Patent Publication Number: US-2011052122-A1

Title: Optical assembly and method for connecting optical transceiver units by an optical assembly

Description:
RELATED APPLICATIONS 
     This application claims the benefit of European Application No. 09167513.2 filed on Aug. 7, 2009, the entire contents of which are herein incorporated by reference. 
     FIELD 
     An optical assembly is disclosed which may be used to connect optical transceivers by parallel optical paths. The disclosure also relates to a method for connecting optical transceiver units by parallel optical paths. 
     BACKGROUND 
     In an MPO (Multi-Fiber Push-On)-based dual fiber system (i.e., transmit-receive pairs of fibers), optical transceivers may be connected via an optical transmission cable comprising a plurality of optical fibers. The optical transmission cable is respectively terminated on both ends by a connector. The connector may be designed as a multi-fiber connector such as an MPO (Multi-Fiber Push-On) connector or an MTP (Mechanical Transfer Push-On) connector. The optical transceivers can be connected to the optical transmission cable by modules. Each of the modules has a first side with an MPO connector to connect a first side of each module with a connector terminating the optical transmission cable. Another side of each of the modules contains single connectors which are connected to the optical transceiver unit by single patch cord cables. 
     In prospective optical transmission systems, it is intended that the optical transceivers are provided with multi-fiber parallel connectors so that they can directly be connected to a parallel optical transmission cable without using modules between the parallel optical transmission cable and an optical transceiver (i.e., parallel optics). The optical transmission path disposed between transceiver units to be connected comprises a first optical transmission cable which is installed, for example, in the wall or under the floor of a building. Such an optical transmission cable, usually called backbone trunk cable, is connected by a second flexible optical transmission cable called patch cord cable on both of its ends to the transceiver units. 
     A backbone trunk cable is usually terminated on both of its ends with non-pinned connectors. In order to couple transceiver units via the backbone trunk cable, a patch cord cable is respectively connected between one of the non-pinned connectors of the backbone trunk cable and an input port of each of the optical transceivers. A patch cord cable provided to be connected between a backbone trunk cable and an optical transceiver has to be equipped with the pinned connector and the non-pinned connector. The pinned connector has to be provided at the side of the patch cord cable where the patch cord cable has to be connected with the backbone trunk cable. The non-pinned connector is provided on the side of the patch cord cable where the patch cord cable is to be connected to the port of the optical transceiver. If several backbone trunk cables have to be connected, in line, by a respective patch cord cable, the patch cord cable has to be equipped at both of its sides by pinned connectors. 
     In the near future it is intended to change (i.e., migrate) from a dual fiber cable technology to a parallel fiber cable technology due to the demand for more bandwidth. The parallel fiber cable technology provides a higher bandwidth system since light signals are transferred parallel by a plurality of e.g. twelve optical fibers arranged between connectors of the parallel fiber cable. When migrating from an MPO-based dual fiber system to an optical fiber technology based on a parallel transmission of optical signals, the user is faced with different requirements for patch cord cables. In structured cabling systems, patch cord cables with pinned and non-pinned connectors are needed to couple a backbone trunk cable to an optical transceiver and patch cord cables having pinned connectors on both sides have to be used to connect two backbone trunk cables. 
     An optical assembly is described in which optical transmission cables are used to interconnect backbone trunk cables and to connect a backbone trunk cable to an optical transceiver in an easy way for accommodating the migration. Furthermore, a method for connecting optical transceiver units by an optical assembly is disclosed. 
     SUMMARY 
     The present application is directed to an optical assembly comprising a first optical transmission cable comprising first connectors being of a first type, and a second optical transmission cable comprising second connectors being of a second type. The first optical transmission cable comprises ends respectively being terminated with one of said first connectors. The second optical transmission cable comprises ends respectively being terminated with one of said second connectors, wherein connectors of different types are configured to be connected with each other. The second connectors are respectively configured to be connected to an optical transceiver unit. 
     Also disclosed is a method for connecting optical transceiver units by an optical assembly comprising the steps of providing a first optical transmission cable and a second optical transmission cable. Furthermore, first connectors being of a first type and second connectors being of a second type are provided wherein connectors of different types are configured to be connected with each other and said second connectors are configured to be connected to an optical transceiver unit. Ends of said first optical transmission cable are terminated by said first connectors. Ends of said second optical transmission cable are terminated by said second connectors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The optical assembly and the method for connecting optical transceiver units by the optical assembly are illustrated by the following figures, in which 
         FIG. 1  shows an MPO-based dual fiber system to connect optical transceivers; 
         FIG. 2  shows an embodiment of an optical assembly having a parallel data path disposed between optical transceivers; 
         FIG. 3  shows an embodiment of an optical assembly used for parallel transmission of optical signals between transceiver units; and 
         FIG. 4  shows an optical assembly used to connect backbone trunks in an optical assembly based on a parallel transmission of optical signals. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an MPO-based dual fiber system comprising an optical transmission cable  1000  formed as a backbone trunk cable. The backbone trunk cable  1000  comprises a plurality of optical fibers which are terminated at one of their respective ends  1001  by a connector  1010  and at the other of their respective ends  1002  by a connector  1020 . The connectors  1010  and  1020  are respectively formed as MPO connectors of a non-pinned type. 
     An optical transceiver  1600  is connected to the MPO connector  1010  by a module  1100 . The module  1100  comprises an MPO connector  1110  of a pinned type which may be coupled to MPO connector  1010  of a non-pinned type. The module  1100  comprises single connectors  1120  which are coupled with connector  1110  by optical fibers  1130 . Each of the single connectors  1120  is coupled by a single patch cord cable  1500  to a port of optical transceiver  1600 . 
     The end  1002  of the backbone trunk cable  1000  is connected to an optical transceiver unit  1700  by a module  1200  and single patch cord cables  1400 . The module  1200  comprises a connector  1210  and single connectors  1220 . The connector  1210  is coupled to the single connectors  1220  by optical fibers  1230 . The connector  1210  may be formed as an MPO connector of a pinned type which is coupled to MPO connector  1020  of a non-pinned type. Each of the single connectors  1220  is connected to the optical transceiver  1700  by a single patch cord cable  1400 . 
     In prospective optical transmission systems, the transceiver units will be equipped with ports which may directly be connected to a parallel optical transmission cable without using modules between a backbone trunk cable and a transceiver unit. The transceiver unit may be directly coupled to the backbone trunk cable by optical transmission cables called patch cord cables.  FIG. 2  shows an optical assembly adapted to provide optical signals parallel via optical fibers of the optical transmission cables disposed between two transceiver units  2300 ,  2400  having parallel data input/output ports. 
     The optical assembly comprises an optical transmission cable  2000  configured as a backbone trunk cable. The backbone trunk cable comprises optical fibers  2030 . A respective end  2031  of the optical fibers is connected to a connector  2010  and the respective other ends  2032  of the optical fibers  2030  are connected to a connector  2020 . The connectors  2010  and  2020  may be formed as MPO connectors of a non-pinned type. 
     A transceiver unit  2300  has a port  2310  which is configured to be directly connected to a parallel optical transmission cable. The backbone trunk cable  2000  is connected to the transceiver unit  2300  by the optical transmission cable  2100  formed as patch cord cable. The patch cord cable  2100  comprises optical fibers  2130  which are terminated on a first of their ends  2131  by a connector  2110 . The other respective ends  2132  of the optical fibers  2130  are terminated by a connector  2120 . The connectors  2110  and  2120  may be formed as MPO connectors. MPO connector  2110  is formed as a connector of a pinned type. MPO connector  2120  is formed as a connector of a non-pinned type. 
     The transceiver unit  2400  is equipped with a port which is configured to be directly connected to a parallel optical transmission cable. In order to connect the backbone trunk cable  2000  to the transceiver unit  2400 , an optical transmission cable  2200  formed as a patch cord cable is provided between MPO connector  2020  and parallel port  2410  of transceiver unit  2400 . The patch cord cable  2200  comprises an MPO connector  2210  and an MPO connector  2220 . MPO connector  2210  is formed as a connector of a pinned type which is adapted to be connected with non-pinned connector  2020 . MPO connector  2220  is formed as a non-pinned type connector which is configured to be coupled with port  2410  of transceiver  2400 . 
       FIG. 3  shows an embodiment of an optical assembly comprising optical transmission cables  10 ,  20 , and  30  which are used to connect optical transceiver units  100  and  200  with each other. The optical assembly comprises the optical transmission cable  10  which is formed as a backbone trunk cable. Optical transmission cable  10  may be installed under the floor or in the wall of a building. Optical transmission cable  10  may be used to connect transceivers located in different rooms of the building. The optical transmission cable  10  comprises a plurality of optical fibers  13  having respective ends  131 ,  132 . The ends  131  of optical fibers  13  are terminated by connector  11  located at an end  101  of backbone trunk cable  13 . The other respective ends  132  of optical fibers  13  are terminated by connector  12  located at an end  102  of backbone trunk cable  10 . According to the embodiment of the optical assembly shown in  FIG. 3 , both of the connectors  11 ,  12  are configured as MPO connectors of a pinned type comprising pins  103 ,  104 . 
     Optical transceiver  100  is provided with a port  110  for parallel transmission of optical signals in the direction to and from optical transceiver  100 . The parallel port  110  of transceiver  100  is configured to be directly connected to an optical transmission cable used for parallel transmission of light signals. 
     An optical transmission cable  20  which is formed as a patch cord cable is disposed between port  110  of optical transceiver  100  and MPO connector  11  of backbone trunk cable  10 . The patch cord cable  20  comprises connectors  21 ,  22  located on respective ends  201  and  202  of optical transmission cable  20 . The optical transmission cable  20  comprises a plurality of optical fibers  23 . Respective ends  231  of optical fibers  23  are terminated by connector  21  which may be formed as an MPO connector. Respective ends  232  of optical fibers  23  are terminated by connector  22  which may also be an MPO connector. Both connectors  21  and  22  of patch cord cable  20  are formed as connectors of a non-pinned type. That means connectors  21  and  22  have no pins but respective cavities  203 ,  204 . The cavities  203  are configured to receive pins  103  of the pinned connector  11 . The cavities  204  of connector  22  are configured to hold connector  22  at the port  110  of transceiver  100 . 
     Transceiver  200  has a port  210  which is configured to receive and transmit optical signals via the optical path comprising optical transmission cables  10 ,  20 , and  30 . Optical transmission cable  30  comprises an end  301  terminated by connector  31  and an end  302  terminated by connector  32 . Optical transmission cable  30  is formed as a patch cord cable including a plurality of optical fibers  33 . Respective ends  331  of the optical fibers are terminated by connector  31 . The other respective ends  332  of optical fibers  33  are terminated by connector  32 . The connectors  31 ,  32  may be formed as MPO connectors of a non-pinned type. Connector  31  comprises cavities  303  adapted to receive pins  104  of connector  12  to couple connector  31  with connector  12 . Connector  32  includes cavities  304  adapted to hold connector  32  at transceiver unit  200 . 
     Optical fibers  13 ,  23 , and  33  are formed to transmit optical signals in a parallel manner between transceiver units  100  and  200 . In contrast to the embodiment of an optical assembly shown in  FIG. 2 , the optical assembly of  FIG. 3  comprises connectors  21 ,  22  for patch cord cable  20  and connectors  31 ,  32  for patch cord cable  30  having no pins. The connectors which terminate the ends of the patch cord cables are formed as connectors of a non-pinned type. Furthermore, the backbone trunk cable  30  is equipped with connectors  11 ,  12  having pins  103 ,  104 . 
     The backbone trunk cable is a cable which is more rugged in comparison with the patch cord cable. The backbone trunk cable has a minimum bend radius in a range of 40 mm to 80 mm, whereas the patch cord cable is more flexible having a minimum bend radius of more than 100 mm. Since the backbone trunk cable is pulled through channels in the floor or in the wall its maximum tensile load being in a range of between 400 to 600 N is much higher than the maximum tensile load of a patch cord cable being of about 200 N. The backbone trunk cable  30  is firmly installed in a wall or in a floor of a building. The patch cord transmission cables  20  and  30  may be flexibly arranged between the pinned-type connectors of the backbone trunk cable and the ports of electronic devices such as parallel transceivers units  100 ,  200 . 
       FIG. 4  shows an embodiment of two backbone trunk cables  10 ,  10 ′ which are connected by a patch cord cable  40 . The backbone trunk cables  10  and  10 ′ comprise MPO or MPT connectors of a pinned type. The patch cord cable  40  comprises MPO or MPT connectors  41 ,  42  of a non-pinned type. The connectors  41 ,  42  are located on both ends  401 ,  402  of patch cord cable  40 . The connectors  41  and  42  are of a non-pinned type. 
     The optical assembly shown in  FIGS. 3 and 4  allows that patch cord cables having the same type of connector at both of their ends may be used to couple backbone trunk cables with transceiver units or to interconnect backbone trunk cables. In contrast to an embodiment of an optical assembly shown in  FIG. 2  the complexity of an optical assembly is reduced since the same kind of interconnection cables terminated on both ends with the same type of connectors are used to couple backbone trunk cables and parallel optical transceiver units. The optical assembly and the method for connecting transceiver units by the optical assembly makes the migration to the parallel fiber cable technology simple and straight-forward for the craft. 
     When using MPO/MTP patch cords having no pins, there is no risk of damaging pins on MPO/MPT connectors when installing the patch cords. Using patch cords equipped with non-pinned connectors eases the handling of the patch cord cables and reduces the risk of damage during handling. The optical assembly shown in  FIGS. 3 and 4  also avoids damaged connectors due to wrong combinations of two pinned connectors in one MPO adapter. Since both of the ends of the patch cord cables are terminated with connectors having cavities, a damage occurring when coupling the connectors with the transceiver units is avoided.