外文翻译---双速MIL-STD-1553B兼容的光纤数据总线

A DUAL SPEED, MIL-STD-1553B COMPATIBLE FIBER OPTIC DATA BUS M.S. Blaha. C.H. DeGennaro, S.F. Utley AT&T Bell Laboratories Whippany, New Jersey 07981 Abstract A demonstration system of a dual speed, fiber optic data bus is described. This work is based on a previously described concept (1) which envisioned a data bus populated with MIL-STD-1553B avionic components which evolve as equipment is upgraded to higher data rates. The approach described herein provides for the coexistence of bus nodes operating at 1 Mb/s, and 20 Mb/s, on a single fiber bus medium. The 1 Mb/s interface of each node is 1553B compatible, making use of readily available hardware and software. Both existing, 1 Mb/s 1553B compatible interfaces and new equipment operating at 20 Mb/s have been shown to work simultaneously on the single bus structure. The design provides a sound, low-risk method for transitioning from current 1Mb/s equipment to a unified bus structure incorporating both existing 1553B compatible components and newly designed higher speed equipment. Introduction The AT&T Fiber Optic 1553/MSDRT Data Bus provides an efficient means of improving the data handling capabilities of the 1553B data bus. Through the use of fiber optics and high speed digital multiplexing techniques, a single fiber optic bus can provide both 1 Mb/s and 20 Mb/s transmission capability when supported by 1553B bus hardware. The 20 Mb/s operation is based on the Multiple Speed Data Rate Transmission (MSDRT) concept, which involves multiplexing 20 Mb/s data with standard 1553B protocol in a manner which is invisible to 1 Mb/s users. This dual-speed capability provides retrofit high-speed capability to existing systems based on 1553B, and allows for graceful system growth in the event of system upgrades. A dual speed single fiber transmission bus was chosen over an approach using separate busses for 1 Mb/s transmission and for higher speed transmission because the single fiber bus approach is more reliable, less expensive, and lighter weight. The fiber optic bus is compatible with 1553B hardware, application and protocol software, and error handling routines, resulting in reduced cost and schedule impact for future technology upgrades. In addition, the use of fiber optics offers inherent immunity to electro-magnetic interference, RF interference, electro-magnetic pulses, and is non-radiating. Approach The fiber optic data bus was designed to directly interface with existing 1553B bus controllers and remote terminal hardware. This was done to take advantage of existing technology and thereby reduce development time and cost. Operational control and error handling routines of the bus were accomplished by the 1553B application and protocol software. The bus is configured as a common point broadcast network capable of supporting up to 31 nodes. It is composed of Fiber Optic Interface Units (FOIUs), and an optical bus structure consisting of fiber optic cables, connectors, and dual-redundant passive star couplers. The 20Mb/s operation is based on the MSDRT concept, which involves the multiplexing of 20Mb/s Manchester encoded data in place of 1553B data words. The 20Mb/s transfers are initiated whenever the bus controller requests a transfer from one 1553B user having high-speed add-on circuitry, to another similarly configured user. Figure 1 illustrates the format used in the demonstration system when inserting the 20Mb/s data into the 1Mb/s data bits. Figure 1. Message Containing High-Speed Data Figure 2 depicts the basic architecture of the 1553B MSDRT Data Bus. Each FOIU has an optical output and optical input, which are connected via fiber to the star coupler. FOIU outputs are connected to inputs of the transmissive star coupler, and the optical signal is distributed to all of its outputs. Each of the star couplers outputs are subsequently connected by fiber back to the FOIUs inputs. This effectively forms an optical broadcast bus, which is identical in function to the 1553B bus it replaces. A transmissive star coupler provides a passive transmission path having an adequate optical loss characteristic and minimal impact on system optical dynamic range requirements. Figure 2. Fiber Optic Network Architecture For purposes of increased reliability, the 1553B standard requires that the bus consist of dual-redundant transmission channels. As a consequence, the fiber optic 1553Bl MSDRT Data Bus was configured as a dual-redundant system, as represented in Figure 3. All FOIUs actually consist of two separate channels, labeled A and B in the figure, each having a separate 1553B interface connection, and each having optical connections to separate star couplers. Figure 3. Dual-Redundant Fiber Optic 15638/20-Mbit Bus Configuration FOIUs are connected directly to 1553B I/O ports associated with user equipment, and provide the necessary translation of tri-level 1553B signal format to the bi-level optical format. In addition, the FOIU provides the optical transceiver function, which transmits and receives the optical signals on the fiber optic bus structure. This makes it possible to retrofit any system interconnected by a 1553B electrical bus with a fiber optic 1553B bus by merely replacing the wire portion of the bus with FOIUs and the optical bus structure, The FOIUs are designed to handle both l Mb/s and 20Mb/s communication, or just 1Mb/s transfers, depending on their application in the system. The demonstration system was developed as a direct replacement for the wire portion of any existing 1553B bus. This required that the fiber optic bus interface directly with any 1553B I/O connector and be compatible with any legitimate 1553B interface level. In addition, the high-speed 20Mb/s test units were designed to be operable with any 1553B device on the bus without causing disruption. A system configuration diagram of the fiber optic bus system is shown in Figures 3 and 4. Figure 3 illustrates the system with two low-speed FOIUs singled out, while Figure 4 depicts what could be the same system, but with the high- speed test set specifically illustrated. Figure 4. Fiber Optic Bus Configuration Showing High-Speed Test Set Demonstration System Fiber Optic Bus Hardware The demonstration system fiber optic bus structure was realized using readily available fiber optic components. A single bus structure was made up of connector fiber optic cables and a 1616 port transmissive star coupler (expansion to a 32 port coupler is also considered to he feasible). The FOIUs housed optical transmitters, optical receivers, low-speed logic and level-shift circuit boards, and where employed, the high-speed transmitter and receiver logic. In addition the units contained their own power supplies. These units were mounted on the exterior cabinetry of user equipment being demonstrated, and hooked directly into the 1553B I/O connector. Each FOIU contained two logic boards, each serving one of the dual-redundant channels. Circuits were realized using Small Scale Integrated Transistor-Transistor Logic (SSI ITL) logic chips and discrete components. Mounted on each of these boards was an optical transmitter and an optical receiver. Translation of this design to smaller versions such as a single SEM-E Module is feasible. The optical transmitter chosen for this application was a high-radiance light emitting diode (LED).The diode was operated at less than full output, launching -5.5 dBm (average) optical power into 100 micron core fiber. The dual speed optical receiver was packaged in a module measuring 3 1.5 0.5 for mounting onto the logic and level-shift board. This burst-capable device, developed by AT&T, as a sensitivity of approximately -34 dBm (average) for 10 - Bit Error Rate (BER), and uses a simplified edge detection technique. Highly stable operation over a temperature range from -55C to +85 has been demonstrated. The fiber optic cable assemblies were fabricated using lengths of avionic fiber optic cable connectorized with the AT&T biconic connector. The cable contains 1001140 micron graded index fiber, and has been used in production AVS/B Harrier fighter aircraft. Commercial 1616 port transmissive star couplers installed with biconic couplers were purchased. The input to output- port loss exhibited by the star coupler was 13.5 dB5 dB of loss. High-speed Test Set The high-speed test set was designed to prove the feasibility of the MSDRT Concept. As the avionics used in the bus demonstration system consisted only of low-speed equipment associated with the 1553B bus, a tester was designed to exercise the high-speed FOIUs. The test set consists of an FOIU containing a high-speed receiver board, an FOIU containing a high-speed transmitter board, and a high-speed tester, as indicated in Figures 4 and 5. During operation, the high-speed transmitter and receiver are associated with a remote terminal and the bus controller, respectively. The function of the tester is to generate the 20Mb/s pseudo-random words to be transmitted by the FOIU containing the high-speed transmitter circuitry. High- speed data is actually transmitted when its associated 1553B remote terminal is commanded by the bus controller to send. The high-speed receiver associated with the bus controller receives the high-speed words, sends the high-speed data to the tester for verification and sends the bus controller a sequence of false words to maintain the appearance of ordinary bus operation. The tester makes a bit-for-bit comparison of the high speed data transmitted over the bus with the data received. The number of complete message transfers is displayed on the face of the tester as well as a count of any errors detected. The message transfer sequence between the components making up the high-speed test set is illustrated in Figure 5. Figure 5. Single Direction 20 Mb/s Data Transfer Sequence from Remote Terminal to Bus Controller Optical Power Budget The optical power budget for the fiber optic bus system is tabularized in Table 1. The expected typical values were derived from quoted manufacturers specifications. Expected worst case entries take into account component aging and temperature dependencies from -55 to +85 . The values listed in the last column were the results of measurements taken on both channels of 13 prototype units. Round-trip optical loss measurements were taken by connecting a source to the fiber normally connected to an FOIU output and measuring the return signal strength on the fiber normally connected to the FOW input. Consequently, this measurement includes losses due to four connectors. 100 ft. of fiber optic cable, and the star coupler. Table 1. Prototype Optical Power Budget 双速 MIL-STD-1553B 兼容的光纤数据总线 摘要 一个示范系统的双速度 ,光纤数据总线进行了描述。它主要是基于先前的概念进行工作的，这种概念想象数据总线是由 MIL-STD-1553B 总线的航空组件组成的，这种航空组件可随着设备升级为更高的数据率。 这种方法的描述，在这个方面提供了用单一的光纤总线为媒介，使总线节点在 1 Mb/s 和 24 Mb/s 并存运行，每一个 1 Mb/s 的接口是在 1553B 总线上兼容的，并且可以利用现成的硬件和软件，目前已经证实， 1 Mb/s 的 1553B 总线兼容接口和 20Mb/s 的新操作 设备可以同时工作在单总线结构上，这种设计为从目前 1 Mb/s 的设备过渡到一个合并了现存兼容的 1553B 总线和最新更高速度的一种统一的总线结构提供了一种合理的，低风险的方法。 介绍 AT&T 光学纤维的 1553/MSDRT 数据总线提供了一种有效的手段去提高 1553B数据总线的数据的处理能力，通过使用光学纤维和高速数字复用技术， 1553B 总线硬件支持的单根光纤总线可以提供 1Mb/s 和 20Mb/s 的传输能力。 20Mb/s 的操作基于多种速度数据率的传输概念，其中涉及多路复用 20Mb/s数据和标准 1553B协议在一起， 其方式对 1Mb/s 用户是不可见的。这种双速能力在 1553B 的基础上可以对现有的系统提供高速改造的能力，并且允许系统升级而变的更好。 一个双速度单纤维传输总线被选中了，由于它使用了分离的总线为 1Mb/s 传输和更高的速度传输 ,因为单纤维总线的方法更可靠 ,价格也不太贵 ,重量更轻的。光纤技术的总线可以兼容 1553B 总线的硬件，应用，协议软件和常规的错误处理，这使得降低了成本和进度，对未来技术的升级有很大的影响，另外，使用光纤对电磁干扰、射频干扰、电磁脉冲具有固有的免疫能力，既抗辐射。 方法 光纤数据总线接口被设计来 直接与现有 1553B 总线控制器和远程终端的硬件连接。这样做的目的是利用现有的技术 ,因而减少开发时间和成本。 总线的操作控制和错误处理是由 1553B 的应用和协议软件完成的。 总线配置成了一个可以支撑 31 个节点的共同广播网络， 它由光纤接口单元(FOIUs),和一种光学总线结构组成的，这种光学总线包含有光纤电缆、连接器和双冗余星型耦合器。 20Mb/s 的操作是基于 多种速度数据率的传输 的概念，涉及到多种 20Mb/s 的曼彻斯特码代替 1553B 的数据字。每当总线控制要求传输从一个有着高速附加电路的 1553B 到到另外一个有着 相同配置的用户时， 20Mb/s 的传输的便会开始。图 1 说明了当一个 20Mb/s 的数据嵌入到 1Mb/s 数据位中时，一个典型的系统所用的格式。 图 1 包含高速数据的消息 图 2 描述了 1553B 多种速度数据率 的数据总线的基本结构，每一个光纤接口单元都有一个光纤输入和光纤输出，通过光纤连接到星型耦合器上。光纤接口单元输出连接到了传输星型耦合器的输入，并且光信号分到所有的输出。每一个星型耦合器的输出被随后连接回光纤接口单元的输入。这就有效地形成了一个光广播总线，其相同的功能由 1553B 总线来代替。一个传输的星型耦合器 提供了有着适当的光学特性和最小损失影响，对系统的光学动态范围的要求的一个被动传输路径。 图 2 光学网络体系结构 为了提高可靠性的目的， 1553B 总线基准要求总线是由双冗余通道构成的，结果，光纤 1553B 的多数据速率传输数据总线配置成为了一个双冗余系统，例如图 3.所有的光纤接口单元实际上包含这两种分离的通道，在图中标记为 A 和 B，每一种都已一个分离的 1553B 接口的连接方式，每一种都有光纤连接的分离星型耦合器。 图 3 双冗余光纤 15638/20Mbit 的总线配置 光纤接口单元是直接连接到 1553B 的输 入输出端口的与用户相关的设备，并提供了必要的三电平的 1553B 信号格式和双层的光学格式的转化。此外，光纤接口单元提供了光收发功能，可以中光纤总线结构上传输和接收光学信号。这就使得它可以改造由 1553B电气总线的光纤 1553B总线仅仅通过代替总线上光纤接口的电线部分和光总线结构互联的任何系统，光纤接口单元设计是用来处理 1Mb/s和 20Mb/s 两者之间的通讯，或者只有 1Mb/s 的传输，取决于他们应用的系统。 作为任何现存的 1553B 总线的电线部分直接的替代物，示范系统是非常成熟的。这就要求光纤总线接口直接可以和 任何 1553B 的 I/O 连接器连接，而且可以与任何合法的 1553B 接口电平相适应。此外，高速 20Mb/s 试验装置在设计上可以操作任何总线上的 1553B 装置，而不会造成破坏。一个光纤总线系统的系统配置图如图 3 和图 4 所示。图 3 所示的为系统的两种低速光纤接口单元信号输出，而图 4 描述的可能是同一系统，但用的是高速测试装置来详细描述的。 图 4 光纤总线配置展示