How are submarine cables installed on cable vessels?

How are submarine cables installed on cable vessels?

With the booming global telecommunications industry, the demand for submarine communications has grown in tandem. Submarine cable installation typically utilizes specially designed cable vessels capable of storing thousands of kilometers of coiled cable in their hangars. Special amplifiers are typically spaced approximately 40 kilometers apart to boost the transmission signal voltage and prevent cable loss.

However, cable vessels must take necessary precautions when laying fiber optic cables on the seabed to ensure that the amplifiers do not break or become damaged, thereby ensuring decades of uninterrupted operation. To this end, cable vessels employ specialized techniques, which will be described in more detail in this article.

Technology Types Used

There are four main installation technique s commonly used for different sections of cable routes:

1. Shoreline

Directional drilling is often used to minimize impacts when installing submarine cable ducts that pass beneath the coast and through any coral reefs close to the coast.

2. Shallow Waters

In these areas, especially those with high fishing activity, burying the submarine cable is crucial to minimize damage. Trawl equipment, such as beam trawls, can be used to completely cut through submarine cables. When crossing soft-bottom areas (ideal for anchoring, trawling, and other bottom fishing techniques), the cable is typically buried to protect it from fishing gear.

3. Hard Bottom Areas

When crossing areas where burying the cable is not possible and anchors are planned, armored cables are typically used. Once installed, these cables do not move horizontally.

4. Deep Sea Areas

In areas where bottom fishing gear or anchors are not planned, the submarine cable is simply laid directly on the seabed. To date, no adverse effects have been observed.

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Burial Equipment

The cable-laying vessel tows an underwater tiller, which continuously digs the trench and lays the fiber optic cable. The burial equipment requires strong propulsion power from the vessel to operate and tow.

The attached tiller has a height control function and can be raised and lowered. A CCTV camera is also connected to the tiller to verify that the cable is properly inserted into the tiller.

A magnetometer is used to verify that the cable is properly buried behind the tiller.

When the cable repeater link passes through the attached tiller, the lowering arm rises and closes. This tiller has three separate lines extending from the vessel: an umbilical cable for various operations, a streamer for towing the tiller, and the submarine cable itself, which needs to be buried.

Installation

Laying submarine cable is a commercial operation with minimal environmental impact, even during maintenance, operation, and repairs. However, there are concerns about the impact of fiber-optic cables, which must meet industry standards. Previously, submarine cable laying relied primarily on long lines, such as transcontinental telecommunications lines, which are not cost-effective, and cable-laying vessels were unable to handle short cables.

The ideal method involves excavating a trench in the seabed, which is free from natural processes. A flexible cable, which is more durable and less expensive than a cable, is then laid from a cable-laying vessel. Finally, the cable is laid in a subsequent operation. Alternatively, the submarine cable can be laid first and buried in a second operation.

The cable used for this operation must be corrosion-resistant and typically features steel strands to reduce the risk of damage. If an obstruction arises during the laying process, a portion of the cable can be retrieved, re-laid onto a separate track, and rerouted to avoid the obstruction. Alternatively, operations can be suspended until the obstruction is cleared.

The powerful cable utilizes a direct drive to steer the plow; however, for optimal performance, motor-assisted steering is preferred. This involves the use of electromagnetic detectors that react to the ferromagnetic properties of the wire. A second laying operation requires the use of a plow, preferably one that exploits high-velocity water currents to create a trench.

Utilities

Previously used small-diameter fiber-optic cables were easily damaged by fishing vessels . To reduce the risk of damage, modern submarine cables are buried using specialized underwater plows. Although these cables remain vulnerable to rocky bottoms and underwater slopes, special measures are being implemented using specially equipped cable-laying vessels to manage and, when necessary, repair them.