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The method according to claim 1, wherein a fiber formed by a strand other than the measurement target fiber is used as the reference fiber.ĥ. The method according to claim 1, wherein a fiber formed by a strand drawn by using the same base material as a base material used when the measurement target fiber is manufactured is used as the reference fiber.Ĥ. The method according to claim 1, wherein the length of the reference fiber at the time of measuring the power of the transmission light is adjusted such that the cut-off wavelength of the reference fiber is shorter than the predicted cut-off wavelength of the measurement target fiber by at least 10 nm.ģ.
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A method of measuring a cut-off wavelength of a silica-based fiber, the method comprising: preparing a single mode fiber as a reference fiber preparing a measurement target fiber estimating, at an estimation unit, a relationship between a length of the measurement target fiber and a cut-off wavelength thereof in advance based on a refractive index profile thereof, thereby predicting a predicted cut-off wavelength adjusting, at an adjustment unit, a length of the reference fiber such that the length of the reference fiber is longer than a length of the measurement target fiber so that the length of the reference fiber is adjusted such that a difference between a logarithmic value, in common logarithm, of the length of the reference fiber and a logarithmic value, in common logarithm, of the length of the measurement target fiber is 0.5 or more at the time of measuring power of transmission light transmitted through the reference fiber and the reference fiber propagates only light of a base mode at the predicted cut-off wavelength of the measurement target fiber measuring, at a measurement unit, wavelength dependence of power of transmission light transmitted through the reference fiber and wavelength dependence of power of transmission light transmitted through the measurement target fiber and calculating, at a calculation unit, a cut-off wavelength of the measurement target fiber based on wavelength dependence that is represented as a ratio of the power of transmission light transmitted through the measurement target fiber to the power of transmission light transmitted through the reference fiber.Ģ.