Reconfigurable Optical Chaotic Logic Operations with Fast Rate of Picoseconds Scale
XU Geliang, XU Jian, KONG Lingli, HUANG Qifeng, QIU Xianting, GUO Yangyang, and CHENG Feng
In order to realize dynamic and reconfigurable optical chaotic logic operations, a specific technical scheme based on Vertical Cavity Surface Emitting Laser (VCSEL) feedback by its own light and linear electro-optic modulation effect has been proposed. The normalized injection current is modulated as logic input, the transverse electric field is modulated as control signal, and the logic output is demodulated by the difference between the average value and the threshold value of the x-polarized light intensity from the output of VCSEL. By transforming the logic operation relationship between control signal and logic input, the system can switch freely among basic logic operations such as NOT, AND, NAND, OR, NOR, XOR and XNOR. When the code width is 600 ps and the noise intensity is as high as 2.75×109, the success probability of the logic operation still equals 1, indicating that the system has good anti-noise performance. And when the noise intensity equals 2.5×109, the success probability always equals 1 if the code width is at least 579 ps. The above results have great reference value for the development of fast and stable combinational logic operation devices.
  • Jun. 22, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 5 174 (2021)
  • DOI:10.3788/gzxb20215005.0506008
Visible DCO-OFDM System Based on LWT
ZHAO Li, DONG Hanghang, and ZHANG Feng
In order to solve the problems of high peak-to-average ratio of traditional orthogonal frequency division multiplexing technology, complex-valued signal structure cannot be directly applied to intensity modulation direct detection system, Lifting Wavelet Transform (LWT) is applied to Orthogonal Frequency Division Multiplexing (OFDM). The orthogonal wavelet basis is selected as the subcarrier. By predicting and updating the signal, the high and low frequencies of the signal are separated. Combined with the multiple reflection channel model of Visible Light Communication (VLC), the DCO-LWT-OFDM system model was established, and the iterative decomposition and renewal reconstruction formulas of LWT-OFDM signals were deduced. The performance of the DCO-LWT-OFDM system was simulated and verified by experiments. Simulation results show that in a 4 m×4 m×3 m indoor space, when the bit error rate of the system is 10-4, the performance of the DCO-LWT-OFDM system is about 5 dB higher than that of the DCO-FFT-OFDM system, and the overall efficiency is improved by 70%. When the system peak-to-average ratio is 10 dB, the value of complementary cumulative distribution function of DCO-FFT-OFDM system is close to 10-1, and the value of complementary cumulative distribution function of DCO-LWT-OFDM system is 0. In the experimental verification, 1 W LED lamp beads were selected to build the point-to-point DCO-LWT-OFDM VLC system on the optical guide, the transmission distance was 20 cm, the system modulation error rate was 11.4 dB, and the reliability could reach 10-4. This paper provides an effective way to improve the transmission rate of visible light communication, reduce the bit error rate and restrain the system PAPR.
  • Jun. 22, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 5 121 (2021)
  • DOI:10.3788/gzxb20215005.0506002
Investigation for Relationship between Sidewall Roughness of Silicon-on-insulator Waveguide and Loss of Guided-mode
WANG Bin, SUN Degui, and SHANG Hongpeng
The optical loss caused by Waveguide Sidewall Roughness (SWR) of Silicon-on-insulator (SOI) is one of the restrictions to the adoptions of silicon photonic integrated circuits. In this paper, the anisotropic SWR of an SOI waveguide is measured by Conformal Laser Scanning Microscope (CLSM) and with introduction of a Three-dimensional (3D) anisotropic SWR, the traditional theoretical model for defining the Optical Propagation Loss (OPL) coefficient, so that a more accurate theoretical model is obtained. Numerical simulations show that the waveguide structure determined Correlation Length (CL) and the SWR have the synchronous effects on the OPL. Fabry-Perot (F-P) cavity modulation resonance output is used to accurately measure the OPL, and the measured values are agreeable with the simulation result, implying the improved model has more believability. For a waveguide with a 4 μm width, when the average horizontal and vertical SWR values are 22 nm and 23 nm, respectively, the simulation results of OPL coefficient for both TE- and TM-mode are 4.5~5.0 dB/cm, while the experimental result is 4.9 dB/cm. Hence, the outcomes and conclusion obtained are very valuable to be referred for research and development of SOI waveguide devices.
  • Jun. 22, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 5 151 (2021)
  • DOI:10.3788/gzxb20215005.0506005
Fabrication and Experiment of a Small-size Anti-bending Optical Fiber
CAO Shanshan, GUO Chaoyang, XU Haitao, YOU Guanglei, LIU Zhizhong, ZHENG Jiajin, and WEI Wei
  • Jun. 22, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 5 112 (2021)
  • DOI:10.3788/gzxb20215005.0506001
A Polyaniline Membrane Micro-nano Fiber Hydrogen Ion Probe
GU Xingchen, LI Lijun, MA Qian, SUN Jiajia, LI Min, SHAO Changsheng, and LÜ Yumeng
A polyaniline film micro-nano optical fiber liquid hydrogen ion concentration probe is proposed, and the hydrogen ion concentration sensing characteristics of this fiber probe are investigated. The sensing part consists of a single-mode fiber, a small-core-diameter fiber and a single-mode fiber pair fusion spliced together, and polyaniline material is coated on the small-core-diameter fiber as a sensitive film. Firstly, a theoretical analysis of the sensing principle of the fiber optic probe and the structure change mechanism of the polyaniline main chain was conducted. Then, the effect of different film thicknesses on the sensing characteristics of the fiber optic probe was verified and analyzed by hydrogen ion concentration sensing experiments. Finally, experimental interference tests on the change of liquid refractive index were completed and the response-recovery time and stability performance of the probe were evaluated. The experimental results show that the main chain structure of polyaniline changes under the action of hydrogen ions. The interference spectrum of the fiber optic probe drifts in the short-wave direction with the increase of hydrogen ion concentration, and the detection range increases with the rise of polyaniline film thickness, while the sensitivity and linearity decrease significantly. The sensitivity of the fiber optic probe is -15.74 nm/mol/L for the hydrogen ion concentration range of 10-6~10-1 mol/L, and the response and recovery time are 25 s and 35 s, respectively. The experiments verify the change of polyaniline film’s optical properties after reacting with hydrogen ions and provide a new method for liquid hydrogen ion concentration detection. This fiber optic hydrogen ion concentration probe also has the advantages of high concrete film strength, simple fabrication, and low cost.
  • Jun. 22, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 5 166 (2021)
  • DOI:10.3788/gzxb20215005.0506007
Intensity Demodulation Technology of FBG Time Division Multiplexing Based on Sagnac Ring
WANG Xiaoli, DONG Bo, CHEN Enqing, and LI Yang
A method of fiber Bragg grating time-division multiplexing intensity demodulation based on Sagnac fiber ring is presented. The time-multiplexing sensing system, consisted of the several FBG gratings with the same central-wavelength, can demodulate the signals by observing the intensity changes of the output spectrum of the FBG gratings. In the signal processing module, the wavelet analysis and Gaussian simulation algorithm are combined to demodulate the system signal together. The experimental results show that the signal-to-noise ratio of the system signal is increased by about 36% from 8.06 dB to 11.7 dB, which effectively improves the anti-interference ability of the system and the detection accuracy for the external parameters. The proposed method effectively increases the number of fiber Bragg grating sensors in the demodulation system with less cost and can be widely applied to various sensor systems or parameter detection systems.
  • Jun. 22, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 5 130 (2021)
  • DOI:10.3788/gzxb20215005.0506003
Low Power Consumption Visible Light Communication Technology Based on Bilevel Pulse Width Modulation
WANG Guifa, GUO Mengyue, GU Jiamei, TANG Min, WEI Zhengjun, WANG Jindong, and WANG Shentao
pulse width modulation technology is proposed. Bilevel pulse width modulation is analyzed in terms of bandwidth requirement, junction capacitance and error performance, and compared with non return to zero on key modulation, pulse position modulation and digital pulse interval modulation.The results show that the two-level pulse width modulation and the non-return-to-zero on-off keying modulation have the same time slot error rate, but the additional power consumption is only M/2 of the non-return-to-zero on-off keying modulation, and M is the modulation order. Although the bilevel pulse width modulation requires higher signal-to-noise ratio compared with pulse position modulation and digital pulse interval modulation, the additional power consumption is only half of that of pulse position modulation and digital pulse interval modulation, and the bandwidth requirement is also less than that of pulse position modulation and digital pulse interval modulation, it has great advantages in power and bandwidth sensitive visible light communication system.
  • Jun. 22, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 5 139 (2021)
  • DOI:10.3788/gzxb20215005.0506004
Hybrid Temperature and Strain Dual-parameter Sensor Based on Fiber Bragg Grating and Multi-mode Interference of Hollow-core Fiber
SHEN Jiaxin, WANG Wei, ZHANG Junying, CHEN Haibin, GUO Zilong, and ZHANG Xiongxing
To solve the measurement problems of fiber-optic strain sensors caused by temperature sensitivity, a hybrid temperature-strain dual-parameter based on fiber Bragg grating and multimode interference of hollow core fiber was proposed. The sensor is composed of a hollow core fiber fused between two single mode fibers, and the inner diameter of the hollow core fiber is smaller than the core of the single mode fibers, besides, on the core of one single mode fiber, near the fiber end, a fiber Bragg grating is pre-written. The hollow core fiber has a length of centimeters, in which, the optical wave is propagating in a multimode form. Combining the different responsitivities of the hollow core fiber and fiber Bragg grating to the temperature and the strain, the two parameters can be simultaneously demodulated by solving of the dual-parameter coupling matrix, and the problem of temperature-strain cross sensitivity of a single fiber Bragg grating or hollow core fiber sensor can be effectively solved. A hybrid fiber Bragg grating- hollow core fiber sensor was fabricated by using of a fiber Bragg grating with a center wavelength of 1 550.172 nm and a hollow fiber of 2.5 cm long and inner diameter of 5 μm. The experiment on the strain and temperature measurement shows temperature sensitivities of 10.530 6 pm/℃ and 1.802 1 pm/℃, strain sensitivities of 0.720 7 pm/με and 1.243 2 pm/με from the hollow core fiber and fiber Bragg grating respectively.
  • Jun. 22, 2021
  • Acta Photonica Sinica
  • Vol.50 Issue, 5 158 (2021)
  • DOI:10.3788/gzxb20215005.0506006
Dynamic Propagation Characteristics of 1.55-μm Wavelength Laser in Rain and Fog Coexisting Weather
Yu Renjiao, Li Zhenhua, Lai Jiancheng, Wang Chunyong, and Wu Zhixiang
Objective The coexistence of rain and fog is a common atmospheric phenomenon in winter. When laser is transmitted in rain and fog weather, the attenuation is not only affected by rain but also by fog. Because of the small rainfall rate, fog attenuation is usually greater than rain. Globally, numerous studies have been conducted on the transmission characteristics of laser in rain and fog individually, but research on laser transmission characteristics in rain and fog coexisting weather is inadequate. To the best of our knowledge, the interaction between raindrops and fog droplets has not been considered. In this study, based on the mechanism of rain clearing fog, we improve the existing models and propose a prediction model of atmospheric attenuation in rain and fog coexisting weather, which dynamically shows the changes of atmospheric attenuation and transmittance with time in rain and fog coexisting weather. We believe that the findings of this study will have reference significance for the estimation and evaluation of atmospheric attenuation in wireless optical communication and related fields.Methods In rain and fog coexisting weather, the precipitation process has a significant effect on fog removal. As fog is removed by raindrops, the scale distribution of fog will change. In this article, we employ the general dynamic equation considering wet deposition to study the dynamic change of fog with the removal of raindrops. Then, we use the lognormal scale distribution model of raindrops and Gamma distribution model of radiation fog and advection fog to calculate the total attenuation of rain and fog after clearing. Further, we employ Lambert-Beer law to reckon the transmittance of laser after a certain distance. Finally, the numerical results are compared with the Monte-Carlo simulation results to verify the rationality of the proposed model to a certain extent.Results and Discussions The rainfall intensity positively correlates with the fog removal effect. Since the rainfall in rain and fog coexisting weather is small, the attenuation of fog gradually decreases with the removal of fog by rain (Fig. 1). When the rainfall rate is 1 mm/h, the transmittance of advection fog tends to be stable after 5 h of rainfall, whereas, the radiation of fog takes a longer time (Fig. 2). The water content of advection fog is higher than that of radiation fog, so the albedo of advection fog is higher than that of radiation fog. Owing to the obvious removal of advection fog by rain, the density of advection fog decreases, the proportion of raindrops per unit volume increases, the absorption increases, the scattering weakens, and the albedo of particle swarm increases (Tables 4 and 5). When the transmission distance is 1000 m and transmittance is less than 5%, the transmittance calculated using the Monte-Carlo method is larger than that calculated using the Lambert-Beer law, and vice versa in other cases.Conclusions In this article, we employed the lognormal scale distribution model of raindrops and Gamma distribution model of radiation fog and advection fog to study dynamic change of fog with raindrop removal using the general dynamic equation considering wet deposition. Based on the basic principle of atmospheric attenuation, the attenuation of laser propagation in the atmosphere changes with the fog scale distribution model. Because most of the radiation fog droplets are medium-sized aerosols, they are difficult to be wet removed by rainfall, so the transmittance increases slowly with time. The droplet size of the advection fog is large and quickly removed in the case of moderate and heavy rain, and then the transmittance is at a fixed value. Through Monte-Carlo simulation analysis of laser transmission in the atmosphere, in the case of small attenuation, the photon moving step is larger, the scattering times in a fixed distance range are less, the particles hardly reach the receiving plane after the collision, and the calculation results of the Monte-Carlo method are minute. With the increase in particle number density and transmission distance, the number of scattering increases, and the transmittance calculated using the Monte-Carlo method is slightly higher than that calculated using the Lambert-Beer law. Over time, owing to the removal of fog by rainfall, the droplet number density decreases, and the numerical difference between the two methods increases.
  • Jun. 15, 2021
  • Chinese Journal of Lasers
  • Vol.48 Issue, 13 1306002 (2021)
  • DOI:10.3788/CJL202148.1306002
Technology for Integrating Space Object Multidimensional Detection and Laser Communication
Xu Miao, Shi Haodong, Wang Chao, Liu Zhuang, Fu Qiang, Li Yingchao, Dong Keyan, and Jiang Huilin
Significance Humans need to observe various targets, including space, air, ground, and sea targets. Space targets include satellites, space debris, ballistic missiles, and hypersonic vehicles. Air targets include aircraft, airships, and small craft. Ground and sea targets include surface ships and ground vehicles. The past 20 years have seen an average of 12 collisions between space debris and space payloads every year. In addition, foreign ships and aircraft frequently invade our territorial waters and airspace and repeatedly spy on the activities in our important places. Therefore, the detection, identification, early warning, interception, and even striking of these abovementioned targets are an important and urgent research topic presently.Multidimensional detection based on combined polarization detection, spectrum detection, and other optical technologies can provide the shape, material, location, and other information of the target simultaneously, effectively improving the dimensions and accuracy of space target information. At the same time, with the help of space laser communication, massive information can be quickly and safely transmitted to orbiting satellites and management departments, which can provide the decision-making basis for further disposal in time.Progress In terms of space target detection, the United States has the largest and highest level of space target detection systems, followed by Russia. Europe starts late, but their system has rapidly developed in recent years. China is the latest to start and mainly performs ground-based observations. However, in recent years, China has conducted space-based observation tests and devised various detection methods, including photoelectric observation, radar monitoring, radio detection, and other detection methods.In multidimensional detection, polarization detection technology has the advantages of highlighting the target, penetrating smoke, and identifying the truth and falsehood of the target. Spectral detection technology can distinguish the physical characteristics of the target material. Intensity detection technology has high light energy utilization and resolution, but it also has its own weaknesses. The information obtained by intensity detection is less and easily disturbed by the environment. Moreover, loss of the receiving energy and decrease in imaging resolution can be introduced by polarization detection. Table 1 gives a comparison of the advantages and disadvantages of several detection technologies. Therefore, combining the three abovementioned detection methods to give full play to their own characteristics and advantages helps not only in overcoming the difficulties of space target detection but also in greatly improving the overall detection performance. Changchun University of Science and Technology conducted a multidimensional oil species differentiation test; the test results are shown in Figure 3.The X2000 flight terminal was developed in the United States from the aspect of integrating detection, imaging, and communication. It can realize the functions of bidirectional communication, bidirectional laser ranging, and high-resolution imaging. The United States also proposed the ACLAIM scheme, in which the laser communication antenna and space camera sharing a front telescope and a detector array is employed as the acquisition and tracking system and an imaging receiver. In China, satellite payloads were developed toward the direction of multifunctionality and integration to increase the system function and reduce the volume, mass, and power consumption of the load. This study proposes a new scheme for space target detection and information transmission, which integrates the four functions of laser ranging, spectral polarization imaging, super-resolution imaging, and laser communication into one. The system design and development were performed. Figure 17 depicts the system composition.Conclusions and Prospect In summary, we introduce herein the research status of the technology of multidimensional detection and laser communication integration for space objects and summarize the principle, characteristics, and application of the related technologies. The preliminary research results of our team in the related aspects are as follows: 1) for space object multidimensional detection, the detection mechanism is studied, and a large aperture and a wide field-of-view space-based telescope super-resolution imaging optical system is designed; 2) a prototype of simultaneous and time-sharing polarization imaging detection for complex space targets is developed; 3) ground and sea surface tests are conducted. As regards space laser communication, the optical principle of one-point to multipoint simultaneous space laser communication is proposed for the first time by our team at home and abroad. Accordingly, a principal prototype is developed and a demonstration test is performed. For detection and communication integration, the urgent need for this space security technology is expounded, and the system design idea and a specific implementation scheme are given.Our country should further perform an in-depth research on ultra-high-resolution imaging, full-polarization and hyperspectral multidimensional detection, space- and ground-based combined optical detection, multi-to-multi space laser communication, and integrated laser and microwave network communication to solve the problems of the incomplete detection of low-orbit targets, unclear detection of high-orbit targets, slow response of the dynamic target, and difficulties in numbering space objects, which can provide a technical guarantee for the space security in China.
  • Jun. 11, 2021
  • Chinese Journal of Lasers
  • Vol.48 Issue, 12 1206002 (2021)
  • DOI:10.3788/CJL202148.1206002