<title>Fiber Optics For The Shipboard Data Multiplex System</title>

Abstract

AbstractThe Navy's commitment to the application of data bus technology to shipboard internal communication stems from the necessity ofreducing cable congestion and weight. The Shipboard Data Multiplex System is a general purpose data bus system intended to take the placeof most of the point -to -point cabling and associated hardware presently used for information transfer aboard ships of the Fleet. It uses bothfrequency and time multiplexing of a two -level set of redundant interconnections to provide a highly reliable data bus capable of distributingall forms of periodic and aperiodic signals.We report here a demonstration of the feasibility of substituting fiber optics for the coaxial cable presently used by this system. Primaryconcerns were whether the interface hardware could handle the FDM signals on the bus without excessive distortion and degradation of theirsignal to noise ratios.This paper describes methods used to demonstrate that the intermodulation distortion and signal -to -noise ratio requirements of theSDMS can be met by the necessary interface components.IntroductionThis paper reports the first phase of an effort to demonstrate and evaluate the feasibility of applying fiber optics technology to the ad-vanced development model of the Shipboard Data Multiplex System (SDMS), a multiterminal multiplexing (data bus) system. SDMS is in-tended to serve as a general purpose information transfer system taking the place of most of the point -to -point cabling and associated hard-ware presently used for information transfer aboard naval ships.1 , 2 It has been built by the Autonetics Division of Rockwell Internationalunder contract to the Naval Sea Systems Command. This new system uses frequency and time multiplexing of a two -level set of redundantinterconnections to provide higher reliability and survivability with lower weight than present point -to -point systems. It is potentially capableof distributing throughout a ship all forms of periodic and aperiodic signals, either analog or digital.Two -level multiplexing, wherein user access is provided through remote multiplexers (RMs) which transfer information to area multi-plexers (AMs) and thence to a common data bus, allows many access points to be serviced without the attenuation that would result fromseparate connections to a common data bus. The first stage of multiplexing, consisting primarily of pulse coding in the RMs, is followed bytime multiplex transmission to the AMs at base band. Each AM serves up to eight RMs on a direct basis. Each dual redundant RM is