Optical fiber

Abstract

Provided is an optical fiber capable of sufficiently reducing the connection loss at a fusion splice point with a CSMF. The optical fiber is configured such that the refractive index of inner cladding(12) is substantially the same as the refractive index of outer cladding (13) while the concentration of the up-dopant in the inner cladding (12) is set so that the rate of increase of the refractiveindex due to the up-dopant is between 0.25% and 0.5%, inclusive.

Description

technical field [0001] The present invention relates to an optical fiber capable of expanding the core by thermal diffusion. Background technique [0002] Semiconductor optical waveguides typified by silicon optical waveguides are highly expected as technologies that contribute to the integration of optical communication devices. For example, silicon waveguides with functions such as optical modulators, optical detectors, and optical switches have been realized, and the utilization of optical communication has begun. [0003] In order to propagate light input to or output from the semiconductor optical waveguide, the semiconductor optical waveguide is often connected to a CSMF (Conventional Single Mode Fiber: Conventional Single Mode Fiber). However, while the mode field diameter of a semiconductor optical waveguide is about 1 μm, the mode field diameter of CSMF is about 10 μm. Therefore, if the CSMF is butt-connected to the semiconductor optical waveguide, the connection ...

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Problems solved by technology

However, if the mode field diameter of the semiconductor optical waveguide is enlarged to the s

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