WO2002039164A2

WO2002039164A2 - High temperature fiber optic splint

Info

Publication number: WO2002039164A2
Application number: PCT/US2001/030621
Authority: WO
Inventors: Abdessamad Elyamani
Original assignee: Tycom (Us) Inc.
Priority date: 2000-11-09
Filing date: 2001-10-01
Publication date: 2002-05-16
Also published as: AU2002211318A1; WO2002039164A3

Abstract

A high temperature optical fiber splice splint (10) comprised of a material capable of withstanding an ambient temperature of at least 135 ±5 °C without of deforming is disclosed. Surrounding the inner sleeve (110), are first support member ,(120) and second support member (130). These support members help to protect the fibers from bending forces that may be applied to the splint when the splint is placed into ist final applicatiob. The support members (120 and 130) can be made from any one of a wide variety of materials, for example, quartz and PEI. Surrounding the support members (120,130) and the inner sleeve (110), which includes the optical fibres (150-155), is outer sleeve(140). The outer sleeve (140) can be made PVDF. PVDF has exellent resistence to common fuels, oils, solvents, acids and the like.

Description

HIGH TEMPERATURE FIBER OPTIC SPLINT

FIELD OF THE INVENTION

The present invention relates to optical fiber splints. More specifically, the present invention relates to high temperature optical fiber splints that can withstand substantially high temperatures without substantially deforming or causing the inner adhesive to melt and substantially go out of the splint.

BACKGROUND OF THE INVENTION Fusion bonding, or splicing, of optical fibers is well known for providing extended lengths of optical fiber cable. Optical fiber splints are used to protect those types of splices. Currently known optical fiber splints, like those disclosed in U.S.

Patent No. 5,731,051, hereby incorporated by reference, include a hot-melt tube and one or more support elements disposed within a heat shrinkable tube. The materials used for the hot-melt tube and heat shrinkable tube components of the splints disclosed in the '051 patent include common materials such as ethylene vinyl acetate and cross-linked polyethylene, respectively. Using splints comprised of these materials presents drawbacks, especially if the splints are utilized in high temperature applications where the splints may be exposed to temperatures above approximately 120°C. In these higher temperature applications, the splints need to be able to withstand periods of increased temperature without deforming or permitting a significant amount of the inner adhesive go out of the splint. For example, if a splint is included in a joint assembly, which is molded at an elevated temperature, the splint must be able to withstand the elevated temperature of the molding process without deforming in order to protect the spliced optical fibers. Therefore, the splint described in the '051 patent is not adequate for use in a high reliability system, e.g., submarine or undersea. In these fiber optic transmission systems, the reliability requirement is typically 25 years because submarine systems are generally subjected to greater stresses than, for example, terrestrial systems during installation and are not easily accessible once installed. Accordingly, there is a need for a high temperature optical fiber splice splint that is capable of withstanding high temperatures without substantially deforming.

SUMMARY OF THE INVENTION In accordance with one embodiment of the present invention, there is provided a high temperature optical fiber splice splint comprised of a material capable of withstanding an ambient temperature of at least 130 +/- 5 °C without deforming.

BRIEF DESCRIPTION OF THE DRAWINGS The various features of the invention will best be appreciated by simultaneous reference to the description that follows and the accompanying drawings, in which:

Fig. 1 is an exploded perspective view of a high temperature fiber optic splice splint in accordance with one embodiment of the present invention;

Fig. 2 is partial perspective view of the high temperature splint of Fig. l j

Fig. 3 is a side view of the high temperature splint of Fig. 1;

Fig. 4 is a cross-sectional view of the high temperature splint as taken along line 4-4 of Fig. 3; and

Fig. 5 is a partial cut-away view of a joint incorporating the high temperature fiber optic splint of Fig. 1.

DETAILED DESCRIPTION

Figure 1 illustrates an embodiment of the high temperature fiber optic splice splint in accordance with one aspect of the present invention. The high temperature splint 10 includes an inner sleeve 110, a first support member 120, a second support member 130, and an outer sleeve 140. The high temperature splint 10 of the present invention can withstand temperatures of about 130 +/- 5 °C without deforming as a result of the materials used to comprise the high temperature splint 10. For example, the outer sleeve 140 of the splint can be formed of modified Polyvinylidene Fluoride or PVDF, commonly lαiown as KYNAR^® as well as PTFE (outer sleeve 140). The inner sleeve 110 of the splint can be formed of nylon multi-polymer resin, commonly lαiown as EL V AMIDE^® 8063 made by Dupont (inner sleeve 110). Likewise, first and second support members 120 and 130 can be quartz (first support member 120) and polyetherimide or PEI, commonly known as ULTEM^® (second support member 130). The present high temperature splint is not limited to these materials, but can be made using any high temperature materials that will withstand temperatures of about 130 +/- 5 °C without deforming. The high temperature splint of the present invention is used to protect mass fusion splices of up to about 12 optical fibers. These fibers can be either single-mode or multi-mode fibers. However, the present invention is not limited to any particular type of optical fiber.

Figures 2-4 further illustrate the structure and materials used in an embodiment of the present invention. Figure 2 shows a partial perspective view of an embodiment of the present invention in which fiber optic splice(s) 150-155 are threaded through inner sleeve 110 of the splint 10.

In this embodiment of the present invention, the inner sleeve 110 can be ELVAMIDE⁷ 8063 produced by Dupont as described above. ELVAMIDE⁷ 8063 has a melting temperature of approximately 158°C and a tensile strength of approximately 7.5 kpsi. Its specific gravity is approximately 1.08 and it has a Flexcural modulus of approximately 131 kpsi. Surrounding the inner sleeve 110, are first support member 120 and second support member 130. These support members help to protect the fibers from bending forces that may be applied to the splint when the splint is placed into its final application. The support members 120 and 130 can be made from any one of a wide variety of materials, for example, quartz and PEI as described above. Surrounding the support members 120, 130 and the inner sleeve 110, which includes the optical fibers 150-155, is outer sleeve 140. The outer sleeve 140, in this embodiment, as previously described, can be made from PVDF. PVDF has excellent resistance to common fuels, oils, solvents, acids, and the like, is self-extinguishing and has a continuous operating temperature between approximately -55°C to 175°C. The diameter of the PVDF sleeve prior to shrinkage is approximately 0.220 inches with a wall thickness of approximately 0.010 inches. The shrinkage temperature of PVDF is approximately 175°C and it has a tensile strength of approximately 5500 psi. As can be seen in Figure 3, the inner sleeve 110 has an elliptical shape and defines an inner elongated aperture of length Lj that is approximately 40.00 ±0.20mm. The height Hj of the inner sleeve 110 is approximately 1.3 ±0.10 mm and the width is approximately 1.9mm. Also shown are the first and second support members 120 and 130, respectively, which add strength to the splint. The first support member 120, which in this embodiment is quartz, is disposed on a first portion 112 of the inner sleeve 110 and includes a first flat side 122 and a second semi-circular side 124. The first support member has a height H₂ of approximately 2.00 ±O.lOmm, a width of approximately 4.0 ±O.lOmm and a length of approximately 40.00 ±0.20mm. The second support member 130 is similar in shape to the first support member 120, but is formed of polyetherimide in this embodiment. The second support member is disposed on a second portion 114 of the inner sleeve 110 and has a height H of approximately 1.95 ±O.lOmm, a width of approximate 3.90 ±O.lOmm and a length of approximately 40.00 ±0.25mm. The width W_t of the high temperature splint ranges from approximately 4.13mm to approximately 4. 30 mm and the length H_t of the high temperature splint ranges from approximately 6.00 mm to approximately 6.50 mm . Surrounding this inner sleeve 110, and thus support members 120, 130, is outer sleeve 140 which has an elongated tubular structure.

To form the splint 10 around the spliced optical fibers 150-155, the splint 10 is heat cured. In the heat curing process, inner sleeve 110 is melted and outer sleeve 140 is heat shrunk. Thus, support members 120 and 130 are securely positioned between the inner sleeve 110 and the outer sleeve 140. Outer sleeve 140 is initially a heat shrinkable plastic tube, which can shrink to approximately 50% its diameter and approximately 10% longitudinally when heated. Heat is applied at the splint center first and then gradually applied towards the ends of the splint in order to prevent air bubbles from forming within the splint during heat curing. Between the optical fibers 150-155 there is adhesive material, which when heated acts to stabilize the optical fibers 150-155 within the inner sleeve 110. During heat curing, the inner sleeve 110 can reach approximately 130 +/- 5 °C or greater and the outer sleeve 140 can reach approximately 165 +/- 5 °C or greater. To achieve these temperatures, two parallel heated surfaces can be used. One surface is placed above the splint and one surface is placed below the splint. The surfaces are set to approximately 170 ±5°C for approximately 75 ±5 seconds.

Following the shrinking process, the high temperature splint 10 is nearly cylindrical with an approximate diameter of 6.00 mm . During the heating process, some of the adhesive material present between the fibers 150-155 and the inner sleeve 110 will be expelled and adhered to the fiber coating at each end of the splint In addition, sometimes the high temperature splint might have a slight amber color tint following curing. The high temperature properties of the splint 10 are utilized in numerous applications. One such application is a fiber optic cable joint, as illustrated in Figure 5. The joint includes an outer tube assembly 510 covered by molded polyethylene, with first and second strain reliefs 520 and 530 surrounding a splice box 540. Splice box 540 contains at least one high temperature splint of the present invention. To form the joint, the splint box 540 and other internal guides for the optical cables contained within the assembly 510 are placed within a mold cavity. The temperature of the mold itself is regulated in order to balance the fluid properties of the polyethylene. Once the assembly 510 is placed within the mold, the mold is heated and fluid polyethylene is injected into the mold to surround the assembly 510. Once the molding shot is completed, the assembly 510 is checked to see if the polyethylene has completely surrounded the assembly 510. If there are any blank spots, holes, or weak spots where the polyethylene did not cover the entire assembly 510 then up to another two molding cycles can be completed. However, if after the third time, the assembly 510 is not completely covered with polyethylene, then the entire assembly 510 has to be taken apart and each piece is reassembled in another joint where the molding will be attempted again.

During the molding process, the mold and the assembly 510 sitting within the mold cavity are heated in order for the polyethylene to flow and surround the assembly 510. The outer portions of the assembly can see temperatures of around 500°F and the internal portions of the splice box 540, and specifically the high temperature splint, can see temperatures of around 130 ±5°C. Thus, the splint of the present invention must be capable of withstanding an ambient temperature of at least 130 +/- 5 °C without deforming, in order to protect the spliced fibers.

For example, when high temperatures, such as those experienced by a splint in the mold cavity are reached, the high temperature splint of the present invention does not soften or lose its shape. Instead, by maintaining its structure, the spliced optical fibers of the splint described in Figures 1 to 4 remain stationary and supported. Therefore the high temperature splint of the present invention does not deform at high temperatures. In addition, the inner material is not melted and expelled out of the splint, which keeps the splices covered and eliminates a direct contact with the strength members. This direct contact might create microbending and consequently a high optical loss and might cause the fibers to beak at the splices .

The disclosed embodiments are illustrative of the various ways in which the present invention may be practiced. Other embodiments can be implemented by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

WHAT IS CLAIMED IS:

1. A high temperature optical fiber splice splint comprised of a material capable of withstanding an ambient temperature of at least 130 +/- 5°C without deforming.

2. The splint of claim 1 wherein the material is selected from the group consisting of modified polyvinylidene fluoride, nylon multi-polymer resin and combinations thereof.

3. The splint of claim 1 wherein the splint includes: an inner sleeve; a first support member disposed on a first portion of the inner sleeve; a second support member disposed on a second portion of the inner sleeve; and an outer sleeve, wherein the inner sleeve and the first and second support members are disposed within the outer sleeve.

4. The splint of claim 3 wherein the first support member is comprised of quartz and the second support member is comprised of polyetherimide.

5. The splint of claim 3 wherein the inner sleeve has an elliptical shape and further comprising a plurality of optical fiber splices disposed within the inner sleeve.

6. The splint of claim 5 wherein at least 12 optical fiber splices are disposed within the inner sleeve.

7. The splint of claim 3 wherein the first and second support members each include a first flat side and a second semi-circular side.

8. A high temperature optical fiber splice splint, comprising: at least one optical fiber splice; a nylon multi-polymer resin inner sleeve, wherein the at least one optical fiber splice is disposed within the inner sleeve; a first support member disposed on a first portion of the inner sleeve; a second support member disposed on a second portion of the inner sleeve; and a modified polyvinylidene fluoride outer sleeve, wherein the inner sleeve and the first and second support members are disposed within the outer sleeve.

9. The splint of claim 8 wherein: the inner sleeve has an elliptical shape; the first and second support members each include a first flat side and a second semi-circular side; and wherein the outer sleeve is an elongated tubular structure.

10. The splint of claim 8 wherein the first support member is comprised of quartz.

11. The splint of claim 8 wherein the second support member is comprised of polyetherimide.