Fiber Optic Media Research Articles

Distributed flight control system using fiber distributed data interface (FDDI)

The design of fault-tolerant distributed control systems is discussed. The application described is a generic flight control system (FCS) for a fighter aircraft. The system is designed for high redundancy and expandability to meet various requirements. The communication network is based on the fiber distributed data interface (FDDI), which provides a high level of electromagnetic interference resistance and reliability. The choice of fiber optic media also provides an extremely high bandwidth and tremendous growth capability for future communications needs. This study is not specific to FDDI or flight control systems. The methods and configurations presented should be applicable to many real-time control implementations. >

Real-time fiber optic network for an integrated digital protection and control system

The authors present a real-time network using an optical-fiber transmission line and implement the prototype network system for a proposed integrated digital protection and control system. A single network structure is investigated which supports both protection and control functions. It realizes high-speed communications among the power equipment. As a communication protocol the IEEE 802.4 token passing bus protocol with fiber-optic medium is employed, taking substation environments into account. Two implementation schemes for the communication scheme are suggested which are based on the IEEE 802.4 specifications. An allocation method is presented for setting the network parameter and some performance indices are analyzed. Through the experiments, it is shown that the proposed prototype network system satisfies the necessary requirements in substations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An FDDI overview: Some questions answered

The Fiber Distributed Data Interface, a standard specially designed for use with fiber optic media, is based on the X3T9.5 ANSI standard. The FDDI network uses a dual counter rotating ring topology which guarantees reliability, availability, and security. Transmitting over fiber optic media, FDDI provides a throughput of 100 Mb/s and allows a large distance between the two nodes; up to 12 km in multimode fibers and 20 km in single mode fiber. FDDI allows backbone applications where computers and workstations connected to medium speed LANs can exchange data with other LANs or LAN segments in an FDDI extended network configuration. FDDI allows also back-end and front-end applications. Bridging methods such as encapsulation, translation, etc. are currently valid, and must be used for specific applications that need the corresponding technique. Today's FDDI prices will be dramatically reduced within the coming years by a factor of 20–30% per year.

FDDI- A LAN among MANS

FDDI (Fiber Distributed Data Interface) is a 100 Mbit/sec local area network (LAN) based on a token ring protocol operating over an optical fiber medium. Though not a metropolitan area network (MAN), FDDI can operate over distances normally considered as the province of MANs. With the addition of FDDI-II capabilities, and the newly defined mapping for FDDI over SONET, FDDI now offers MAN functionality for large organizations needing to provide integrated services over a widely based high performance private network. This paper updates earlier efforts on this subject, giving an up-to-date overview of FDDI, FDDI-II and SONET mapping. At the end of the paper a brief look at the possible future for FDDI technology is given.

A robust fiber optic active star coupler for the SAE linear token-passing multiplex data bus

The Society of Automotive Engineers (SAE) linear token-passing multiplex data bus draft standard (AS4074.1, version 2.0) calls for two sets of fiber-optic medium characteristics which support a generous power loss budget of about 30 dB. Since there are applications for this bus needing an even greater loss budget one solution is to make the access coupler (the star) an active (powered) network component. A description is given of a simple, low-power, high-reliability active star coupler design meeting the overall requirements of the SAE high-speed data bus (HSDB) standard without changes to the fiber-optic implementation characteristics. The basic active star network is introduced and important quantities defined. Technical issues which influence the active star design are discussed. These include the properties of the protocol which have the greatest effect on the design of the active star, such as the initialization procedure, the system monitoring and control times, the preamble, and the intertransmission gap time. Component options are introduced and a completed design presented. Its performance in a high-speed data-bus environment is characterized and modifications to the standard for best active star performance are suggested.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analog Data Transmission via Fiber Optics

In the SLAC Linear Collider Detector (SLD), as in most high-energy particle detectors, the electromagnetic noise environment is the limiting factor in electronic readout performance. Front-end electronics are particularly susceptible to electromagnetic interference (EMI), and great care has been taken to minimize its effects. The transfer of preprocessed analog signals from the detector environs, to the remote digital processing electronics, by conventional means (via metal conductors), may ultimately limit the performance of the system. Because it is highly impervious to EMI and ground loops, a fiber-optic medium has been chosen for the transmission of these signals. This paper describes several fiber-optic transmission schemes which satisfy the requirements of the SLD analog data transmission.

A Highly Reliable LAN Protocol

As a research project for NASA's Langley Research Center, we developed a variation on MIL-STD-1553B (the military standard for avionics buses) whose goal was increased fault tolerance. The resulting protocol, called implicit passing (ITP), replaces an explicit with brief soundoff messages from all nodes participating on the LAN. Since every node participates on every token cycle, bus silence is an error indication and initiates recovery action. By encoding state information in the headers of the transmitted words, nodes are continuously aware of the global state of the network. This local knowledge of the global network state allows the system to continue operation in spite of nodal failures. A station which fails but then recovers can quickly assess the global network state and then safely rejoin the active nodes. ITP features high throughput and bounded message delay, and achieves high reliability through tolerance of failed nodes and automatic resynchronization when failed nodes are revived. The protocol is ideally suited for a bus topology and fiber optic media.

A Fault-Tolerant Network Protocol for Real-Time Communications

We present a network access protocol suitable for use in real-time applications. It features high throughput, bounded message delay, tolerance of failed nodes, automatic resynchronization when failed nodes are revived, deadlock avoidance, and high reliability. The protocol is ideally suited for a bus topology and fiber-optic media. Measured performance data is provided from an implementation of 45 nodes operating on a 10-Mbps fiber-optic bus.

Trends in U.S. Broad-Band Fiber Optic Transmission Systems

Fiber optic media are rapidly penetrating the telecommunications network. They are used as undersea and terrestial trunk lines, central-office loops, optical data links, and will eventually be included within the distribution plant which connects directly into individual premises. The rapid implementation of lightwave systems is occurring because the high bandwidths and low losses of optical fibers enable broad-band communication services to be provided between widely spaced repeaters and also allows users to upgrade currently installed systems to meet future needs. This paper will describe current applications and show how future trends will depend upon the continuing evolution of lightwave components and optical fiber designs.

Standardization Efforts in Fiber Optics

Experience with copper-based local area networks combined with the inherent characteristics of fiber optics is providing increased impetus for the development of fiber optic network standards. The installed base of networks that use copper wire, twisted shielded pair, and coaxial cable indicates that there will be many applications where networks will use a mix of both copper and fiber optic media. Successful standardization efforts must take this into account. There is indeed a great deal of standardization effort underway that involves fiber optic networking. Within the SAE AE9 Committee there are four standardization efforts to support the military. The IEEE (under project 802) has published four draft standards for copper-based networks and the 802.8 Fiber Optic Technical Advisory Group is studying integration of optical fibers into each of these networks. Other IEEE efforts include discussion and study of all-fiber networks. CBEMA is working on a token-passing ring network, and the Instrument Society of America is pursuing a mixed copper/fiber optic network implementation. Generally, requirements for fibers, sources, detectors, connectors, switches, branching devices, and other system elements are being established. This paper discusses some of the standardization efforts that are underway.