Purpose : An optical waveguide fiber which is made substantially bend resistant.
Constitution : A core having a central region with a higher index of refraction than an integral surrounding region is joined for a segment of its periphery to a clad member, so as to leave a gap between core and cladding.
Bend resistance improvement begins when a relatively small fraction, for example, about half, of the core member periphery is detached. A detachment percentage between about 50% and 99.9% of the core member periphery should be achieved, with the preferred range between about 95% and 99.9%.
Waveguides include single mode, multimode and polarization maintaining waveguides. Additional core isolation from external forces is provided by an additional semi-detached cladding layer. Only a segment of the periphery of core member (6) is fused to clad (8) along the length of waveguide (5). Also, only a segment of the periphery of clad (8) is fused to clad (10) along the length of waveguide (5). The gaps (7) and (9), which are present along the length of waveguide (5), serve to provide a double isolation of core member (6) from external forces. That is, the stress fields set up in clad layer (10) are only partially transmitted to clad (8), because of the limited contact between the two clads. Likewise, stress fields experienced by clad (8) cannot be fully transmitted to core member (6) due to the limited area of contact between these two waveguide parts. The area of attachment between core member (6) and clad (8) may occur at any part of the inside surface of clad (8). Also, the orientation of the area of attachment between clad (8) and clad (10) may occur at any part of the inside surface of clad (10). In general, the area of attachment of clad (8) to clad (10) and the area of attachment of core member (6) and clad (8) do not influence one another.