Local area network
US4641375A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 7, 1985 |
| Grant date | Feb 3, 1987 |
| Priority date | — |
| Expiry date | Mar 7, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L12/44
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
In a local area network (LAN), of the Ethernet type, one of the segments, i.e. one bus, is replaced by a star coupler connected via optical fibre pairs to a number of stations. Each pair includes a GO fibre and a RETURN fibre. As in the usual Ethernet system, collision detection relies on measuring signal level on the medium, if it is too large then a collision condition exists. In an optical fibre system a similar collision detection technique is used. To detect collision, it is nescessary to be aware of the network's attenuation as "seen" by the station. To do this a low level pilot tone is sent from each station, each station having its own tone frequency. The amplitude of this tone when it returns to its own station indicates the system's attenuation, and this is used to detect collision. In an alternative the pilot signals are pseudo-random bit sequences.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.