Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority benefits to Chinese Patent Application No. 200720119293.0 filed on Apr. 4, 2007, the contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to optical components, and particularly to a variable optical attenuator with a photoelectric detector. 
   2. Description of the Related Art 
   Telecommunication and data transfers over networks are increasingly being implemented using optical components. To enable the power of an optical beam to be reduced in a controlled manner, various types of variable optical attenuators (VOA) have been developed. Amongst these, a micro-electro-mechanical system (MEMS)-type attenuator is commonly-used. The MEMS optical attenuator comprises a pair of collimators and a MEMS driving shade. Since mode field diameters vary depending on the wavelength, this kind of MEMS optical attenuator may have large wavelength-dependent losses. 
     FIG. 1  illustrates another type of MEMS optical attenuator, comprising an optical fiber holder  101  which holds optical fibers  1011  and  1012 , a lens  103  and a mirror  104 . As the mirror  104  rotates, the light entering the optical fiber  1012  is changed. 
   However, the above-mentioned MEMS optical attenuators are not capable of detecting their own attenuation performance, and therefore their reliability cannot be guaranteed. 
   SUMMARY OF THE INVENTION 
   In view of the above-described problems, it is one objective of the invention to provide a variable optical attenuator that is capable of detecting its own attenuation performance and thus integrating more function in one device. 
   To achieve the above objectives, in accordance with one embodiment of the invention, provided is a variable optical attenuator, comprising a collimator, a variable optical attenuator chip, wherein the variable optical attenuator further comprises a photoelectric detector; and the photoelectric detector receives and senses light beam from the variable optical attenuator chip. 
   In certain classes of this embodiment, the collimator comprises an optical fiber holder and a lens. 
   In certain classes of this embodiment, the optical fiber holder holds two optical fibers. 
   In certain classes of this embodiment, the optical fiber holder holds one optical fiber. 
   In certain classes of this embodiment, the photoelectric detector is a photodiode. 
   The variable optical attenuator of the invention is capable of detecting attenuation change of itself via the variable optical attenuator chip. Thus, real-time monitoring and feedback are implemented, and attenuation performance of the variable optical attenuator is improved. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a variable optical attenuator of the prior art; 
       FIG. 2  illustrates a variable optical attenuator of a first embodiment of the invention; 
       FIG. 3  illustrates a variable optical attenuator of a second embodiment of the invention; 
       FIG. 4  illustrates a variable optical attenuator of a third embodiment of the invention; 
       FIG. 5  illustrates a variable optical attenuator of a fourth embodiment of the invention; and 
       FIG. 6  illustrates a variable optical attenuator of a fifth embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Detailed description will be given in the examples below with reference to accompanying drawings. 
   EXAMPLE 1 
   As shown in  FIG. 2 , a variable optical attenuator of a first embodiment of the invention comprises a collimator  11 , a variable optical attenuator chip  12 , an optical filter  13 , and a photoelectric detector  14 . The collimator  11  comprises a lens  111  and an optical fiber holder  112 . The variable optical attenuator chip  12  is disposed between the lens  111  and the optical fiber holder  112 . The optical fiber holder  112  comprises a first optical fiber  1121  and a second optical fiber  1122 . The optical filter  13  is disposed at the front end of the lens  111 , and operates to split light. Part of light is transmitted by the optical filter  13  and then received by the photoelectric detector  14 . In this embodiment, the photoelectric detector  14  is a photodiode. 
   In the first embodiment of the invention, light exiting the first optical fiber  1121  of the optical fiber holder  112  is attenuated by the variable optical attenuator chip  12 , and then reaches the optical filter  13  via the lens  111 . Most of the light is reflected by the optical filter  13  and focused onto the second optical fiber  1122  of the optical fiber holder  112 , and the rest of the light is transmitted to the photoelectric detector  14  by the optical filter  13 . Thus, as the variable optical attenuator chip  12  operates, the photoelectric detector  14  is capable of detecting attenuation change of the variable optical attenuator, and real-time monitoring and feedback are implemented. 
   EXAMPLE 2 
   As shown in  FIG. 3 , the variable optical attenuator of a second embodiment of the invention comprises a collimator  21 , a variable optical attenuator chip  22 , an optical filter  23 , and a photoelectric detector  24 . The collimator  21  comprises a lens  211 , a first optical fiber holder  212  and a second optical fiber holder  213 . The variable optical attenuator chip  22  is disposed between the lens  211  and either the first optical fiber holder  212  or the second optical fiber holder  213 . The optical filter  23  is disposed at the front end of the lens  211 , and operates to split light. Part of light is transmitted by the optical filter  23  and then received by the photoelectric detector  24 . In this embodiment, the photoelectric detector  24  is a photodiode. 
   In the second embodiment of the invention, light exiting the first optical fiber  2121  of the first optical fiber holder  212  is attenuated by the variable optical attenuator chip  22 , and then transmitted to the optical filter  23  via the lens  211 . Most of the light is reflected by the optical filter  23 , and then focused onto the second optical fiber  2131  of the second optical fiber holder  213 , and the rest of the light is transmitted to the photoelectric detector  24  via the optical filter  23 . Thus, as the variable optical attenuator chip  22  operates, the photoelectric detector  24  is capable of detecting attenuation change of the variable optical attenuator, and real-time monitoring and feedback are implemented. 
   EXAMPLE 3 
   As shown in  FIG. 4 , the variable optical attenuator of a third embodiment of the invention comprises a collimator  11 , a variable optical attenuator chip  12 , an optical filter  13 , and a photoelectric detector  14 . The collimator  11  comprises a lens  111  and an optical fiber holder  112 . The variable optical attenuator chip  12  is disposed between the lens  111  and the optical filter  13 . The optical filter  13  is disposed at the front end of the lens  111 , and operates to split light. Part of light is transmitted by the optical filter  13  and received by the photoelectric detector  14 . In this embodiment, the photoelectric detector  14  is a photodiode. 
   In the third embodiment of the invention, light exiting the first optical fiber  1121  of the optical fiber holder  112  is transmitted via the lens  111 , attenuated by the variable optical attenuator chip  12 , passed onto the optical filter  13 . Most of the light is reflected by the optical filter  13 , and then focused onto the second optical fiber  1121  of the optical fiber holder  112 , and the rest of the light is transmitted to the photoelectric detector  14  by the optical filter  13 . Thus, as the variable optical attenuator chip  12  operates, the photoelectric detector  14  is capable of detecting attenuation change of the variable optical attenuator, and real-time monitoring and feedback are implemented. 
   EXAMPLE 4 
   As shown in  FIG. 5 , a variable optical attenuator of a fourth embodiment of the invention comprises a collimator, an optical filter  13 , and a photoelectric detector  14 . The collimator comprises a lens  111  and an optical fiber holder  112 . The optical filter  13  is disposed at a front end of the lens  111 , and operates to split light. Part of light is transmitted by the optical filter  13  and then received by the photoelectric detector  14 . In this embodiment, the photoelectric detector  14  is a photodiode, and the optical filter  13  is a rotable optical filter. 
   In the fourth embodiment of the invention, light exiting the lens  111  via the first optical fiber  1121  of the optical fiber holder  112  is attenuated by the optical filter  13 . Most of the light is reflected by the optical filter  13 , and then focused onto the second optical fiber  1122  of the optical fiber holder  112 , and the rest of the light is transmitted to the photoelectric detector  14  via the optical filter  13 . Thus, the photoelectric detector  14  is capable of detecting attenuation change of the variable optical attenuator, and real-time monitoring and feedback are implemented. 
   EXAMPLE 5 
   As shown in  FIG. 6 , a variable optical attenuator of a fifth embodiment of the invention comprises a collimator  11 , a variable optical attenuator chip  12  and a photoelectric detector  14 . The collimator  11  comprises a lens  111  and an optical fiber holder  112 . The variable optical attenuator chip  12  is disposed at a front end of the lens of the lens  111 , and operates to split light. Part of light is transmitted by the variable optical attenuator chip  12  and then received by the photoelectric detector  14 . In this embodiment, the photoelectric detector  14  is a photodiode. 
   In the fifth embodiment of the invention, light exiting the lens  111  via the first optical fiber  1121  of the optical fiber holder  112  is attenuated by the variable optical attenuator chip  12 . Most of the light is reflected by the variable optical attenuator chip  12 , and then focused onto the second optical fiber  1122  of the optical fiber holder  112 , and the rest of the light is transmitted to the photoelectric detector  14  via the variable optical attenuator chip  12 . Thus, as the variable optical attenuator chip  22  operates, the photoelectric detector  14  is capable of detecting attenuation change of the variable optical attenuator, and real-time monitoring and feedback are implemented. 
   The variable optical attenuator of the invention detects its own attenuation change via the variable optical attenuator chip. Thus, real-time monitoring and feedback are implemented, and the attenuation performance of the variable optical attenuator is improved. 
   While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

Technology Category: 3