control root-mean-square propagation algorithm linearly polarized laser chirped pulse amplification femtosecond laser fiber laser Chinese Optics Letters
2024, 22(4): 041403
Author Affiliations
Abstract
1 Information Materials and Intelligent Sensing Laboratory of Anhui Province, Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education, School of Physics and Opto-electronics Engineering, Anhui University, Hefei 230601, China
2 School of Instrument Science and Opto-electronics Engineering, Laboratory of Optical Fibers and Micro-nano Photonics, Hefei University of Technology, Hefei 230009, China
3 School of Opto-electronic Engineering, Zaozhuang University, Zaozhuang 277160, China
Random lasers are a type of lasers that lack typical resonator structures, offering benefits such as easy integration, low cost, and low spatial coherence. These features make them popular for speckle-free imaging and random number generation. However, due to their high threshold and phase instability, the production of picosecond random lasers has still been a challenge. In this work, we have developed three dyes incorporating polymer optical fibers doped with various scattering nanoparticles to produce short-pulsed random fiber lasers. Notably, stable picosecond random laser emission lasting 600 ps is observed at a low pump energy of 50 µJ, indicating the gain-switching mechanism. Population inversion and gain undergo an abrupt surge as the intensity of the continuously pumped light nears the threshold level. When the intensity of the continuously pumped light reaches a specific value, the number of inversion populations in the “scattering cavity” surpasses the threshold rapidly. Simulation results based on a model that considers power-dependent gain saturation confirmed the above phenomenon. This research helps expand the understanding of the dynamics behind random medium-stimulated emission in random lasers and opens up possibilities for mode locking in these systems.
random laser polymer optical fiber gain-switched laser picosecond pulse Chinese Optics Letters
2024, 22(4): 040603
Author Affiliations
Abstract
1 Applied Physics Division, Soreq NRC, Yavne, Israel
2 Applied Physics Institute, The Hebrew University, The Edmond J. Safra Campus - Givat Ram, Jerusalem, Israel
Here we report on a simple-to-implement and cost-effective approach for laser pulse contrast enhancement, based on the ${\chi}^{(3)}$ nonlinear self-focusing effect. An intentionally induced and gently controlled self-focusing in a thin glass transforms the time-dependent intensity into variation in beam divergence. Followed by a spatial discriminating filter, only the strongly focused fraction traverses the setup, at the expense of efficiency. A numerical model, accounting for the pulse and material parameters via a Gaussian ABCD matrix, provides an estimate for the instantaneous beam waist and transmission efficiency, which enables us to evaluate the resulting contrast enhancement. The estimated contrast enhancement spans between 0.5 and 2.5 orders of magnitude, in conjunction with approximately 25%–90% estimated efficiency, depending on the pulse parameters. In a preliminary experiment we demonstrated the effect with 10s-μJ sub GW regime with approximately 40 $\%$ efficiency and a contrast improvement of more than or equal to 20 dB.
nonlinear optics pulse contrast self-focusing ultrafast laser High Power Laser Science and Engineering
2024, 12(2): 02000e18