Patent Publication Number: US-2004047630-A1

Title: Optical broadband transmission device and distribution method

Description:
[0001] The present invention relates to an optical broadband transmission device for a high-bit-rate data transmission, particularly also of multimedia contents, from a supply node to a user node as claimed in the preamble of claim  1  as known from WO 00/74278 A1.  
       [0002] According to the prior art, digital data streams are transmitted to a user, for example, by means of so-called ATM (asynchronous transfer mode) protocols. The increasing demand for the transmission to a user of multimedia content in addition to voice data requires transmission media with a wide bandwidth. In the literature, numerous methods and devices based on the transmission of data streams via copper or fiberglass lines and by means of complicated protocols are described. By comparison, an Ethernet protocol is a very simple protocol for transmitting multimedia data streams when sufficient bandwidth is provided at the physical level, i.e. in the form of a suitable transmission medium.  
       [0003] In this connection, it is desirable to transmit, in particular, the last part of the transmission link (“the last mile”) by means of an Ethernet protocol and by using single-wire lines, wire bundles or twisted pairs which can be constructed to be shielded or unshielded. Conventional Ethernet data transmissions are based on point-to-multipoint and point-to-point data transmissions. In principle, adding voice transmission capabilities has hitherto been carried out in two different ways:  
       [0004] (a) adding a specific device to the Ethernet in order to provide for conventional ISDN (integrated services digital network) telephony devices and POTS (plain old telephone system) telephony devices. This principle is usually called a LAN (local area network) telephone; and  
       [0005] (b) allocating particular frequency bands to voice data on a copper line.  
       [0006] The devices and methods relating to point (b) are described in U.S. Pat. No. 6,088,368 and known by the name 10BaseS. The 10BaseS method provides a transmission rate of 10 Mbs (megabit per second) over a maximum length of 1200 m. Further existing methods are designated in the first column of the table below and their characteristics such as transmission rate, cable type, maximum length and connecting device are in each case designated in columns 2 to 5.  
                               TABLE                           Transmis-       Maximum   Connecting       Designation   sion rate   Cable type   length   device                  10BaseT    10 Mbs   UTP    100 m   RJ-45       10Broad36    10 Mbs   Coax   1800 m       10BaseFL    10 Mbs   2 × MMF,   2000 m   ST                850 nm       10BaseS    10 Mbs   UTP   1200 m   RJ-45       100BaseTX    100 Mbs   2 × UTP,    100 m   RJ-45               cat. 5       100BaseFX    100 Mbs   2 × MMF,   2000 m   SC               1300 nm       100BaseT4    100 Mbs   4 × UTP,    100 m   RJ-45               cat. 3       100BaseS    100 Mbs   4 × UTP,    430 m               cat.       1000BaseLX   1000 Mbs   2 × MMF,    550 m   SC               1300 nm               2 × SMF,   5000 m   SC               1300 nm       1000BaseSX   1000 Mbs   2 × MMF    275 m   SC               62.5/125,850               2 MMF,    550 m   SC               50/125,                850 nm       1000BaseCX   1000 Mbs   twinax    25 m   HSSC                  
 
       [0007] Single unshielded twisted pairs (UTP), i.e. those implemented once, are generally known and are widely used for connecting a terminal of a user. As can be seen from the above table, however, the transmission rate is no more than 10 Mbs. However, this transmission rate of 10 Mbs provided in accordance with the 10BaseS method and used in conventional devices is not sufficient by far for transmitting simultaneously an MPEG-2 video data stream, a voice data stream and an acceptable user data stream. Higher transmission bandwidths would allow telecommunication devices to provide video data, voice data and user data streams on the basis of single sources for, for example, residential areas, particularly multi-dwelling units or office units as long as the line lengths are sufficient, i.e. typically at last 500 to 1000 m.  
       [0008] Furthermore, optical fibers and optical components are used in optical transmission technology in a familiar manner. The use of optical glass fibers in areas of sensors and particularly in optical communication technology for transmitting data streams is known from “Wolfgang Bludau, Lichtwellenleiter in Sensorik und optischer Nachrichtentechnik”, [optical waveguides in sensors and optical communication technology], Springer Verlag, ISBN 3-540-63848-2 (1998). Optical waveguiding forms the basic concept of optical transmission technology in this case and, in particular, the difference between step-index and gradient-index glass fibers should be pointed out.  
       [0009] On page 33 of the Springer publication, semiconductor materials, glass, polymers and lithium niobate are mentioned as substrate materials, i.e. as materials which are used as a starting basis for the production of optical waveguides (optical fibers or briefly fibers). Similarly, the difference between the ray-optical light propagation in an optical fiber provided with a step-index profile and with a parabolic profile is illustrated on page 45 (FIG. 3. 7  of the disclosure).  
       [0010] Conventional optical receivers and transmitters are described, for example, in the publication “Optics, Optoelectronics and Photonics Engineering Principals and Applications by Allan Billings, Prentice Hall, ISBN 0-13-709115-X (1993)”.  
       [0011] A method to transmit data streams with a bandwidth of 100 Mbs is called 100BaseS and can be found in row 8 in the above table. As can be seen from the table, the device and the method of the “100BaseS” needs four unshielded twisted pairs which are usually not provided in target areas which essentially comprise residential areas or MDUs (multi dwelling units) to be networked.  
       [0012] In addition, the device and the method of the “100BaseS” have the disadvantage that the achievable line lengths are not sufficient.  
       [0013]FIG. 5 shows a known device for transmitting data streams between a supply node  104  and a user node  105  via an electrical transmission line  501 , a first connecting device  106  being used for connecting the supply node  104  to a first node connection  112  and a second connecting device  107  being used for connecting the user node  105  by means of a second node connection  113 .  
       [0014] These conventional devices for transmitting data streams via the electrical transmission line  501  which, for example, use one of the cable types shown in the above table have the disadvantage, among other things, that only small data streams can be transmitted.  
       [0015] A further disadvantage of transmission devices according to the prior art consists in that only short distances can be bridged which are not suitable for use, for example, in multi-dwelling units (MDUs).  
       [0016] Another disadvantage of transmission devices according to the prior art consists in that preferred transmission protocols such as, e.g. 100BaseT Fast Ethernet protocols cannot be used since bandwidths of conventional transmission devices, i.e. of the physical layer or, respectively of the transmission medium are not adequate.  
       [0017] It is thus an object of the present invention to provide for data streams with a wide bandwidth from one or more supply nodes to one or more user nodes and, at the same time, to bridge transmission path lengths which are sufficient for being able to supply multi-dwelling units (MDUs) or office units with data streams.  
       [0018] The above objects are achieved by an optical broadband transmission device as claimed in claim  1  and a distribution method for data streams as claimed in claim  12 .  
       [0019] The device according to the invention, having the features of claim  1 , and the method according to the invention as claimed in claim  12  have the advantage that data streams with a high data rate can be transmitted.  
       [0020] A further advantage of the device according to the invention and of the method according to the invention consists in that an efficient transmission medium can be used without having to have recourse to complex transmission structures or mediums.  
       [0021] The core of the invention is a device and a method for broadband transmission of data streams by means of an efficient transmission medium.  
       [0022] According to a preferred development of the present invention, a diode transmitter module has a first optical transmitter diode and a second optical transmitter diode so that data stream transmission is provided at different optical wavelengths.  
       [0023] According to a further preferred development of the present invention, the transmission device according to the invention has electrical and optical components which are capable of transmitting data streams at a transmission rate of 100 Mbs (megabits per second).  
       [0024] According to yet another preferred development of the present invention, a laser transmitter module has a laser transmitter unit which is connected to an optical fiber via a coupling unit in order to provide one or more wavelengths for a data stream transmission, wherein long transmission lengths can be achieved.  
       [0025] According to a further preferred development of the present invention, building equipment is provided with a LAN (local area network) switching device or LAN switch, respectively, which makes it possible to transmit a data stream from a router device to first and second LAN modem devices.  
       [0026] According to another preferred development of the present invention, bidirectional transmission of data streams is provided.  
       [0027] According to another preferred development of the present invention, the optical fiber for transmitting data streams is a single plastic optical fiber (POF).  
       [0028] According to another preferred development of the present invention, the optical fiber for transmitting data streams is a step-index fiber.  
       [0029] According to another preferred development of the present invention, the optical fiber for transmitting data streams is a gradient-index fiber.  
       [0030] Exemplary embodiments of the invention are shown in the drawings and explained in greater detail in the description following.  
     
    
    
     [0031] In the drawings:  
     [0032]FIG. 1 shows a device for transmitting data streams by means of an optical fiber between a first optical transceiver and a second optical transceiver according to an exemplary embodiment of the present invention;  
     [0033]FIG. 2 shows an exemplary embodiment of a diode transmitter module for transmitting data streams arriving at a supply node, shown in FIG. 1, by means of a first optical transmitter diode and a second optical transmitter diode according to an exemplary embodiment of the present invention;  
     [0034]FIG. 3 shows a laser transmitter module which contains a laser transmitter unit and a coupling unit, for transmitting data streams according to an exemplary embodiment of the present invention;  
     [0035]FIG. 4 diagrammatically shows a representation of building equipment which illustrates how data streams are supplied to first and second LAN modem devices from a router device via a LAN switch; and  
     [0036]FIG. 5 shows a conventional device for transmitting data streams. 
    
    
     [0037] In the figures, identical reference symbols designate identical or functionally identical components.  
     [0038]FIG. 1 shows a device for transmitting data streams by means of an optical fiber  101  between a first optical transceiver  102  and a second optical transceiver  103  according to an exemplary embodiment of the present invention.  
     [0039] The device shown in FIG. 1 has as the central element an optical fiber  101  which connects a first optical transceiver  102  to a second optical transceiver  103 . This device can be used for transmitting data streams between a supply node  104  and a user node  105  with much greater bandwidth than is possible with a wire-connected transmission medium according to the prior art. The transmission rate according to the method is typically 100 Mbs whereas, according to the prior art, a maximum of 10 Mbs are provided with an electrical transmission line with the same transmission length (500 to 1000 m). Referring to FIG. 1, the first supply node  104  is connected to a first connecting device  106  via a first node connection  112  which is constructed as electrical connection (plug connection). The output of the first connecting device  106  is (electrically) connected via a first line connection to a first processing circuit  110 , the first line connection  108  only being used for connecting the first connecting device  106  and, therefore, is constructed to have a correspondingly short line length. The first processing circuit  110  processes the signal supplied via the first line connection  108 , i.e. the data stream, and supplies the processed signal to the first optical transceiver  102 . The first optical transceiver  102  is coupled to the optical fiber  101  in such a manner that data streams can be sent both to the optical fiber  101  and data streams can be received from the optical fiber  101 , i.e. a bidirectional operating mode is provided. Exemplary embodiments for transmitting optical data streams to the optical fiber  101  are given in the subsequent description, referring to FIGS. 2 and 3.  
     [0040] A second optical transceiver  103  is connected to a second end of the optical fiber  101 . Similarly to the first optical transceiver  102 , the data streams into the second optical transceiver  102  are converted from an optical data stream into an electrical data stream or conversely. An output signal of the second optical transceiver  103  is supplied to a second processing circuit  111  which supplies a processed data stream as an electrical signal to a second connecting device  107  via a second line connection  109 . The second connecting device  107  is connected to the user node  105  via a second node connection  113  from which the data streams are distributed further as will be explained below by means an exemplary embodiment, referring to FIG. 4.  
     [0041] It should be pointed out that, according to the exemplary embodiment of the present invention described above, the first connecting device  106 , the first line connection  108 , the first processing circuit  110  and the first optical transceiver  102  can be provided in a first common plug housing in the optical broadband transmission device, in order to ensure compatibility with existing connecting devices according to the prior art to a supply node  104 .  
     [0042] Furthermore, the second connecting device  107 , the second line connection  109 , the second processing circuit  111  and the second optical transceiver  103  can be provided in a first common plug housing in the optical broadband transmission device in the exemplary embodiment of the present invention described above, in order to ensure compatibility with existing connecting devices according to the prior art to a user node  105 .  
     [0043]FIG. 2 illustrates an exemplary embodiment of a diode transmitter module  206  for transmitting data streams arriving at a supply node  104 , shown in FIG. 1, by means of a first optical transmitter diode  201  and a second optical transmitter diode  202  according to an exemplary embodiment of the present invention.  
     [0044] In the device shown in FIG. 2, a diode transmitter module  206  consists of a first optical transmitter diode  201  and a second optical transmitter diode  202  which sends out radiations of different wavelengths, for example in the red and green spectral band. The optical radiation of the from the [sic] first optical transmitter diode  201  and the optical radiation of the second optical transmitter diode  202  is in each case supplied to a first optical fiber branch  203  and, respectively, a second optical fiber branch  204 . The two optical fiber branches  203  and  204  are combined in a fiber branch device  205  and are optically connected to the optical fiber  101 . The device according to FIG. 2, shown in the exemplary embodiment of the present invention, makes it possible to transmit data streams on different carriers, in this case different wavelengths.  
     [0045] It should be pointed out that the diode transmitter module  206  shown in FIG. 2 is constructed as diode receiver module at the receiving end and the first and second optical transmitter diodes  201  and  202 , respectively, have to be replaced by first and second optical receiver diodes.  
     [0046] Furthermore, the first and second optical transceivers  102  and  103 , respectively, can be formed of in each case a combination of a diode transmitter module  206  with a diode receiver module, the first and second processing circuits  110  and  11  being correspondingly modified.  
     [0047]FIG. 3 shows a laser transmitter module  303  which contains a laser transmitter unit  301  and a coupling unit  302 , for transmitting data streams according to an exemplary embodiment of the present invention.  
     [0048] In the exemplary embodiment, shown in FIG. 3, of the present invention, a laser transmitter module  303  consists of a laser transmitter unit  301  and a coupling unit  302 . In distinction from the device shown in FIG. 2, the device shown in FIG. 3 has the advantage that one or more wavelengths can be emitted by means of the laser transmitter unit  301  with a high spectral power density so that, on the one hand, long transmission lengths can be bridged via the optical fiber  101  and, on the other hand, data streams can be transmitted on one or more carriers in accordance with one or more wavelengths.  
     [0049] The laser transmitter module  303  shown in FIG. 3 can be used instead of the diode transmitter module  206 , shown in FIG. 2, but a corresponding laser receiver module must be provided for receiving the respective data streams as explained with reference to FIGS. 1 and 2.  
     [0050]FIG. 4 diagrammatically shows a representation of building equipment  401  which illustrates how data streams are supplied to first and second LAN modem devices  404  and  405 , respectively, from a router device  402  via a LAN switch  403 .  
     [0051] In the exemplary embodiment shown in FIG. 4, the dashed line represents building equipment  401 . The building equipment  401  contains a LAN (local area network) switch  403  which forwards data streams to a first LAN modem device  404  and second LAN modem device  405 . At the LAN switch  403 , video data  406  can be supplied. The building equipment  401  is connected to a router device  402 , building equipment for, for example, multi-dwelling units (MDUs) or office units being provided according to the exemplary embodiment of the present invention.  
     [0052] The present embodiments of the invention thus provide a device and a method for the inexpensive transmission of data streams with a high bit rate between a supply node  104  and a user node  105 .  
     [0053] In particular, the optical fiber  101  can be designed as a plastic optical fiber (POF) which provides for further cost reduction. This enables the fiber branch device  205  to be dispensed with and both signals can be injected or one can be extracted and one can be injected.  
     [0054] The connection between the first optical transceiver  102  and the second optical transceiver  103  has a transmission length of typically 500 to 1000 m so that an optical access to building equipment can be set up by means of inexpensive plastic optical fibers.  
     [0055] The optical transceivers can also be manufactured inexpensively since no long transmission lengths need to be bridged. In this arrangement, a first LAN modem device is connected via a first intermediate access device  407  and the second LAN modem device  405  is connected via a second intermediate access device  408 , in each case to the LAN switch  403 .  
     [0056] Increasing building networking, particularly in multi-dwelling units and office unit [sic] or business spaces, building automation and advances in building system technology lead one to expect that the device according to the invention and the method according to the invention will find increasing application possibilities.  
     [0057] Although the present invention was described above by means of preferred exemplary embodiments, it is not restricted to these but can be modified in many ways.  
                               List of reference designations                                                101   Optical fiber           102   First optical transceiver           103   Second optical transceiver           104   Supply node           105   User node           106   First connecting device           107   Second connecting device           108   First line connection           109   Second line connection           110   First processing circuit           111   Second processing circuit           112   First node connection           113   Second node connection           201   First optical transmitter diode           202   Second optical transmitter diode           203   First optical fiber branch           204   Second optical fiber branch           205   Fiber branching device           206   Diode transmitter module           301   Laser transmitter unit           302   Coupling unit           303   Laser transmitter module           401   Building equipment           402   Router device           403   LAN switch           404   First LAN modem device           405   Second LAN modem device           406   Video data           407   First intermediate access device           408   Second intermediate access device           501   Electrical transmission line           MDU   Multi-dwelling unit           POF   Plastic optical fiber           UTP   Unshielded twisted pair