Small Diameter Low Attenuation Optical Fiber Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical fibers with reduced cladding and coating diameters face challenges in achieving low attenuation, low bend losses, and large mode field diameters due to increased microbending sensitivity and compromised protective functions of thinner coatings.
Innovation Solution
The development of coated optical fibers with a core, cladding, primary coating, and secondary coating, where the cladding has a depressed-index region and the coatings have specific thickness and modulus profiles to achieve low attenuation, low bend losses, and large mode field diameters, while maintaining compact size and puncture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the cladding diameter is reduced to decrease cable size and cost, then the cable diameter and cost are reduced, but the microbending sensitivity increases significantly
Solution Approach 1:
The patent applies parameter changes by modifying the refractive index distribution within the cladding through a depressed-index trench region. This changes the optical confinement characteristics to reduce mode field diameter and improve bend insensitivity, allowing smaller cladding diameters to achieve acceptable microbending performance
Solution Approach 2:
The patent uses composite material structures with multiple coating layers (primary and secondary coatings with different moduli) and a composite refractive index profile in the cladding. This composite structure provides both mechanical protection against microbending and optical confinement, enabling reduced cladding diameter while maintaining reliability
2Volume of moving object
If the primary and secondary coating thicknesses are reduced in reduced-cladding diameter fibers, then the coating diameter is decreased, but the microbend performance and protective function are compromised
Solution Approach 1:
The patent changes the mechanical parameter of the primary coating by using a low-modulus material (0.1-1.0 MPa) that can accommodate microbending stresses. This allows thinner coating layers to provide adequate protection while reducing overall coating diameter
Solution Approach 2:
The patent employs a composite coating structure with a soft primary coating layer and a harder secondary coating layer. This composite approach allows the primary layer to absorb microbending stresses while the secondary layer provides mechanical protection, enabling reduced coating thicknesses without sacrificing microbend performance
3Volume of moving object
If the cladding diameter is reduced to achieve compact fiber design, then the fiber size is reduced, but the mode field diameter decreases and cutoff wavelength increases
Solution Approach 1:
The patent changes the optical parameters by introducing a depressed-index trench in the cladding, which modifies the mode field distribution. This allows the mode field diameter to be controlled and maintained at appropriate levels despite the reduced cladding diameter
Solution Approach 2:
The patent applies local quality changes by creating a specific refractive index trench region at a particular location in the cladding (at radius r3). This localized modification of the refractive index profile affects the mode field confinement and cutoff characteristics, enabling compact fiber design with controlled optical properties
4Ease of manufacture
If conventional coating solutions are used in reduced-cladding diameter fibers, then the manufacturing process is simple, but the attenuation and bend losses remain high
Solution Approach 1:
The patent changes the mechanical parameter of the primary coating by using a low-modulus material (0.1-1.0 MPa) that reduces stress transfer to the glass fiber. This parameter change significantly reduces microbending-induced attenuation and bend losses while maintaining ease of coating application
Data Source
AI summary
An optical fiber comprising: a core having an outer radius r1; a cladding having an outer radius r4≤31 microns; a primary coating surrounding the cladding having an outer radius r5, a thickness tp>10 microns, in situ modulus EP of 0.5 MPa or less, and a spring constant χP<1 MPa, where χP=2EP r4/tP; and a secondary coating surrounding said primary coating, the secondary coating having an outer radius r6, a thickness tS=r6-r5, in situ modulus ES of 1200 MPa or greater; tS greater than 9.5 microns, wherein r6 is 50 to 67.5 microns. The fiber has a mode field diameter MFD greater than 8.2 microns at 1310 nm; a fiber cutoff wavelength of less than 1310 nm; and a bend loss at a wavelength of 1550 nm, when wrapped around a mandrel having a diameter of 10 mm, of less than 1.0 dB/turn.