Floodable Subsea Cable Conduit Design
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Solution Overview
Problem
Conventional subsea optical fiber cables face manufacturing costs and complexity due to the need for hermetically sealed stainless steel tubing to protect against hydrogen darkening and water-related degradation, which can be costly and prone to failure at numerous seals.
Innovation Solution
Employing floodable optical fiber conduits with tight buffered optical fibers and periodic vents, allowing the interior to be in fluid communication with the surrounding water, while using hermetically sealed conduits to limit exposed fiber length and integrate with floodable conduits for extended communication capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hermetically sealed stainless steel tubing is used to protect optical fibers from water and hydrogen darkening, then fiber protection and reliability are improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent extracts the hermetic sealing function from the traditional stainless steel conduit structure and replaces it with a simpler plastic conduit design that accepts controlled water ingress. The sealing function is then selectively applied only at critical connection points using gel-filled seals and waterproof connectors, rather than requiring continuous hermetic sealing along the entire cable length.
Solution Approach 2:
The patent applies different protection strategies to different sections of the cable: flooded sections use simple plastic conduits with water permeability, while connection points and splice locations use gel-filled sealed sections. This local differentiation of protection quality reduces overall complexity while maintaining reliability where needed.
2Reliability
If hermetically sealed stainless steel tubing with redundant seals is used, then protection against water penetration is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive stainless steel conduits with cheaper plastic conduit materials that do not require hermetic sealing. The system accepts that water will ingress into the conduit but designs the fiber protection strategy around this reality, using cost-effective gel-filled sections at connection points rather than expensive continuous metal sealing.
Solution Approach 2:
The patent removes the expensive hermetic sealing requirement from the conduit design and extracts only the essential sealing function to specific connection points using gel-filled seals, significantly reducing manufacturing costs while maintaining adequate water protection.
3Reliability
If gel-filled sealed conduits are used to prevent fluid migration, then fiber protection from hydrogen darkening is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies gel-filled sealing only locally at connection points and splice locations where fibers transition between flooded and protected sections, rather than filling the entire conduit length. This localized application maintains hydrogen darkening prevention where needed while dramatically reducing system complexity.
Solution Approach 2:
The patent uses gel-filled seals as an intermediary material at connection points to provide both mechanical sealing and hydrogen barrier functions, simplifying the overall design by combining multiple protection functions into a single material solution at critical locations.
4Ease of operation
If tight buffered optical fibers with length between 5 and 200 meters are used in floodable conduits, then ease of installation and sensor attachment are improved, but exposure to water-related degradation increases
Solution Approach 1:
The patent applies different buffer types to different fiber sections: tight buffering is applied to exposed flooded sections to provide mechanical protection and ease of handling, while hermetically sealed protected sections use standard buffering. This local differentiation optimizes both installation ease and degradation resistance for each fiber section.
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
This design reduces manufacturing costs and eliminates the need for extensive sealing, enabling reliable long-distance communication in deep water environments with reduced risk of hydrogen darkening and mechanical degradation, while allowing for extended use and lower material costs.
Implementation Method 1
an outer cable jacket enclosing the one or more floodable optical fiber conduits and having periodic cable vents to provide fluid communication between an exterior of the subsea cable and an interior of the subsea cable
Implementation Method 2
The loose tubes of the subsea cable have periodic tube vents to provide fluid communication across a wall of the tube
Implementation Method 3
at least one tight buffered optical fiber within an interior of the loose tube for transporting optical signals
Data Source
Figure 1~4
Figure 5~6
AI summary
In at least some embodiments, a disclosed subsea cable (400) includes one or more floodable optical fiber conduits (200) each having at least one tight buffered optical fiber (202) for transporting optical signals. Each tight buffered optical fiber (202) may have a relatively limited length. The subsea cable (400) may further include multiple strength members (300A,300B) contra-helically wound around or together with the one or more floodable optical fiber conduits. There may also or alternatively be included at least one hermetically sealed optical fiber conduit (100) having at least one protected optical fiber spliced to one of the tight buffered optical fibers (200). At least some implementations splice each of the tight buffered optical fibers to corresponding protected fibers for the long-haul communications. Flooding of the floodable conduits may be provided via connectors at the subsea cable ends, via breakout locations where sensors are attached, and/or via vents in the conduit wall. Some method embodiments deploy the disclosed subsea cable designs in a body of water, putting the interior of at least one floodable optical fiber conduit in fluid communication with the body of water while supporting extended use for communicating signals, particularly in deep water where temperatures are relatively low. Because the floodable conduits have pressure-equalized interiors they may be formed from plastic or other materials that ease the process of attaching sensors to the subsea cables.