Abstract:
An optical device is provided, including two dual-fiber collimators, two single-fiber collimators, two filters connected respectively to the two dual collimators, and two mirrors. The two dual-fiber collimators are interconnected by coupling an optical fiber thereof to each other. One mirror is fixed in position, and the other mirror is mounted on a mechanism capable of moving up and down so as to switch an optical path.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to optical devices, and more particularly, to a reconfigurable optical add/drop multiplexer (ROADM) applied to optical transmission networks.  
         BACKGROUND OF THE INVENTION  
         [0002]    A conventional optical add/drop multiplexer (OADM), as shown in FIG. 1, is widely applied to optical transmission networks for adding or dropping optical wavelength signals at network nodes for data exchange. In response to increase in number of available wavelengths for each optical fiber in the optical transmission networks, the optical add/drop multiplexer should be designed to be capable of processing a wider range of wavelengths. Optical add/drop multiplexers are generally classified as fixed-type OADMs and reconfigurable-type OADMs (ROADMs). A fixed-type OADM transmits an upstream or downstream signal of a fixed wavelength at a network node, and a ROADM regulates the wavelength of the upstream or downstream signal at the network node, so as to evenly distribute network wavelength resources and thus to improve network dataflow capacity.  
           [0003]    Therefore, ROADMs that provide dynamic reconfiguring ability for optical transmission networks, thus become actively-developed products by manufacturers.  
         SUMMARY OF THE INVENTION  
         [0004]    A primary objective of the present invention is to provide a ROADM optical device applicable to an optical transmission network, which ROADM optical device is assembled by at least a fiber collimator, a filter, and an optical element for forming a 2×2 optical path switch.  
           [0005]    In accordance with the above and other objectives, the present invention provides an optical device, comprising: a first input end for receiving a multiple-wavelength optical signal, wherein the multiple-wavelength optical signal includes an optical signal to be dropped, and the first input end has a first filter that is capable of isolating the optical signal to be dropped, from the multiple-wavelength optical signal; a second input end for receiving an optical signal to be added, which has the same wavelength as the optical signal to be dropped; a first output end; a second output end coupled to the first input end, and having a second filter for allowing the optical signal to be dropped and the optical signal to be added to pass therethrough; and a switching member.  
           [0006]    When the switching member is situated at a first position, the first output end outputs the optical signal to be dropped that passes through the first filter, and the second output end outputs the optical signal to be added and the multiple-wavelength optical signal exclusive of the optical signal to be dropped. When the switching member is situated at a second position, the second output end outputs the multiple-wavelength optical signal exclusive of the optical signal to be dropped and the optical signal to be dropped that passes through the first filter, and the first output end outputs the optical signal to be added. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The present invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein:  
         [0008]    [0008]FIG. 1 (PRIOR ART) is a schematic diagram of a conventional optical add/drop multiplexer applied to optical transmission networks;  
         [0009]    [0009]FIG. 2 is a schematic diagram of an optical device according to a first preferred embodiment of the invention,  
         [0010]    [0010]FIG. 3 is a schematic diagram of the optical device shown in FIG. 2 with a switched optical path;  
         [0011]    [0011]FIG. 4 is a schematic diagram of an optical device according to a second preferred embodiment of the invention,  
         [0012]    [0012]FIG. 5 is a schematic diagram of the optical device shown in FIG. 4 with a switched optical path;  
         [0013]    [0013]FIG. 6A is a front view of an optical device according to a third preferred embodiment of the invention;  
         [0014]    [0014]FIG. 6B is a side view of the optical device according to the third preferred embodiment of the invention,  
         [0015]    [0015]FIG. 7A is a front view of the optical device with a switched optical path according to the third preferred embodiment of the invention; and  
         [0016]    [0016]FIG. 7B is a side view of the optical device with a switched optical path according to the third preferred embodiment of the invention 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    [0017]FIGS. 2 and 3 illustrate an optical device  10  according to a first preferred embodiment of the present invention. This optical device  10  comprises two dual-fiber collimators  101 ,  104 , two single-fiber collimators  102 ,  103 , two filters  105 ,  106 , and two reflective mirrors  107 ,  108 . The two filters  105 ,  106  are mounted in front of the dual-fiber collimators  101 ,  104 , or the filters  105 ,  106  are connected to the dual-fiber collimators  101 ,  104 , respectively Alternatively, surfaces of the dual-fiber collimators  101 ,  104  are subject to a film-coating treatment. An optical fiber from the dual-fiber collimator  101  and an optical fiber from the dual-fiber collimator  104  are interconnected to form a combined optical fiber  117 . Besides, the reflective mirror  107  is fixed in position, and the reflective mirror  108  is assembled on an up-and-down movable mechanism (not shown) for allowing the reflective mirror  108  to switch an optical path.  
         [0018]    As shown in FIG. 2, when wavelength-division-multiplexing (WDM) wavelengths λ 1 , λ 2  . . . λ n  are inputted to an optical fiber  113  connected to the dual-fiber collimator  101 , the filter  105  allows a selected wavelength (such as λ 1 ) to pass therethrough, but reflects other wavelengths (such as λ 2  . . . λ n ) back to the dual-fiber collimator  101  to be coupled to the optical fiber  117 . The wavelength λ 1  passing through the filter  105  is subject to reflection twice by a first optical surface of the reflective mirror  107  and once by a second optical surface of the reflective mirror  108 , and then enters into the dual-fiber collimator  104  to be outputted via an optical fiber  116  coupled to the dual-fiber collimator  104 . The wavelengths λ 2  . . . λ n  coupled to the optical fiber  117  also enter into the dual-fiber collimator  104  and are reflected by the filter  106 , so as to allow the wavelengths λ 2  . . . λ n  to be outputted via the optical fiber  116 . The wavelength λ 1  added to an optical fiber  114  connected to the single-fiber collimator  102 , is reflected by a first optical surface of the reflective mirror  108  and then enters into the single-fiber collimator  103  to be dropped out from an optical fiber  115  coupled to the single-fiber collimator  103  The above description depicts a non-operating situation of the optical device  10 , wherein an input/output network does not interfere with an add/drop network.  
         [0019]    As shown in FIG. 3, when the reflective mirror  108  is removed, the wavelength λ 1  passing through the filter  105  is reflected by the first optical surface of the reflective mirror  107 , and enters into the single-fiber collimator  103  to be dropped out via the optical fiber  115  connected to the single-fiber collimator  103 . The wavelength λ 1  added to the optical fiber  114  connected to the single-fiber collimator  102 , is reflected by the first optical surface of the reflective mirror  107 , and enters into the dual-fiber collimator  104  to be outputted via the optical fiber  116  coupled to the dual-fiber collimator  104 . Besides, the filters  105 ,  106  reflect the wavelengths λ 2  . . . λ n , so as to allow the wavelengths λ 2  . . . λ n  to be coupled to and outputted via the optical fiber  116  Therefore, optical wavelength signals can be desirably dropped from or added to an optical transmission network through the use of the optical device  10 .  
         [0020]    [0020]FIGS. 4 and 5 illustrate an optical device  20  according to a second preferred embodiment of the invention. This optical device  20  comprises: two dual-fiber collimators  201 ,  204 , two single-fiber collimators  202 ,  203 , two filters  205 ,  206 , and three reflective mirrors  207 ,  208 ,  209 . The fiber collimators  201 ,  202 ,  203 ,  204  and the filters  205 ,  206  are assembled in the same manner as described in the first embodiment. The reflective mirrors  207 ,  208  are fixed in position, and the reflective mirror  209  is assembled on an up-and-down movable mechanism (not shown) for allowing the reflective mirror  209  to switch an optical path  
         [0021]    As shown in FIG. 4, when WDM wavelengths λ 1 , λ 2  . . . λ n  are inputted to an optical fiber  213  connected to the dual-fiber collimator  201 , the filter  205  allows a selected wavelength (such as λ 1 ) to pass therethrough, and reflects other wavelengths (such as λ 2  . . . λ n ) back to the dual-fiber collimator  201  to be coupled to an optical fiber  217 . The wavelength λ 1  passing through the filter  205  is reflected by a first optical surface of the reflective mirror  207 , and then enters into the dual-fiber collimator  204  to be outputted via an optical fiber  216  connected to the dual-fiber collimator  204 . The wavelengths λ 2  . . . λ n  coupled to the optical fiber  217  also enter into the dual-fiber collimator  204 , and are reflected by the filter  206  to be coupled to and outputted via the optical fiber  216 . The wavelength λ 1  added to an optical fiber  214  connected to the single-fiber collimator  202 , is reflected by the first optical surface of the reflective mirror  207 , and then enters into the single-fiber collimator  203  to be dropped out from an optical fiber  215  coupled to the single-fiber collimator  203  Therefore, under a non-operation condition of the optical device  20 , an input/output network does not interfere with an add/drop network  
         [0022]    As shown in FIG. 5, with the reflective mirror  209  being added, the wavelength λ 1  that passes through the filter  205  is reflected twice by a first optical surface of the reflective mirror  209  and once by a first optical surface of the reflective mirror  208  to enter into the single-fiber collimator  203 . Then, the wavelength λ 1  is dropped out via the optical fiber  215  connected to the single-fiber collimator  203  The wavelength λ 1  added to the optical fiber  214  connected to the single-fiber collimator  202 , is reflected by the first optical surface of the reflective mirror  209 , and then enters into the dual-fiber collimator  204  to be outputted via the optical fiber  216  of the dual-fiber collimator  204 . Besides, the filters  205 ,  206  reflect the wavelengths λ 2  . . . λ n , so as to allow the wavelengths λ 2  . . . λ n  to be coupled to and outputted via the optical fiber  216 . Therefore, optical wavelength signals can be desirably dropped from or added to an optical transmission network through the use of the optical device  20   
         [0023]    [0023]FIGS. 6A, 6B,  7 A and  7 B illustrate an optical device  30  according to a third preferred embodiment of the invention. This optical device  30  comprises: two dual-fiber collimators  301 ,  304 , two single-fiber collimators  302 ,  303 , two filters  305 ,  306 , a specially film-coated flat glass  307 , flat glass  308  with high permeability, and a prism  309  with high permeability The flat glass  307  is coated or attached on its bottom surface with a reflective film to form a reflective mirror  310 , and a top surface of the flat glass  307  is coated or adhered at a predetermined position with a reflective film to form a reflective mirror  311 . The prism  309  is also coated or adhered on a surface thereof with a reflective film to from a reflective mirror  312 . The fiber collimators  301 ,  302 ,  303 ,  304  and the filters  305 ,  306  are assembled in the same manner as described in the first embodiment The flat glass  308  is assembled on a rotatable mechanism (not shown) for allowing the flat glass  308  to switch an optical path.  
         [0024]    As shown in FIG. 6A, when WDM wavelengths λ 1 , λ 2  . . . λ n  are inputted to an optical fiber  313  connected to the dual-fiber collimator  301 , the filter  305  allows a selected wavelength (such as λ 1 ) to pass therethrough, and reflects other wavelengths (such as λ 2  . . . λ n ) back to the dual-fiber collimator  301  to be coupled to an optical fiber  317 . When the flat glass  308  is rotated to reach a first position (as shown in FIG. 6B), the wavelength λ 1  that passes through the filter  305  is refracted by the flat glass  308 , reflected by the reflective mirror  312 , and further reflected by a first optical surface of the reflective mirror  311  so as to enter into the single-fiber collimator  303  where the wavelength λ 1  can be dropped out from an optical fiber  315  coupled to the single-fiber collimator  303 . The wavelength λ 1  added to an optical fiber  314  connected to the single-fiber collimator  302 , is refracted by the flat glass  308 , reflected by the reflective mirror  312 , and further reflected by the reflective mirror  310  and a second optical surface of the reflective mirror  311 , so as to enter into the dual-fiber collimator  304  wherein the wavelength λ 1  can be dropped from an optical fiber  316  coupled to the dual-fiber collimator  304  Therefore, optical wavelength signals can be desirably dropped from or added to an optical transmission network through the use of the optical device  30 .  
         [0025]    As shown in FIGS. 7A and 7B, when the flat glass  307  is rotated to reach a second position, after being refracted by the flat glass  308  and reflected by the reflective mirror  312 , the wavelength λ 1  that passes through the filter  305  is not reflected by the first optical surface of the reflective mirror  311 , but is reflected directly by the reflective mirror  310  and enters into the dual-fiber collimator  304  where the wavelength λ 1  can be outputted via the optical fiber  316  coupled to the dual-fiber collimator  304 . The wavelengths λ 2  . . . λ n  that are reflected by the filter  305  to be coupled to the optical fiber  317 , enter into the dual-fiber collimator  304  and are reflected by the filter  306  to be coupled to and outputted via the optical fiber  316  The wavelength λ 1  that is added to the optical fiber  314  connected to the single-fiber collimator  316 , after being refracted by the flat glass  308  and reflected by the reflective mirrors  312 ,  310 , enters into the single-fiber collimator  303  where the wavelength λ 1  can be dropped out via the optical fiber  315  connected to the single-fiber collimator  303  Therefore, under a non-operation condition of the optical device  30 , an input/output network does not interfere with an add/drop network.  
         [0026]    In conclusion from the above embodiments, the ROADM optical device according to this invention is simply accomplished by assembling two dual-fiber collimators, two filters, two single-fiber collimators, and a set of optical elements for forming a 2×2 optical path switch.  
         [0027]    The invention has been described using exemplary preferred embodiments However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements