查看更多>>摘要：Photonic Hal l effect (PHE) can be realized in the multiple-channel photonic crystal waveguide. By modulating the polarization state of the incident light, the light can propagate in any one or more of the fou r channels of the waveguide, while the light ener g y in the other channels is ver y weak. Its fascinating behavior can be explained by the theory of interference of the two component waves. We believe that ou r results wi l l have important applications in photonic integrated circuits.
查看更多>>摘要：An electrically tunable large aperture liquid crystal (LALC) lens consisting of dual hole-patterned electrodes with different diameters is demonstrated. The proposed LALC lens can realize a tunable focal length and a switchable optical aperture by changing the driving models (DM). The experimental results show that the focal length of the LALC lens ranges from 325 mm to 220 mm when the operating voltage is changed from 24 V to 66 V by DM1, and it varies from 310 mm to 200 mm with the supplied voltages of 24-59 V by DM2. The optical aperture of the LALC lens can be switched between 4 mm-diameter and 5 mm-diameter. Furthermore, the turn-on time is significantly decreased by the over-driving method. Because of its low root mean square (RMS) error (<0.08 A), the LALC lens, as an ideal optical lens, can exhibit excellent imaging performance in the optical imaging system. These results demonstrate that the proposed LALC lens has potential applications in the fields of imaging, biometrics and optical data storage because of its tunable focal length and switchable optical apertures.
查看更多>>摘要：To improve low-latency support of passive optical networks, direct-sequence spread spectrum time division multiple access implements bi-directional byte-interleaved transmission by encoding each bit of a bi-polar sequence with orthogonal chip pattern. Consequently, guard-interval between consecutive up-link bytes can be removed and latency caused by multi-point control protocol interaction can be reduced. However, direct sequence spread spectrum requires bi-polar signaling, which is not possible with direct detection and several solutions exist, such as, biased and differential transmission. In this work, we investigate the performance of direct-sequence spread spectrum time division multiple access with direct detection and also analyze both up-link and down-link situations. Experimental results of transmission over a 20 km dispersion uncompensated link show: The 31-bits direct-sequence reduces required received signal power to -12 dBm and the performance is limited by dark-current. With differential transmission in up-link direction, modified duo-binary has 5 dB better performance than PAM4. Also, in up-link direction, differential transmission has 3 dB better performance than biased transmission.
查看更多>>摘要：We propose a novel optical information hiding system based on complex-amplitude ptychographic encoding and visual cryptography. The information to be hidden is a binary image. In the process of hiding, the binary image is firstly decomposed into two visual keys(one is amplitude, another one is phase) by visual cryptography, and then the two visual keys are synthesized into a complex-amplitude sample. Placing it in the optical path of the ptychography diffraction imaging, a series of overlapping diffraction patterns are collected as the ciphertext. Ciphertext is highly uncorrelated and indecipherable compared to the binary image, resulting in high security. During the extraction process, it is necessary to reconstruct the amplitude and phase of the complex-amplitude sample, that is, two visual keys. Then perform incoherent superposition and image processing on them to obtain a binary image, without complicated optical implementations and any additional computation, resulting in the convenience of extraction. In addition, the extended coding of visual cryptography also further improves the security of the system. Simulation results show that this system is easy to implement, has high security and robustness.
查看更多>>摘要：This paper proposes a secure compressed communication scheme in orthogonal frequency division multiplexing passive optical network (OFDM-PON) based on joint compressed sensing and JPEG coding (JCS-JPEG) and multilevel encryption, with a focus to its application in secure storage and transmission. Specifically, working with the under-sampling data of compressed sensing (CS), we combine the JPEG coding standard to deepen compression into the storage and transmission link while inserting random factors into Deoxyribonucleic Acid (DNA) encryption to improve the security of the physical layer. The rationale behind the joint compression is that the data after CS is suitable for block quantization and entropy encoding methods to compress further, similar to the JPEG encoding. For the compression of multimedia data, we demonstrate that it can achieve a satisfactory reconstruction effect and provide an additional 5 to 8 times compression ratio on images. Moreover, we show that the DCT coefficient encryption and random DNA encryption can be seamlessly incorporated into the encryption in CS through the two dimensions of a 2D-chaotic map, thus realizing secure compression and transmission when under-sampling. The proposed scheme is expected to reduce the computational complexity and storage pressure of light resource-constrained sensors, simultaneously improve bandwidth utilization and sensitive information protection in OFDM-PON.
NSTL
Elsevier