Patent Publication Number: US-6668110-B2

Title: Optical switch having improved sealing structure

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical switch, and particularly to an optical switch having an improved sealing structure. 
     2. Description of Related Art 
     An optical switch is a passive optical component for switching optical signals between input fibers and output fibers, and is widely used in optical transmission systems and in optical networks. To assure good performance of the optical switch, the influence of the environment on the switch has to be reduced. Hence, a good sealing structure to protect the optical elements in the switch is increasingly important. 
     A sealing structure for an optical component must provide good stability and isolation, so must exclude dust and vapor from an inside of the optical component. Present sealing structures for optical components mainly use epoxy resin to mount fibers into two housings, with the two housings being engaged together by screws. Such sealing structures provide a low level of isolation, which fails to exclude vapor and dust from an interior of the optical component. Optical efficiency of the optical component is, therefore, at risk. 
     Other sealing structures use a rubber-ring situated at entrances and in junctures between housing halves to achieve a seal. Such rubber-rings are designed to conform to a shape of the entrances and junctures and commonly define circular openings for receiving fiber clamps holding the fibers. However, pressure exerted on the rubber-rings by the fiber clamps is asymmetrical because, although the circular groove of the fiber clamp initially exerts a symmetrical pressure against the circular opening of the rubber-ring, the additional pressure acting against the rubber-ring exerted by the two housing halves when the two housing halves are bound together results in an asymmetric stress in the rubber-ring at the openings. The added stress will result in accelerated aging of the rubber-ring, leading to breakdown and a loss of sealing characteristics over time. This will allow vapor and dust to enter into the optical component, degrading optical efficiency. 
     For the above reasons, an improved sealing structure for optical components is desired which provides dependable isolation. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an optical switch having an improved sealing structure. 
     Another object of the present invention is to provide a sealing structure for optical components having good stability and high isolation from the environment. 
     An optical switch having a sealing structure and connecting to input fibers and output fibers comprises a switching device, a top housing, a bottom housing, a gasket, and a plurality of fiber clamps. 
     The top housing and the bottom housing are similar in shape and when fit together have substantially a bottle shape. The top housing and the bottom housing each define a channel for receiving the gasket. The gasket defines at least one elliptic opening for receiving a fiber clamp holding a fiber. The gasket is received in the channels of the top and bottom housings, and fills the channels when pressure is applied by screws combining the top and bottom housings together. Good isolation is achieved in a space defined between the top and bottom housings. 
     A similar sealing structure can be used to protect other optical components, such as optical couplers, optical connectors and optical attenuators. 
     Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of an optical switch with a sealing structure according to the present invention; 
     FIG. 2 is a frontal view of a quadrate flange of a gasket of the optical switch of FIG. 1, showing an elliptic opening; 
     FIG. 3 is a frontal view of the quadrate flange of FIG. 2, depicting forces exerted against a fiber clamp situated in the elliptic opening of the quadrate flange. 
     FIG. 4 is a frontal view of the quadrate flange of FIG. 2, depicting stress in the quadrate flange around the elliptic opening resulting from the presence of the fiber clamp in the elliptic opening. 
     FIG. 5 is a frontal view of the quadrate flange of FIG. 2, depicting forces exerted against a fiber clamp situated in the elliptic opening of the quadrate flange after a top housing and a bottom housing engage with each other. 
     FIG. 6 is a frontal view of the quadrate flange of FIG. 2, depicting stress in the quadrate flange around the elliptic opening resulting from the presence of the fiber clamp in the elliptic opening, after the top housing and the bottom housing engage with each other. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIG. 1, an optical switch having a sealing structure for switching signals coming from input fibers  42 ,  43  between output fibers  44 ,  45  comprises a switching device  5 , a top housing  10 , a bottom housing  30 , four fiber clamps  40 , four collimators  41 , and a gasket  20 . 
     The top housing  10  and the bottom housing  30  are similar in shape, and when assembled together are substantially in the shape of a bottle. 
     The top housing  10  comprises an inner wall  103  and an outer wall  102 , and defines a plurality of screw holes  101  therein. A ringed channel  104  is defined between the inner wall  103  and the outer wall  102 . A pair of semi-annular openings  105  is defined in each of two lower sides and in each of two shoulders of the top housing  10 . Each pair of semi-annular openings  105  is respectively defined in the inner wall  103  and in the outer wall  102 , and a quadrate groove  106  is formed therebetween. 
     The bottom housing  30  includes an inner wall  303  and an outer wall  302 , and defines a plurality of screw holes  301  therein. A ringed channel  304  is formed between the inner wall  303  and the outer wall  302 . A pair of semi-annular openings  305  is defined in each of two lower sides and in each of two shoulders of the bottom housing  30 . Each pair of semi-annular openings  305  is respectively defined in the inner wall  303  and in the outer wall  302 , and a quadrate groove  306  is formed therebetween. The semi-annular openings  105  and the ringed channel  104  of the top housing  10  are similar to the semi-annular openings  305  and the ringed channel  304  of the bottom housing  30 . The bottom housing further comprises a slot  308 , a mounting hole  309  and mounting walls  307 ,  310 ,  311 . 
     The gasket  20  is substantially the same size and shape as the channels  104 ,  304 . The gasket  20  is made of rubber or other elastic or ductile material. The gasket  20  comprises four quadrate flanges  206  received in the quadrate grooves  106 ,  306 . Referring to FIG. 2, each quadrate flange  206  defines an elliptic opening  208  therethrough. A plurality of through holes  201  are defined through the gasket  20 , placed to coincide with the screw holes  101 ,  301  of the top and bottom housings  10 ,  30 . 
     The switching device  5  comprises a holding element  50 , a reflector  501 , a driving arm  60 , a two-surface mirror  601  and a driving means  70 . The holding element  50  holds the reflector  501  and is mounted in the slot  308  of the bottom housing  30 . The two-surface mirror  601  is held and driven to move up and down by the driving arm  60 . When the two-surface mirror  601  is displaced out of optical paths between the input fibers  42 ,  43  and the output fibers  44 , 45 , the light signals from the input fibers  42 ,  43  are respectively transmitted directly to the output fibers  44 ,  45 . However, when the two-surface mirror  601  is moved into the optical paths, one surface of the two-surface mirror faces the reflector  501  and the two-surface mirror  601  reflects the light signals from the input fiber  42  to the reflector  501 , and then the reflector  501  reflects the signals to the two-surface mirror  601 , thereafter the two-surface mirror  601  reflects the signals to the output fiber  45 ; the signals from the input fiber  43  are reflected to the output fiber  44  by the two-surface mirror  601 . The switching element  5  further comprises a stopper  80  received in the mounting hole  309  of the bottom housing  30 . The stopper  80  is used to limit downward travel of the two-surface mirror  601 . The driving means  70  drives the driving arm  60  to move the two-surface mirror  601  up and down 
     The switch  1  further comprises four fiber clamps  40 . Each fiber clamp  40  comprises a front flange  401 , an annular groove  402  and a rear flange  403 . The fiber clamps  40  are inserted into the elliptic openings  208  of the gasket  20 , and the annular grooves  402  engage with the elliptic openings  208 . 
     Referring to FIGS. 3 and 4, when the fiber clamp  40  is situated in the elliptic opening  208  of the gasket  20 , the forces exerted by the fiber clamp  40  on the quadrate flange  206  and by the quadrate flange  206  on the fiber clamp  40  are asymmetrical. Because of the elliptic shape of the opening  208  in its relaxed state, the forces exerted by the quadrate flange  206  against the circular-shaped fiber clamp  40  (and by the fiber clamp  40  against the quadrate flange  206 ) are larger at the sides than at the top and bottom of the fiber clamp  40 . 
     Referring to FIGS. 5 and 6, when the fiber clamp  40  is situated in the elliptic opening  208  of the gasket  20 , and the top housing  10  and the bottom housing  30  are in engagement with each other, the forces exerted on the fiber clamp  40  by the quadrate flange  206  and on the quadrate flange  206  by the fiber clamp  40  are uniformly the same all around the circumference of the fiber clamp  40 . This is because the top and bottom housings  10 ,  30  press against and deform the quadrate flange  206  so that the elliptic opening  208  is more circular, even without the fiber clamp  40  forcing it to a circular shape. The stress in the quadrate flange  206  around the fiber clamp  40  is, therefore, more uniform, and the quadrate flange is less prone to uneven wear and aging, improving its stability and resistance to wear. 
     In assembly, the switching device  5  is situated in a space (not labeled), which is defined between the assembled top and bottom housings  10 ,  30 . The four collimators  41  are separately mounted in the mounting walls  307 ,  310 ,  311  of the bottom housing  30  for collimating the signals. The input fibers  42 ,  43  and output fibers  44 ,  45  are each held in a corresponding fiber clamp  40  and boot  404 . The fiber clamps  40  are inserted into the openings  208  of the gasket  20 . The annular groove  402  of each fiber clamp  40  engages with inner and outer walls  103 ,  102 ,  303 ,  302  rimming each of a corresponding pair of semi-annular openings  105 ,  305  in each of the top and bottom housings  10 ,  30 , and engages with the opening  208  of the gasket  20 . The gasket  20  is received in the ringed channels  104 ,  304  and quadrate grooves  106 ,  306  of the top and bottom housings  10 ,  30 . When screws (not shown) are threaded through the screw holes  101 ,  301  and through holes  201  and are tightened, the gasket  20  deforms under the pressure, filling the ringed channels  104 ,  304  and quadrate grooves  106 ,  306 . The interior (not labeled) of the housing is thereby well sealed and protected from contamination from outside the housing. 
     The described sealing system, consisting of the top housing  10 , the bottom housing  30 , the gasket  20  and the fiber clamps  40 , can be used to seal other optical components, such as optical couplers, optical connectors and optical attenuators. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.