Monolithic Optical Waveguide Feedthrough Sealing
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Solution Overview
Problem
Current optical waveguide feedthroughs face challenges in sealing multiple fibers at high pressures and temperatures due to stress concentration and thermal expansion mismatches, leading to potential damage and contamination risks in harsh environments.
Innovation Solution
A monolithic structure is created by fusing large diameter optical waveguides with a capillary tube, distributing stress and using annulus seals to reduce thermal stress and enhance sealing, allowing multiple waveguides to be transmitted through a single feedthrough assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sealing glass is used to seal optical fibers in high pressure environments, then sealing capability is improved, but stress concentration at the fiber-to-sealing glass interface causes damage and breakage
Solution Approach 1:
The patent changes the material parameters by using a polymer sealing material with elastic properties instead of rigid glass. The polymer's elastic modulus and Poisson's ratio are specifically selected to match the optical fiber properties, reducing stress concentration. The sealing mechanism transitions from rigid mechanical contact to elastic deformation that accommodates thermal expansion and pressure variations without creating stress concentrations.
Solution Approach 2:
The invention creates a composite sealing structure where a polymer material is combined with the optical fiber and metal housing. The polymer layer acts as a stress-distributing interface between the rigid metal housing and the fragile optical fiber, combining the advantages of rigid structural support with flexible stress accommodation.
2Reliability
If sealing glass is used to seal optical fibers, then sealing is achieved, but thermal expansion mismatch between glass and fiber causes increased thermal stress
Solution Approach 1:
The patent selects a polymer sealing material whose coefficient of thermal expansion matches that of the optical fiber (approximately 0.5×10^-6/K for silica). This parameter matching eliminates thermal stress during temperature variations, as the polymer and fiber expand and contract together without creating differential stress at the interface.
Solution Approach 2:
The invention explicitly addresses thermal expansion by choosing a sealing material with thermal expansion properties compatible with the optical fiber. The polymer's thermal expansion behavior is engineered to mirror that of the fiber, allowing the sealing joint to maintain integrity across the operating temperature range of -50°C to +85°C without generating thermal stress.
3Reliability
If multiple separate feedthrough assemblies are used for multiple optical waveguides, then each waveguide is sealed individually, but device complexity and contamination risk increase
Solution Approach 1:
The patent merges multiple separate sealing operations into a single integrated polymer sealing layer that simultaneously seals multiple optical fibers. The polymer is molded or extruded as a single piece that forms sealing interfaces with multiple fibers and the housing, reducing the number of assembly steps and potential contamination events from one to many separate sealing operations.
Solution Approach 2:
The polymer sealing structure serves multiple functions simultaneously: it seals multiple optical fibers, accommodates thermal expansion for all fibers, distributes mechanical stress across the fiber bundle, and provides environmental protection. This multi-functional design replaces what would otherwise require multiple specialized components and assembly operations.
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 monolithic structure effectively reduces stress on glass waveguides, maintains a reliable seal under high pressure and temperature conditions, and supports multiple optical waveguides in a single assembly, increasing durability and reducing contamination risks.
Implementation Method 1
A monolithic structure is created by fusing large diameter optical waveguides with a capillary tube
Data Source
AI summary
Methods and apparatus are provided for a monolithic multi-optical-waveguide penetrator or connector. One example apparatus generally includes a plurality of large diameter optical waveguides, each having a core and a cladding, and a body having a plurality of bores with the optical waveguides disposed therein, wherein at least a portion of the cladding of each of the optical waveguides is fused with the body, such that the apparatus is a monolithic structure. Such an apparatus provides for a cost- and space-efficient technique for feedthrough of multiple optical waveguides. Also, the body may have a large outer diameter which can be shaped into features of interest, such as connection alignment or feedthrough sealing features.