Patent Publication Number: US-2009226171-A1

Title: WDM optical transmit-receive device

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an optical transmit-receive device, more particularly to a WDM (wavelength division multiplexer) optical transmit-receive device. 
     BACKGROUND OF THE INVENTION 
     Recently, PON (passive optical network) has abruptly increased for optical access technique to become a mainstream within FTTH (fiber to the home) solutions, such as techniques of Diplexer and Triplexer applied for GPON and EPON are greatly valued. Within PON structure, Diplexer equipped in ONU (optical network unit) mainly serves transmitting an optical signal of upstream wavelength at 1310 nm and receiving an optical signal of downstream wavelength at 1490 nm so as to carry out upstream/downstream data transmission, and Triplexer equipped in ONU, except serves same functions as Diplexer does, also receives an optical signal of downstream wavelength at 1550 nm for CATV (community antenna television) signal transmission, but comparatively is more expensive than Diplexer. However, present demand of customer for using CATV signal is not popularized, which makes optical network system builder difficult to adopt between Triplexer and Diplexer. In case of adopting Triplexer, low using demand and high building cost are concerned economically, if Diplexer is selected, it cannot meet future use of CATV signal in quantity. Therefore, how to solve the problem mentioned above becomes a very important issue. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a WDM optical transmit-receive device, which comprises an optical transceiver assembly and an optical receiver assembly. The optical transceiver assembly includes a first optical platform, a first optical filter, a first photodetector and a laser diode, where the first optical platform has a first surface, a first groove recessed from the first surface and a first signal coupling end, the first optical filter is inserted into the first groove, the first photodetector and the laser diode are mounted adjacent to the first optical filter. The optical receiver assembly is disposed at one side of the optical transceiver assembly and includes a second optical platform, a second optical filter, a second photodetector and a connecting fiber, where the second optical platform has a second surface, a second groove recessed from the second surface and a second signal coupling end, the second filter is inserted into the second groove, the second photodetector is mounted adjacent to the second optical filter, the connecting fiber has a first end adjacent to the second optical filter and a second end. If there is no use demand of CATV signal from ONU, then an optical network coupling end is capable of coupling to the optical transceiver assembly which allows Diplexer data transmission of upstream/downstream (1310 nm/1490 nm) by applying the optical transceiver assembly. Contrarily when ONU has use demand of CATV signal, the optical network coupling end is capable of coupling to the optical receiver assembly, such as to the connecting fiber of the optical receiver assembly which enables simultaneous Triplexer data transmission of upstream/downstream (1310 nm/1490 nm/1550) by applying the optical receiver assembly and the optical transceiver assembly. The optical transmit-receive device of this invention which is capable for performing both functions of Diplexer and Triplexer in accordance with ONU demand may provide high expanding convenience in efficiency and low cost for building network system because its price is lower than that of known Triplexer. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a structure of a WDM optical transmit-receive device in according with a preferred embodiment of this invention. 
         FIG. 2  shows another structure of the WDM optical transmit-receive device. 
         FIG. 3  shows action of that the WDM optical transmit-receive device handles optical signal of Diplexer. 
         FIG. 4  shows action of that the WDM optical transmit-receive device handles optical signal of Triplexer. 
     
    
    
     DETAILED DESCRIPTION OF THIS INVENTION 
       FIG. 1  shows a WDM optical transmit-receive device (wavelength division multiplexer) in accordance with a preferred embodiment of this invention, which can be utilized to handle the optical signals of Diplexer (1310 nm/1490) and Triplexer (1310 nm/1490 nm/1550 nm) and comprises an optical transceiver assembly  10 , an optical receiver assembly  20  and a casing  30 . The optical transceiver assembly  10  includes a first optical platform  11 , a first optical filter  12 , a first photodetector  13 , a laser diode  14 , a first fiber  15 , a fourth fiber  16  and a fifth fiber  17 , wherein the first optical platform  11  is disposed within the casing  30  and has a first surface  11   a , a first groove  111  recessed from the first surface  11   a  and a first signal coupling end  110 . In this embodiment, the first optical filter  12  is inserted into the first groove  111 , the first photodetector  13  is mounted adjacent to the first optical filter  12  and capable of receiving the optical signal of wavelength at 1490 nm, the laser diode  14  is mounted adjacent to the first optical filter  12  and capable of transmitting the optical signal of wavelength at 1310 nm. The first fiber  15  is mounted at the first signal coupling end  110  and has a first end  5   a  mounted adjacent to the first optical filter  12  and a second end  15   b  disposing a fiber connector  151 . Besides, the fourth fiber  16  is mounted between the first photodetector  13  and the first optical filter  12 , the fifth fiber  17  is mounted between the laser diode  14  and the first optical filter  12 , and preferably the first fiber  15 , the fourth fiber  16  and the fifth fiber  17  are lens fiber. 
     With reference to  FIGS. 1 and 2 , the optical receiver assembly  20  which is disposed at one side of the optical transceiver assembly  10  includes a second optical platform  21 , a second optical filter  22 , a second photodetector  23 , a connecting fiber  24 , a second fiber  25  and a third fiber  26 . The second optical platform  21  is disposed within the casing  30  and has a second surface  21   a , a first lateral  21   b , a second lateral  21   c  opposite to the first lateral  21   b , a second groove  211  recessed from the second surface  21   a , a reflective groove  212  recessed from the second surface  21   a  and a second signal coupling end  210 , where the second groove  211  communicates with the first lateral  21   b  and the second lateral  21   c , the reflective groove  212  communicates with the second groove  211 . In this embodiment, the second optical filter  22  which is inserted into the second groove  211  has a coating surface  22   a  and a back  22   b  opposite to the coating surface  22   a , the coating surface  22   a  is capable of reflecting the optical signals of wavelength at 1310 nm and 1490 nm and allowing the optical signal of wavelength at 1550 nm to pass through. The second photodetector  23  is mounted adjacent to the back  22   b  of the second optical filter  22  and capable of receiving the optical signal of wavelength at 1550 nm. The connecting fiber  24  has a first end portion  24   a  which is mounted adjacent to the coating surface  22   a  of the second optical filter  22  and may be affixed into the reflective groove  212  and a second end portion  24   b , in this embodiment, the first end portion  24   a  has a lens structure  241  formed thereon, the second end portion  24   b  is capable of coupling to the second end  15   b  of the first fiber  15  of the optical transceiver assembly  10 , and preferably the second end portion  24   b  disposes a second fiber connector  242  that is capable of connecting to the first fiber connector  151  of the first fiber  15 . With reference again to  FIG. 1 , the second fiber  25  is mounted at the second signal coupling end  210  of the second optical platform  21  and one end of the second fiber  25  is mounted adjacent to the coating surface  22   a  of the second optical filter  22 . There is an included angle approximately 90 degree between the first end portion  24   a  of the connecting fiber  24  and the second fiber  25  in this embodiment. Besides, the third fiber  26  is mounted between the second photodetector  23  and the second optical filter  22 , and preferably the second fiber  25  and the third fiber  26  are lens fiber. 
     The action about handling the optical signal of Diplexer (1310 nm/1490 nm) in accordance with this invention is shown by  FIG. 3 , which is to couple the second end  15   b  of the first fiber  15  of the optical transceiver assembly  10  to an optical network coupling end  40 . In this embodiment, the optical transceiver assembly  10  only handles the optical signal of Diplexer (1310 nm/1490 nm) without any action from the optical receiver assembly  20  in this case. The laser diode  14  is assigned to emit the optical signal of upstream wavelength at 1310 nm which enters the fifth fiber  17  first, reflected by the first optical filter  12  to enter the first fiber  15 , finally upstream outputted via the optical network coupling end  50 . The first photodetector  13  is assigned to receive the optical signal of downstream wavelength at 1490 nm, in which the optical signal of downstream wavelength at 1490 nm enters the first fiber  15  via the optical network coupling end  40 , passing through the first optical filter  12  and then entering the fourth fiber  16 , finally received by the first photodetector  13 . 
     The action about handling the optical signal of Triplexer (1310 nm/1490 nm/1550 nm) in accordance with this invention is shown by  FIG. 4 , which is respectively to couple one end of the second fiber  25  of the optical receiver assembly  20  to the optical network coupling end  40  and connect the second fiber connector  242  of the connecting fiber  24  with the first fiber connector  151  of the first fiber  15  of the optical transceiver assembly  10 . In this embodiment, the optical receiver assembly  20  and the optical transceiver assembly  10  are simultaneous to handle the optical signal of Triplexer (1310 nm/1490 nm/1550 nm). The laser diode  14  is assigned to emit optical signal of upstream wavelength at 1310 nm which enters the fifth fiber  17  first, reflected by the first optical filter  12  to enter the first fiber  15 , and then entering the connecting fiber  24  and reflected by the second optical filter  22  to enter the second fiber  25 , finally upstream outputted via the optical network coupling end  40 . The second photodetector  23  is assigned to receive the optical signal of downstream wavelength at 1550 nm, in which the optical signal of downstream wavelength at 1550 nm enters the second fiber  25  via the optical network coupling end  40 , passing through the second optical filter  22  and then entering the third fiber  26 , finally received by the second photodetector  23 . The optical signal of downstream wavelength at 1490 nm enters the second fiber  25  via the optical network coupling end  40 , reflected by the second optical filter  22  to enter the connecting fiber  24 , and then entering the first fiber  15  and passing through the first optical filter  12  to enter the fourth fiber  16 , finally received by the first photodetector  13 . 
     Accordingly, the optical transmit-receive device of this invention which is capable of performing either Diplexer transceiver or Triplexer transceiver function in accordance with ONU demand may provide high expanding convenience in efficiency and low cost for building network system because its price is lower than that of known Triplexer transceiver. 
     While the present invention has been particularly illustrated and described in detail with respect to the preferred embodiments thereof, it will be clearly understood by those skilled in the art that various changed in form and details may be made without departing from the spirit and scope of the present invention.