Fiber optic configurations supporting confidentiality in passive DQDB systems

A method is proposed to support confidentiality in broadcast fiber-optic LAN/MAN (local/metropolitan area network) systems. This approach, which is different from the conventional approach, is based on a fundamental property of fiber optics, viz., optical bidirectionality. That is, two distinct transmissions in opposite directions can occur simultaneously on the same channel. This property can be used to arrive at network structures to support privacy in a broadcast environment. The basic idea is that when two stations are engaged in a private conversation, they can effectively jam (or blank out) the reception at all other stations. In this sense, security close to that of point to point links is achieved in a broadcast environment. It is shown that this concept can be successfully applied to LAN/MAN systems, specifically, in the context of DQDB, to the proposed IEEE 802.6 MAN standard. Performance issues in terms of throughput are also discussed