Optical fiber and method for producing optical fiber

• US 10,451,796 B2
• Filed: 08/02/2017
• Issued: 10/22/2019
• Est. Priority Date: 08/02/2016
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Enomoto, Tadashi, Fujii, Takashi, Hattori, Tomoyuki, Sohma, Kazuyuki
• Primary Examiner(s): Lepisto, Ryan A
• Assistant Examiner(s): Chiem, Erin D
• Application Number:
  US16/322,559
• Publication Number:
  US 20190187366A1
• Time in Patent Office: 811 Days
• CPC Class Codes: C03B 2203/22 Radial profile of refractive index, composition or softening point
• CPC Class Codes: C03B 2203/23 Double or multiple optical cladding profiles
• CPC Class Codes: C03C 25/1065 Multiple coatings
• CPC Class Codes: C03C 25/12 General methods of coating; Devices therefor
• CPC Class Codes: G02B 6/02395 Glass optical fibre with a protective coating, e.g. two layer polymer coating deposited directly on a silica cladding surface during fibre manufacture G02B6/02052, G02B6/02057, G02B6/024, G02B6/032, G02B6/105, G02B6/14 take precedence; coating on fibre gratings G02B6/02104; multilayer core or cladding G02B6/036; reinforcing splice joints G02B6/2558; optical cables, i.e. comprising protective structures external to the protective coating such as a jacket or plural coated optical fibres G02B6/44; coating of glass to obtain optical fibres C03C25/104
• CPC Class Codes: G02B 6/036 core or cladding comprising multiple layers multicore optical fibres G02B6/02042; microstructured properties G02B6/02295; omniguide fibres G02B6/023
• CPC Class Codes: G02B 6/44 Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables cables incorporating electric conductors and optical fibres where features relating to the optical fibres are not of interest H01B11/22

Abstract

Provided is an optical fiber in which a primary coating layer and a secondary coating layer are formed on an outer circumference of a bare optical fiber including a core and a cladding. A Young'"'"'s modulus of the primary coating layer is 0.1 to 1.0 MPa, a relationship between lateral rigidity D and flexural rigidity H of the optical fiber as expressed by formulas below satisfies D/H²≤3×10¹⁷ N⁻¹ m⁻⁶, the primary coating layer contains 0.3 to 2.0 wt % of a photoinitiator including phosphorus, and the primary coating layer contains polypropylene glycol having a weight-average molecular weight of 1000 to 5000. The formulas include

$H=H_g+H_s=\pi r_g^4{E}_g+\pi \left(r_{s_{\iota }}^4-r_p^4\right)E_s\mathrm{and}$ $D=0.897E_p+2.873\left(E_s-E_p\right){\left(\frac{E_p}{E_s}\right)}^{0.8311}{\left(2\frac{r_s-r_p}{r_s-r_g}\right)}^{1.189},$

• • where r represents a radius (m), E represents a Young'"'"'s modulus (Pa), a subscript g represents glass (the bare optical fiber), a subscript p represents the primary coating layer, and a subscript s represents the secondary coating layer, respectively.

Claims

1. An optical fiber in which a primary coating layer and a secondary coating layer are formed on an outer circumference of a bare optical fiber including a core and a cladding, wherein

a Young'"'"'s modulus of the primary coating layer is 0.1 to 1.0 MPa,

a relationship between lateral rigidity D and flexural rigidity H of the optical fiber as expressed by formulas below satisfies D/H²≤

3×

10¹⁷ N<sup>−

1</sup> m<sup>−

6</sup>,

the primary coating layer contains 0.3 to 2.0 wt % of a photoinitiator including phosphorus,

the primary coating layer contains polypropylene glycol having a weight-average molecular weight of 1000 to 5000, and the formulas include

2. The optical fiber according to claim 1, wherein

the Young'"'"'s modulus of the primary coating layer is 0.1 to 0.7 MPa.

3. The optical fiber according to claim 1, wherein

the Young'"'"'s modulus of the primary coating layer is 0.1 to 0.5 MPa.

4. The optical fiber according to claim 1, wherein

the optical fiber is a multimode optical fiber in which a core diameter of the core is 47.5 to 52.5 μ

m, a relative refractive index difference of the core to the cladding is 0.8% to 1.2%, and a trench portion is provided in a cladding region.

5. A method for producing an optical fiber in which a primary coating layer and a secondary coating layer are formed on an outer circumference of a bare optical fiber including a core and a cladding, the method comprising:

forming the primary coating layer and the secondary coating layer such that a Young'"'"'s modulus of the primary coating layer is 0.1 to 1.0 MPa, and a relationship between lateral rigidity D and flexural rigidity H of the optical fiber as expressed by formulas below satisfies D/H²≤

3×

10¹⁷ N<sup>−

1</sup> m<sup>−

6</sup>;

containing 0.3 to 2.0 wt % of a photoinitiator including phosphorus in the primary coating layer; and

containing polypropylene glycol having a weight-average molecular weight of 1000 to 5000 in the primary coating layer, wherein the formulas include