A versatile communication system in a ship with 120 stations, each having voice and data transmission is envisaged. The proposed fibre optic network has a bus topology ideally suited for distribution in ship-like environment. Use has been made of standard ETHERNET chip sets manufactured by INTEL. This makes the stations compact, easier to maintain and inexpensive. The ETHERNET proto-col is primarily designed for packet data transmission. The collision detection and backoff protocol makes the packet transmission probabilistic and is therefore not suitable for voice transmission. This problem is overcome in the present design by a scheme where the required number of voice slots are dynamically allocated. That is, having established a connection for voice communication between stations, fixed slots are assigned for voice transmission and reception. The data transmission continues to use CSMA/CD Protocol. A simple hardware addition to the ETHERNET chip set makes the scheme workable. Drops in the fiber optic bus network is through passive star couplers. Four to eight star couplers are used in the present scheme with repeaters between adjacent star couplers. The repeaters will not be usual repeaters, as ordinary repeaters would cause loops to be formed between adjacent stars, thereby causing data to recirculate. This recirculation is avoided by making the repeater intelligent and also performing the task of detecting collisions between signals originating from stations connected to different star couplers.

Fibre Optic Bus Network For Voice And Data Transmission In A Ship

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