Visible light communication has advantages such as high speed, broadband, green, safety, and low cost. Moreover, visible light communication is not subject to electromagnetic interference, so it is useful in a wide range of application scenarios such as aviation, hospitals, and mines. However, due to the limited spectrum and coverage provided by a single LED, multiple LED coverage is adopted in the indoor layout to provide seamless connection, which also brings spectrum interference in overlapping areas. This paper proposes an indoor visible light interference suppression method based on the backward forward markup (BFM) algorithm. This method not only solves the problem of spectral interference, but also improves throughput while ensuring user fairness. The simulation results show that the BFM algorithm has brought significantly improvements in various aspects, with system throughput increased by 75% and fairness factor increased by 0.3.
KEYWORDS: Telecommunications, Data communications, Design and modelling, Computing systems, Optical fibers, Data transmission, Data conversion, Optical communications, Data processing, Signal processing
Aiming at the characteristics of the self-designed and developed Fiber Tree Bus (FTB) terminal, such as more terminals, more interactive data and various node communication protocols, an intelligent data monitoring terminal is designed by using FPGA and QT software of host computer, a high-speed data transmission system is constructed, which is used to monitor and locate the data transmitted on the optical fiber bus. The system is divided into data transmission module, data analysis module, data transmission module receiving all data flow on fiber data bus, data analysis module caches all data, abnormal location. The test results show that the bus terminal satisfies the requirement of monitoring all terminal nodes on the self-designed FTB system, and the system runs RS422, gigabit network, CAN and other communication data. The monitoring terminal can receive all communication data, can locate the abnormal condition of each node, and the system runs smoothly.
Optical fiber bus technology is an important research direction in communication systems of electronic devices in special vehicle platforms. According to the requirements for communication quality between devices in special vehicle platforms, an optical fiber bus based on gigabit passive optical network topology is proposed. A data cache-based predictive weighted interpolated polling dynamic bandwidth allocation method is presented and investigated for the optical fiber bus’s upstream bandwidth allocation. The network controller establishes a weighted buffer area for the communication requirements in the polling period according to the type and data volume of the network terminal (NT) data stream and dynamically allocates the bandwidth of each optical NT to better meet the communication requirements for different data within the special device platform. Verification is done by means of OPNET software simulation and the establishment of a NT simulation test system in the laboratory. This proves that the proposed dynamic bandwidth allocation algorithm can reduce the end-to-end delay of RS422 port data by more than 50% and meet the Ethernet and controller area network port data delay requirements.
KEYWORDS: Optical fibers, Data transmission, Data communications, Time division multiplexing, Optical communications, Optical networks, Field programmable gate arrays, Passive optical networks, Fiber optic communications, Control systems
Passive Optical Network (PON), which possess the advantages of high efficiency, high speed and high bandwidth utilization, is a type of fiber channel technology that acquires the most concern. As a type of key technology in military weapon electronic system, the target of fiber channel data bus is to offer actual-time, high-speed and reliable communication link between instruments. In this article, a type of fiber channel data bus, which is based on PON topology, is raised and elaborated. The elaboration is concentrated on the designation of the topology and protocol used in the fiber channel data bus. On this basis, the research emphasis is the upstream Media Access Control (MAC) layer in the Network Terminal (NT) of the fiber channel data bus which is designed. Firstly, the upstream synchronization method and frame structure in GPON standards are analysed. Then, the upstream MAC layer control is actualized through Xilinx FPGA devices.
This paper first briefly describes the transport protocol, topology, technical characteristics and application status of the typical military electronic system MIL-STD-1553B bus. With respect to defects such as the bus bandwidth shortage, limited fault tolerance and complicated maintaining, this paper proposes a PON architecture based bus-type optical fiber data bus (FTB) technology with high bandwidth, low latency and strong fault tolerance. This paper mainly studies the bus topology based on the passive optical network (PON) architecture, the physical layer design based on burst mode laser drive circuit (BM-LDD) as well as the digital burst automatic power control circuit, and the design based on multi-point control protocol (MPCP) of time-division response mode. The designed optical fiber bus provides real-time, high-speed and highly reliable communication links for information exchange (video, audio, radar, distributed sensor data, etc.) between various electronic systems of military weapons. It can also accumulate technology for engineering application of optical fiber data bus technology.
In the indoor visible light communication (VLC) system, the light source has the dual function of illumination and communication. Due to the different size of indoor space and indoor facilities, it will inevitably lead to different indoor light power distribution. In order to achieve the optimal communication effect, the layout of the light source must be reasonably designed so that the receiving power distribution is relatively uniform on the same horizontal plane in the room. The current layout methods are mostly based on the square plane three-dimensional space, while the layout methods of the rectangular plane three-dimensional space are rarely studied. In this paper, a room with size 5m×4m×3m is used as a model. Firstly, according to the shock response principle, the optimal layout of four LED lights is obtained through theoretical calculations, so that the received light power fluctuation in the z=h plane in this room is minimized. Then, according to a set of simulation parameters, the theoretical optimal layout with the minimum fluctuation of receiving optical power in the h=0.75m plane in the room is calculated, and then Matlab is used to simulate the received optical power distribution of the plane under different layouts. The simulation results are consistent with the theoretical calculations. Finally, the illumination distribution under the optimal layout is calculated to verify that the designed optimal layout meets the international illumination standards. The light source layout model designed in this paper not only meets the illumination standards, but also ensures the reliability of communication. It provides an optimization method for the layout of indoor visible light communication LED light source.
KEYWORDS: Data communications, Telecommunications, Fiber optics, Data transmission, Interfaces, Optical communications, Systems modeling, Optical fibers, System integration, Network architectures
A new kind of fiber optic data bus (fiber tree bus, FTB) is presented, mainly aiming at some defects of available standard bus, which is lack of real-time performance, has no information interactive transmission index, and uncontrollable transmission delay when it is applied in high bandwidth, distributed real-time information transmission and interactive conditions. The internal working mode, tree topology and Transfer protocol of FTB are designed. The main technical characteristics and real-time transmission performance of FTB are introduced in details. A photoelectric information transmission system has been established based on FTB, to meet the application requirements of the military vehicle-borne photoelectric system. It can access and transmit a variety of communication data at the same time, such as Gigabit Network, CAN, RS232, RS485, RS422, SDI, etc. The compared results of analysis and test show that the new bus system is capable of transferring a various types of real-time information. The characteristics and advantages of FTB application are summarized finally.
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