JPS569704A - Optical transmission line of aggregate type with absorbing layer - Google Patents

Abstract

PURPOSE: To make the loss of the entire part of a transmission line less than a certain limit by so constituting the same that the mutual relations of the outside diameter of the active region of an optical guide, the minimum distance from the center of said waveguide up to an absorption layer, the specific refractive index difference of said waveguide and a propagation wavelength region are within the specific range.

CONSTITUTION: An optical fiber forming an optical waveguide is constituted around a core 1 and a clad 2 by an absorbing layer 3. When the outside diameter of the active region of the waveguide is defined as 2a(μm), the minimum distance from the center of the waveguide up to the absorbing layer as (l)(μm), the specific refractive index difference of the waveguide as Δ, and a propagation wavelength region as ≤λ(μm), these are so constituted as to satisfy aΔ^1/2(b/a-1)/λ>0.43. These make it possible to keep the loss α as a whole of an image fiber occuring in the absorbing layer less than the range where there are no problems at the longest distance 100m normally used. In the transmission of a visible light region, it is sufficient to consider up to λ=0.7μm; therefore, in this case, said formula becomes aA^1/2(b/a-1)<0.3.

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