外文翻譯---雙速MIL-STD-1553B兼容的光纖數(shù)據(jù)總線

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 雙速 MIL-STD-1553B 兼容的光纖數(shù)據(jù)總線 摘要 一個示范系統(tǒng)的雙速度 ,光纖數(shù)據(jù)總線進行了描述。它主要是基于先前的概念進行工作的，這種概念想象數(shù)據(jù)總線是由 MIL-STD-1553B 總線的航空組件組成的，這種航空組件可隨著設(shè)備升級為更高的數(shù)據(jù)率。 這種方法的描述，在這個方面提供了用單一的光纖總線為媒介，使總線節(jié)點在 1 Mb/s 和 24 Mb/s 并存運行，每一個 1 Mb/s 的接口是在 1553B 總線上兼容的，并且可以利用現(xiàn)成的硬件和軟件，目前已經(jīng)證實， 1 Mb/s 的 1553B 總線兼容接口和 20Mb/s 的新操作 設(shè)備可以同時工作在單總線結(jié)構(gòu)上，這種設(shè)計為從目前 1 Mb/s 的設(shè)備過渡到一個合并了現(xiàn)存兼容的 1553B 總線和最新更高速度的一種統(tǒng)一的總線結(jié)構(gòu)提供了一種合理的，低風險的方法。 介紹 AT&T 光學纖維的 1553/MSDRT 數(shù)據(jù)總線提供了一種有效的手段去提高 1553B數(shù)據(jù)總線的數(shù)據(jù)的處理能力，通過使用光學纖維和高速數(shù)字復(fù)用技術(shù)， 1553B 總線硬件支持的單根光纖總線可以提供 1Mb/s 和 20Mb/s 的傳輸能力。 20Mb/s 的操作基于多種速度數(shù)據(jù)率的傳輸概念，其中涉及多路復(fù)用 20Mb/s數(shù)據(jù)和標準 1553B協(xié)議在一起， 其方式對 1Mb/s 用戶是不可見的。這種雙速能力在 1553B 的基礎(chǔ)上可以對現(xiàn)有的系統(tǒng)提供高速改造的能力，并且允許系統(tǒng)升級而變的更好。 一個雙速度單纖維傳輸總線被選中了，由于它使用了分離的總線為 1Mb/s 傳輸和更高的速度傳輸 ,因為單纖維總線的方法更可靠 ,價格也不太貴 ,重量更輕的。光纖技術(shù)的總線可以兼容 1553B 總線的硬件，應(yīng)用，協(xié)議軟件和常規(guī)的錯誤處理，這使得降低了成本和進度，對未來技術(shù)的升級有很大的影響，另外，使用光纖對電磁干擾、射頻干擾、電磁脈沖具有固有的免疫能力，既抗輻射。 方法 光纖數(shù)據(jù)總線接口被設(shè)計來 直接與現(xiàn)有 1553B 總線控制器和遠程終端的硬件連接。這樣做的目的是利用現(xiàn)有的技術(shù) ,因而減少開發(fā)時間和成本。 總線的操作控制和錯誤處理是由 1553B 的應(yīng)用和協(xié)議軟件完成的。 總線配置成了一個可以支撐 31 個節(jié)點的共同廣播網(wǎng)絡(luò)， 它由光纖接口單元(FOIUs),和一種光學總線結(jié)構(gòu)組成的，這種光學總線包含有光纖電纜、連接器和雙冗余星型耦合器。 20Mb/s 的操作是基于 多種速度數(shù)據(jù)率的傳輸 的概念，涉及到多種 20Mb/s 的曼徹斯特碼代替 1553B 的數(shù)據(jù)字。每當總線控制要求傳輸從一個有著高速附加電路的 1553B 到到另外一個有著 相同配置的用戶時， 20Mb/s 的傳輸?shù)谋銜_始。圖 1 說明了當一個 20Mb/s 的數(shù)據(jù)嵌入到 1Mb/s 數(shù)據(jù)位中時，一個典型的系統(tǒng)所用的格式。 圖 1 包含高速數(shù)據(jù)的消息 圖 2 描述了 1553B 多種速度數(shù)據(jù)率 的數(shù)據(jù)總線的基本結(jié)構(gòu)，每一個光纖接口單元都有一個光纖輸入和光纖輸出，通過光纖連接到星型耦合器上。光纖接口單元輸出連接到了傳輸星型耦合器的輸入，并且光信號分到所有的輸出。每一個星型耦合器的輸出被隨后連接回光纖接口單元的輸入。這就有效地形成了一個光廣播總線，其相同的功能由 1553B 總線來代替。一個傳輸?shù)男切婉詈掀?提供了有著適當?shù)墓鈱W特性和最小損失影響，對系統(tǒng)的光學動態(tài)范圍的要求的一個被動傳輸路徑。 圖 2 光學網(wǎng)絡(luò)體系結(jié)構(gòu) 為了提高可靠性的目的， 1553B 總線基準要求總線是由雙冗余通道構(gòu)成的，結(jié)果，光纖 1553B 的多數(shù)據(jù)速率傳輸數(shù)據(jù)總線配置成為了一個雙冗余系統(tǒng)，例如圖 3.所有的光纖接口單元實際上包含這兩種分離的通道，在圖中標記為 A 和 B，每一種都已一個分離的 1553B 接口的連接方式，每一種都有光纖連接的分離星型耦合器。 圖 3 雙冗余光纖 15638/20Mbit 的總線配置 光纖接口單元是直接連接到 1553B 的輸 入輸出端口的與用戶相關(guān)的設(shè)備，并提供了必要的三電平的 1553B 信號格式和雙層的光學格式的轉(zhuǎn)化。此外，光纖接口單元提供了光收發(fā)功能，可以中光纖總線結(jié)構(gòu)上傳輸和接收光學信號。這就使得它可以改造由 1553B電氣總線的光纖 1553B總線僅僅通過代替總線上光纖接口的電線部分和光總線結(jié)構(gòu)互聯(lián)的任何系統(tǒng)，光纖接口單元設(shè)計是用來處理 1Mb/s和 20Mb/s 兩者之間的通訊，或者只有 1Mb/s 的傳輸，取決于他們應(yīng)用的系統(tǒng)。 作為任何現(xiàn)存的 1553B 總線的電線部分直接的替代物，示范系統(tǒng)是非常成熟的。這就要求光纖總線接口直接可以和 任何 1553B 的 I/O 連接器連接，而且可以與任何合法的 1553B 接口電平相適應(yīng)。此外，高速 20Mb/s 試驗裝置在設(shè)計上可以操作任何總線上的 1553B 裝置，而不會造成破壞。一個光纖總線系統(tǒng)的系統(tǒng)配置圖如圖 3 和圖 4 所示。圖 3 所示的為系統(tǒng)的兩種低速光纖接口單元信號輸出，而圖 4 描述的可能是同一系統(tǒng)，但用的是高速測試裝置來詳細描述的。 圖 4 光纖總線配置展示