Method of identifying optical fibers in a cable
An optical fiber includes a primary covering layer, a secondary covering layer transparent to a laser beam, an intermediate covering layer less than 100 nm thick between the primary covering layer and the secondary covering layer and including a coloring element whose coloring properties can be modified by using the laser beam to irradiate the intermediate covering layer to write data.
1. An optical fiber including a primary covering layer, a secondary covering layer transparent to a laser beam, an intermediate covering layer less than 100 nm thick between said primary covering layer and said secondary covering layer and including a coloring element whose coloring properties can be modified by using said laser beam to irradiate said intermediate covering layer to write data; and wherein the coloring element is dispersed continuously throughout the intermediate layer.
2. The optical fiber claimed in claim 1 wherein said coloring element is a ThermoChrome dye.
3. The optical fiber claimed in claim 2 wherein said coloring element is a material based on cyanine or phthalocyanine.
4. The optical fiber claimed in claim 1 wherein said coloring element constitutes from 0.1% by weight to 10% by weight of all of the substances of said covering layers.
5. The optical fiber claimed in claim 1 wherein the data that is written comprises bar codes.
6. The optical fiber claimed in claim 1 wherein the data that is written comprises visual codes.
7. The optical fiber claimed in claim 1 wherein the data that is written is permanent.
8. The optical fiber claimed in claim 1 wherein the data that is written is coded.
9. The optical fiber claimed in claim 1 wherein the data that is written is incremental.
10. An optical cable including an optical fiber as claimed in claim 1 .
11. The method claimed in claim 10 of identifying optical fibers in a cable when each fiber has an intermediate covering layer including a coloring element, which method further includes a laser marking step for writing data, said intermediate covering layer of at least one of said fibers being irradiated by a laser beam to modify the coloring properties of said coloring element.
12. The identification method claimed in claim 11 , further including a step of using a laser reader to read data written on said intermediate covering layer of a fiber.
13. A method of identifying an optical fiber as claimed in claim 1 , including a laser marking step for writing data by irradiating said intermediate covering layer of said fiber using a laser beam to modify the coloring properties of said coloring element.
14. The identification method claimed in claim 13 wherein the data writing step is repeated several times on the same fiber.
15. The identification method claimed in claim 14 wherein said data is written in adjacent areas of the same fiber.
16. The identification method claimed in claim 14 wherein said data is written in different portions of the same fiber.
17. The identification method claimed in claim 13 , further including using a laser reader to read data written on said intermediate covering layer of said fiber.
18. An optical fiber including a primary covering layer, a secondary covering layer transparent to a laser beam, an intermediate covering layer between said primary covering layer and said secondary covering layer and including a coloring element whose coloring properties can be modified by using said laser beam to irradiate said intermediate covering layer to write data; and wherein the coloring element is dispersed continuously throughout the intermediate layer.