Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04Q—SELECTING
  • H04Q11/00—Selecting arrangements for multiplex systems
  • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/02—Wavelength-division multiplex systems
  • H04J14/03—WDM arrangements
  • H04J14/0305—WDM arrangements in end terminals

Definitions

• the invention relates to optical networks, for example optical communication networks such as local area networks.
• optical signal wavelength switching to achieve communication between a transmitting terminal and a selected receiving terminal has already been proposed in for example CA-A-1,052,865 and "Future Optical Carrier Frequency Technology in Glass Fibre Networks" by Clemens
• an optical wideband network has a plurality of first transmitting and first receiving terminals; and a common control system, the terminals being optically coupled together such that signals from each first transmitting terminal are transmitted to all the first receiving terminals, and the control system being adapted to control the
• SUBSTITUTE SHEET wavelength of signals transmitted by and/or detected by the terminals whereby the network may be configured into a plurality of topologies of groups of three or more terminals by the control system.
• the invention provides a network which is much more versatile than conventional networks in allowing variable topologies to be set up by the common control system making use of the wavelength switching principle and without having to change the physical topology. This enables the physical topology to be constructed with a minimum of optical waveguide leading to low cost and simplicity.
• the control system may be positioned at a central site from where it will control which terminals are connected in groups. Furthermore, it can allow several different groups of terminals to operate simultaneously, the topology of each group being independent of the other groups.
• the control system can also be used to allocate channels of different bandwidths depending on the capabilities of the terminals, and has applications in telephone communication and video.
• the terminals will be optically coupled via monomode optical fibres to minimise power loss and to exploit fully the wavelength multiplexing capability.
• monomode optical fibres to minimise power loss and to exploit fully the wavelength multiplexing capability.
• other optical waveguides could be used where appropriate.
• each first transmitting terminal includes tuning means for setting the wavelength of the respective optical carrier signals, the control means being adapted to control the tuning means of one or more groups of terminals whereby communication is achieved between the terminals in each group.
• each first receiving terminal includes tuning means for setting the wavelength to which the receiving terminal is sensitive.
• each transmitting terminal is optically coupled with a common wavelength multiplexing means which provides a plurality of multiplexed outputs, each output being coupled with a respective first receiving terminal.
• the wavelength multiplexing means may be a conventional wavelength multiplexer in combination with a wavelength demultiplexer or a power combiner/splitter combination.
• the network comprises a plurality of stations each having a first transmitting terminal and a second transmitting terminal and a first receiving terminal and a second receiving terminal arranged such that point to point communication between the stations may be achieved via the second transmitting and receiving terminals simultaneously but independently of communication between groups of three or more stations via the first transmitting and receiving terminals.
• Figure 2 is a schematic block diagram of a second example
• Figure 3 is a schematic block diagram of a third example
• Figure 4 is a modification of the Figure 3 example.
• Figure 5 and 6 illustrate networks formed by a plurality of subsidiary networks.
• SUBSTITUTESHEET The example shown in Figure 1 is a local area network having N stations 1 , each station having an optical signal transmitter 2 and an optical signal receiver 3.
• the transmitters 2 are tunable, as explained below, so that an optical carrier signal of a selected wavelength is transmitted.
• Each receiver 3 is sensitive to a fixed optical wavelength, the optical wavelength being different for each receiver.
• the transmitters 2 are all connected to a power combiner 4 in which the signals from the transmitters 2 are combined and fed to a wavelength demultiplexer 5 having N outputs connected to respective receivers 3.
• the tuning of the sources 2 is controlled by a central network control terminal 6 provided in the network.
• the network control terminal 6 causes the transmitter 2 of station A to transmit a carrier signal having a wavelength corresponding to •that sensed by the receiver of station B.
• the transmitter 2 of station B transmits a signal which is sensed by the receiver of station C and the transmitters of stations C and D are similarly controlled so that a small communication ring is set up.
• the monomode fibre connections between the stations and the wavelength demultiplexer 5 would be configured as a star.
• the power combiner 4, however, can be a distributed component and therefore this part of the network could be configured " in a tree and branch structure to minimise optical fibre. ⁇
• the network control terminal 6 is equivalent to the stations 1 and can be lcoated anywhere within the network. The network apart from the stations is therefore totally passive.
• the network control terminal 6 may be located at a central site with the splitting/combining function but only if operationally convenient.
• the transmitters 2 transmit optical carrier signals with a fixed wavelength different for each station 1 but the receivers 3 are tunable by the network control terminal 6.
• the transmitters 2 are optically coupled via monomode optical fibres with a wavelength multiplexer 7 whose output is connected to a power splitter 8 having N outputs connected to respective receivers 3.
• this network allows one to many communication to be achieved.
• the network control tunes each of a selected group of receivers 3 to the wavelength of a transmitter 2 which is to generate a broadcast message.
• the tuning range of the filters of the receivers 3 can cover the whole of the optical window e.g. 1250 mm to 1600 mm.
• the number of stations 1 will be limited by the power splitter 8 to about three hundred, whereas coherent systems enable the number stations to be up to 1000 or more.
• the network shown in Figure 3 is identical to that shown in Figure 2 except that the wavelength multiplexer has been replaced by a power combiner 9. This realises the simplest passive network at the expense of extra loss due to the power combiner 9.
• SUBSTITUTESHEET Figure 4 illustrates a modified version of the Figure 3 example.
• the power splitter 8 and power combiner 9 of Figure 3 have been replaced by an N-way transmissive star coupler 10.
• This network is far more versatile than either of the networks of Figures 1 and 2 since it allows both the transmitters 2 and receivers 3 to be tunable.
• the losses introduced by the power splitter 8 and power combiner 9 in the Figure 3 example have been reduced to the level of losses in the Figures 1 and 2 examples. This can allow assignment of wavelengths on an "on demand" or traffic basis rather than allocation to specific terminals.
• the network control terminal 6 is formed by a standard terminal * on the network (which could be located anywhere in the network) interfaced to a control computer. All call/topological set ups between terminals are arranged via the control computer and thus each terminal 1 communicates with the network control terminal 6 during call set up.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Optical Communication System (AREA)

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• 1986
  • 1986-03-10 JP JP61501596A patent/JPS62502234A/ja active Pending
  • 1986-03-10 WO PCT/GB1986/000134 patent/WO1986005649A1/en not_active Application Discontinuation
  • 1986-03-10 EP EP86901930A patent/EP0214263A1/de not_active Withdrawn

Non-Patent Citations (1)

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