Abstract:
An optical fiber splice protector is provided which includes a first tube being substantially hollow and being locatable along a portion of the length of at least one optical fiber, the portion including a bare optical fiber section of the optical fiber. A longitudinal support is also locatable along the portion of the length of the optical fiber that includes the bare optical fiber splice section of the optical fiber, the longitudinal support being enclosable by the first tube along the length of the optical fiber. The first tube is of high temperature resistant material that is resistant to temperatures above 125 degrees Celsius.

Description:
TECHNICAL FIELD 
   The invention relates to an optical fibre splice protector. More particularly, the invention relates to an optical fibre splice protector suitable for use in high temperatures. 
   BACKGROUND ART 
   Optical fibres are glass or plastic fibres designed to guide light along their length by confining as much light as possible in a propagating form. They are widely used in fibre-optic communication, which permits transmission over long distances and high data rates. They are also used to form sensors, and in a wide variety of other applications. 
   As sensors optical fibres can be used to measure strain, temperature, pressure and other parameters. The small size and the fact that no electrical power is needed at the remote location give the fiber optic sensor advantages over conventional electrical sensors in certain applications. Another advantage is that optical fibres function at very high temperatures and can therefore be used in very high temperature environments, which have, for example, temperatures that are too high for semiconductor sensors to function properly. 
   Optical fibre sensors have been developed for use in oil, gas or other wells to measure temperature, pressure and other parameters down-hole. Most wells where optical fibres are used have high temperatures of operation which are above 125 degrees Celsius. Many of these wells are heavy oil wells, where the installation of fibre optics is preferred for their use in high temperature environments as they are often used to monitor the temperatures required when steam injection is used to lower the viscosity of the heavy oils. 
   There are two ways in which to deploy the optical fibre into wells. One way is to deploy the optical fibre through a small metal or high temperature plastic tube, and the tube can then be installed into a well before or after the optical fibre is deployed. Another way is to install the optical fibre cable directly into a well. The optical fibre cable is formed from optical fibres which are inside a metal tube. The optical fibre cable can contain one or several optical fibres. In the first case, optical fibre is continuously installed into the well, but in the second case there is a minimum of one optical fibre splice needed to be made in order to connect the down hole cable and optical fibre sensor together. Carbon coated polyamide optical fibres have been widely used in oil wells which have high temperatures of above 125 degrees Celsius. 
   Currently when a splice is made on an optical fibre that is to be used directly down-hole in a well, the bare fibre splice is left without any protection after the splice is made. The reason for this is that currently available optical fibre protectors cannot operate at the very high temperatures which are present in wells. 
   One of the advantages provided by the current invention is that an optical fibre splice protector is provided that can be used in very high temperatures and thus can protect optical fibre splices which are in very high temperature and chemically corrosive environments such as, for example, down-hole in wells. The optical fibre splice protector of the current invention is light, flexible and, as it has its own internal support; it does not require the splice to be supported separately after it has been applied to the optical fibre. In addition, the splice protector can be made on a very small scale and it can easily be integrated with small fibre coils. 
   DISCLOSURE OF THE INVENTION 
   According to a first aspect of the invention there is provided an optical fibre splice protector, the splice protector including,
         a first tube being substantially hollow and being locatable around a portion of the length of at least one optical fibre, the portion including a bare optical fibre splice section of the optical fibre;   a longitudinal support also being locatable along the portion of the length of the optical fibre that includes the bare optical fibre splice section of the optical fibre;   the longitudinal support being enclosable by the first tube along the length of the optical fibre; and   the first tube being of high temperature resistant material that is resistant to temperatures above 125 degrees Celsius.       

   Preferably, the first tube of high temperature resistant material is resistant to temperatures above 125 degrees Celsius and up to 500 degrees Celsius. 
   In one form of the invention the high temperature resistant material of the first tube is a fluoropolymer material. 
   The optical fibre splice protector may further include a portion of glue material being enclosed by the first tube. Preferably, the portion of glue material is in the form of a third tube of glue material being substantially hollow and which is locatable around a portion of the optical fibre, the portion including at least the bare optical fibre splice section of the optical fibre. 
   According to a second aspect of the invention the optical fibre splice protector may further include a second tube being substantially hollow, and being locatable around the optical fibre, between the first tube and the optical fibre, the second tube enclosing the longitudinal support, and being enclosed by the first tube. 
   According to a third aspect of the invention the optical fibre splice protector may further include a third tube of glue material being substantially hollow and which is locatable around a part of the optical fibre, the part including at least the bare fibre splice section of the optical fibre. 
   The first tube of high temperature resistant material may be heat shrinkable onto the second tube when heat is applied. In the same way, the second tube may be heat shrinkable onto the longitudinal support and the optical fibre when heat is applied. 
   Further, the portion of glue material is melted onto the optical fibre when heat is applied. The second tube may be bonded to the optical fibre by the melted glue material after heat has been applied. 
   In one form of the invention the longitudinal support may be substantially solid. In this case, the longitudinal support may be locatable adjacent to the optical fibre along a portion of its length, the portion including at least the bare optical fibre splice section of the optical fibre. 
   In another form of the invention the longitudinal support may be a substantially hollow tube. The longitudinal hollow tube may be locatable around a portion of the optical fibre along its length, the portion including at least the bare fibre splice section of the optical fibre. 
   Further according to the invention, the optical splice protector may be of a size so as to enclose a bare fibre section of a splice which is less than 2.5 millimeters in length. In such a case, the overall length is less than 10 millimeters and the diameter is less than 2 millimeters. 
   Preferably, the optical fibre splice protector may be used down-hole in a well. 
   According to a fourth aspect of the invention there is provided a method of forming an optical fibre splice protector, the method including,
         placing a length of longitudinal support adjacent a bare optical fibre splice section of an optical fibre; and   enclosing the bare optical fibre splice section on the optical fibre with a first tube of high temperature resistant material that is resistant to temperatures above 125 degrees Celsius, such that the longitudinal support is also enclosed by the first tube.       

   Preferably, the first tube of high temperature resistant material is resistant to temperatures above 125 degrees Celsius and up to 500 degrees Celsius. 
   The method may further include placing a portion of glue material adjacent at least a bare optical fibre splice section of an optical fibre and the longitudinal support, and enclosing both the portion of glue material and the longitudinal tube with the first tube. 
   In one form of the invention the method may even further include applying heat to the first tube and the glue material, the heat causing the first tube to shrink around the optical fibre and the glue material to melt, the melted glue causing the longitudinal support to become glued to the optical fibre. 
   Further according to the invention the method may include enclosing the bare optical fibre splice section on the optical fibre with a second tube, the second tube being substantially hollow, and being located between the first tube and the optical fibre, the second tube enclosing the longitudinal support, and the first tube enclosing both the second tube and the longitudinal support. The second tube may be shrunk around the optical fibre, the glue material and the longitudinal support, when the heat is applied to the first tube. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the invention will now be shown in more detail with reference to the accompanying drawings, in which: 
       FIG. 1  shows a schematic sectional view through an optical fibre splice protector on a bare optical fibre splice section of an optical fibre, according to the invention; and 
       FIG. 2  shows a schematic sectional side view through A-A of the optical fibre splice protector, as shown in  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
   An embodiment of an optical fibre splice protector  10 , according to the invention, which is located around a bare optical fibre splice section  12  on an optical fibre  14 , is shown in  FIGS. 1 and 2 . Optical fibre splice protector  10  can be used in any high temperature application, on an optical fibre which has a high functional temperature. A specific application foreseen for the use of optical splice protector  10  is its use down-hole in wells. Currently temperatures down-hole in oil, gas or other wells, can range between 80 degrees Celsius and 300 degrees Celsius. These wells are however becoming increasingly deeper and the temperatures down-hole will also increase as the depth increases. In addition, wells are now being placed in more environmentally challenging places, some of which involve higher operating temperatures. As a result of this the operating temperatures of down-hole equipment and tools will also need to be increased. 
   Optical fibre splice protector  10  is operable to sufficiently protect optical fibre splices on optical fibres at the high temperatures that are currently prevalent down-hole in wells, and the higher foreseeable temperatures in the deeper wells or in other high temperature environments. 
   Splice protector  10  has a first tube  16  of heat shrinkable high temperature resistant material such as, for example, fluoroplastic polymer tubing. This fluoroplastic polymer tubing is resistant to high temperatures that are greater than 125 degrees Celsius up to about 250 degrees Celsius, and is shrinkable by application of heat. Examples of this fluoroplastic polymer material tubing are PVDF, PFA, PTFE, FEP, MFA, or the like. The operating temperatures, for example, for PVDF is up to +175 degrees Celsius, for PFA it is +205 degrees Celsius and for PTFE it is +250 degrees Celsius. 
   First tube  16  may also be of other high temperature resistant materials such as fiberglass, polymer or rubber material with glass fiber, silica or silicone therein, or ceramics, which are resistant to temperatures up to 350 degrees Celsius or up to 500 degrees Celsius. Preferably the high temperature resistant material of first tube  16  should be heat shrinkable and should have a high level of strength so that it is not easily broken when applied to the bare fibre splice section  12  of an optical fibre  14 . The high temperature resistant material of first tube  16  must also not be too heavy, so that it will not cause the optical fibre  14  to break when fibre splice protector  10  is in use on the fibre. 
   First tube  16  encloses a second tube  18  of hot melting polymer material or thermoplastics, such as, for example, the various types of polyolefins. The most common polyolefins used are polyethylene and polypropylene. The working temperature of tube  18  is generally between −45 degrees Celsius and 125 degrees Celsius. 
   Second tube  18  encloses a longitudinal metal tube  20 , preferably of stainless steel, a glue tube  21 , and bare fibre splice section  12  on optical fibre  14 . Preferably metal tube  20  has high rigidity and tensile strength, and serves to provide support to bare fibre splice section  12  along its length. Glue tube  21 , for example, is made from epoxy resin such as EVA which melts at a temperature of about 102 degrees Celsius and covers the bare fibre splice section  12  forming an adhesive layer around it. Metal tube  20  and second tube are then able to adhere to and become attached to bare fibre splice section  12  when heat is applied. 
   Bare fibre splice section  12  is formed when optical fibre  14  is cut and two parts thereof are spliced together. In order to achieve this, a small section of polyimide or carbon polyimide coating  22  on optical fibre  14  has to be stripped off to reveal the bare optical fibre  24  for splicing. Even though polyimide coating  22  only has a thickness of about 0.02 mm, it is designed for high temperature operation and is quite difficult to remove. There are several ways in which coating  22  can be removed such as by using, for example, hot sulphuric acid, a high powered laser, or electrical arc discharge. Once coating  22  is removed, the bare optical fibre  24  is cut and two separate bare optical fibres  24  are then spliced together to form the bare fibre splice section  12  shown in  FIG. 2 . 
   When using electrical arc discharge in order to remove coating  22 , a section of optical fibre  14  of about 1.4 mm is stripped of its coating. The bare optical fibre  24  within this length has a diameter of 0.125 mm, compared to the diameter of 156 mm of the coated optical fibre  14 . The bare optical fibre  24  is then cleaved by using a standard fibre cleaver. 
   Two cleaved bare optical fibres are spliced together by using a commercially available optical fibre splicing machine. After splicing, the bare fibre splice section  12  is left exposed without a coating and splice protector  10  is then applied to optical fibre  14  around bare fibre splice section  12 . Splice protector  10  then encloses bare fibre splice section  12 , so that optical fibre  14  has mechanical protection in the high temperature and severe chemical environment of a well, down-hole. 
   Once metal tube  20 , glue tube  21 , second tube  18  and first tube  16  have been applied to and enclose the bare fibre splice section  12  on optical fibre  14 , heat is applied thereto. The heat applied leads to glue tube  21  being melted onto optical fibre  14  and adhering onto bare fibre splice section  12 . Second tube  18  is also shrunk onto and around optical fibre  14  by the heat applied. Metal tube  20  is thereby becomes adhered to the melted glue on bare fibre splice section  12  and is enclosed by second tube  18  in a position adjacent along its length to optical fibre  14 . The heat applied also shrinks first tube  16  so that it fits snugly around second tube  18 . As shown in the  FIG. 2 , first tube  16  is longer than second tube  18  and it fully encloses second tube  18 , even when shrunk onto optical fibre  14  around bare fibre section  12  by the heat applied. 
   While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention.