Optical fiber for high-speed fiber-drawing process and coating concentricity monitor

A coating concentricity monitor comprising:

• a light source for generating a light for monitoring having a predetermined wavelength;
• a beam splitter for carrying out power division of the generated light for monitoring to form a first split light and a second split light and emitting them along respectively different paths;
• a first reflector disposed for reflecting the first split light to an optical fiber where said optical fiber comprising:
• a core as a light signal transmission medium, a clad surrounding the core, a first coating layer having a first modulus which surrounds the clad and is formed of an UV-cured polymer material;
• and a second coating layer having a second modulus which surrounds the first coating layer and is formed of an UV-cured polymer material, wherein a difference between the refraction index of the first coating layer and that of the second coating layer is non-zero and ranges from 0 to 0.06, and wherein the value of the second modulus value is higher than the first second modulus;
• a second reflector disposed for reflecting the second split light to the optical fiber;
• a first light-receiving surface to show a pattern of the first split light that has passed through the optical fiber;
• and
• a second light-receiving surface to show a pattern of the second split light that has passed through the optical fiber.