Small Diameter Optical Fiber with Segmented Cladding
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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 while maintaining microbend and macrobend performance, as smaller diameters increase microbending sensitivity and compromise coating effectiveness.
Innovation Solution
The development of coated optical fibers with a cladding diameter of 90 microns or less, featuring a glass core and cladding with specific refractive index profiles and coatings of varying moduli, including a low modulus primary coating and a high modulus secondary coating, to minimize bending-induced signal degradation and enhance mechanical 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 by an order of magnitude
Solution Approach 1:
The cladding is segmented into multiple regions with different refractive indices: a core region, an inner cladding region with first refractive index, and an outer cladding region with second refractive index lower than the first. This segmentation creates a refractive index profile that confines the optical mode more effectively, reducing microbending sensitivity while maintaining small cladding diameter.
Solution Approach 2:
Different regions of the cladding are assigned different refractive index characteristics. The inner cladding region has a higher refractive index to confine light, while the outer cladding region has a lower refractive index to reduce microbending sensitivity. This local differentiation of optical properties resolves the contradiction between small size and bending resistance.
2Volume of moving object
If thinner primary and secondary coating layers are used in reduced-cladding diameter fibers, then the coating diameter is reduced, but the microbend performance and protective function are compromised
Solution Approach 1:
The refractive index parameters of the cladding regions are optimized to achieve strong mode confinement, which allows the fiber to maintain good microbend performance even with thinner coating layers. The specific refractive index relationship (second index lower than first) creates a potential well that protects the optical mode from perturbations caused by reduced coating thickness.
3Volume of moving object
If the cladding diameter is reduced to 90 microns or smaller, then the cable size is decreased, but the attenuation and bend losses increase
Solution Approach 1:
The cladding is divided into inner and outer regions with different refractive indices to create a segmented index profile. This segmentation enables the fiber to maintain strong mode confinement at small diameters, reducing attenuation and bend losses while achieving the desired small form factor for high-density configurations.
Solution Approach 2:
The optical fiber employs a composite structure with core and cladding regions having different refractive index properties. This composite design, with the outer cladding region having lower refractive index than the inner cladding region, creates enhanced optical confinement that reduces energy loss in small-diameter fibers.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These fibers achieve low attenuation, large mode field diameters, and reduced bend losses, ensuring minimal signal degradation and improved mechanical resilience, compliant with G.657 standards, and suitable for high-density fiber configurations.
Implementation Method 1
The glass cladding may include a first inner cladding region and a second inner cladding region... The fiber core has a higher refractive index than the maximum refractive index of the first inner cladding region. The fiber core also has a higher refractive index than the maximum refractive index of the outer cladding region.
Implementation Method 2
The primary coating may be formed from a low modulus material and the secondary coating may be formed from a high modulus material... the primary coating may be formed from a low modulus material having an in situ modulus Ep of 0.35 MPa or less
Data Source
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AI summary
An optical fiber comprising: a core having an outer radius r1; a cladding having an outer radius r4<45 microns; a primary coating surrounding the cladding and having an outer radius r5 and a thickness tp>8 microns, the primary coating having in situ modulus Ep of 0.35 MPa or less and a spring constant χp<1.6 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, wherein > 10 microns and r6 ≤ 85 microns. The fiber has a mode field diameter MFD greater than 8.2 microns at 1310 nm; a 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.