Borosilicate Optical Glass for Fiber Stub Refractive Index Matching
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Solution Overview
Problem
Conventional optical glasses used in optical communication devices face issues such as high connection loss due to refractive index differences with optical fibers, devitrification, and poor thermal expansion matching, leading to reliability concerns and reduced transparency under high-output ultraviolet exposure.
Innovation Solution
A borosilicate glass with a refractive index of 1.44 to 1.46, a coefficient of thermal expansion of 10×10−7 to 50×10−7/°C, and a liquidus viscosity of 105.5 dPa·s or more is developed, incorporating specific oxide compositions to minimize devitrification and maintain transparency under ultraviolet exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SiO2 content in borosilicate glass is increased to match the refractive index of quartz glass, then the refractive index matches that of optical fiber, but crystals mainly composed of cristobalite are precipitated on the glass surface during re-heating and re-softening
Solution Approach 1:
The patent changes the chemical composition parameters of the glass, specifically controlling SiO2 content at 65-75 mass%, B2O3 at 15-25 mass%, and adding Al2O3 at 3-10 mass% to modify the glass structure and prevent crystal precipitation while maintaining refractive index matching
Solution Approach 2:
The patent creates a composite glass system combining multiple oxides (SiO2, B2O3, Al2O3, and other metal oxides) to achieve both refractive index matching and resistance to devitrification, leveraging the synergistic effects of different components
2Reliability
If conventional borosilicate glass is used to match the refractive index of quartz glass, then connection loss is reduced, but the glass lacks sufficient anti-devitrification properties causing crystal precipitation during wire drawing or reheat forming
Solution Approach 1:
The patent modifies the glass composition parameters by limiting SiO2 to 65-75 mass% (lower than conventional high-refractive-index glasses) and adding specific amounts of Al2O3 (3-10 mass%) and other oxides to enhance anti-devitrification properties while maintaining optical performance
Solution Approach 2:
The patent introduces specific oxide components (Al2O3, TiO2, ZrO2) in controlled amounts to locally modify the glass structure and prevent crystal nucleation sites, thereby improving anti-devitrification properties in specific regions of the glass matrix
3Ease of manufacture
If the liquidus viscosity of borosilicate glass is lowered to improve manufacturability, then drawing and forming processes become easier, but crystals are precipitated from the glass surface during drawing process or reheat forming
Solution Approach 1:
The patent optimizes the liquidus viscosity parameter to 105.5 dPa·s or more by adjusting the glass composition, particularly controlling the ratio of network formers (SiO2, B2O3) and adding Al2O3 to strengthen the glass structure and prevent crystal precipitation during processing
4Ease of manufacture
If optical glass with low Vickers hardness is used, then the glass is easier to polish, but the optical fiber part becomes convex and the optical glass part becomes concave when they are brought into contact
Solution Approach 1:
The patent adjusts the Vickers hardness parameter to 700-900 by controlling the glass composition and heat treatment conditions, achieving an optimal balance between polishability and mechanical strength to prevent deformation at the contact interface with optical fibers
5Ease of manufacture
If optical glass with large coefficient of thermal expansion is used, then the glass is easier to manufacture, but large residual stress is generated between the optical glass and optical fiber
Solution Approach 1:
The patent optimizes the coefficient of thermal expansion parameter to 30-50×10−7/°C by adjusting the glass composition, particularly balancing SiO2 and B2O3 content, to match the thermal expansion of optical fibers and minimize residual stress while maintaining manufacturability
6Ease of manufacture
If conventional optical glass is used, then production costs are reduced, but the glass is colored when irradiated with high-output ultraviolet rays and transmittance decreases
Solution Approach 1:
The patent modifies the glass composition parameters by adding specific oxide components (TiO2, ZrO2, Nb2O5) in controlled amounts to enhance ultraviolet resistance and prevent coloration, while maintaining cost-effectiveness through optimized raw material selection
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
The borosilicate glass achieves low connection loss, maintains high accuracy and transparency, and ensures long-term reliability by matching refractive index and thermal expansion with quartz glass, while resisting devitrification and maintaining transmittance under high-output ultraviolet irradiation.
Implementation Method 1
a liquidus viscosity of 105.5 dPa·s or more... crystals are precipitated from the glass surface during drawing process or reheat forming
Implementation Method 2
when the difference in refractive index between an optical fiber and an optical glass is large, there arises a trouble that reflected light is generated at the end face
Implementation Method 3
when the coefficient of thermal expansion of the optical glass is remarkably larger than that of the optical fiber, large residual stress is generated between them
Implementation Method 4
When irradiated with high-output light or ultraviolet rays, the glass is colored and, as a result, transmittance of the glass decreases
Data Source
AI summary
The present invention provides a glass having a refractive index and a coefficient of thermal expansion close to those of quartz glass, respectively, and also having anti-devitrification properties excellent enough to avoid the development of defects such as devitrification on the glass surface even when it is molded by drawing process or reheat forming, more specifically an optical glass for use in optical communication devices, particularly an optical glass for use in a stub.The optical glass of the invention is composed of a borosilicate glass having a refractive index of from 1.44 to 1.46, a coefficient of thermal expansion of from 10×10−7 to 50×10−7/° C., and a liquidus viscosity of 105.5 dPa·s or more.