Abstract:
An apparatus and method for monitoring optical fiber obstructions in an optical split network is described. The monitoring apparatus comprises a broadband-monitoring light source module, an optical circulator, an optical spectral analyzer, a high-density multi-wavelength OTDR, a controlling computer, a wavelength division multiplexer, a specific wavelength optical filter, a monitoring-waveband reflector, and an optical channel selector. The monitoring apparatus utilizes the specific wavelength optical filter and the monitoring-waveband reflector to collectively construct an optical split network optical fiber obstruction monitoring apparatus for the passive optical network having multiple split routes by filtering, reflecting, and transmitting coming lights, so as to achieve the purposes of locating the obstructed split routes and obstruction locations at the same time.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus and method for monitoring optical obstructions in a passive optical network; and, particularly, relates to an apparatus and method for monitoring optical fibers and measuring obstruction locations in a passive optical network by integrating optical filters having specific wavelength and monitoring a monitoring-waveband reflector to filter and reflect inputting lights, achieving the simplicity and high efficiency. 
     2. Description of the Prior Art 
     As a result of the rapid growth of the global Internet, conventional networks cannot handle demands from high-speed data transformation applications due to the revolution in communication industry. Technologies in the developed optoelectronics industry and various applications for different products have timely provided a best solution in response to a demand for large bandwidth in the rapid growth of the global Internet, high-quality media network, and variety of data communications. Various architectures for optical communication network are successively developed and the passive optical network service system is most attended. Therefore, it is necessary to develop an apparatus and method for monitoring respective branches line in a passive optical network to cope with the demands of monitoring in particular network architectures in the future. 
     It is not easy to monitor optical fibers in a passive optical network according to an original design of branch line. In the past, the manner of monitoring that uses the Optical Time Domain Reflectometer (OTDR) was commonly adopted. However, all divergent signals in a locus chart of the OTDR are overlapped and any one of the signals cannot thus be identified alone. To solve such an identification problem, adding an additional active-identifying component is employed but the interaction between a communication network and a host computer in the central office is required, normally augmenting the complexity of the monitoring system; additionally, using excess length shifted fiber with a reflecting element as an identifying component is also employed, but it is difficult in design and installation since the branches line are different in length. Such the monitoring manner by using the OTDR is hardly to be accomplished because of the limitation of the Dynamic Range and the Event Dead Zone of the OTDR when the number of the branches line increases. 
     Additionally, a tunable laser light source, circulator device, and light power meter are also employed in a terminal side with the fiber bragg grating (FBG) fiber which may reach the goal of detecting obstructions though but cannot simultaneously display a real time status of all routes as measuring each branch line. Instead, the tunable laser light source has to cyclically switch to different wavelength monitored, consuming a lot of time when a great number of branch line. Taking this approach may be aware of the split route being obstructed but may not identify a location of the obstruction, remaining a restriction in maintenance. 
     In view of the above, the conventional stuff still has a lot of drawbacks to be fine-designed goods and should be improved. 
     Upon the drawbacks incurred by the above conventional goods, the inventor of the present invention has given every effort in reformation and innovation. After years of painstaking efforts, finally, an apparatus and method of monitoring optical obstructions in an passive optical network has been successfully developed. 
     SUMMARY OF THE INVENTION 
     The objective of the present invention is to provide an apparatus and method of monitoring optical obstructions in an passive optical fiber network, cooperating to the deposition of the passive optical-fiber network service system in home. When the service system got a problem, the branch line may be monitored in a central office whether is off-line or involved with high value of light loss to clearly identify it is an issue of the service system or the optical fiber route and correctly show the route and its location of the obstruction, so as to reduce the business cost and improve the efficiency of maintenance. 
     The apparatus and method of monitoring optical obstructions in an passive optical network of the present invention achieving the above mentioned objectives is to use a set of optical-fiber monitoring and measuring apparatus to real time monitor different monitored wavelength and power of light reflected back from the passive optical network, reaching the both purposes of identifying obstructed branch line and obstruction location. The method is to utilize a optical spectrum analyzer for real time monitoring different monitored wavelength and its power of light reflected back from the passive optical network. A control computer analyzes the measurement and then determines a newest status of any one of the branches line. If an optical fiber is damaged or faulted, a high density and multi-wavelength OTDR is activated, measuring the obstruction location of corresponding wavelength to warn and as a basis for a subsequent process. 
     These features and advantages of the present invention will be fully understood and appreciated from the following detailed description of the accompanying drawings. 
     These features and advantages of the present invention will be fully understood and appreciated from the following detailed description of the accompanying Drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of the architecture of an apparatus and method of monitoring optical obstructions in an passive optical network of the present invention; 
         FIG. 2  is a schematic diagram of reflecting wave, shown by a optical spectrum analyzer, of the apparatus and method of monitoring optical obstructions in an passive optical network of the present invention; 
         FIG. 3  is a schematic diagram of disappearing reflecting wave of an obstructed branch line, shown by a optical spectrum analyzer, of the apparatus and method of monitoring optical obstructions in an passive optical network of the present invention; and 
         FIG. 4  is a comparison diagram illustrating the original and the obstruction locus of an obstructed branch line of a high density and multi-wavelength OTDR of the apparatus and method of monitoring optical obstructions in an passive optical network of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a schematic diagram of the architecture of an apparatus and method of monitoring optical obstructions in an passive optical network of the present invention that comprises: 
     A broadband-monitoring light source module  16  for continuously transmitting a light source of the monitored waveband  17 ; 
     An optical circulator  18  for coupling with the light sent by the broadband-monitoring light source module  16 , delivering the light into an optical network, and then receiving a monitoring light reflected back from the optical network and subsequently sending it into the optical spectrum analyzer  21 ; 
     An optical channel selector  15  for connecting to monitoring apparatuses and each optical fiber route; 
     A wavelength division multiplexer  24  for integrating the optical signals of the service waveband  12  and the monitored waveband  17  and delivering it into the optical fiber  14 ; 
     A specific wavelength optical filter  25  for filtering a specified monitored wavelength optical signal of the waveband  12  and the monitored waveband  17  in the input light; 
     A monitoring waveband reflector  26  for reflecting a specified monitored waveband within the coming light and allowing the optical signals of the service waveband  12  passing through; 
     An optical spectrum analyzer  21  for measuring respective monitored waveband and light power reflected back from the optical circulator  18  and passive optical network; 
     A controlling computer  22  for monitoring the entire process, and for retrieving, analyzing, and comparing wave diagrams and locus charts measured by the optical spectrum analyzer  21  and the high density multi-wavelength OTDR  20  so as to acquire a latest status of whole optical fiber branches line and perform each controlling command; and 
     A high density multi-wavelength OTDR  20  for measuring an optical power of any distance in different branch line of the optical network based on different wavelengths. 
     The monitoring apparatus is primarily placed in the central office  10 . The optical line terminal (OLT)  11  transmits optical signals of the service waveband  12  to the division multiplexer  13 . The monitoring apparatus transmits optical signals of the monitoring waveband  17  via the optical circulator  18  by the broadband-monitoring light source module  16 , and the optical signals are subsequently transmitted to the division multiplexer  13  via the optical channel selector  15 . The division multiplexer  13  integrates the optical signals from the service waveband  12  and the monitoring waveband  17 , and then transmits the signals through the optical fiber  14 , optical cable  23  outside the central office, and the optical splitter  24  for dividing the light to optical branches line. A great portion of the wavelength of the monitored waveband of each optical branch signal will be filtered out when passing through the specific wavelength optical filter  25 . Only optical signal matching a specified monitored wavelength that corresponds to one particular branch line and the optical signals of the service waveband will be allowed to enter the end of each route. The optical signal to the end will firstly pass through the monitoring-waveband reflector  26  where the optical signal of the service waveband  12  may pass through the monitoring-waveband reflector  26  then enter into the optical network unit (ONU)  27  to provide service for subscribers. When the optical signal of the specific monitoring wavelength in the monitoring waveband  17  enters into the monitoring-waveband reflector  26 , a particular monitored wavelength will be reflected. The monitoring-waveband reflector  26  of each branch line is identical and is able to reflect a unique and different specified monitored wavelength. The reflected monitored wavelength returns, along an original route, to the division multiplexer  13  via the specific wavelength optical filter  25 , splitter  24 , optical cable  23 , and optical fiber  14 , and then is received and measured by the optical spectrum analyzer  21  through the optical channel selector  15  and the optical circulator  18  for acquiring a reflective wave diagram of the entire optical branch line. As shown in  FIG. 2 , the controlling computer  22  retrieves the wave diagram for comparing and analyzing the reflective waveforms  191  of different routes to acquire a latest status of the entire optical branch line. When any one of the branch lines has occurred an obstruction, the reflective waveform of the entire branch lines will be like as shown in  FIG. 3  that the reflective waveform  192  of the obstructed route is disappeared. The controlling computer  22 , by comparing and analyzing, may determine which branch line has been obstructed and immediately shifts to a process of measuring obstruction location. 
     The process of measuring obstruction location is that the high density multi-wavelength OTDR  20  sends out a specified measuring wavelength  19  corresponding to the obstructed branch line through the optical channel selector  15 , division multiplexer  13 , optical fiber  14 , optical cable  23 , optical splitter  24 , specific wavelength optical filter  25 , and finally the monitoring-waveband reflector  26 . The high density multi-wavelength OTDR  20  may thus measure a latest locus chart of the branch line analyzed by the controlling computer  22 . As shown in  FIG. 4 , the location of the obstruction  193  on the obstructed branch line can thus be identified and took as a basis for following processes. 
     The application of the present invention can also be extended. As shown in  FIG. 1 , in addition to inputting the monitoring waveband and the specified optical signals for measuring wavelength according to different processes, the optical channel selector (OCS)  15  is capable of connecting to a plurality of division multiplexers  13  and optical networks and apparatuses behind and switching to different optical paths based on the monitoring process by the controlling computer so as to expand a passive optical network and area to be monitored, increasing the beneficial result of usage of the monitoring apparatus and diminishing the cost in monitoring. 
     The present invention is an apparatus and method for monitoring whether the status of an optical fiber at any locations of any optical fiber branches line in a passive optical network is normal or not. Comparing to the monitoring manner utilizing the conventional optical power or the optical time domain reflectometer, the present invention provides a more comprehensive and more efficient manner of monitoring. 
     The apparatus and method for monitoring optical obstructions in an passive optical network of the present invention has the following advantages when is compared to the preceding citations and other conventional techniques: 
     1. The present invention may employ the monitoring apparatus with a specific wavelength optical filter and monitoring waveband reflector at the end of routes to avoid a mutual interference caused by branches line monitoring signals and to increase the identification ability, providing a feasible, reliable, and high efficient method for monitoring multi-branches line in a passive optical network. 
     2. The present invention is easy to establish that the standard monitoring-waveband reflector has to be set up only one time for various optical fiber split routes. 
     3. The present invention may simultaneously monitor and show a latest status of the optical fibers of several branches line, achieving the purpose of fast monitoring and solving the problem that the location of the obstruction in a branch line is hard to be located. 
     4. The present invention may perform a one-sided and long-term automatic monitor, rapidly and clearly identifying an obstruction in the service system or optical fiber routes. The latest status of each branch line may further perform a precautious maintenance to provide a better service quality. 
     5. The present invention may reduce the personnel expense in maintaining network and further ensure the reliability and stability of a passive optical network to raise the efficiency of maintenance whose economic effect is apparent. 
     The above detailed description is a concrete explanation for a practicable embodiment of the present invention rather than a limitation to the claim scope of the application. Any equivalent practice or modification contained in the concept of the present invention should be included in the claim scope of the application. 
     To sum up, the present invention is not only novel in a type of space but also makes several above-mentioned improvements in view of conventional articles that should fully comply with the statutory requirements for a new invention patent regarding novelty and non-obviousness, and thus apply for a patent according to the related laws. The applicant respectfully hopes granting the subject application a patent as well. 
     Many changes and modification in the above-described embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims. 
     Many changes and modifications in the above described embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.