WO1999012063A1

WO1999012063A1 - Polymeric optical fibre with a multilayer protective coating

Info

Publication number: WO1999012063A1
Application number: PCT/DE1998/002334
Authority: WO
Inventors: Jürgen KUSS; Joachim Rosenfeld; Jochen Schlick; Thomas Müller; Reiner Schneider; Joachim SCHÄFER
Original assignee: Siemens Aktiengesellschaft
Priority date: 1997-08-29
Filing date: 1998-08-12
Publication date: 1999-03-11
Also published as: RU2000107818A; CN1269021A; EP1008000A1; JP2001515223A

Abstract

The aim of the invention is to provide a means of optimally adapting a polymeric optical fibre to different mechanical and chemical requirements and different conditions of use. To this end, the protective coating which is applied to the optical jacket consists of at least three layers, said layers having been deposited together and being permanently bonded to each other. The first, inner layer (13) consists of a natural-coloured thermoplastic material, the second layer (14) is the opaque layer, and a third, outer layer (15) consists of a dyed thermoplastic material. By selecting different materials for the various layers, said layers being applied by repeated extrusion, it is possible to produce a customised optical fibre. The inventive fibre is particularly suitable for transmitting data in motor vehicles.

Description

description

Polymer optical fiber with multi-layer protective cover

The invention is in the field of optical elements and is to be used in the design of fiber-shaped optical waveguides which are made of polymeric plastics and are provided with a multilayer protective covering.

Optical waveguides are suitable on the one hand for transmitting large amounts of data and on the other hand for interference-free, i.e. Data transmission that cannot be influenced by electromagnetic fields. In addition to the relatively expensive glass light guides, the inexpensive plastic light guides are suitable for data transmission over short distances of up to approx. 100 m, for example in the fields of mechanical engineering, automotive engineering and the office sector. The basic structure of these light guides, which are also referred to as "polymer optical fibers", has an optical core, an optical jacket and a protective sheath. The core and sheath have a diameter of approximately 1 mm, the protective covering a wall thickness of approximately 0.2 to 1 mm. While the optical transmission properties are primarily determined by the choice of material for the core (for example polymethyl methacrylate) and the sheath (for example a fluoropolymer such as polyvinylidene fluoride or polytetrafluoroethylene), the choice of material for the protective sheathing serves to improve the property profile of the polymeric optical fiber to adapt to the particular environment in which the optical fiber is used (magazine "Draht", 1995, Issue 4, pages 187 to 190; Conference Publication IMechE, 1981, C192 / 180, pages 227 to 229: "Multiplexed Wiπng m the automobile: near term possibility ").

In the simplest case, the protective covering of a polymeric optical fiber is formed in a single layer, for which purpose, inter alia, the Use of the materials polyethylene, polyvinyl chloride and chlorinated polyethylene is known. This protective covering can contain soot to prevent the penetration of extraneous light into the polymeric optical fiber. In order to increase the continuous use temperature of such fibers and to improve the resistance to climatic loads and mechanical influences from outside, polyamide, polyurethane or polyoxymethylene can also be used as the material for the single-layer protective covering. These materials can also be enriched with fire protection agents

(DE 92 09 018 U). - In order to obtain polymer optical fibers with improved heat resistance, it is also known to produce the light-conducting core from a heat-hardenable silicone resin, the core material being injected in the unhardened state into a two-layer jacket tube during its manufacture. The two layers of the jacket hose, the outer layer of which is opaque due to / enrichment with soot, are extruded simultaneously and firmly connected to one another by the extrusion process (DE 38 43 310 C2).

It is also known to use thermoplastic elastomers as the material for the protective covering of polymer optical fibers and to construct this covering in multiple layers (EP 0 395 823 B1). - To influence the damping behavior at low temperatures by means of a multi-layer protective covering, different plastics with the same or different values of the Young's module can also be used (EP 0 162 471 AI).

In order to improve the transmission properties of polymer optical fibers at higher temperatures, it is also known to use a material for the protective sheathing that has a shape retention temperature of at least 120 °. Optical core, optical jacket and protective cover are formed in the production of such fibers in a combined spinning process, the material for the protective covering, for example a polycarbonate, being enriched with organic or inorganic fillers such as carbon black, talc, glass fibers, fibers made from an aromatic polyamide or carbon fibers. The protective covering can also be formed in two layers, the inner layer serving as a cushion for the outer layer. Furthermore, one or two additional coatings can be applied over the protective covering, for example from a polyethylene which can be crosslinked under the action of moisture. Such a polymeric optical fiber can be used in the engine compartment of a motor vehicle for data transmission or for sensory purposes (EP 0 183 853 B1).

Starting from a polymeric optical fiber with the features of the preamble of claim 1, the invention has for its object to design the protective cover so that the property profile of the optical fiber can be easily adapted to different mechanical and chemical / requirements and to different usage properties.

To solve this problem it is provided according to the invention that the protective sheath consists of at least three co-applied, firmly interconnected layers, of which the first, inner layer consists of a natural-colored thermoplastic, the second layer, the opaque layer and a third outer layer consists of a colored thermoplastic.

The at least three-layer design of the protective sheath provided in accordance with the invention and the joint application of these layers result in a large variation. tion width with regard to the performance characteristics of the optical fiber. The inner, natural-colored layer ensures mechanical and optical decoupling of the optical core and the optical cladding from the other layers. The use of a natural-colored plastic closes the mechanical action of color particles or other filler particles on the optical cladding of the fiber and thus an influence the optical damping. This inner layer preferably consists of a thermoplastic elastomer, such as a polyurethane or a polyether block amide. These materials offer good protection against damage to the fiber due to dust-like soiling on the surface of the optical cladding during the opening of the protective cover. The substances mentioned also allow a defined adhesive fit of the protective covering on the optical jacket without increasing the lateral pressure. They also enable safe removal of the protective jacket with regard to the installation of plugs.

The second layer arranged over the inner layer is opaque, which is usually achieved in a plastic layer by adding carbon black. But D e ^¬ lichtundurch lassige layer may also consist of a low-melting metal, and thus also form a diffusion barrier and / or be used for the transmission of low-power electric pulses. The low-melting metals used for this purpose are preferably alloys based on bismuth such as special solders or the Woods metal, the melting temperatures of which are in part below the extrusion temperature of heat-resistant plastics.

The connection of such a metal layer with adjacent plastic layers can be ensured by adhesion promoters that are applied as a thin intermediate layer at the same time as the other layers - for example through the multi-layer extrusion practiced in film production. An adhesion promoter in the form of a thinner intermediate layer can also be used for the firm connection of two plastic layers.

The outer third layer of the protective cover generally offers the possibility of clearly identifying the optical fiber by introducing any dye

Layer. A colored layer can be seen more clearly than e.g. printing applied to a black layer, which can also cause manufacturing problems. However, the third outer layer can also be enriched with further additives or fillers in order to ensure special mechanical or physical or chemical properties. If necessary, a special layer with these properties can be arranged as a fourth layer between the opaque layer and the third embossed layer.

Otherwise, the property profile of the new optical fiber can also be determined by selecting different plastics for the different layers. These plastics include in particular polyamide, polyurethane, polyester, polyolefms, polyvinyl chloride, polyacetals and fluoropolymers. - The property profile of the protective sheath and thus the fiber can also be determined by a special shape of the second and third layers, for example by a surface corrugation of the second layer, which consists of a rigid material such as polyamide, and one with a smooth surface arranged third layer made of a soft material such as polyurethane. Such a configuration ensures high jerk forces after bending, for example after storing a fiber in the wound state.

The performance characteristics of the new protective cover also depend on the thickness of the individual layers. These thicknesses should be approximately 50 to 200 μm for the inner and the opaque layer and approximately 20 to 800 μm for the third outer layer; preferably the wall thickness of each of the two inner layers is approximately H the wall thickness of the outer layer.

Suitable layer combinations for the construction of the protective cover, which can be influenced and optimally combined, include: damping and light emission,

• product design such as coloring,

• mechanical properties such as tensile strength and lateral pressure resistance,

• chemical properties such as solvent resistance, 01 resistance and fuel resistance,

• barrier effect against environmental influences such as radiation, moisture, gases and liquid media,

• thermal properties such as temperature resistance and flame resistance, • physiological harmlessness such as suitability for laying in drinking water and

• Electrical properties such as leakage current behavior, insulation and conductivity and size of the surface resistance.

Three exemplary embodiments of the new optical fiber are shown in FIGS. 1 to 4. 1 shows a polymeric optical fiber with a three-layer protective covering made of polyamide, FIG. 2 shows a fiber with a four-layer protective covering made of different plastics,

Figure 3 is an optical fiber with a special mechanical structure of the protective cover and

Figure 4 shows an optical fiber with an opaque layer of metal.

FIG. 1 shows a cross-sectional sector of a polymeric optical fiber 1 which initially comprises the optical core 11 made of, for example, polymethylacrylate and the optical cladding 12 made of, for example, polyvinylidene fluoride. A protective covering composed of three layers is applied to the jacket 12, each layer consisting of a polyamide and the three layers extruded together in a triple injection head and thereby connected to one another in their border areas and applied together to the optical jacket 12. The inner layer 13 consists of a non-embossed, that is, natural-colored polyamide, the second layer 14 of a polyamide enriched with carbon black and therefore opaque, and the outer layer 15 of a polyamide enriched with a dye. The inner layer 13 and the middle layer 14 serve essentially for the optical quality of the polymeric optical fiber, while the outer layer 15 of the protective sheath essentially determines the mechanical properties, the chemical properties and the product design. The two layers 13 and 14 have a wall thickness of approximately 100 μm, while the outer layer 15 has a wall thickness of approximately 400 μm.

The polymeric optical fiber 2 according to FIG. 2 is constructed in the same way as the fiber according to FIG. 1 with regard to the optical core 11 and the optical cladding 12. enriched polyamide. Layer 23 is a further layer from a copolymer based on ethylene and Vmyl acetate, which is made flame-retardant by adding aluminum oxide hydrate. There is an embossed layer 24 made of a fluoropolymer. - This structure of the polymer optical fiber takes into account in particular the optical properties as well as thermal properties such as flame resistance and temperature resistance.

In the polymeric optical fiber 4 according to FIG. 3, a three-layer protective covering is applied to the optical cladding 12 which surrounds the optical core 11 and which consists of the inner layer 21 made of a polyurethane or also of a polyether block amide, an opaque layer 41 made of a consists of soot-enriched polyamide and an outer layer 42 made of an embe-colored polyurethane. The outer boundary surface of the layer 41 is corrugated in the longitudinal direction of the optical fiber, i.e. the wall thickness is subject to regular fluctuations in the longitudinal direction. The thaler thus formed are filled in by the layer 42. - The special design of layer 41 and the choice of material for layer 42 produce special mechanical properties, namely a high restoring force against bending with sufficient flexibility.

In the case of the polymeric optical fiber 3, as shown in FIG. 4, a five-layer protective covering is applied to the optical core 11 and the optical jacket 12. This consists of the inner layer 21 made of an undyed polyurethane, a thin adhesive layer 31, an opaque layer 32 made of a low-melting metal, a further adhesive layer 33 and an outer layer 34 made of an embossed polyvinyl chloride. This structure of the protective cover takes account of environmental influences in particular, because the metal layer 32 provides protection against the permeation of moisture, gases and liquid media also represents and takes into account the property "electrical conductivity".

Claims

claims

1. Polymeric optical fiber with an optical core and an optical cladding and with a protective covering applied to the optical cladding, which has an opaque layer, characterized in that the protective covering consists of at least three co-applied, firmly connected layers (13, 14th , 15), of which the first, inner layer (13) consists of a natural-colored thermoplastic, the second layer (14) is the opaque layer and a third outer layer (15) consists of an embossed thermoplastic.

2. Optical fiber according to claim 1, so that the opaque layer (14) consists of a thermoplastic plastic.

3. Optical fiber according to claim 1, so that the light-impermeable layer (32) consists of a low-melting metal.

4. Optical fiber according to one of claims 1 to 3, so that two adjacent layers (21, 32) of the protective covering are firmly connected by means of an adhesion promoter (31).

5. Optical fiber according to one of claims 1 to 4, characterized in that the plastic layers of the protective covering are selected from materials based on polyamide, polyurethane, Polyester, polyolef, polyvinylchloride, polyacetals and fluoropolymers.

6. Optical fiber according to claim 5, d a d u r c h g e k e n n z e i c h n e t that the first layer (21) consists of a thermoplastic elastomer such as polyurethane or polyether block amide.

7. Optical fiber according to claim 5 or 6, so that the third outer layer contains additives or fillers such as anti-aging agents, flame retardants, conductive fillers, reinforcing fibers or metal fibers.

8. Optical fiber according to one of claims 1 to 7, characterized in that the second layer (41) consists of a rigid material such as polyamide and is corrugated on its outer surface and that the third layer (42) consists of a soft material such as polyurethane .

9. Optical fiber according to one of claims 1 to 8, so that the wall thickness of the first and second layers (13, 14) of the protective covering H is the wall thickness of the third outer layer (15).