Abstract:
An internal unit is incorporated in a body of a submarine apparatus. The internal unit comprises a plurality of system units placed in a predetermined arrangement, and coupling bars fixed to coupling-bar fixing surfaces of the system units by screws so as to couple the system units in the predetermined arrangement. The system units include at least one electronic-circuit printed board having a part to be adjusted. The coupling-bar fixing surfaces are located at positions shifted from the electronic-circuit-printed board.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to an internal unit and a submarine apparatus having the internal unit and, more particularly, to an internal unit in a submarine apparatus, and a submarine apparatus provided along a submarine cable together laid on a seafloor. 
     The “submarine apparatus” means an apparatus laid on a seafloor, such as a submarine repeater, a submarine branching unit, or a gain equalizer. 
     Currently, in a market of submarine-apparatus, it has been required that a submarine apparatus is delivered to a customer in a shorter period since making a contract with the customer. Therefore, a submarine apparatus is required to be manufactured in a shorter period. 
     FIG. 1 shows a structure of a general submarine repeater  10 . The submarine repeater  10  comprises a cylindrical airtight body  11  that can endure a water pressure on a seafloor, and a cylindrical internal unit  12  incorporated therein. The airtight body  11  comprises a cylindrical outer body  13  and end-surface plates  14  and  15  covering both ends of the outer body  13 . The internal unit  12  is incorporated within the outer body  13  with a buffering member  16  formed of a mesh plate being placed therebetween. The buffering member  16  has a function of conducting heat generated by the internal unit  12  to the airtight body  11 , and also has a function of keeping the internal unit  12  from suffering vibrations and impacts caused during the laying of the submarine repeater  10 . 
     The submarine repeater  10  is connected with a submarine cable  20 . The submarine cable  20  includes an optical fiber  21  transmitting information, and an electric-supply line  22  supplying electric power. The optical fiber  21  and the electric-supply line  22  are drawn into the airtight body  11  via a hole formed in the end-surface plate  14  or  15  so as to be connected with the internal unit  12 . 
     In manufacturing the submarine repeater  10 , it takes a lot of steps to assemble the internal unit  12 . 
     2. Description of the Related Art 
     FIG. 2 to FIG. 6 show a conventional internal unit  30  of a submarine repeater. In FIG. 2 to FIG. 6, circuit units are stacked in a horizontal direction. X indicates a horizontal direction, Z indicates a vertical direction, and Y indicates a depth direction (a longitudinal direction of the internal unit  30 ). FIG. 2 shows a disassembled state of roughly a front half (in a direction Y 2 ) of the internal unit  30 . FIG. 3 is a front view of the internal unit  30 , as seen from Y 2 . FIG. 4 is a plan view of the internal unit  30 , as seen from Z 1 . FIG. 5 is a bottom view of the internal unit  30 , as seen from Z 2 . FIG. 6 is a side view of the internal unit  30 , as seen from X 1 . 
     The internal unit  30  mainly comprises a plurality (for example, four) of system units  31 - 1 ,  31 - 2 ,  31 - 3  and  31 - 4 , four coupling bars  32 - 1 ,  32 - 2 ,  32 - 3  and  32 - 4 , covers  34 - 1  and  34 - 2 , an insulating cylinder  35 , and end-surface covers  36 . 
     The system unit  31 - 1  comprises an optical circuit unit  40  having an optical circuit component, a monitor/power-supply circuit unit  42  including a printed board  41  for address-setting, a control circuit unit  44  including a printed board  43  for adjusting, and a lid member  45  made of metal. The optical circuit unit  40 , the monitor/power-supply circuit unit  42  and the control circuit unit  44  are stacked in this order in a direction X 2 -X 1 , and the lid member  45  covers the outer surface of the control circuit unit  44 . Each of the circuit units  40 ,  42  and  44  is made of metal, and has a box shape with the outer surface being open. The other system units  31 - 2  to  31 - 4  have the same or symmetrical structure as the above-described system unit  31 - 1 . 
     The first system unit  31 - 1  and the second system unit  31 - 2  are fixed to each other by insulating coupling plates  46  and screws with an insulating sheet  47  therebetween so that the optical circuit units  40  of the first system unit  31 - 1  and the second system unit  31 - 2  face each other in a direction X 1 -X 2 . Likewise, the third system unit  31 - 3  and the fourth system unit  31 - 4  are fixed to each other so that the optical circuit units  40  of the third system unit  31 - 3  and the fourth system unit  31 - 4  face each other in the direction X 1 -X 2 . The first system unit  31 - 1  and the third system unit  31 - 3  are aligned in a direction Y 2 -Y 1 , and the second system unit  31 - 2  and the fourth system unit  31 - 4  are aligned in the direction Y 2 -Y 1 . 
     A plane  50  and a plane  51  are formed in directions Z 1  and Z 2 , respectively, by side surfaces of the optical circuit units  40  facing each other as described above. As shown in FIG. 4, the optical fiber  21  is wired along a groove  50   a  in the plane  50 , and is contained in the groove  50   a  with an excess length thereof being processed. As shown in FIG. 5, the electric-supply line  22  is wired along the plane  51 . 
     The coupling bars  32 - 1 ,  32 - 2 ,  32 - 3  and  32 - 4  are narrow boards arranged at every 90 degrees so as to couple and fix the system units  31 - 1 ,  31 - 2 ,  31 - 3  and  31 - 4 , and to conduct heat outwardly from the system units  31 - 1 ,  31 - 2 ,  31 - 3  and  31 - 4 . 
     The first coupling bar  32 - 1  extends along the lid members  45  of the first and third system units  31 - 1  and  31 - 3 , and is fixed to the lid members  45  by screws  52  with an insulating sheet  56  therebetween. The second coupling bar  32 - 2  extends along the lid members  45  of the second and fourth system units  31 - 2  and  31 - 4 , and is fixed to the lid members  45  by screws  53 . The third coupling bar  32 - 3  extends along the plane  50 , and is fixed to the side surfaces (in the direction Z 1 ) of the optical circuit units  40  of the system units  31 - 1 ,  31 - 2 ,  31 - 3  and  31 - 4  by screws  54 . The third coupling bar  32 - 3  covers the optical fiber  21  contained in the groove  50   a . The fourth coupling bar  32 - 4  extends along the plane  51 , and is fixed to the side surfaces (in the direction Z 2 ) of the optical circuit units  40  of the system units  31 - 1 ,  31 - 2 ,  31 - 3  and  31 - 4  by screws  55 . The fourth coupling bar  32 - 4  covers the electric-supply line  22  wired on the plane  51 . 
     By the coupling bars  32 - 1 ,  32 - 2 ,  32 - 3  and  32 - 4  and the screws  52  to  55 , the four system units  31 - 1 ,  31 - 2 ,  31 - 3  and  31 - 4  are fixed at predetermined positions. Each of the screws  52  to  55  is fastened via an insulating bush  57 . Heads of the screws  52  to  55  are covered with insulating caps  58  to  61 , respectively. The insulating caps  58  to  61  are inserted into holes  62  for screwing formed in the coupling bars  32 - 1 ,  32 - 2 ,  32 - 3  and  32 - 4 . 
     Each of the covers  34 - 1  and  34 - 2  is semi-cylindrical, and the covers  34 - 1  and  34 - 2  cover the system units  31 - 1  to  31 - 4  from the side Z 1  and the side Z 2 , respectively. The covers  34 - 1  and  34 - 2  are fixed to the coupling bars  32 - 1  to  32 - 4  by screws  63  and  64 . Fixing the covers  34 - 1  and  34 - 2  as above gives a cylindrical shape to the internal unit  30  in the course of being assembled. 
     The insulating cylinder  35  covers the covers  34 - 1  and  34 - 2  mounted on the internal unit  30  in the course of being assembled. The insulating cylinder  35  insulates the internal unit  30  from the outer body  13  in a state that the internal unit  30  is incorporated in the outer body  13 . 
     Next, the internal unit  30  having the above-described structure is assembled as shown in FIG.  7  and FIG.  8 . The assembling is performed while being verified by an inspector who is another person from an assembling operator so that reliability thereof is secured. 
     First, after making a contract with a customer and deciding on details of system parameters, assembling of the system units  31 - 1 ,  31 - 2 ,  31 - 3  and  31 - 4  begins. The optical circuit unit  40 , the monitor/power-supply circuit unit  42  in which an address is set by operating the address-setting printed board  41 , and the control circuit unit  44  are stacked, and properties thereof are adjusted by operating the adjusting printed board  43 . Then, the lid member  45  is mounted thereon. This step prepares each of the system units  31 - 1  to  31 - 4  with the adjusted properties (step  70 ). 
     Next, the first system unit  31 - 1  and the second system unit  31 - 2  are combined to each other by the coupling plates  46 , back to back, i.e., in such a manner that the optical circuit units  40  of the first system unit  31 - 1  and the second system unit  31 - 2  face each other. Also, the third system unit  31 - 3  and the fourth system unit  31 - 4  are combined to each other by the coupling plates  46 , back to back, so that the optical circuit units  40  of the first system unit  31 - 3  and the second system unit  31 - 4  face each other (step  71 ). 
     The first coupling bar  32 - 1  and the second coupling bar  32 - 2  are fixed by the screws  52  and  53  (step  72 ). 
     Screw torques of the screws  52  and  53  are verified (step  73 ). 
     The optical fiber  21  is contained along the groove  50   a  in the plane  50  (step  74 ). 
     A containment state of the optical fiber  21  is verified (step  75 ). 
     The third coupling bar  32 - 3  is fixed by the screws  54  (step  76 ). 
     Screw torques of the screws  54  are verified (step  77 ). 
     The insulating caps  58  to  60  are mounted by inserting (step  78 ). 
     A mounting state of the insulating caps  58  to  60  is verified (step  79 ). 
     The cover  34 - 1  is fixed by the screws  63  (step  80 ). 
     Screw torques of the screws  63  are verified (step  81 ). 
     The electric-supply line  22  is contained along the plane  51  (step  82 ). 
     A containment state of the electric-supply line  22  is verified (step  83 ). 
     The fourth coupling bar  32 - 4  is fixed by the screws  55  (step  84 ). 
     Screw torques of the screws  55  are verified (step  85 ). 
     The insulating caps  61  are mounted by inserting (step  86 ). 
     A mounting state of the insulating caps  61  is verified (step  87 ). 
     The cover  34 - 2  is fixed by the screws  64  (step  88 ). 
     Screw torques of the screws  64  are verified (step  89 ). 
     Finally, the insulating cylinder  35  is inserted (step  90 ). 
     The verifying steps are performed by an inspector who is another person from an assembling operator, as mentioned above, during which the assembling steps are suspended. 
     The structure of the internal unit  30  requires an inspection in which a verification is performed for each of the assembling steps. Thus, the number of the verifying steps becomes large. This increases the number of times the assembling steps are suspended, lengthening manufacturing moves. Thus, it takes a long period of time to assemble the internal unit  30 . 
     Since both the address-setting printed board  41  and the adjusting printed board  43  are incorporated in the system units  31 - 1  to  31 - 4 , it is not possible to stop assembling the internal unit  30  in the course of the steps for a later completion. Therefore, after making a contract with a customer and deciding on details of system parameters, assembling of the internal unit  30  begins from the start by assembling the system units  31 - 1 ,  31 - 2 ,  31 - 3  and  31 - 4 . Hence, it takes a long period of time to complete the internal unit  30  after making a contract with a customer. 
     Additionally, the system units  31 - 1  to  31 - 4  are covered with the lid members  45 , and the first and second coupling bars  32 - 1  and  32 - 2  are fixed on the lid members  45  of the system units  31 - 1  to  31 - 4 . Therefore, when the above-mentioned already set address needs to be changed after starting assembling the internal unit  30 , some of the already assembled components need to be disassembled, and consequently be reassembled. Thus, it takes a longer period of time to complete the internal unit  30 . 
     SUMMARY OF THE INVENTION 
     It is a general object of the present invention to provide an improved and useful internal unit and a submarine apparatus having the internal unit in which the above-mentioned problems are eliminated. 
     A more specific object of the present invention is to provide an internal unit and a submarine apparatus having the internal unit which can be assembled in a shortened period of time. 
     In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention an internal unit incorporated in a body of a submarine apparatus, the unit comprising: 
     a plurality of system units placed in a predetermined arrangement, the system units including at least one electronic-circuit printed board having a part to be adjusted; and 
     coupling bars fixed to coupling-bar fixing surfaces of the system units by screws so as to couple the system units in the predetermined arrangement, 
     wherein the coupling-bar fixing surfaces are located at positions shifted from the electronic-circuit printed board. 
     According to the present invention, in the state where the coupling bars are fixed to the coupling-bar fixing surfaces by the screws, the electronic-circuit printed board is accessible so as to adjust properties thereof after the coupling bars are fixed to the system units. Therefore, even before making a contract with a customer, the internal unit can be assembled to a certain step in the course of assembling. Then, after making the contract with the customer, the assembling of the internal unit can be resumed from the step. Hence, the internal unit can be assembled in a short period of time. 
     In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention an internal unit incorporated in a body of a submarine apparatus, the unit comprising: 
     a plurality of system units placed in a predetermined arrangement, the system units including an optical-fiber containing portion containing an optical fiber, an electric-supply-line containing portion containing an electric-supply line, and at least one electronic-circuit printed board having a part to be adjusted; and 
     coupling bars fixed to coupling-bar fixing surfaces of the system units by screws so as to couple the system units in the predetermined arrangement, 
     wherein the coupling-bar fixing surfaces are located at positions shifted from the optical-fiber containing portion, the electric-supply-line containing portion, and the electronic-circuit printed board. 
     According to the present invention, in the state where the coupling bars are fixed to the coupling-bar fixing surfaces by the screws, the coupling bars do not cover the optical-fiber containing portion. Therefore, the containment state of the optical fiber does not have to be verified immediately after the optical fiber is contained in the optical-fiber containing portion, but only has to be verified, along with the screw torques of the screws, after the optical fiber is contained in the optical-fiber containing portion and the coupling bars are fixed to the coupling-bar fixing surfaces by the screws. 
     Additionally, according to the present invention, in the state where the coupling bars are fixed to the coupling-bar fixing surfaces by the screws, the coupling bars do not cover the electric-supply-line containing portion. Therefore, the containment state of the electric-supply line does not have to be verified immediately after the electric-supply line is contained in the electric-supply-line containing portion, but only has to be verified, along with the screw torques of the screws, after the electric-supply line is contained in the electric-supply-line containing portion and the coupling bars are fixed to the coupling-bar fixing surfaces by the screws. 
     Thus, the number of times the internal unit is transferred between assembling steps and verifying steps in the course of assembling is reduced, decreasing manufacturing moves of the internal unit. Therefore, the internal unit can be assembled in a short period of time. 
     Additionally, in one of the internal units according to the present invention, each of the system units may have inclined surfaces on both sides thereof; and 
     the inclined surfaces may form the coupling-bar fixing surfaces. 
     According to the present invention, the coupling-bar fixing surfaces can be located at positions shifted from the optical-fiber containing portion, the electric-supply-line containing portion, and the electronic-circuit printed board in a rational manner. 
     Additionally, one of the internal units according to the present invention may further comprise a plurality of covers fixed to the coupling bars by screws so that each of the covers lies across the coupling bars adjacent in a circumferential direction, 
     wherein the covers adjacent in the circumferential direction may be placed so as to form a gap therebetween, the gap being located at a position opposing each of the screws fixing the coupling bars. 
     According to the present invention, the screw torques of the screws fixing the coupling bars can be verified along with the screw torques of the screws fixing the covers, after the covers are fixed to the coupling bars by the screws. 
     In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a submarine apparatus comprising: 
     a cylindrical airtight body; and 
     one of the internal units according to the present invention incorporated in the body. 
     According to the present invention, since manufacturing moves of the internal unit can be shortened, manufacturing moves of the submarine apparatus can accordingly be shortened. Therefore, the submarine apparatus can be manufactured in a short period of time. 
     Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a structure of a submarine repeater; 
     FIG. 2 is a perspective view of a disassembled state of a conventional internal unit; 
     FIG. 3 is a front view of the internal unit shown in FIG. 2; 
     FIG. 4 is a plan view of the internal unit shown in FIG. 2; 
     FIG. 5 is a bottom view of the internal unit shown in FIG. 2; 
     FIG. 6 is a side view of the internal unit shown in FIG. 2; 
     FIG. 7 is a flowchart of steps of assembling the internal unit shown in FIG. 2; 
     FIG. 8 is a flowchart of steps following the steps shown in FIG. 7; 
     FIG. 9 shows a structure of a submarine repeater according to an embodiment of the present invention; 
     FIG. 10 is a perspective view of a disassembled state of an internal unit according to an embodiment of the present invention incorporated in the submarine repeater shown in FIG. 9; 
     FIG. 11 is a front view of the internal unit shown in FIG. 10; 
     FIG. 12 is a plan view of the internal unit shown in FIG. 10; 
     FIG. 13 is a bottom view of the internal unit shown in FIG. 10; 
     FIG. 14 is a side view of the internal unit shown in FIG. 10; 
     FIG. 15 is a flowchart of steps of assembling the internal unit shown in FIG. 10; 
     FIG. 16 is a flowchart of steps following the steps shown in FIG. 15; 
     FIG. 17 is a front view showing a state of the internal unit after a step  223  shown in FIG. 15 is finished; 
     FIG. 18 is a front view showing a state of the internal unit after a step  226  shown in FIG. 15 is finished; and 
     FIG. 19 is a front view showing a state of the internal unit after a step  230  shown in FIG. 15 is finished. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A description will now be given, with reference to the drawings, of embodiments according to the present invention. 
     FIG. 9 shows a structure of a submarine repeater  110  incorporating an internal unit  130  according to an embodiment of the present invention. The submarine repeater  110  comprises a cylindrical airtight body  111  that can endure a water pressure on a seafloor, and the cylindrical internal unit  130  incorporated therein. The airtight body  111  comprises a cylindrical outer body  113  and end-surface plates  114  and  115  covering both ends of the outer body  113 . The internal unit  130  is incorporated within the outer body  113  with a buffering member  116  formed of a mesh plate being placed therebetween. The buffering member  116  has a function of conducting heat generated by the internal unit  130  to the airtight body  111 , and also has a function of keeping the internal unit  130  from suffering vibrations and impacts caused during the laying of the submarine repeater  110 . 
     The submarine repeater  110  is connected with a submarine cable  120 . The submarine cable  120  includes an optical fiber  121  transmitting information, and an electric-supply line  122  supplying electric power. The optical fiber  121  and the electric-supply line  122  are drawn into the airtight body  111  via a hole formed in the end-surface plate  114  or  115  so as to be connected with the internal unit  130 . 
     FIG. 10 to FIG. 14 show the internal unit  130  according to the present embodiment incorporated in the submarine repeater  110  shown in FIG.  9 . FIG. 10 to FIG. 14 correspond to FIG. 2 to FIG. 6, respectively, in terms of manners of views. The internal unit  130  has basically the same structure as the above-described internal unit  30 . Thus, elements in FIG. 10 to FIG. 14 corresponding to the elements shown in FIG. 2 to FIG. 6 are referenced by reference numbers of the reference numbers in FIG. 2 to FIG. 6 plus  100 . 
     The internal unit  130  mainly comprises a plurality (for example, four) of system units  131 - 1 ,  131 - 2 ,  131 - 3  and  131 - 4 , four coupling bars  132 - 1 ,  132 - 2 ,  132 - 3  and  132 - 4 , four covers  200 - 1 ,  200 - 2 ,  200 - 3  and  200 - 4 , an insulating cylinder  135 , and end-surface covers  136  on both ends. 
     The system unit  131 - 1  comprises an optical circuit unit  140 - 1  having an optical circuit component module  210 - 1 , a power-supply circuit unit  212 - 1  including a power-supply module  211 - 1 , and a control circuit unit  213 - 1 . The optical circuit unit  140 - 1 , the power-supply circuit unit  212 - 1  and the control circuit unit  213 - 1  are stacked in this order in a direction X 2 -X 1 . Each of the circuit units  140 - 1 ,  212 - 1  and  213 - 1  is made of metal. A printed board  214 - 1  for address-setting and adjusting is mounted on the outer surface of the control circuit unit  213 - 1 . In other words, the adjusting/address-setting printed board  214 - 1  is openly mounted on the control circuit unit  213 - 1 . The control circuit unit  213 - 1  has a trapezoidal shape when viewed from Y 2 , and has coupling-bar fixing surfaces  215 - 1  and  216 - 1  on both sides. The coupling-bar fixing surfaces  215 - 1  and  216 - 1  are inclined in a form of a roof. The other system units  131 - 2  to  131 - 4  have the same or symmetrical structure as the above-described system unit  131 - 1 . The adjusting/address-setting printed board  214 - 1  is properly adjusted, in which an address is set and properties are adjusted. 
     In this structure according to the present embodiment, since the adjusting/address-setting printed board  214 - 1  has both functions of adjusting and address-setting, the system unit  131 - 1  is smaller than the conventional system unit  31 - 1  shown in FIG.  3 . Thus, the internal unit  130  is smaller than the conventional internal unit  30  shown in FIG.  2  and FIG.  3 . 
     The first system unit  131 - 1  and the second system unit  131 - 2  are coupled with each other back to back by insulating coupling plates  146  and screws so that the inner surface of the optical circuit unit  140 - 1  of the first system unit  131 - 1  and the inner surface of an optical circuit unit  140 - 2  of the second system unit  131 - 2  face each other in a direction X 1 -X 2  with an insulating sheet  147  therebetween. Likewise, the third system unit  131 - 3  and the fourth system unit  131 - 4  are coupled with each other back to back in the direction X 1 -X 2 . The first system unit  131 - 1  and the third system unit  131 - 3  are aligned in a direction Y 2 -Y 1 , and the second system unit  131 - 2  and the fourth system unit  131 - 4  are aligned in the direction Y 2 -Y 1 . 
     Shallow grooves  220  and  221  are formed in directions Z 1  and Z 2 , respectively, by side surfaces of the optical circuit units  140  of the system units  131 - 1  to  131 - 4  facing each other as described above. As shown in FIG. 12, the optical fiber  121  is wired along the groove  220 , and is contained in the groove  220  (an optical-fiber containing portion) with an excess length thereof being processed in the groove  220 . As shown in FIG. 13, the electric-supply line  122  is wired along the groove  221  (an electric-supply-line containing portion). 
     As viewed from Y 2 , the coupling-bar fixing surface  215 - 1  is positioned approximately 45 degrees clockwise from the groove  220 , and the coupling-bar fixing surface  216 - 1  is positioned approximately 45 degrees counterclockwise from the groove  221 . A coupling-bar fixing surface  216 - 2  of the second system unit  131 - 2  is positioned approximately 45 degrees counterclockwise from the groove  220 , and a coupling-bar fixing surface  215 - 2  of the second system unit  131 - 2  is positioned approximately 45 degrees clockwise from the groove  221 . 
     The coupling bars  132 - 1  to  132 - 4  are narrow boards arranged at every 90 degrees so as to couple and fix the system units  131 - 1  to  131 - 4  to enhance a vibration resistance and an impact resistance of the internal unit  130 , and also have a function of conducting heat outwardly from the system units  131 - 1  to  131 - 4 . 
     The first coupling bar  132 - 1  extends along the coupling-bar fixing surface  215 - 1  of the first system unit  131 - 1  and a coupling-bar fixing surface  215 - 3  of the third system unit  131 - 3 , and is fixed to the coupling-bar fixing surfaces  215 - 1  and  215 - 3  by screws  152  with an insulating sheet  156  therebetween. The second coupling bar  132 - 2  extends along the coupling-bar fixing surface  216 - 2  of the second system unit  131 - 2  and a coupling-bar fixing surface  216 - 4  of the fourth system unit  131 - 4 , and is fixed to the coupling-bar fixing surfaces  216 - 2  and  216 - 4  by screws  153 . The third coupling bar  132 - 3  extends along the coupling-bar fixing surface  216 - 1  of the first system unit  131 - 1  and a coupling-bar fixing surface  216 - 3  of the third system unit  131 - 3 , and is fixed to the coupling-bar fixing surfaces  216 - 1  and  216 - 3  by screws  154 . The fourth coupling bar  132 - 4  extends along the coupling-bar fixing surface  215 - 2  of the second system unit  131 - 2  and a coupling-bar fixing surface  215 - 4  of the fourth system unit  131 - 4 , and is fixed to the coupling-bar fixing surfaces  215 - 2  and  215 - 4  by screws  155 . 
     The first to fourth coupling bars  132 - 1  to  132 - 4  are positioned away from the optical fiber  121  and the electric-supply line  122 , and are also positioned away from the adjusting/address-setting printed board  214 - 1  of the first system unit  131 - 1  and adjusting/address-setting printed boards  214 - 2  to  214 - 4  of the second to fourth system units  131 - 2  to  131 - 4 . Thus, the first to fourth coupling bars  132 - 1  to  132 - 4  do not cover the optical fiber  121 , the electric-supply line  122 , and the adjusting/address-setting printed boards  214 - 1  to  214 - 4 . 
     The coupling bars  132 - 1  and  132 - 3  and the screws  152  and  154  couple the first and third system units  131 - 1  and  131 - 3  with each other. The coupling bars  132 - 2  and  132 - 4  and the screws  153  and  155  couple the second and fourth system units  131 - 2  and  131 - 4  with each other. Each of the screws  152  to  155  is fastened via an insulating bush  157 . Heads of the screws  152  to  155  are covered with insulating caps  158  to  161 , respectively. The insulating caps  158  to  161  are inserted into holes  162  for screwing formed in the coupling bars  132 - 1  to  132 - 4 . 
     In the system units  131 - 1  to  131 - 4 , electronic components generating large amounts of heat, such as a laser diode, are placed in the proximity of the coupling bars  132 - 1  to  132 - 4  so as to facilitate a radiation of the heat. 
     Each of the four covers  200 - 1  to  200 - 4  has a shape of a quarter cylinder with an opening angle of approximately 90 degrees. Each of the four covers  200 - 1  to  200 - 4  lies across adjacent two coupling bars of the coupling bars  132 - 1  to  132 - 4  in a circumferential direction, and is fixed to the adjacent two of the coupling bars  132 - 1  to  132 - 4  on both sides by screws  163 . The cover  200 - 1  lies across the coupling bars  132 - 1  and  132 - 2 , and covers the optical fiber  121 . The cover  200 - 2  lies across the coupling bars  132 - 3  and  132 - 4 , and covers the electric-supply line  122 . The cover  200 - 3  lies across the coupling bars  132 - 1  and  132 - 3 , and covers the adjusting/address-setting printed boards  214 - 1  and  214 - 3 . The cover  200 - 4  lies across the coupling bars  132 - 2  and  132 - 4 , and covers the adjusting/address-setting printed boards  214 - 2  and  214 - 4 . 
     The covers  200 - 1  to  200 - 4  are adjacent to each other in the circumferential direction with gaps  201  therebetween. The gaps  201  are formed at positions of the above-mentioned screws  152  to  155 . 
     Fixing the covers  200 - 1  to  200 - 4  as above gives a cylindrical shape to the internal unit  130  in the course of being assembled. 
     The insulating cylinder  135  covers the internal unit  130  in the course of being assembled in which the covers  200 - 1  to  200 - 4  are mounted. The insulating cylinder  35  insulates the internal unit  130  from the outer body  113  in a state that the internal unit  130  is incorporated in the outer body  113 . 
     Next, the internal unit  130  having the above-described structure is assembled as shown in FIG.  15  and FIG.  16 . The assembling is performed while being verified by an inspector who is another person from an assembling operator so that reliability thereof is secured. 
     First, the optical circuit unit  140 , the power-supply circuit unit  212  and the control circuit unit  213  are prepared. In the adjusting/address-setting printed board  214  of the control circuit unit  213 , an address is not set yet. The optical circuit unit  140 , the power-supply circuit unit  212  and the control circuit unit  213  are stacked so as to form each of the system units  131 - 1  to  131 - 4 . Properties thereof are not adjusted yet (step  220 ). Since the addresses are not set yet, and the properties are not adjusted yet, it does not require much labor to assemble each of the system units  131 - 1  to  131 - 4 . 
     Next, the first system unit  131 - 1  and the second system unit  131 - 2  are combined to each other by the coupling plates  146 , back to back, i.e., in such a manner that the inner surface of the optical circuit unit  140 - 1  of the first system unit  131 - 1  and the inner surface of the optical circuit unit  140 - 2  of the second system unit  131 - 2  face each other. Likewise, the third system unit  131 - 3  and the fourth system unit  131 - 4  are combined to each other back to back by the coupling plates  146  (step  221 ). 
     Since the addresses are not set yet, and the properties are not adjusted yet, the system units  131 - 1  to  131 - 4  may be combined arbitrarily. 
     Then, the first coupling bar  132 - 1  and the second coupling bar  132 - 2  are fixed by the screws  152  and  153  (step  222 ). 
     Next, the optical fiber  121  is contained along the groove  220  (step  223 ). FIG. 17 shows a state of the internal unit  130  after the step  223  is finished. 
     Subsequently, screw torques of the screws  152  and  153  are verified, and a containment state of the optical fiber  121  is verified (step  224 ). 
     Then, the third coupling bar  132 - 3  and the fourth coupling bar  132 - 4  are fixed by the screws  154  and  155  (step  225 ). 
     Next, the electric-supply line  122  is contained along the groove  221  (step  226 ). 
     FIG. 18 shows a state of the internal unit  130  after the step  226  is finished. The above-mentioned steps  225  and  226  are performed by overturning the internal unit  130  in the course of being assembled. 
     Subsequently, screw torques of the screws  154  and  155  are verified, and a containment state of the electric-supply line  122  is verified (step  227 ). 
     Then, the adjusting/address-setting printed boards  214 - 1  to  214 - 4 , which are exposed on both sides of the internal unit  130  in the course of being assembled, are adjusted so as to adjust the properties of the system units  131 - 1  to  131 - 4  and to set the addresses thereof (step  228 ). 
     Next, the insulating caps  158  to  161  are mounted by inserting (step  229 ). 
     Then, the four covers  200 - 1  to  200 - 4  are fixed by the screws  163  (step  230 ). FIG. 19 shows a state of the internal unit  130  after the step  230  is finished. 
     Subsequently, a mounting state of the insulating caps  158  to  161  is verified, and screw torques of the screws  163  are verified (step  231 ). The mounting state of the insulating caps  158  to  161  is verified through the gaps  201 . 
     Finally, the insulating cylinder  135  is inserted (step  232 ). 
     Hereinafter, a description will be given of features of the above-described structure and the assembling steps of the internal unit  130 . 
     (1) The number of times the assembling steps are suspended in the course of assembling the internal unit  130  is reduced to half, in comparison with a conventional internal unit. 
     Since the verifying steps are performed by an inspector who is another person from an assembling operator as mentioned above, each time the verifying step is performed, the assembling steps are suspended. 
     As shown in FIG.  15  and FIG. 16, the verifying step  224  comes after the two assembling steps  222  and  223 , the verifying step  227  comes after the two assembling steps  225  and  226 , and the verifying step  231  comes after the two assembling steps  229  and  230 . Thus, the number of times the assembling steps are suspended in the course of assembling is reduced to half, in comparison with a conventional case in which one verifying step comes after one assembling step. This shortens manufacturing moves of the internal unit  130 , and thus, the internal unit  130  can be assembled in a short period of time, compared to a conventional internal unit. 
     (2) The internal unit  130  is assembled in flexible manners. 
     System parameters, such as an output power and an address of a system unit, are determined according to a contract with a customer. As described above, the internal unit  130  has a structure that allows the adjustment of the properties and the setting of the addresses of the system units  131 - 1  to  131 - 4  to be performed in the course of the assembling. Therefore, even when details of the system parameters are not determined yet, the assembling of the internal unit  130  can be started and be performed to the step  227 . In other words, the internal unit  130  can be produced and stored in stock, in which the internal unit  130  is assembled to a state before the step  228 . Then, after making a contract with a customer, the assembling of the internal unit  130  can be resumed from the step  228 . Hence, it takes a short period of time to complete the internal unit  130  after making the contract with the customer. 
     In addition, the adjustment of the properties and the setting of the addresses are performed all at once with respect to the system units  131 - 1  to  131 - 4  arranged neatly in the above-mentioned order. Therefore, the adjustment of the properties and the setting of the addresses are easy to perform, compared to system units not neatly arranged. 
     Further, since the adjusting/address-setting printed boards  214 - 1  to  214 - 4  are exposed outwardly in a state of the internal unit  130  in which the system units  131 - 1  to  131 - 4  are coupled by the coupling bars  132 - 1  to  132 - 4 , the assembling operator can access the adjusting/address-setting printed boards  214 - 1  to  214 - 4  from outside of the internal unit  130  in that state. Therefore, in the state of the internal unit  130  in which the system units  131 - 1  to  131 - 4  are coupled by the coupling bars  132 - 1  to  132 - 4 , the properties can be readjusted and the addresses can be reset. Hence, even when details of the contract with the customer are changed in the course of assembling the internal unit  130 , the internal unit  130  does not need to be disassembled, let alone be reassembled. This prevents lengthening manufacturing moves of the internal unit  130 , and thus, the internal unit  130  can be completed in a short period of time. 
     Besides, the present invention is not limited to the above-mentioned submarine repeater  110 , but also is applicable to a submarine branching unit diverging information, or a gain equalizer. 
     That is, the present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese priority application No. 2001-135502 filed on May 2, 2001, the entire contents of which are hereby incorporated by reference.