Bend insensitive single mode fiber

A bend insensitive single mode comprising:

• a bare glass fiber (11) with a round cross section and two resin protective layers (12, 13) with circular cross sections surrounding the outer of the bare glass fiber (11);
• wherein
• the bare glass fiber (11) is composed by a core layer (111) with a round cross section and two claddings (112, 113) with circular cross sections,
• a refractive index of the core layer (111) is higher than refractive indexes of the two claddings (112, 113);
• a refractive index difference (Δ1) between the core layer (111) and the first cladding (112) Δ1 is between 0.0033˜0.0072, a refractive index difference (Δ2) between the first cladding (112) and second (113) claddings Δ2 is between −0.0016˜0, a thickness (a) of the core layer (111) is between 2.7˜4.1 μm, a thickness (b) of the first cladding (112) is between 0.5˜2.3 μm and a thickness (c) of the second cladding (113) is between 56.7˜59.8 μm;
• and
• the second cladding (113) is made of pure SiO2, a refractive index profile of the core layer (111) follows a power function distribution, and the refractive index profiles of the two claddings (112 and 113) follow a ladder-type distribution.