NO328696B1 - Device for making a data connection - Google Patents

Abstract

The device establishes a connection between an interconnection point (12, NTBA) of a telecommunications network (14) and at least one internal user (18). An S0 bus is connected between the interconnection point and the user. The S0 bus is an optical transmission line (22). The interconnection point and the user are connected to the transmission line via respective digital opto-converters (26,28).

Description

The invention relates to a device for creating a data connection between digital communication devices, such as a handover point (NTBA) in a telecommunications network and at least one internal user, where a So bus is connected between the handover point and the at least one user.

Devices according to the nature of this technique are known. In this way, a consumer-owned branch system connected to an ISDN ("integrated services digital network") handover point is usually provided with a so-called So-bus. Over this So bus, data processing equipment, such as personal computers, notebooks and the like, and telecommunications equipment can communicate with the handover point for a data transfer purpose. The structure and operation of such So buses are generally known, so that within the scope of the present description this will not be discussed in more detail.

It is known to develop these So buses wired over twisted copper double conductors (2 double conductors). Cable of this type is provided with a metallic screen to reduce electromagnetic disturbances in the data transmission (EMV protection). For the operation of the So buses, it is envisaged that both the handover point and the connection modules (ISDN cards or similar) assigned to the consumers are operated with a voltage supply, usually the mains voltage of 220 volts. Through this connection arrangement, it turns out that through the shielding of the wired So buses and the neutral conductor of the voltage supply, a conductor loop can be formed in which, in the event of an overvoltage that occurs in the supply voltage network, such as through a lightning strike or the like, can appear in a voltage induction. From here arises the danger of interference or at least causing damage to a function of a consumer who is connected to the So bus.

From EP0760587A, a hybrid fibre-coaxial broadband connection network is known for connecting telecommunications subscribers to radio base stations, where the radio base stations are connected to branches in coaxial sections of the hybrid connection network as ISDN subscribers.

US5673258 describes the development of a So bus for data transmission, where the So bus for bidirectional data transmission consists of two copper lines for each direction of transmission.

The invention therefore has the task of providing a device of the type indicated, which enables a data transfer in a simple way and which provides overvoltage protection.

According to the invention, this task is solved with a device characterized by the features that appear in the accompanying patent claim 1. Through the fact that the So bus is an optical transmission line and at least one consumer is connected to the transmission line via a digital/opto at all times -, respectively opto/digital converter, the data transfer can advantageously be realized optically over the So bus. For this, there is a need for an additional metallic screen wire, so that the danger of a conductor loop forming over the supply voltage network will not exist. This provides optimal surge protection for the consumers connected to the So bus, respectively the handover point to the telecommunications network.

In preferred embodiments of the invention, it has been envisaged that the optical transmission line comprises a polymer fiber. This makes it possible to build up a So bus over relatively large distances in a simple and cost-effective way. Such polymer optical fibers allow a low-loss data transmission over large distances. In addition, such optical polymer fibers are insensitive to electromagnetic disturbances, so that their applications for data transmission are optimally suited. Furthermore, it is advantageous that optical polymer fibers offer a large transmission capacity, so that an adaptation to a broadband transmission method, in particular ATM or IEEE 1394, is possible in a simple way compared to the So-bus standard.

In further preferred embodiments of the invention, it has been envisaged that the digital/opto converter or the opto/digital converter at all times comprises an optical transmitter and an optical receiver. With this, a bidirectional data transfer to maintain the So-bus data traffic becomes possible in a simple way. In this way, two channels with up to 40 dB dynamic range can be advantageously transmitted for each polymer fiber.

Through the low component costs, the transmitter in an NTBA and the receiver in the communication interface board can be integrated into the computer to enable a direct optical So-bus connection without additional equipment.

Further preferred embodiments of the invention appear from the features mentioned in the other incomplete claims.

The invention is explained in more detail in the subsequent embodiment examples with the help of the associated drawings. They show:

Figure 1 schematically in a block diagram device according to the invention; Figure 2 device according to the invention in a first construction stage; Figure 3 is a block diagram of a digital/opto converter; Figure 4 is a block diagram of an optical receiver; Figure 5 shows a characteristic for a coincidence demodulator in the optical receiver; Figure 6 schematically in a block connection diagram, a second embodiment variant of the device according to the invention; Figure 7 schematically shows the signal sequence before and after a digital/opto-converter and the Figures at any time in block connection diagrams different applications of the 8 to 22 device according to the invention. Figure 1 shows in a block diagram the basic construction of the device 10 of the invention. The device 10 comprises a handover point 12, a so-called NTB A, between a telecommunications network 14 and a branch facility 16 on the consumer side. The branch facility 16 comprises at least one consumer 18, usually several consumers 18. The consumer 18 is, for example, a data processing facility (personal computer). The consumer 18 is connected to the handover point 12 via a So-bus 20. The So-bus 20 is, in a standard manner, a component of a communication system based on ISDN. The So-bus is formed by an optical transmission line 22. The optical transmission line 22 comprises a polymer fiber 24, which is connected on one side to the handover point 12 and on the other side is connected to the consumer 18.1 handover point 12 is arranged a digital/ opto-converter 26, while on the consumer side an opto/digital converter 28 is arranged. A data connection at the consumer 18 with another consumer not shown over the telecommunications network 14 is consequently achieved internally, i.e. on the consumer side, to the handover point 12 over an optical So -bus. For transmission over the optical So bus, the digital signals are modulated or demodulated into optical signals at any time in the converters 26 and 28, respectively. Figure 2 shows an equivalent circuit diagram of the optical So buses 20. The digital/opto converter 26 comprises a transmitter 30, which maintains the connection with the telecommunications network 14 over the handover point 12. The transmitter 30 is connected to a modulator 32 as well as a demodulator 34. The modulator 32 is connected to an optical transmitter 36, while the demodulator 34 is connected to an optical receiver 38. The optical transmitter 36 and the receiver 38 respectively are connected with the polymer fiber 24. Furthermore, the converter 24 comprises a voltage supply 40 to provide a supply voltage for the modulator 32 and the demodulator respectively 34. The supply voltage for the modulator 32 and the demodulator 34 is, for example, 5 V. This supply voltage is transformed from a voltage provided over the telecommunications network 14, which is, for example, 40 V.

The opto-to-digital converter 28 arranged on the consumer side has a construction analogous to the construction of the digital-to-opto converter 26 of a transmitter 30', a modulator 32', a demodulator 34', an optical transmitter 36', a optical receiver 38', as well as a voltage supply 40'. The voltage supply 40' is connected to a mains part 42 which provides and correspondingly down-transforms a supply voltage from a voltage supply system on the consumer side, such as for example on the basis of 220 V.

The optical transmitters 36 and 36' respectively and the optical receivers 38 and 38' respectively are connected by polymer fibers 24 over the connection 44.

The optical polymer fiber 24 has, for example, a cross-section of 1 mm and an attenuation of 70 dB/km. An optimal attenuation range for the polymer fiber 24 with PMMA as core material (polymethyl methacrylate) is consequently in a range of 560 nm. The optical transmitters 36 and 36' respectively are formed with a GaN light emitting diode with a transmitter wavelength of approx. 560 nm. A power of the optical transmitter 36 is, for example, 1,200 uW at a current of 20 mA. The optical receivers 38 and 38' respectively are formed by photodiodes.

The modulation of the digital signals in the optical signals is achieved through a three-stage frequency modulation (frequency shift keying), which is explained in more detail with the help of Figure 7. As is known, the So bus line code [AMI (alternate mark inversion) code] is defined as pseudoternary code with three different potentials where +Ui = 750 mV corresponds to +1, 0 V corresponds to 0 and -Ui = -750 mV corresponds to -1. The voltage fluctuation is thus 1.5 V. Through voltage pulses with the corresponding three voltage potentials, binary data codes can thus be transmitted. Through the three-stage frequency modulation, the voltage potential +Ui is converted to a frequency fi, the voltage potential 0 V is converted to a frequency f2 and the voltage potential -Ui is converted to a frequency f3.1 in accordance with the hereby established frequencies fi . a frame sync word, the voltage output is 1.2 V, i.e. UY =

600 mV and -Ui' = -600 mV. These changed voltage potentials are transformed into changed proportional frequencies fi' and fa'. The frequency f2 for the voltage potential 0 V remains the same. In this way, the three-stage frequency modulation can be easily adapted to a data transfer and the active rest state. The resting state can be recognized independently of the level of the received signals.

Figure 3 clarifies in a block diagram the connections of the converters 26 and 28 respectively to the telecommunications network 14 and to the consumer 18 respectively. The modulators 32 and 32' respectively are formed by a voltage-controlled oscillator 44a, while the demodulators 34 and 34' are formed by an FM-MF amplifier 48 with coincidence modulator 50. The construction and operation of these demodulators 34 and 34', respectively, are explained in more detail with the help of Figure 4. To the voltage oscillator 44a is assigned a voltage adaptation link 48, over which the frequency adaptation of the transmitting voltage potentials, which is explained with of Figure 7, is achieved. Furthermore, an emergency voltage supply 50 is provided, through which operation of the So buses 20 is possible in the event of a failure of a regular voltage supply.

The equivalent circuit diagram of the demodulators 34 and 34', respectively, is shown in Figure 4. These include the amplifier 48 which is connected after the coincidence demodulator 50. An input termination 52a of the amplifier 48 is connected to the optical receiver 38. The amplifier 48 and the coincidence demodulator 50 are connected to an internal voltage supply 52 which obtains its voltage supply + Ub from the voltage supply

40. The coincidence demodulator 50 is further controlled by a phase shifter 54, which consists of an inductor, capacitor and an adjustable ohmic resistance. The amplifier 48 exhibits a relatively high gain such as 68 dB and limiting characteristics such as 30 dB AM suppression at 200 uV input voltage. Through this, it is achieved that the amplifier 48 delivers to the coincidence demodulator 50 in the optical reception performance range - at the connection 52a - of -40 dBm to -5 dBm in a constant, objectionable, symmetrical, limited voltage. With

this is the coincidence demodulator output voltage independent of the optical input power and strongly proportional to the offered transmitter frequency response in accordance with the frequency-modulated optical signals transmitted over the So bus 20. The phase shifter 54 ensures a high constant in the frequency modulation converter characteristic. As no linear FM/AM transmission of the signals occurs, but rather only three voltage potential states must be recovered from the transmitting frequencies f1, f2 and f3, the phase shifter 54 can be sized so that the lower frequency fiav and the upper frequency fhay (see figure 5) at maximum frequency response, lies in the turning points 56 of the discriminator function. With this, a further noise reduction is achieved for the digital -1 and +1 states. By changing the quality of the phase shifter circuit 54, the distance of the reversal points 54 can be adjusted. With this, there is a setting option for the three-stage frequency modulation. Especially with systems that work quickly over the ISDN network, an adaptation of the three-stage frequency modulation can be easily achieved.

A current regulation coupling 56 is connected to the coincidence demodulator 50, which supplies the demodulated signal with a low pass 58. Through the current regulation coupling 56, a current distribution change is made possible, even though the output of the coincidence demodulator 50 initially only contains a direct current-carrying signal. With this, an adaptation to different So-bus isolating transformers is made possible. By means of the low-pass 58, a post-amplification of the signals is achieved for a signal conditioning ("Deem-phasis"). The low pass 58 is formed in three steps. At the output end 60 of the modulator 34, which is also the input end of the transmitter 30 (figure 2), the demodulated, digital signal Si is present.

Figure 6 shows in a block connection diagram an embodiment variant of the device 10 according to the invention. With this, the consumer 18 already explained in Figure 1 is connected to the handover point 12 and, via the So bus 20, a further consumer 18', for example an ISDN telephone, is connected. The So-bus 20 is consequently divided, once for the consumer 18' which is formed by ISDN telephone, where a known embodiment can be chosen here, such as multi-conductor copper wire or the like. Furthermore, a section of the So-bus 20 is formed as polymer fiber 24, where the explained data transmission is achieved through the converters 26 and 28 respectively. The turning points of the S-shaped converter characteristic are set through the operational efficiency of the circuit by means of the parallel resistance.

Through this design, it is achieved that the entire device 10 can be operated without its own voltage supply to the handover point 12 (NTBA). A power consumption of the consumer 18' can be, for example, 4.5 watts, while the power consumption of the consumer 18 via the converter 26 can be kept below 415 mW. With this, a voltage supply at the device 10 can be assumed through the existing voltage supply over the telecommunications network 14, which is usually from 40 V to 60 V. A further, internal voltage supply with a voltage supply network, such as 220 V, can therefore be equalized. Consequently, it is not necessary to insert corresponding network parts.

In Figures 8 to 22, different design variants using the device 10 according to the invention are explained. Figures 8 to 22 show at all times block connection diagrams that particularly clarify schematically a multiplex/demultiplex operation and/or a bidirectional operation of the device 10. Figure 8 shows, for example, a device on the sending side, where a So bus 60 is connected to a digital/opto converter 26' and a So bus 62 is connected to a digital/opto converter 26". The digital/opto converters 26' and 26" are connected to a common optical transmitter 36 via a connection point 64 over which the optical signals can be fed into the polymer fiber 24.1 digital/opto-converter 26', for example, a conversion to the frequencies fi, f2 and f3 is possible, while in the digital/opto-converter 26" a conversion to the frequencies U, fs and U- This enables a mutually non-interfering multiplex operation. Figure 9 shows an embodiment variant where the digital/opto-converters 26' and 26" are assigned at all times to an optical transmitter 36. The optical transmitters are then connected via the polymer fibers 68 and 70 respectively with an optical coupler 66, which is connected to the polymer fiber 24. In the embodiment in Figure 9, the optical transmitters 36 work with the same wavelength X. The conversion is achieved in the digital/opto-converter 26' to the frequencies f1, f2 and få, and in digital /the opto-converter 26" to the frequencies few, U and f5.

On the other hand, Figure 10 shows an exemplary embodiment in which the optical transmitters 36 work at different wavelengths, for example the optical transmitter assigned to the digital/optoconverter 26' with a wavelength X\ and that of the digital/optoconverter 26" assigned optical transmitter 36 with a wavelength Å, 2. With this, a conversion to the same frequencies f1, f2 and few can be achieved in the digital/opto-converters 26' and 26", respectively, as the multiplex operation is realized through the different wavelengths X\ respectively X2.

Figure 8 and Figure 9 consequently depict a frequency multiplex operation, while Figure 10 depicts a wavelength multiplex operation.

According to the design example drawn in Figure 11, combinations of wavelength multiplex operation and frequency multiplex operation are also possible. Here, the So bus 60, 62, 72 and 74 are at all times connected to the digital/opto converters 26, where the digital/opto converters 26 which are connected to the So buses 60 and 72 convert to the frequencies fi, f2 and f3 , and the digital/opto converters 26 which are connected to the So buses 62 and 74, convert to the frequencies U, fs and fis. According to the design, the upper optical transmitter 36 works here with the wavelength Å,i, while according to the design, the lower optical transmitter 36 works with the wavelength X2-

In Figures 12 to 15 inclusive, a complementary situation is depicted to one of Figures 8 to 11, respectively, at the device 10 on its receiving side. While a multiplex operation is achieved on the transmitter side, on the receiver side a demultiplex operation, either in frequency demultiplex operation, wavelength demultiplex operation or combined frequency and wavelength demultiplex operation, is possible.

According to Figure 12, the polymer fiber 24 is connected to an optical receiver 38, which is connected via a divider 76 to opto/digital converters 28. The opto/digital converters 28 are at all times connected to a So bus 60' and 62 '. Here, the opto/digital converter 28 converts from the frequencies fi, f2 and f3, while the opto/digital converter 28' converts from the frequencies fit, fs and £5.

A corresponding analog device appears according to Figure 13, in which the polymer fiber 24 is connected to the polymer fibers 80 and 82 over an optical divider 78, which at all times leads to an optical receiver 38. The optical receivers 38 are assigned to opto/digital the converters 28' and 28". The optical receivers 38 here work with the same wavelength, so that the conversion from the frequencies fi, f2 and f3 is achieved in the opto/digital converter 28', while the conversion from the frequencies f3, fit and fs is achieved in the opto/digital converter 28".

On the other hand, Figure 14 shows an embodiment in which the optical receivers 38 work in different wavelength ranges X. Here, between the polymer fiber and the optical receiver 38 shown at the top, there is a first assigned filter 84 and the optical receiver 38 shown below with an assigned second filter 86. Here, the filter 84 is transparent for optical signals with the wavelength Xi, while the filter 86 is transparent for optical signals with the wavelength X2. With this, the opto/digital converters 28' and 28" respectively work with the conversion of the same frequencies fi, f2 and f3. Figure 15 shows a combined wavelength demultiplex and frequency demultiplex operation. Here, wavelength demultiplex operation is primarily achieved through the filters 84 and 86 respectively and i connecting the frequency demultiplex operation over the opto/digital converters 28, which are arranged to convert the frequencies fi, f2 and f3, respectively U, f5 and £5. Figures 16 to 18 show schematically different combination possibilities for connections of digital/opto converters 26 with opto/digital converters 28 within a device 10. Figure 16 shows that a digital/opto converter 26 is connected to two So buses 60 and 62 and undertakes a conversion to the frequencies fi, f2, f3, f4, f5 and U. At the same time, an opto/digital converter 28 is provided which undertakes a conversion from the frequencies f1, f2, f3, f4, f5 and f6 on the So buses 60' and 62' respectively.

According to Figure 17, two digital/opto-converters 26 are used, which are connected to an opto/digital converter 28. The device according to Figure 18 is in a similar way, but reversed, where a digital/opto-converter 26 is connected with two opto/digital converters 28.

Figures 19 to 22 show different connection devices for a bidirectional multiplex or demultiplex operation. The transmission can further be achieved in wavelength multiplex/demultiplex operation (figures 19 to 21 inclusive) or in a combined wavelength multiplex/demultiplex operation and frequency multiplex/demultiplex operation. The individual structural elements are provided with the same reference numbers as in the preceding figures and are thus not explained again.

All in all, it is clear that there are many application possibilities for the realization of optical So-buses over polymer fibers 24. Depending on the layout and the number of inserted digital/opto-converters 26 and opto/digital converters 28 respectively with respect to their frequency f, respectively their wavelengths X, it is possible in a simple way to build up complex systems.

Claims (9)

1. Device (10) for creating a data connection between a handover point (12, NTBA) of a telecommunications network (14) and at least one internal consumer (18), where a So is connected between the handover point (12) and the at least one consumer (18) bus (20), characterized in that the So bus (20) is an optical transmission path (22), and the handover point (12) and the at least one consumer (18) are connected to the transmission line (22) via a digital/opto converter (26, 28). 2. Device as stated in claim 1, characterized in that the optical transmission line (22) is a polymer fiber (24). 3. Device as stated in one of the preceding claims, characterized in that the digital/opto-converter (26, 28) comprises an optical transmitter (36, 36') and an optical receiver (38, 38'). 4. Device as stated in one of the preceding claims, characterized in that means are provided over which the modulation of the digital signals in the optical signals is achieved over a three-stage frequency modulation. 5. Device as stated in one of the preceding claims, characterized in that means are provided by which an adaptation is achieved from frequencies (fi, f2, fa) to a data transfer, respectively from frequencies (fi', f2, fa') to an active resting state. 6. Device as stated in claim 3, characterized in that the optical transmitter (36, 36') is controlled from a voltage-controlled oscillator (44). 7. Device as stated in claim 3, characterized in that the optical receiver (38, 38') is connected to a limiting FM-MF amplifier (48) with a coincidence demodulator (50). 8. Device as stated in claim 7, characterized in that the coincidence demodulator (50) is controlled from an adjustable phase shifter whose goodness determines the transfer function demodulation characteristic for an FSK modulation. 9. Device as set forth in claim 7, characterized in that the coincidence demodulator (50) is connected after a current control coupling (56) and a low pass (58).