Author Affiliations
Abstract
1 Department of Information Science and Engineering, Hunan University of Humanities, Science and Technology, Loudi 417000, China
2 School of Physics and Electronics, Hunan Normal University, Changsha 410081, China
To overcome the unbalanced signal-to-noise ratio (SNR) among data-carrying subcarriers (SCs) induced by the imperfect frequency response of optoelectronic devices and various interferences, a channel-independent partial data-carrying SCs precoding (PDSP) method based on orthogonal circular matrix transform (OCT) is proposed and experimentally investigated in an intra-symbol frequency average (ISFA)-enabled discrete multi-tone (DMT) visible light communication (VLC) system. After transmission over 1.9 m free space, at the optimal bias current of 100 mA, the experimental results show that the bit error ratio (BER) performance can be improved by up to an order of magnitude with conventional full data-carrying SCs precoding (FDSP) and PDSP scheme, compared to that without a precoding scheme. Moreover, the BER performance can further be enhanced when the ISFA algorithm with optimal taps is employed. Compared with the FDSP scheme, the proposed PDSP scheme owns a similar BER performance and a significant reduction in required multiplication and addition operations, and it may be a good option to efficiently combat the unbalanced impairments of DMT-VLC transmission systems.
partial data-carrying subcarriers precoding OCT intra-symbol frequency-averaging visible light communication Chinese Optics Letters
2023, 21(2): 020602
1 湖南人文科技学院, 湖南 娄底 417000
2 华南理工大学发光材料与器件国家重点实验室和光通信材料研究所, 广东 广州 510640
采用高温熔融法制备了单掺Tm3+和Tm3+/Ho3+共掺碲酸盐玻璃, 测试了808 nm激光泵浦下玻璃的红外和上转换荧光光谱。 Tm3+/Ho3+共掺碲酸盐玻璃上转换荧光光谱主要由695 nm红光、 544 nm绿光、 474 nm蓝光和740 nm红光四个发光带组成。 通过分析样品的光谱性能和能量转换机制, 发现很少报道的740 nm红光可能是由Tm3+: 1D2 →3F2, 3能级跃迁产生的。 在掺杂0.5 mol％ Tm2O3的样品中添加0.3 mol％ Ho2O3, 695 nm红光、 740 nm红光和474 nm蓝光等上转换发光强度明显增大, 大约分别是单掺0.5 mol％ Tm2O3样品中发光强度的3倍, 2.5倍和14倍。 这些情况说明存在着强烈的Ho3+→Tm3+反向能量传递。 单掺Tm3+碲酸盐玻璃中1D2能级(发射740 nm红光)上的粒子集居主要来源于合作上转换(CU)过程, 而3F2, 3能级(发射695 nm红光)上的粒子集居除了来源于CU过程之外, 还有740 nm红光的发射和1G4能级上部分粒子的无辐射跃迁(1G4→3F2, 3)两条途径, 因此样品中695 nm红光强度明显要大于740 nm红光强度。 通过交叉驰豫作用CR2和CR3以及反向共振能量转移RET2, Tm3+/Ho3+共掺碲酸盐玻璃中Tm3+的1G4能级(发射474 nm蓝光)上的粒子集居数比单掺Tm3+时出现了净增加。 Tm3+的1G4能级上粒子集居数的增加可能进一步强化了该能级的无辐射跃迁、 740 nm红光的发射以及CU过程, 并进而促使Tm3+的3F2, 3能级上的粒子集居。 所以, 当Tm3+/Ho3+共掺碲酸盐玻璃与单掺Tm3+碲酸盐玻璃中掺杂相同浓度的Tm3+时, 前者的红光和蓝光等上转换荧光强度均比后者要大。 本文还研究了Tm3+之间以及Tm3+与 Ho3+之间的交叉弛豫和能量传递等效应, 并进一步探讨了Tm3+与 Ho3+之间的能量转换机制。
碲酸盐玻璃 上转换发光 能量转换 红外 Up-conversion Tm3+/Ho3+ doped Tellurite glasses Energy transfer
