Submarine Network Series: Part 2- Past Evolution of Submarine Transmission Systems

The history of submarine cables can be traced back to the late 1840s when a newly discovered natural polymer called gutta percha provided the basic means for insulating cables for undersea use. In 1850, a relatively short-distance cable was submerged between the UK and France, but unfortunately, it lasted only for a few messages and was replaced by a more durable successor a year later. The first cable connecting Europe to the US became operational on August 16, 1858, but the deployment of cables across the Pacific Ocean proved to be more challenging, and transpacific telegraph cables only became operational in 1902.

It took approximately fifty more years for newer advanced cables to support voice and data communications to be deployed. TAT-1 was the first transatlantic cable used for telephony, which became operational on September 25, 1956, connecting Scotland to Clare Ville, initially supporting transmission of just 36 telephone channels. The first coaxial cables capable of transmitting frequency-multiplexed voice signals became operational in the 1960s, which eventually led to optical technology in 1986 and 1988, using optical fiber links for high-speed/capacity submarine communications.

Some significant milestones in the submarine era history include the first submarine cable supporting phone data (from San Francisco to Oakland) in 1884, the first submarine high-voltage direct current cable connecting the island of Gotland to mainland Sweden in 1954, and the first deployment of repeaters in the 1940s, boosting the TAT-1, which was the first telephone cable crossing Atlantic. The first transpacific submarine coaxial telephone cable linking Japan, Hawaii, and the US mainland was operational in 1964. The first submerged international fiber-optic cable that connected Belgium to the United Kingdom was in 1986, and the first submerged transoceanic fiber-optic cable, named TAT-8, that connected the USA to the United Kingdom and France, was in 1988.




Figure 1 depicts the historical evolution of submarine transmission systems leading to optical technology. In Figure 2, a transatlantic cable capacity comparison is illustrated from TAT-1 in 1956 to TAT-14 in 2001. Figure 3 shows the worldwide submarine cable map, which comprises 487 cables, stretching over 1.3 million km, and 1245 landing stations that are currently in service or under construction. These networks were deployed by consortia of major telecom network operators.

However, during the current century, major cloud service providers such as Google, Facebook, and Microsoft have become active investors in submarine networks. From 2016 to 2018, Google invested approximately $47 billion dollars in capital expenditure (capex) to expand and upgrade Google Cloud infrastructure. Nowadays, Google counts 134 points of presence (PoPs) and 14 major subsea cable investments globally, interconnecting all six continents. These investments have played a significant role in enabling Google to provide reliable and high-speed cloud services to customers globally.

Submarine Network Series: Part 1- The Evolution and Future of Submarine Networks: A Focus on Space Division Multiplexing

The Submarine series of posts discusses the evolution of submarine networks alongside terrestrial ones over the past several decades. While there are similarities between these two network categories, such as the need to cover ultralong-haul distances and transport huge amounts of data, there are also important differences that have dictated their different evolutionary paths. The series focuses on space division multiplexing (SDM) as the ultimate solution to cover future capacity needs and overcome problems of both networks.

The introduction section provides a brief history of submarine cables, which were first submerged to transmit telegraphy data approximately one and a half centuries ago. Today, submarine cable systems have become a basic component of the whole global backbone network infrastructure and serve as the most crowded, yet isolated, of deep-water networks. The traffic generated by end-users has been boosted beyond the average 50% annual growth rate due to the COVID-19 pandemic, increasing the need for speed and more bandwidth.

We will review recent and future submarine technologies, focusing on all critical sectors: cable systems, amplifiers' technology, submarine network architectures, electrical power-feeding issues, economics, and security. The authors provide an overview of all recently announced SDM-based submarine cable systems, compare their performance (capacity-distance product), and analyze the reasons that led to the first SDM submarine deployment. They also report up-to-date experimental results of submarine transmission demonstrations and perform a qualitative categorization that relies on their features.

Based on all latest advances and their study findings, the authors try to predict the future of SDM submarine optical networks mainly in the fields of fiber types, fiber counts per cable, fiber-coating variants, modulation formats, as well as the type and layout structure of optical amplifiers. Results show that SDM can offer higher capacities (in order of Pb/s) compared to its counterparts, supported by novel network technologies: pump-farming amplification schemes, high counts up to 50 parallel fiber pairs, thinner fiber coating variants (200 µm), and optimum spectral efficiency (2-3 b/s/Hz).

Then we will conclude that tradeoffs between capacity and implementation complexity and cost will have to be carefully considered for future deployments of submarine cable systems. SDM can provide a solution to cover future capacity needs and overcome problems of both submarine and terrestrial networks.

Google Cloud Platform - Submarine Network

Advanced Optical Series: Part 5 - A Deep Dive into Subsea Cabling: The Backbone of Global Computer Networking

Introduction:

Subsea cabling is an essential component of the global computer network. It is responsible for transmitting vast amounts of data between continents and connecting people and businesses worldwide. In this blog post, we will take a deep dive into the world of subsea cabling, exploring its history, technology, benefits, and challenges.

History of Subsea Cabling: 

The first subsea cable was laid across the English Channel in 1851. It was a copper cable covered in gutta-percha, a natural rubber, to protect it from seawater. Since then, subsea cabling has evolved dramatically, from simple copper cables to fiber optic cables capable of transmitting terabits of data per second.

Technology of Subsea Cabling: 

Subsea cables are made of several layers, each designed to protect the cable and ensure data is transmitted with minimal loss or disruption. The outer layer is typically made of polyethylene or other plastics to provide insulation and protect the cable from damage. The next layer is a steel armor designed to protect the cable from external pressure and damage from anchors and fishing nets. Inside the armor, the cable consists of several optical fibers, each capable of transmitting data at high speeds.

Benefits of Subsea Cabling: 

Subsea cabling offers several benefits for global computer networking. It is more reliable than satellite communication, as it is not affected by atmospheric conditions or solar flares. Subsea cabling also provides faster data transfer speeds and lower latency, making it ideal for real-time applications like video conferencing and online gaming.

Challenges of Subsea Cabling: 

Despite its benefits, subsea cabling also faces several challenges. The installation and maintenance of subsea cables are complex and expensive, requiring specialized ships and equipment. The cables are also susceptible to damage from natural disasters like earthquakes and storms, as well as human activities like fishing and anchoring.

Future of Subsea Cabling: 

The demand for subsea cabling is only expected to grow as more people and businesses connect to the internet. To meet this demand, researchers are exploring new technologies like self-healing cables, which can detect and repair damage automatically. There is also a growing interest in using subsea cables for renewable energy transmission, allowing offshore wind farms to transmit energy to the mainland.

Conclusion: 

Subsea cabling is the backbone of global computer networking, connecting people and businesses worldwide. It has come a long way since the first cable was laid across the English Channel, and it continues to evolve and improve. Despite its challenges, subsea cabling offers numerous benefits and is essential for the future of global communication and connectivity.

Advanced Optical Series: Part 4 - Unlocking the Future of Data Transmission: Exploring Optical Switching Technologies

In the realm of data transmission and telecommunications, the demand for faster, more efficient methods of routing and switching data is ever-present. Optical switches, leveraging the power of light, have emerged as key enablers in meeting these demands. In this blog post, we'll explore two groundbreaking optical switch technologies: the O-E-O Optical Switch and the All-Optical Switch, shedding light on their mechanisms, applications, and the transformative impact they hold for the future of connectivity.

O-E-O Optical Switch: Bridging the Optical-Electrical Gap

The O-E-O Optical Switch represents a critical bridge between optical and electrical domains, seamlessly integrating both to facilitate efficient data routing and switching. Here's how it works:

1. Optical-to-Electrical Conversion: Incoming optical signals are converted into electrical signals using photodetectors, allowing for easy processing and manipulation.

2. Electrical Switching: The electrical signals are then routed through electronic switches or routers, where they can be processed, analyzed, and directed to their intended destinations.

3. Electrical-to-Optical Conversion: Once the data has been processed, it is converted back into optical signals using lasers or light-emitting diodes (LEDs) for onward transmission through optical fibers.

(a) O-E-O Switch (b) Photonic Switch (c) All-Optical Switch

Key features and applications of O-E-O Optical Switches include:

• Compatibility: O-E-O switches are compatible with existing electronic switching infrastructure, making them easy to integrate into existing networks.
• Signal Regeneration: The conversion of optical signals to electrical and back to optical ensures signal regeneration, enhancing signal quality and reliability.
• Telecommunications and Data Centers: O-E-O switches find applications in telecommunications networks and data centers, where they facilitate high-speed data routing and switching over long distances.

All-Optical Switch: Pioneering Direct Optical Routing

In contrast to O-E-O switches, All-Optical switches operate entirely in the optical domain, without the need for optical-to-electrical conversion. Here's how they work:

1. Photonic Switching: All-Optical switches use various mechanisms such as nonlinear optics, semiconductor optical amplifiers, or photonic crystals to manipulate and route optical signals directly.

2. Wavelength or Time-Division Multiplexing: All-Optical switches can route multiple optical signals based on their wavelength or time-slot, enabling efficient utilization of the optical spectrum.

3. Ultra-Fast Operation: By eliminating the need for optical-to-electrical conversion, All-Optical switches offer ultra-fast switching speeds, significantly reducing latency and improving network performance.

Key features and applications of All-Optical switches include:

• High-Speed Networks: All-Optical switches are ideal for high-speed optical networks, such as long-haul telecommunications networks and backbone infrastructure.
• Energy Efficiency: By operating entirely in the optical domain, All-Optical switches consume less power compared to O-E-O switches, making them more energy-efficient.
• Future-Proofing: All-Optical switches are well-suited for future-proofing optical networks, as they offer scalability and compatibility with emerging optical technologies.

All optical Switch with 3 network ports and 3 local access ports

Shaping the Future of Connectivity

As the demand for high-speed, reliable data transmission continues to grow, optical switches are poised to play a central role in shaping the future of connectivity. Whether bridging the optical-electrical gap with O-E-O switches or pioneering direct optical routing with All-Optical switches, these technologies represent significant milestones in the evolution of optical networking.

Looking ahead, ongoing research and development in areas such as integrated photonics, quantum optics, and machine learning promise to further enhance the performance and efficiency of optical switches, unlocking new capabilities and applications. From telecommunications networks to data centers and beyond, optical switches are driving the transformation towards faster, more resilient, and energy-efficient communication infrastructures.

Advanced Optical Series: Part 3 - Exploring Broadcast-and-Select and Wavelength-Selective Architectures: Advancing Optical Networks

In the fast-paced world of telecommunications, the quest for faster, more efficient data transmission methods is relentless. Enter Broadcast-and-Select and Wavelength-Selective architectures, two groundbreaking technologies at the forefront of optical network innovation. In this blog post, we'll delve into the intricacies of these architectures, their applications, and the transformative impact they are poised to have on the future of connectivity.

Understanding Broadcast-and-Select Architecture

Broadcast-and-Select (B&S) architecture represents a fundamental shift in the way optical networks are structured. At its core, B&S architecture relies on the concept of broadcasting optical signals to multiple destinations simultaneously, followed by selective routing to the intended recipient. This approach offers several advantages:

1. Efficient Resource Utilization: By broadcasting signals, B&S architecture eliminates the need for point-to-point connections, leading to more efficient utilization of network resources and reduced complexity in routing.

2. Scalability: B&S architecture scales gracefully with network size and bandwidth demands, making it well-suited for large-scale optical networks such as metropolitan and backbone networks.

3. Low Latency: With minimal routing overhead, B&S architecture ensures low latency transmission, making it ideal for applications that require real-time data delivery, such as video streaming and online gaming.

Broadcast-And-Select OADM Architecture

Exploring Wavelength-Selective Architecture

Wavelength-Selective (WS) architecture leverages the unique properties of light to enable high-speed data transmission over optical fibers. Unlike traditional architectures where each optical signal is transmitted on a separate wavelength, WS architecture allows multiple signals to coexist on the same wavelength, with each signal encoded using a unique modulation format or code. Key features of WS architecture include:

1. Wavelength Reuse: By multiplexing multiple signals onto the same wavelength, WS architecture maximizes spectral efficiency and enables efficient utilization of the optical spectrum.

2. Flexibility: WS architecture offers flexibility in allocating wavelengths to different signals dynamically, allowing for adaptive resource allocation and optimized network performance.

3. Interference Mitigation: Through advanced signal processing techniques, WS architecture mitigates crosstalk and signal interference, ensuring reliable data transmission even in dense wavelength-division multiplexing (DWDM) environments.

Wavelength-Selective OADM Architecture

Applications and Future Outlook

Both Broadcast-and-Select and Wavelength-Selective architectures find applications across a wide range of domains, including telecommunications, data centers, and high-performance computing. These architectures are instrumental in enabling high-speed data transmission, improving network scalability, and reducing operational costs.

Looking ahead, the future of optical networks is bright, with ongoing research and development aimed at further enhancing the performance and efficiency of B&S and WS architectures. Emerging technologies such as silicon photonics, coherent detection, and software-defined networking (SDN) are poised to unlock new capabilities and applications, driving the evolution of optical networks towards faster, more reliable, and energy-efficient communication infrastructures.

In conclusion, Broadcast-and-Select and Wavelength-Selective architectures represent significant milestones in the evolution of optical networking technology. By harnessing the power of light and innovative network designs, these architectures are poised to revolutionize the way we transmit and process data, paving the way for a more connected and digitally empowered future.