Abstract:
The present invention relates to an in-line fiber optic device including a housing and an opening extending through the housing defining an optical pathway, the pathway including an optically significant element for altering a signal transmitted through the pathway, and the device including a housing with a removable portion to permit access to the optical path. The present invention also relates to a fiber optic device with a housing defining an optical path with a first and second ferrule, the optical path including an optically significant element and a first end of the housing about an outer end of the first ferrule removable to permit access to the first end of the first ferrule. The present invention further relates to a system for altering the signal being transmitted through an optical fiber telecommunications connection. The present invention also relates to a method of providing an optically significant element in an optical fiber telecommunications assembly.

Description:
FIELD OF THE INVENTION 
   The present invention relates to in-line optical devices for optical fiber telecommunications applications. More specifically, the present invention relates to an in-line optical device with a removable rear housing. 
   BACKGROUND OF THE INVENTION 
   In the fiber optical telecommunication systems, it is sometimes advantageous to moderate or attenuate the signal transmitted over the optical fiber. Some form of attenuation medium, such as a mirror or a filter, may be placed in the path of the signal to provide this desired attenuation effect. This attenuation medium may be housed within a structure which is inserted between and mates with a connector at an end of a fiber optic cable and an adapter which mates with and aligns connectors from two optical fiber cables. 
   In-line optical devices providing different levels of attenuation may be available for insertion within the optical transmission to permit the level of attenuation to match the requirements of the particular devices connected by the cables. 
   When installing a fiber optic in-line device, it is desirable to ensure that no contaminants such as moisture or dust are present on the polished ferrule end faces within the device. Such contaminants may alter the power of the signal transmitted through the device and change the level of attenuation or other signal alteration provided by the device. In many of the known formats (for example, SC and FC) of mating adapter and connector designs for optical fiber cables, one of the ferrule end faces may be difficult to access directly to clean. Improvements to the structure of in-line devices are desirable to improve access to the ferrule end faces within the device for inspection and cleaning. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a fiber optic device defining a housing with an optical pathway. The housing includes a removable portion about a first end of the optical pathway to permit access to the first end of the pathway. The pathway includes an optically significant element for altering an optical signal transmitted through the device. The optically significant element may be a filter, an air gap or some form of attenuator. The pathway may include a ferrule with an end face adjacent the removable portion of the housing and removal of the housing allowing access to the end face to clean the end face. 
   The present invention further relates to system for providing attenuation in an optical fiber telecommunications connection. 
   The present invention further relates to a method for providing an attenuation device in an optical fiber telecommunications connection. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be more completely understood by considering the detailed description of various embodiments of the invention that follows in connection with the accompanying drawings. 
       FIG. 1  is a side view of a prior art fiber optic connector positioned for insertion into a fiber optic adapter. 
       FIG. 2  is a front perspective view of the fiber optic connector of  FIG. 1  with the front cover moved to expose an end face of a ferrule. 
       FIG. 3  is a side view of an assembly of the fiber optic connector and adapter of  FIG. 1 , with an in-line fiber optic device according to the present invention positioned between the connector and adapter. 
       FIG. 4  is an exploded side view of the assembly of the connector, in-line fiber optic device and adapter of FIG.  3 . 
       FIG. 5  is a side perspective view of the in-line fiber optic device of  FIG. 4 , with the front cover and inner door removed. 
       FIG. 6  is an exploded side perspective view of the in-line fiber optic device of FIG.  5 . 
       FIG. 7  is a side cross-sectional view of the in-line fiber optic device of  FIG. 4  taken along the centerline of the ferrule within the device with the inner door positioned within the rear housing. 
       FIG. 8  is an exploded side cross-sectional view of the in-line fiber optic device of FIG.  7 . 
       FIG. 9  is an end view of the front end of the rear housing of the in-line fiber optic device of FIG.  3 . 
       FIG. 10  is a close view of the area within circle of  FIG. 9 , with a first alternative optically significant element. 
       FIG. 11  is a close view of the area within circle of  FIG. 9 , with a second alternative optically significant element. 
       FIG. 12  is a close view of the area within circle of  FIG. 9 , with a third alternative optically significant element. 
   

   While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   As shown in  FIG. 1 , a known fiber optic connector  10  and a known adapter  12  mate with each other and provide a location for optically connecting devices within a telecommunications installation. Adapter  12  has a pair of openings  24  at opposite ends which are configured to mate with a connector body  18  of connector  10 . Connector  10  is mounted to an optical fiber cable  14  and includes a strain relief boot  16 , connector body  18 , and a front cover  20  covering the end of connector  10 . When a connector  10  is inserted into each opening  24 , the optical fiber within the connectors  10  are aligned so that signals can be transmitted from one telecommunications device to another. Further details of the connectors and adapters shown in  FIG. 1  can be found in U.S. Pat. No. 5,883,995, issued Mar. 16, 1999, and U.S. Pat. No. 6,142,676, issued on Nov. 7, 2000, the disclosures of which are incorporated herein by reference. 
     FIG. 2  shows connector  10  with front cover  20  raised to expose a ferrule  11  with an end face  13  positioned within an opening  15  for receiving and mating with an alignment sleeve. In the middle of end face  13  is an end of an optical fiber  17 . 
   As disclosed in the above-referenced patents, front cover  20  provides protection to a polished end face of the optical fiber within connector  10  and prevents accidental exposure to light pulses transmitted over cable  14 . An alignment channel  26  receives an alignment rail within opening  24  to properly position connector  10  within adapter  12 . A pin channel  28  receives a pin within opening  24 , after the pin has engaged and opened front cover  20 . A catch  22  mounted to connector  10  by a deformable arm  30  provides a releasably mechanism for holding connector  10  and adapter  12  together when connector  10  is fully inserted within opening  24 . 
   It is often necessary or desirable to insert an in-line device in an optical fiber path to alter the signal being transmitted over the path. The in-line device may include an optically significant element, such as a filter, to block certain wavelengths of the signal, or an attenuator, to reduce the intensity of the signal. In the present application, the in-line optical device shown is preferably described as an in-line attenuator including an attenuation medium as the optically significant element. However, the in-line device could include a filter in place of the attenuation medium as the optically significant element. 
   Regardless of the function of the device, the in-line device of the present invention includes an optical path with at least one ferrule end enclosed in a sleeve within a housing. Such a ferrule end is difficult to reach to clean contaminants from the optical path. A portion of the housing about the ferrule end and a portion of the sleeve are removable to allow access to the ferrule end for cleaning. 
   Referring now to  FIGS. 3 and 4 , an assembly  32  including connector  10 , adapter  12  and an in-line fiber optic device  34  is shown. In-line fiber optic device  34  includes a front housing  40  which is shaped in the same fashion as connector body  18  of connector  10 . Front housing  40 , up to line  42 — 42  in  FIG. 4 , includes front cover  20 , catch  22 , alignment channel  26  and pin channel  28 , in generally the same configuration as housing  18 . Front housing  40  is thus configured to be inserted into opening  24  of adapter  12 . When in-line fiber optic device  34  is inserted into adapter  12 , catch  22 , mounted to a deformable arm  44 , operates to releasably hold in-line fiber optic device  34  to adapter  12 . In-line fiber optic device  34  further includes a rear housing  36  defining an opening  38  for receipt of connector  10 . Rear housing  36  is releasably mounted to in-line fiber optic device  34  by a spring tab  46  and a removable member  48 , which will be discussed in further detail below. 
   Referring now to  FIG. 5 , opening  38  in rear housing  36  of in-line fiber optic device  34  is shown. Within opening  38  is a pair of alignment rails  52  on an inner surface of opposing side walls  35 , which cooperate with alignment channels  26  on either side of connector  10  to properly position connector body  18  within in-line fiber optic device  34 . Also within opening  38  is a pair of doorstop pins  54  on the inner surface of opposing walls  35  which serve to limit the travel of inner door  60 , shown in  FIGS. 7 and 8 . Also within opening  38  is a pair of shutter pins  58  on the inner surface of opposing side walls  35  which engage and open front cover  20  as connector  10  is inserted within opening  38 , allow signals to be transmitted from cable  14  through connector  10  and through in-line fiber optic device  34 . Along an inner surface of an upper wall  37  are ledges  56 , which releasably engage catch  22  of connector  10  to releasably hold connector body  18  within opening  38 . 
   At the end of front housing  40  opposite from rear housing  36  is a pivot  50  about which front cover  20  is mounted and rotates to permit or block transmission of signals through in-line fiber optic device  34 . 
   Referring now to  FIG. 6 , a ferrule  66  is located within front housing  40  and includes a polished end face  68 , in the center of which is a segment of optical fiber  70 . Removable member  48  is inserted through a mounting slot  63  in upper wall  37  of rear housing  36  and engages a mounting slot  62  in front housing  40  to hold in-line fiber optic device  34  together. A pair of tabs  74  on removable member  48  engages a pair of slots  76  in front housing  40  so that removable member  48  is more securely held within slot  62 . Ferrule  66  is positioned within an opening  72  in an inner wall  92  of front housing  40  for receiving a sleeve  80  (see  FIGS. 7-9 , discussed below). 
   Referring now to  FIGS. 7 ,  8  and  9 , additional detail of in-line fiber optic device  34  is shown. Door  60  extends down from a pivot  61  adjacent the inner surface of upper wall  37  and is biased to against doorstop pins  54 . Ledges  56  have an inner surface  57  which engages catch  22  of connector  10 . Insertion of connector  10  within opening  38  forces door  60  up against the inner surface of upper wall  37  of rear housing  36 . Shutter pins  58  engage front cover  20  and force shutter  20  up, exposing ferrule  11  situated within an opening  15  and having an end face  13  and including a optical fiber  17  (see FIG.  2 ). End face  13  enters an opening  82  of sleeve  80  (opening  82  and opening  78  are at opposite ends of sleeve  80 ) and engages end face  68  of ferrule  66  with optical fiber  17  optically aligned with optical fiber  70 . 
   Upper wall  37  of rear housing  36  extends over front housing  40  so that mounting slot  63  overlays mounting slot  62 , allowing removable member  48  to be inserted. Spring tab  46  includes a locking ledge  64 , which engages spring catch  84  of rear housing  36 . Spring tab  46  and removable member  48  cooperate to removably hold rear housing  36  and front housing  40  together. A front inner face  94  of rear housing  36  engages inner wall  92  of front housing  40  to limit the depth of insertion of front housing  40  into rear housing  36 . 
   Within front housing  40  is channel  72  containing a hub  86 . Inserted into opposite ends of hub  86  are ferrule  66  and a ferrule  166 . Ferrule  166  includes a polished end face  168  and an optical fiber segment  170 . Optical fibers  70  and  170  are axially aligned to permit the transmission of signals through hub  86 . Positioned within hub  86  between ferrules  66  and  166  is an optically significant element  88 . Optically significant element  88  may be a mirror, a filter, or similar object which serves to attenuate, filter or otherwise modify the signal being transmitted. Ferrule  166  extends through a front end of front housing  40  within an opening  90 , which will receive the sleeve of adapter  12  when in-line fiber optic device  34  is inserted into adapter  12 . 
   Alternatively, optically significant element  88  may be an airgap  188  located between optical fiber segments  70  and  170  within hub  86  (see FIG.  10 ). Alternatively, the optically significant element between optical fiber segments  70  and  170  may be an offset splice  288  within hub  86  (see FIG.  11 ). Alternatively, a length of high attenuation fiber  270  extending through hub  86  from polished end  68  to polished end  168  may be included in place of optical fiber segments  70  and  170  (see FIG.  12 ). Such a high attenuation fiber segment  270  would be part of the optical path between polished end faces  68  and  168  as well as the optically significant element within hub  86 . 
   As shown in the FIGS. above, rear housing  36  is held to front housing  40  by removable member  48  and spring tab  46 . Rear housing  36  may also be held to front housing  40  by a friction fit between the outer surface of front housing  40  and the inner surface of rear housing  36  when in-line fiber optic device  34  is to be used in an environment where little or no stress is placed on cable  14  which might act to pull the front and rear housings apart, or where an external support structure might serve to prevent stress on cable  14  from being transmitted to in-line fiber optic device  34 . Either removable member  48  or spring tab  46 , or both, may be added to in-line fiber optic device  34  to prevent the housings from being accidentally separated, while still allowing rear housing  36  to be removed to permit access to end face  68 . 
   To provide an optically significant element in an existing optical fiber transmission circuit, connector  10  would be removed from adaptor  12 . Rear housing  36  is removed from front housing  40  of in-line fiber optic device  34  and end face  68  is cleaned to remove any contaminants such oil, dust or similar material is removed from the end of optical fiber  70 . Methods of cleaning may include blowing with compressed air, wiping with an alcohol pad or other solvent-laden cleaning products, or other contaminant removal procedures. To provide accurate attenuation within in the optical fiber transmission circuit, it is desirable that the optical connection between different fiber segments be as free of contaminants as possible. Rear housing  36  is replaced onto front housing  40  and secured in place by spring clip  46  and removable member  48 . 
   Once end face  68  has been cleaned, connector  10  is then inserted within opening  38  so that ferrule  11  within connector  10  is positioned within opening  82  and optical fiber  17  within cable  14  is optically aligned with optical fiber  70 . When connector  10  is fully inserted, catch  22  of connector  10  engages inner surfaces  57  of ledges  56  to releasably hold connector  10  and in-line fiber optic device  34  to one another. Front end  40  is inserted into opening  24  of adapter  12  so that ferrule  166  is engaged within a sleeve inside adapter  12 . 
   The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.