Printer Friendly

Siemens: fiber optics for naval applications.

Siemens: Fiber Optics for Naval Applications

The complexity of surface and underwater warships to be introduced in the '90s is posing totally new challenges to naval designers. A particularly sensitive area is the shipboard electronics developed to keep these advanced technology weapons systems platforms, which rely on fast information exchange, operating at maximum efficiency. This requires a continuous stream of data and commands that control and monitor all aspects of the vessel's operation. In current warships this information is transferred back and forth between complex systems through a maze of heavy cabling, requiring numerous bulkhead penetrations, junction boxes and manned switchboards. These installations, which have remained virtually unchanged in their principles since WW II, tend to lack flexibility and to be costly. But these shortcomings are not the sole reason for a new approach.

In the early stages of a ship's design it is the usual practice to specify this dedicated point-to-point wiring network, thereby locking both the weapon system and ship design phases closely together. Because of the long interval between a ship's conception and its eventual commissioning, this almost invariably leads to a premature design "freeze". This explains why the ship's electronic systems and associated weapons are rarely up-to-date when the ship finally enters into service, thereby virtually forcing an early update.

These problems are about to be solved by the introduction of multiplexed distributed digital data networks based on a modern fiber-optics technology. One of the first such system concepts is the DAVONET (Data And Voice Optical Network) which has been developed jointly by Philips and Siemens. It is a universal, digital information transmission and distribution system for data, voice and video signals. Its concept is based on its predecessors, the FOCON and the SIFONET, but with all-round improved performance. Special importance has been attached to standardization in the user-specific system functions, interfaces and general configuration.

Under this approach, instead of miles of different cabling specifically designed for each ship type, general-purpose multiplex fiber-optic cables can be installed in accordance with a plan which does not need to be varied with subsequent modifications of the vessel's systems. Adding new equipment, or accommodating updates of older systems, becomes as simple as plugging a TV-set into standard house wiring outlets. No longer is the ship functionally dependent on complex networks of dedicated wiring. This ability to "wire" a new ship according to a standard diagram, long before the ship's systems are fully defined, enables both the vessel and the systems to be developed at their own pace. The overlapping of the two development cycles will not only compress ship construction schedules, but also result eventually in ships with more advanced and up-to-date weaponry. With the introduction of fiber-optics another benefit will accrue: It will eliminate the electro-magnetic interference problem to which the previous maze of cables had been a major contributor.

As envisioned currently the DAVONET covers the demands of tactical command and control, ship operation and navigation and serves all internal communication needs. It permits the transmission of all signals either via separate, albeit identically equipped networks, or simultaneously via one and the same network. In other terms, a high operating reliability is achieved through channel redundancy because in case of damage the network can route the signals through alternative, intact sections. This is of major importance because investigations into the causes of the loss of the destroyer "Sheffield" during the Falklands conflict showed that a breakdown of internal communications played a major part in the disaster.

Other advantages of the DAVONET are great operational flexibility thanks to computer and software-supported connection and communication management, a feature which permits simple system expansion and ease of modification. The system has been designed to meet NATO standards, but with its modular interfaces and protocols for open systems it is also in full accordance with ISO, CCITT and IEEE standards. On a medium-sized modern warship about 40 to 50 tons of copper wiring are installed: fiber-optic cables weigh a fraction of this, a weight-saving which may enable more fuel or weaponry to be carried. Due to the single serial broadband transmission four-core cable strand which replaces metal multi-core wires, fiber-optic cables also cost much less.

The technical concept of the DAVONET closely resembles that of a survivable ground forces tactical communications network, where the net is linked by nodes and is accessible through periphery interfaces. The DAVONET features a decentralized and modularized network where the nodes are called BAU (Bus Access Units) and the individual subscriber access points BIU (Bus Interface Units). The basic topological structure is a simple ring, giving each BAU two connections to the system. However, for enhancing survivability an automatic reconfiguration feature has been added in that the system is cross-connected, providing each BAU with a third link into the network. This means that all BAUs are linked with each other by three independent cable paths and ensures that in case of damage all stations are connected by at least one cable. For example, if one BAU is destroyed, the adjacent BAUs lose only one of three cable links and their functioning, and also that of the net, remains unaffected because the signals are automatically re-routed through the undamaged sections.

The network subscribers, which may be electronic devices generating or receiving data streams, but also speech subscribers for example, enter and receive signals via the BIUs, ten of which are attached to each BAU. NATO or commercial-standard interfacing and protocols are available for data interchange. Users with time-critical data and speech messages are connected via special BIUs with fixed channel or dynamic channel access. BIUs for speech subscribers are designed to differentiate between priorities for tactical and nontactical communications. This also includes radio switching for external communications. Since the DAVONET is totally digital it is organized as a time-division multiplex system: the subscriber information is segmented in time and fed synchronously with the system's 34.8 MHz clock into the time slots of the signal path. It is thus theoretically possible to obtain 1 088 independent transmission channels, each offering a capacity of 32 kbit/sec. It is obvious that signals derived from the ship's sensors and fire directors will take absolute priority via fixed channels.

Channel assignment and network supervision is a complicated operation. The supervisory function, i.e. checking the operability of each element of the network, is accomplished by BITE (Built-In Test Equipment) incorporated in each BAU/BIU unit. In case of failure the message is forwarded automatically to the central computer where the exact location of the BAU and type of malfunction are indicated. Communication management is handled via modifiable parameters which reside in the random access memories (RAM) of both the management computer and the BIUs. Parameters which need not be changed are stored in the BIUs as firmware. However, the computer is not essential for the operation of the network. Once this has been initialized, programmed and started, the computer is needed only for possible reprogramming and fault location. The BAU/BIU units are constructed in modular board form and are housed in easily accessible boxes. The modules for the electro-optic conversion interface with the fiber-optic cables are integrated in hermetically sealed cases. The units feature an autonomous power supply which enhances the survivability of the network.

The Philips-Siemens DAVONET is under advanced development for the NATO Frigate 90 project with funding from the German Ministry of Defence. It promises to bring a totally new dimension to internal ship's communications in terms of rapid data flow, survivability and ease of installation.

Under consideration for the future is the extension of the system from communication and weapon management tasks to the nautical sectors of the ship, including the propulsion machinery, electrical power management, monitoring of the hull, damage control and other tasks.
COPYRIGHT 1989 Armada International
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Publication:Armada International
Date:Jun 1, 1989
Previous Article:Honeywell solves the harsh-environment sensing problems.
Next Article:Normalair-Garrett: onboard oxygen generation for military aircraft.

Related Articles
Fiber optics in military communications: the dawn of a new era.
KVH Unveils DSP-3000 Tactical-grade Fiber Optic Gyro.
KVH Receives Production Order for Guidance Component in U.S. Navy Mark 54 Torpedoes.
Ports pursuing high-tech security.
KVH Awarded $3.2 Million Order for Fiber Optic Gyro-based Inertial Measurement Units.
Infineon to Finalize Restructuring of the Fiber Optics Business: Manufacturing Facility in Czech Republic to be Sold to Siemens VDO Automotive.
Newmark Knight Frank to market Metropark 2, 3.
SPAWAR Expands Deployment of Fiber Optic Cross-Connect System from Calient Networks.
KVH Receives $2.6 Million Order for Fiber Optic Gyro-based Inertial Measurement Units.

Terms of use | Copyright © 2016 Farlex, Inc. | Feedback | For webmasters