Arrangement for controlling the bandwidth in equipment for transmitting via singel-mode fibre regardless of signal format

Abstract: The invention relates to an arrangement for controlling the bandwidth in equipment for transmitting via single-mode connections between equipments regardless of their signal format. The arrangement comprises a transmitting channel (1) and a receiving channel (2). The transmitting channel comprises a converter arrangement and a single-mode transmitter (6). The converter arrange­ ment comprises an amplifier (5) and possibly a multi-mode detector (9). The converter arrangement converts an electrical signal or a multi-mode signal into a form which is suitable for feeding into the single-mode transmitter (6). The receiving channel comprises a single-mode detector (8) and a converter arrangement. The converter arrangement comprises an amplifier (7) and possibly a multi-mode transmitter (11). The converter arrangement converts the electrical signal from the single-mode detector into an electrical signal or a multi-mode signal. According to the invention, the transmitting and receiving channels comprise controllable filters (10) for controlling the bandwidth of the arrangement, which can be utilized in charging the customer.

Description: FIELD OF THE INVENTION The invention relates to a telecommunications network comprising an arrangement for controlling the bandwidth in equipment for transmitting via single-mode connections, that is to say via optical signals in single-mode fibre. The arrangement enables the bandwidth to be controlled as required by the customer and for differentiated charging. PRIOR ART Commercially available equipment for data communication via optical fibre is today normally based on multi-mode technology. Communication is used, for example, between local networks, channel extensions and intelligent multiplexors. The network of Televerket, however, is built up with single-mode fibres due to their better transmission characteristics. Multi-mode fibres cannot be simply joined to single-mode fibres without strong signal attenuation, and it has therefore been previously necessary to arrange separate multi-mode connections in parallel with the single-mode connections at considerable costs. The arrangement according to the invention enables multi-mode fibres and single-mode fibres to be coupled together. In data communication on electrical lines, it has previously not been possible to utilize optical fibres. The arrangement according to the invention also enables electrical connections to be coupled together with single-mode fibres. By using the existing Televerket network, the customer utilization of the fibres can also be controlled, which can be used in charging. The arrangement according to the invention particularly enables the customer's useful bandwidth to be controlled. SUMMARY OF THE INVENTION The invention thus provides a telecommunications network comprising an arrangement for controlling the bandwidth in equipment for transmitting via single-mode connections between equipments regardless of their signal format as defined in claim 1. BRIEF DESCRIPTION OF THE DRAWINGS The invention is described in detail below with reference to the attached drawings, in which: Figure 1 is a basic diagram of the arrangement according to the invention, and Figure 2 shows an embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Figure 1 shows an overview of the application of the present invention. The customer application consists of equipment which is located in different sites and the customer wishes to be able to communicate between these. The customer equipment is in this case adapted for communication in a multi-mode fibre. In data communication, multi-mode fibre is the type generally found. Since the multi-mode fibre has a bigger core, approximately 50 µm, it is easier to build inexpensive optical transmitters and to join such fibres. However, multi-mode fibre has worse transmission characteristics than single-mode fibre, with the result that multi-mode fibre is not suitable for telecommunication. The Televerket network therefore utilizes single-mode fibre with a small core, approximately 10 µm. This type of fibre was originally more expensive to produce, but the fibre is now less expensive than multi-mode fibre due to the large amounts of fibre which are used in the telecommunication network. Due to the different core sizes of the fibre types, it is not possible to couple these directly together without great losses. For this reason, multi-mode fibre has been previously installed for producing the communication in Figure 1 between equipment of multi-mode type despite the existing single-mode fibre network. Figure 2 shows an embodiment of the arrangement which forms a link between a multi-mode connection and the single-mode fibre. The arrangement is divided into two channels, a transmitting channel 1 and a receiving channel 2. The customer equipment is coupled by means of multi-mode fibres 3 to the single-mode fibres 4 via the arrangement. The transmitting channel comprises a variable amplifier 5 and a transmitter 6. The transmitting channel also comprises a detector 9 for receiving signals from the customer equipment which are transmitted via the multi-mode connection 3. The detector 9 converts the optical signals into electrical signals which are fed to the amplifier 5. The receiving channel also comprises an amplifier 7, a detector 8 and a transmitter 11. The amplifiers 5 and 7 are analog amplifiers with a wide bandwidth. Moreover, they must be direct-current coupled. The characteristics of the amplifiers mean that the arrangement can be used regardless of the signal protocol of the equipment since the signals are converted completely linearly. The transmitters 6 and 11 convert the signals from the amplifier into light signals which are transmitted in the respective fibre. The equipment communicates with another equipment located at a distance, which other equipment is connected to the single-mode fibre via a similar arrangement. The signals are received by the detector 8 which converts the light signals into electrical signals. The amplifier 7 has a gain which is adapted in such a manner that the electrical signals from the detector 8 are converted to the same electrical signals which were fed to the amplifier 5. When the arrangement is coupled in, the gain of the amplifiers is finely adjusted so that the link becomes completely transparent. Here, too, the arrangement comprises a transmitting channel 1 and a receiving channel 2. According to the invention, the transmitting and receiving channels each comprise an electrical filter. The aim of the filter is to limit the bandwidth of the arrangement. The bandwidth can also be limited by the choice of amplifier. By determining the bandwidth of the arrangement, the transmission capacity of the arrangement is controlled. This also provides control over the customer's use of the network and makes it possible to charge the customer afterwards. According to the invention, the bandwidth of the filters 10 can be controlled from a centre which controls the network. The control signals can be transmitted via the single-mode fibres of the network by using multiplex circuits, for example for wavelength multiplex or via electrically coded signals which are transmitted via the fibres. The invention thus makes it possible to offer general links with adjustable transmission capacity. The links are adjusted as required by the customer and charged thereafter. The arrangement according to the invention thus enables the customer to be charged in accordance with the transmission capacity of the link. Some preferred embodiments of the present invention have been described above. The invention is limited only by the patent claims below.

Claims: A telecommunications network, for the duplex transmission of data, and arranged so that a first data signal can be modulated on an optical carrier and launched into a multi-mode fibre, and an optical carrier modulated with a second data signal can be demodulated to extract the second data signal, characterised in that said telecommunications network includes a monomode optical transmission path and a convertor for transferring a data signal from a multi-mode optical fibre to a single mode optical fibre and vice versa, said convertor being transparent to optical carrier, or signal modulation, format, said convertor having first means for converting (9, 5), a modulated optical carrier received from a multi-mode optical fibre into a first electric signal, a first optical transmitter (6), for converting said first electric signal to a signal modulated on an optical carrier launched into a mono-mode optical fibre, second means for converting (8, 7), an optical carrier modulated with a data signal received from a mono-mode optical fibre into a second electric signal, a second optical transmitter for converting said second electric signal into an optical carrier modulated with a data signal launched into a multi-mode optical fibre, and means (10), for controlling transmission capacity available for transmission and/or reception over said first and second mono-mode optical fibres. A telecommunications network as claimed in claim 1, characterised in that said means (10), for controlling said transmission capacity is a bandwidth filter having a controllable passband. A telecommunications network as claimed in claim 2, characterised in that said telecommunications network includes central control means which transmits a signal to said means (10) for controlling said bandwidth filters passband. A telecommunications network as claimed in claim 3, characterised in that said central control means is arranged to adjust said bandwidth filters passband in response to a command signal received from a subscriber. A telecommunications system as claimed in either claim 3, or 4, characterised in that said signal to said means (10) for controlling said bandwidth filters passband is wavelength division multiplexed onto said mono-mode optical fibre. A convertor for use in a telecommunications network as claimed in any of claims 1 to 5, adapted for transferring a data signal from a multi-mode optical fibre to a single mode optical fibre and vice versa, characterised in that said convertor is transparent to optical carrier, or signal modulation, format, said convertor having first means for converting (9, 5), a modulated optical carrier received from a multi-mode optical fibre into a first electric signal, a first optical transmitter (6), for converting said first electric signal to a signal modulated on an optical carrier launched into a mono-mode optical fibre, second means for converting (8, 7), an optical carrier modulated with a data signal received from a mono-mode optical fibre into a second electric signal, a second optical transmitter for converting said second electric signal into an optical carrier modulated with a data signal launched into a multi-mode optical fibre, and means (10), for controlling transmission capacity available for transmission and/or reception over said first and second mono-mode optical fibres. A convertor as claimed in claim 6, characterised in that said means (10), for controlling said transmission capacity is a bandwidth filter having a controllable passband.

Inventors: VUCINS VIESTURS, VUCINS, VIESTURS
Applicants: TELIA AB
Application year: 1990
Main classification: H04B10
IPC codes: H04B10