With the rapid expansion of global connectivity and offshore infrastructure, cables laid beneath water bodies have become critical to modern communication and power transmission. Two terms frequently used in this context are underwater cable and subsea cable. While they are often used interchangeably, they differ in scope, application, and technical requirements.
This blog provides a detailed comparison between underwater cables and subsea cables, explaining their differences in design, usage, installation, and long-term performance.
Understanding Underwater Cables
Underwater cables refer broadly to any cables installed beneath water bodies. These can be laid across rivers, lakes, canals, reservoirs, and shallow coastal waters. Their primary purpose is to transmit electricity, data, or control signals over relatively short distances.
Underwater cables are commonly used in:
- River crossings
- Harbour and port facilities
- Inland hydroelectric projects
- Water treatment plants
- Short-distance power or data transmission
Due to their limited exposure to extreme marine conditions, underwater cables are generally simpler in construction compared to subsea cables.
Understanding Subsea Cables
Subsea cables are specifically designed for installation on or beneath the seabed, often at great depths. They are a vital part of global infrastructure, carrying telecommunications signals and electrical power across oceans and seas.
Subsea cables are widely used for:
- International internet and telecom connectivity
- Offshore wind farms and oil platforms
- Intercontinental power transmission
- Deep-sea scientific monitoring
These cables must withstand extreme pressure, saltwater corrosion, seismic activity, and marine life interference, making their design far more complex.
Key Differences Between Underwater Cable and Subsea Cable
Scope and Terminology
Underwater cable is a broad term that includes any cable laid underwater, regardless of location or depth. Subsea cable is a specialised category within underwater cables, specifically engineered for marine and oceanic environments.
Installation Environment
Underwater cables are usually installed in shallow or inland waters with relatively stable conditions. Subsea cables operate in harsh marine environments, often thousands of metres below sea level, where conditions are unpredictable and extreme.
Design and Construction
Underwater Cable Design
Underwater cables typically feature basic insulation and protective sheathing to resist moisture ingress. Depending on the application, they may include light armouring to protect against abrasion and minor impacts.
The design prioritises flexibility, ease of installation, and cost efficiency, as these cables are often laid in accessible environments.
Subsea Cable Design
Subsea cables are engineered with multiple protective layers, including:
- Conductor core
- Insulation layers
- Metallic water barriers
- Steel wire armouring
- Anti-corrosion coatings
These layers ensure resistance to high pressure, corrosion, mechanical damage, and marine organisms. Subsea cables are designed for decades of uninterrupted service with minimal maintenance.
Depth and Distance Capabilities
Underwater cables are generally limited to short distances and shallow depths. They are suitable for projects where maintenance access is relatively easy and environmental stress is low.
Subsea cables, on the other hand, span vast distances often thousands of kilometres, and operate at extreme depths. Transoceanic subsea cables form the backbone of the global internet, carrying massive volumes of data between continents.
Installation Techniques
Underwater Cable Installation
Underwater cable installation is typically straightforward and may involve manual placement, trenching, or the use of small vessels. Installation time is relatively short, and costs are moderate.
Subsea Cable Installation
Subsea cable installation is a highly specialised process involving survey vessels, remotely operated vehicles (ROVs), cable-laying ships, and advanced seabed mapping technology. The process requires meticulous planning to avoid underwater hazards and ensure long-term stability.
Durability and Lifespan
Underwater cables are designed for moderate durability, with lifespans depending on environmental conditions and usage. They may require periodic inspection and maintenance.
Subsea cables are built for exceptional durability, often designed to last 25 to 40 years or more. Their robust construction minimises the need for repairs, which are complex and costly in deep-sea environments.
Cost Comparison
Underwater cables are relatively cost-effective due to simpler materials, shorter lengths, and easier installation. They are suitable for localised projects with limited budgets.
Subsea cables involve significant investment. Costs include specialised materials, advanced engineering, deep-sea installation, and long-term monitoring. However, their value lies in their ability to deliver high-capacity, reliable transmission over vast distances.
Applications and Use Cases
Underwater Cable Applications
- Inland power transmission
- Short-distance data communication
- Industrial and municipal infrastructure
- Water management systems
Subsea Cable Applications
- Global internet connectivity
- Offshore renewable energy transmission
- Oil and gas platform operations
- International power grids
Maintenance and Repair
Underwater cable repairs are usually accessible and can often be carried out with minimal disruption. In contrast, repairing subsea cables requires specialised vessels and equipment, making maintenance operations time-consuming and expensive.
As a result, subsea cables are designed with extensive fault prevention measures to reduce the likelihood of failure.
Environmental and Regulatory Considerations
Underwater cable installations typically face fewer regulatory challenges, particularly in inland water bodies. Subsea cable projects, however, must comply with international maritime laws, environmental protection standards, and cross-border agreements.
Environmental impact assessments are critical for subsea projects to protect marine ecosystems and seabed habitats.
Which One Should You Choose?
The choice between underwater cable and subsea cable depends on project scope, environment, distance, and performance requirements. Underwater cables are ideal for short-range, cost-sensitive applications in controlled environments. Subsea cables are essential for long-distance, high-capacity transmission in challenging marine conditions.
Understanding these differences ensures the right cable solution is selected for reliability, safety, and long-term performance.
Final Thoughts
While underwater cables and subsea cables share the common purpose of underwater transmission, they differ significantly in design, application, and complexity. Underwater cables serve local and shallow-water needs, whereas subsea cables support the global exchange of power and information.
Choosing the right cable system requires careful evaluation of environmental conditions, technical demands, and future scalability. With proper planning and engineering, both underwater and subsea cables play vital roles in connecting the modern world.
Contact Linden Photonics to get a Underwater Cable quote or Call Us at (978) 392-7985