NL1009443C2 - Telecommunication network. - Google Patents

Description

BACKGROUND OF THE INVENTION The invention relates to a telecommunications network, comprising a central, an intermediate network between the central and local distribution / collection stations, hereinafter referred to as curbs, and a local network between the curb and subscriber terminals for each curb.

10 In a local telecommunications network, there are two technical options for transmitting broadband signals, namely FTTH (Fiber To The Home) and ADSL (Asymmetry Digital Subscriber Line). Both techniques have advantages and disadvantages.

The main disadvantage of FTTH is that it is (still) expensive and that it is still unknown territory for operators. In addition, it should also be mentioned as a drawback that FTTH has to be installed in a whole area in one go in order to be able to supply broadband. This is therefore only possible in 20 new housing estates. The advantage is that FTTH has an unlimited bandwidth and that it is therefore future-proof.

ADSL - via (existing) "twisted pair" cores - has the disadvantage that it has a limited bitrate. However, in combination with FTTC (Fiber To The Curb) - ADSL only needs to bridge the distance between the "curb" and subscriber - this drawback is largely obviated. The advantage is that it does not have to be installed as a whole. Any customer who wants broadband 30 can get an ADSL connection.

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SUMMARY OF THE INVENTION

The invention aims to combine both advantages of FTTH and ADSL.

According to the invention, a fiber to the curb (FTTC) is installed, whether or not in addition to the (already existing) twisted pair, for broadband services, which are mostly downstream oriented. In new construction, this fiber can be laid up to the curb together with the twisted pair. With the curb, the broadband 10 signal is sent to the subscribers via an infrared radiator. Subscribers who do not want broadband services only have their normal telephone line via the twisted pair connection. Customers who do want a broadband service receive an optical receiver that can receive the signal from the radiator; a few hundred meters can thus be bridged.

The advantage can be mentioned that the bandwidth is much higher than that of ADSL. It is estimated at several hundred MHz. The bandwidth limitation is formed by reflections caused by multi-way transmission followed by the associated pulse broadening. This problem can be largely avoided by making the receiver directional using a reflector or lens.

Another advantage is that costs are only incurred for the customers who need a broadband service. A pre-investment in the form of a fiber to the curb and a transmission tower with infrared radiator is of course necessary.

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An advantage of infrared over radio is that it is much cheaper and does not require transmission licenses. The disadvantage can be mentioned that the operational reliability is somewhat less than the normal twisted pair or FTTH. Among other things, in heavy fog and rain, the connection may get worse. Since this only concerns broadband services and the normal telephone (narrowband) is transported via the twisted pair, this objection can be considered acceptable.

10 It is possible for neighboring areas to crosstalk and thus cause interference. In cases where this is a problem, this can be avoided by using different light polarities in adjacent areas. A second possibility to prevent crosstalk is by modulating a carrier wave with the broadband signal before it is presented to the infrared transmitter. By giving neighboring areas different carriers (different wavelength, frequency or polarization), crosstalk 20 is avoided.

Since consumer components (LEDs and infrared receivers as used in remote controls) can be used, it is likely that the concept of the present invention will be economically attractive.

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IMPLEMENTATION EXAMPLES

Figure 1 shows an embodiment of a telecommunications network according to the invention. Shown is a central (PBX) 1, which is connected by an intermediate network 2 to local distribution / collection stations 3, called "curbs". The curbs are connected to the exchange by both a conventional, narrow-band, twisted pair cable 4, and by an optical fiber 5, with which broadband signals 10 can be transmitted. If desired, the copper cable 4 can be omitted. On or near each curb 3, one or - see at the top curb in the figure - several IR (round) radiators 6 are placed, which are fed with the broadband signal transmitted by the optical fiber 5. The IR radiators are in locations where there is direct view to the houses 7 of the subscribers. An IR receiver 8 is mounted on the outside of the houses, which receives the IR signal from the radiator and offers it via a non-shown interface to subscriber equipment such as a PC or NC (Network computer) 9.

Figure 2 shows in more detail an IR receiver 8. This is formed by an O / E converter 12, for example a photodiode, in the focus of a reflector 12. A lens can also be used for concentrating incoming light. 14; the figure uses both. The optical signal from the cooperating radiator 6, bundled via the lens 14 and reflector 12, is converted by the photodiode into an electrical signal.

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Finally, it is noted that although it can be foreseen that also with broadband downstream traffic, upstream traffic will usually be narrowband, whereas in local network 10 there is still a need for an upstream broadband connection, subscriber locations 7 can be provided with IR radiators for this purpose ( such as the radiators 6), while an IR receiver (such as the IR receivers 8) can be arranged at the curb. In the intermediate network 2, the upstream 10 broadband traffic can be transmitted via the fibers 5.

Such a broadband upstream connection in the local network 10, formed by an IR radiator on the side of a subscriber 7 and an IR receiver on the side of the curb, is shown schematically in Figure 1 at 15.

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Claims (7)

Telecommunications network, comprising a central (1), an intermediate network (2) between the central and local distribution / collection stations, hereinafter referred to as curbs (3) 5, and a local network (10) per curb between the curb and subscriber connections characterized in that the local network for the transmission of broadband signals on the side of the curb comprises an optical radiator (6) and on the side of the subscribers (7) optical receivers (8) co-operating with said radiator. Telecommunication network according to claim 1, characterized in that the intermediate network for the transmission of broadband signals comprises optical fibers (5). Telecommunication network according to claim 2, characterized in that the intermediate network for the transmission of narrowband signals comprises twisted pair cables (4). Telecommunication network according to claim 1, characterized in that the local network for the transmission of narrowband signals comprises twisted pair cables. Telecommunication network according to claim 1, characterized in that the optical receiver is directionally sensitive by means of a reflector (13) or a lens (14). Telecommunication network according to Claim 1, characterized in that local networks of the optical radiators in juxtaposed areas have different light polarities. Telecommunications network according to claim 1, characterized by modulation means for modulating on a carrier wave the broadband signals transmitted from the curb to the subscriber stations, the wavelength, frequency or polarity of the different modulated carriers or of the different modulating signals in adjacent local networks are mutually different. 1 0 0 3 4 4 3 ^