外文翻译---双速MIL-STD-1553B兼容的光纤数据总线

1、A DUAL SPEED, MIL-STD-1553B COMPATIBLEFIBER OPTIC DATA BUSM.S. Blaha. C.H. DeGennaro, S.F. UtleyAT&T Bell Laboratories Whippany, New Jersey 07981AbstractA 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 operati

2、ng 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 a

3、nd newly designed higher speed equipment.IntroductionThe 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

4、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, a

5、nd 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.ApproachThe fiber optic data bus was designed to directly interface with existing 1553B bus controllers and remote terminal h

6、ardware. 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 coupler

7、s. 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 DataFigure

8、 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 replace

9、s. 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 ArchitectureFor 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 ConfigurationFOIUs are connected directly to 1553B I/O ports associated with user equipment, and provide the necessa

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