A2 200 micron whitepaper

A2 200 micron whitepaper

Deployment of optical fibre cable in limited space and in tight bend conditions demands reduced diameter optical fibre and cable with bend insensitive fibre. To address this need, optical fibre with 200 micron outer coating diameter instead of 250 micron for conventional fibre has been developed. This application note outlines various advantages of 200 micron fibre and its backward compatibility with conventional fibre.

Optical fibre is used in all modern optical communications including long-haul, regional, access, and FTTX networks. An optical fibre is made up of three layers, namely, core, cladding, and coating. Light is guided down the centre of the fibre called the “core”. The core is surrounded by an optical material called the “cladding” that contains the light in the core using an optical phenomenon called “total internal reflection.” The f ibre is coated by a buffer layer that protects it from moisture and physical damage. The buffer or “coating” is what one strips off the fibre for termination or splicing. More protection is provided by the cable which has the fibres and strength members inside an outer protective covering called a “jacket” or a “sheath.”

The fibre coating is made of a UV curable polymer called acrylate, which acts to protect the inner glass. Dual layered coating structures are generally applied, which use a low-modulus inner or buffer layer to cushion the fibre surrounded by a high-modulus outer coating to increase the f lexural rigidity and distribute the lateral external forces.

Glass cladding and outer coating diameter are standardised to 125 μm and 250 μm respectively in various international standards and recommendations. Standardisation of these two critical dimensions of silica glass optical fibre has ensured- compatibility between optical networks across the globe. Currently, single mode optical fibre with a reduced 200 μm coating diameter and 125 μm cladding diameter is commercially available. The 125 μm cladding diameter ensures backward compatibility with existing optical network. Fig. 1 shows a comparison between 250 μm and 200 μm coated fibre. This reduced diameter optical fibre opens up options for producing cable with more compact designs allowing more penetration depth in access and FTTX networks.