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What it took to build the undersea internet cable between Chennai and Andaman & Nicobar Islands

An industry executive explains the key elements of the CANI undersea cable system, the process of laying it down, and the ordeals that have been overcome from start to finish.  

Between the coast of Chennai and the beaches of the Andaman & Nicobar Islands archipelago, there’s a 2,300 kilometre network of submarine optic fibre cables. The Chennai-Andaman & Nicobar Islands system, or CANI for short, is the only submarine cable that serves Indian territory alone — a similar system for the Lakshadweep Islands is being planned. Systems like CANI — at a larger, intercontinental level — are what makes the global nature of the internet possible, offering several terabits per second of broadband capacity between countries.

Starting from November 2019 to August 2020, Bharat Sanchar Nigam Limited, the state-owned telecom operator, laid the bulk of the cable system on the floor of the Bay of Bengal, straddling the vast distance between the Tamil Nadu capital and the islands (port cities in Thailand and Myanmar are far closer to Andaman & Nicobar Islands than Chennai).

The fibre cables were made by NEC, a Japanese telecommunications conglomerate. Ashutosh Zutshi, Vice President of Submarine Network Solutions at NEC’s India subsidiary, gave a talk at a webinar on August 11, where he spoke about the details of CANI’s construction that shed some light on how such systems get built, what challenges they face, and how they work. The webinar was organised by the National Telecommunication Institute for Policy Research, Innovation & Training.

The three elements of an undersea cable system

“The entire submarine cable network can be divided into three categories: the first one is the wet plant. The second one is what is called the dry plant. And the third is the marine operations,” Zutshi said.

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“The wet plant is what goes into the water”— the elements of the cable system that go “into the seas and oceans,” Zutshi explained. “That is the [optic fibre] cable itself, the repeaters required for keeping the power levels [consistent], and the branching units which branch out the cables to various countries, if need be.”

And then there are joint boxes. “Joint boxes connect various types of cable systems and various legs of a cable system, because it’s not possible to construct thousands of kilometers of cables in one go,” Zutshi said. The cables are armoured and insulated extensively, with systems at a greater depth being tougher. The “dry plant” on the land connects the cable system to terrestrial networks, and feeds the cables (and the repeaters placed underwater in regular intervals) the power they need to run. Submarine cables ideally terminate at beaches, where a large amount of sand can be dug up and replaced quickly, protecting the cable. On land, the place where the cables terminate are called landing stations.

  • Marine operations: Before the cable is actually laid, engineers need to plan ahead and figure out rock bottom — what the seabed looks like. “Marine operations are anything and everything to do with the laying of the cables in the sea, their maintenance and repair,” Zutshi said. “There are some major components [in this phase]; the first of these is the Marine Route Survey. Before you start deploying the cable, we have to conduct a survey of the ocean bed to understand the contours of the seabed and plan the cable route accordingly. The planning is called marine engineering; this decides how the cable has to be laid, how it has to be routed in order to ensure the long term safety of the cable. Because once the cable is laid, it has to stay there for a couple of decades, at least 20–25 years,” Zutshi said. Marine ops also step in when an undersea cable fault has to be repaired; this is done by fishing up the cable to sea level, fusing the fault shut, and dumping the cable back into the ocean floor.
  • Land cable suffers more damage: “Ironically, it is the land cable that suffers more damage as compared to the submarine cable,” Zutshi revealed. While cable cuts have been known to happen undersea, they’re far more common on land because the cables are closer to the ground and activities like construction and digging can damage the cables, something that there’s practically no risk of on the ocean floor.

List of activities in laying a CANI-like system

Zutshi outlined several activities that go into building undersea cable systems from start to finish. These are:

  1. Desktop study and pre-survey coordination: This step includes designing a pre-survey cable route, roughly giving an idea of what the route will look like before the marine engineers figure out the specifics. Pre-survey coordination, Zutshi said, means “You have to do a recce of all the landing sites to see if the locations are suitable, and figure out what type of insulation is required [for the cable] and how the survey needs to be conducted.”
  2. Marine route survey and post-survey coordination: In this step, the ocean floor is studied and the specifics of the route are mapped. And then there are permits. “In principle, there are lots of permits required for setting up a cable landing station and the submarine system required depending upon the country involved,” Zutshi said. In India, he said, a survey permit is to be obtained for the crew and the vessel, with approvals needed from the Ministries of Defence and Home Affairs. “There are higher mountains under the sea than there are over the land. So there are very steep regions in some locations along the seabed, so proper care has to be taken during cable deployment. It’s a very exciting and interesting world under the sea,” Zutshi said.
  3. Plants assembly and loading: Armed with information obtained from the route survey, heavy equipment — and hundreds of kilometres of cable — are loaded onto the vessel laying the cable. One end of the cable is tethered to the land, and the line unspools and drops to the ocean floor as the vessel moves away from the coast towards the other landing station. “Irrespective of the length of the cable, whether it is a few hundred or few thousand kilometres, the entire length is manufactured in one go — submarine cables are not manufactured in pieces. It’s a continuous length of cable that is loaded into the ship,” Zutshi said. The cable, is, however, cut up during laying whenever a repeater has to be inserted to boost the optic fibre signal.
  4. Pre-lay grapnel run: Before the cable is laid, the vessel sweeps debris out of the ocean floor, literally clearing the way for the cable to be laid. “This is done to clear the debris or any kind of hazardous material at the seabed to avoid cable damage. It’s primarily done along the route where the cable is required to be buried. So if the burial happens along a place where there is a lot of debris, the burial equipment will get damaged and the cable itself can get damaged as well,” Zutshi said.
  5. Cable landing, laying, and burial: After the cable is laid, the route and the line are inspected, and the manhole on the beach where the cable makes contact with land is buried in the sand. A gigantic “plow machine” parts the seabed as the vessel moves to secure the cable, so that it isn’t just resting on the ocean floor but is buried within — but this is not done when the ocean floor is coral or rock. “Once the cable is laid, testing of the end to end system is done, which is called segment testing and integration. Then the final commissioning and acceptance testing is done for the entire system, followed by necessary maintenance training of the resources,” Zutshi said.

Challenges in laying undersea networks

Undersea networks cannot be built all the time, and their positions can cause headaches.

  • When can they be built? “Obviously, it’s important to conduct marine activities during good weather. So monsoon season is a no go. You cannot do any activity during monsoon. So whether it is surveying, whether it’s cabling, it all has to be done during good weather conditions, which is post monsoon,” Zutshi said. For CANI, that translated to a four-month window between January 2020 and April 2020.
  • Transport: Among the Andaman & Nicobar Islands themselves, transport and accommodation were scarce for engineers working on the project. “We had to hire choppers at many locations,” Zutshi said, adding that engineers from NEC had to request accommodation in government-run guesthouses due to a lack of hotels.
  • Landing stations had to be built from scratch: In every landing location (except for Port Blair) the buildings housing the network equipment and the landing stations had to be constructed afresh. That delayed things, but Zutshi said things were sped up in a slightly unusual way: “We did something which is normally not done in any project. We were deploying really expensive equipment in one of the rooms while construction of the building was still under way. So that’s something which we did in the interest of completing the work on time.”
  • Fishermen protests: “There were some issues related to procurement, with fishermen protesting in some locations, particularly Chennai. There were some environmental related issues raised by these people; luckily, with the BSNL support we got over that,” Zutshi revealed. These protests have not been reported previously.
  • Airlifting Japanese engineers: When the lockdown struck, Japanese engineers working with NEC were stranded in the Andaman & Nicobar Islands. “They [the local administration] arranged the permissions for them to be evacuated right from the island. Otherwise they would have required to come back to Chennai for going back. So they arranged the immigration clearance in the Islands itself and they could go back,” Zutshi revealed. That may have been a significant relief, considering how much a trip back to Chennai — over 2,000 kilometers from Port Blair — might add to travel time to the East Asian country.
  • Beach erosion and repairs: While this isn’t a problem that CANI has necessarily faced, beach erosion is a growing worldwide phenomenon due to climate change-led rising sea levels. It can essentially expose manholes painstakingly covered by a bulk of sand, by simply eroding the coastline. SEA-ME-WE, a cable system that lands in Chennai, had a beach manhole slip into the sea, Zutshi said. While the cable that was landing in that manhole didn’t get damaged, such issues can disrupt connectivity, he warned. “Luckily for CANI, the beach manhole is located right at the edge of the road [bordering the beach]. So there is sufficient distance from the beach manhole to the sea,” he added. There’s also activities like fishing, anchor dropping, and more that can lead to cables being damaged. Getting a vessel out to repair such faults is time-consuming and requires permits.

Quotes have been lightly edited for clarity.

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