Claims
- 1. An optical fibre cable in which a thermotropic liquid crystalline polymer is used to provide a support member in the cable characterized in that said polymer is present as a coating surrounding and contacting the optical fibre, that the linear thermal expansion coefficient of the coating is negative and is less than that of the optical fibre, and wherein a strain of less than 0.2% is introduced into the optical fibre when the cable is subjected to temperatures over the range of -50.degree. C. to +150.degree. C.
- 2. An optical fibre cable according to claim 1 in which the support member has a load capacity of at least 5 kg when subject to a strain of 0.2%.
- 3. An optical fibre cable according to claim 1 in which the support member has a linear thermal expansion coefficient of not less than -1.times.10.sup.-5 /.degree.K.
- 4. An optical fibre cable according to claim 1 in which a thermotropic liquid crystalline polymer is used to provide a support member in the cable characterised in that the support member is in the form of a sheath having a linear thermal expansion coefficient which is negative and is not less than -5.times.10.sup.-6 /.degree.K.
- 5. An optical fibre cable according to either of claims 2 or 3 in which the linear thermal expansion coefficient of the support member closely matches the linear thermal expansion coefficient of the optical fibre.
- 6. A process of forming an optical fibre cable reinforced with a support member comprising melt extruding an elongated tube of thermotropic, liquid crystalline polymer through a die around an optical fibre under conditions such that the tube surrounds and contacts the optical fibre and the linear thermal expansion coefficient of the tube is negative and is less than that of the optical fiber and such that a strain of less than 0.2% is introduced into the optical fibre when the cable is subjected to temperatures over the range -50.degree. C. to +150.degree. C.
- 7. A process of extruding a support member according to claim 6 in which the draw down is controlled so as to produce a strength member having a linear thermal expansion coefficient not less than -5.times.10.sup.-6 /.degree.K.
- 8. A process of extruding a support member according to claim 6 in which the draw down is controlled so as to produce a strength member having a linear thermal expansion coefficient which closely matches that of the optical fibre selected for use in the optical fibre cable.
- 9. A process of forming an optical fibre cable according to claim 6 in which the compressive strain induced on the optical fibre from extruding the thermotropic fibre around the fibre is controlled by means of the extrusion conditions to counteract dimensional changes in the optical fibre resulting from temperature variations.
- 10. A process of forming an optical fibre cable according to claim 9 wherein the thermal expansion coefficient of the thermotropic coating is less than that of the optical fibre so that a compressive strain is induced on the optical fibre.
- 11. A process of forming an optical fibre cable according to claim 8 wherein the melt is extruded onto the optic fibre and the coated fibre leaving the die is subjected to conditions so that the ratio of the cross-sectional area of the die to the cross sectional area of the coated fibre produced is less than 4:1.
- 12. A process of forming a support member according to either of claims 6 or 11 in which the member formed by extrusion is annealed below the melting point of the thermotropic polymer.
- 13. An optical fibre cable according to either of claims 1 or 3 in which the linear thermal expansion coefficient of the coating surrounding and contacting the fibre is negative and the coating exerts a compressive strain on the optic fibre.
Priority Claims (2)
Number |
Date |
Country |
Kind |
8316739 |
Jun 1983 |
GBX |
|
8328369 |
Oct 1983 |
GBX |
|
Parent Case Info
This is a continuation of application Ser. No. 619,194, filed June 11, 1984, which was abandoned upon the filing hereof.
US Referenced Citations (5)
Foreign Referenced Citations (5)
Number |
Date |
Country |
0091253 |
Dec 1923 |
EPX |
0129372 |
Dec 1984 |
EPX |
3108109 |
Sep 1982 |
DEX |
1371740 |
Oct 1974 |
GBX |
1538853 |
Jan 1979 |
GBX |
Non-Patent Literature Citations (2)
Entry |
Katsuyama et al., "Transmission Loss of Coated Single-Mode Fiber at Low Temperatures" Applied Optics vol. 19, No. 24, 12/80, pp. 4200-4205. |
Lagakos et al., "Minimizing Temperature Sensitivity of Optical Fibers" Applied Optics, vol. 20, No. 19, 10/81, pp. 3276-3278. |
Continuations (1)
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Number |
Date |
Country |
Parent |
619194 |
Jun 1984 |
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