Plastic optical fiber, medical lighting device, medical sensor device, medical phototherapy device, and plastic optical fiber cord

A plastic optical fiber having a multilayer structure that comprises

• a core (X),
• a first cladding (Y), and
• a second cladding (Z),
• wherein the core is made of an organic polymer material having
• a water-absorbing ratio of not less than 0.001% and not more than 0.29% and
• a total light transmittance of not less than 80% and
• containing not less than 0.01% by weight and not more than 10% by weight of a plasticizer;
• a relationship between a refractive index of the core (X) and a refractive index of the first cladding (Y) is defined by inequality:
• X−Y>0.01, and
• a relationship between the refractive index of the first cladding (Y) and a refractive index of the second cladding (Z) is defined by inequality:
• Y−Z>0.05,
• wherein the plastic optical fiber satisfies inequalities (1) and (2):
• 2
• ≤
• x
• ≤
• 18
• ,
• (
• 1
• )
• wherein x is represented by formula:
• (thickness of the first cladding)×100/(diameter of the fiber) (%);
• and
• 5
• ≤
• y
• ,
• (
• 2
• )
• wherein y is represented by formula:
• (thickness of the second cladding)×100/(diameter of the fiber) (%).