To provide a clad mode light elimination structure that is resistant to reduction in reliability such as high-refractive index resin, an optical fiber and the like.SOLUTION: A clad mode light elimination structure 1 comprises: an optical fiber 10 that includes a clad exposure part 14 having a clad 12 exposed with one part of a coating 13 eliminated; high-refractive index resin 30 that has a refractive index more than that of the clad 12; a holding member 20 that holds one part of the optical fiber 10 and the high-refractive index resin 30; a lid member 40 that converts clad mode light L irradiated through the high-refractive index resin 30 to heat; and a space 50 that is lower in thermal conductivity than the lid member 40. The high-refractive index resin 30 is provided so as to cover the clad exposure part 14. The lid member 40 includes: a facing part 41 that faces the high-refractive index resin 30; and protrusion parts 42A and 42B that protrude from the facing part 41 to a holding member 20 side. The space 50 is located between the lid member 40 and the high-refractive index resin 30, and contacts with at least one part of the high-refractive index resin 30. Between the protrusion parts 42A and 42B and the holding member 20, resin 70 is provided that is lower in the thermal conductivity than the protrusion parts 42A and 42B.SELECTED DRAWING: Figure 2
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