Multiplex communications – Wide area network – Packet switching
Patent
1989-02-07
1991-04-23
Eisenzopf, Reinhard J.
Multiplex communications
Wide area network
Packet switching
370 4, 370 1, H04J 1400
Patent
active
050105434
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of dividing an optical signal into a number of distinct channels for transmission to different receiving stations and a network employing such a system. Such a method may be used for telephony or for other forms of data transmission.
A typical network to which the present invention might be applied comprises a central control station, a single fibre transmission line linking the control station to a node and a large number of fibre transmission lines extending from the node to individual subscriber stations. To spread the capital cost of the optical system up to and including the node as widely as possible it is desirable to spread the equipment cost between users and where necessary maximize the number of subscribers connected to a given node. In practice time division multiplexing can be used to connect as many as a thousand subscribers to one node. As a result even though the data transmission rates between one subscriber and the node may be comparatively low the data transmission rate between the node and the control station needs to be very much higher if the node is not to act as a data "bottleneck". With conventional methods of time division multiplexing the complexity of the equipment required at the node and/or at each subscriber station to cope with the assembly/disassembly of many multiplexed channels and the conversion between high and low data rates is such that it brings severe disadvantages in terms of cost and reliability. This significantly reduces and in some cases eliminates altogether the advantages achieved in the first place by connecting many customers to a single node.
According to one aspect of the present invention an optical encoder for an optical communications system comprises an optical source for generating an optical signal corresponding to a received time-domain mulitplexed signal of two or more information channels having a tuning means arranged to vary the wavelength of the optical signal so that those portions of the optical signal corresponding to a respective distinct channel are generated at a distinct wavelength.
The present invention provides a time division multiplexed optical signal in which each channel is encoded into a wavelength multiplex using only one optical source for all the channels avoiding the requirement for mulitple optical sources, i.e. one per channel as required, for example, in the system described by Miller in U.S. Pat. No. 4,467,468. A further advantage of the present invention is that it does not require the channels to be interleaved bit by bit but can be employed to wavelength encode asynchronous channels of variable bit length section.
An encoder according to the first aspect of the present invention finds application in an optical communications system according to the second aspect of the present invention, namely in an optical communications system having a control station, a first optical path connecting the control station to a node and secondary optical paths connecting the node to two or more receiving stations including an optical encoder: according to the first aspect of the present invention; a first transmitting means for transmitting the optical signal from the control station via the first optical path to the node; a passive wavelength analyser at the node arranged to direct respective wavelength channels via the secondary optical paths to the receiving stations.
Where the time domain multiplex signal has channels which are bit interleaved the encoder is preferably arranged to repeatedly sweep the optical frequency through a preselected wavelength range. The rate of sweep is chosen such that each channel bit is coded to a distinct wavelength, the process being repeated each set of interleaved channel bits. However, the present invention in its broader aspect does not require the wavelengths for each successive channel to be in any order. The turning means may select wavelength in any order as will be required for the more general asynchronous time domain multiplexed described above.
For
REFERENCES:
patent: 4467468 (1984-08-01), Miller
patent: 4704715 (1987-11-01), Shibazaki et al.
patent: 4726010 (1988-02-01), Ali et al.
Electronics Letters, vol. 20, No. 10, May 10, 1984, (London, GB), N. A. Olsson et al: "2 Gbit/s Operation of Single-Longitudinal-Mode 1.5 um Double-Channel Planar Buried-Heterostructure C.sup.3 Lasers", pp. 395-397.
Summaries of Technical Papers of the Optical Fiber Communication Conference, Feb. 24-26, 1986, (Atlanta, Georgia, U.S.), W. T. Tsang: "Single-Frequency Semiconductor Lasers?", pp. 14-16.
Technical Digest--Western Electric, No. 72, Oct. 1983, (New York, U.S.), P. S. Henry et al: "Multiplexer Using Coupled-Cavity Laser", p. 19.
British Telecommunications public limited company
Eisenzopf Reinhard J.
Negash Kinfe-Michael
LandOfFree
Optical multiplexing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical multiplexing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical multiplexing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1626180