Submarine Optical Cable

Overview of submarine optical cable

Submarine optical cable refers to a kind of optical fiber cable laid in deep-sea or shallow sea, or in the seabed of river channel, which is used for optical signal and network signal transmission and connection.

Classification of submarine optical cable

According to the application scope of submarine optical cables, it can be mainly divided into submarine single armour (SA) fiber cable, submarine double armour (DA) fiber cable, submarine single armour light (SAL) fiber cable, submarine light-weight protected (LWP) fiber cable, submarine light-weight (LW) fiber cable, submarine light-weight armour (LWA) fiber cable and their respective characteristics are as follows:

  •  Submarine light-weight optical cable (LW): generally suitable for deployment, construction and recycling in areas with a water depth of more than 1000 meters and at least 8000 meters deep.
  • Submarine light-weight protected optical cable (LWP): Generally suitable for deployment, construction and recycling in areas with a water depth of more than 1000 meters and at least 8000 meters deep, but it has certain anti-wear and anti-fish bite capabilities.
  • Submarine light-weight armour optical cable (LWA): Generally applicable to the deployment, burial, construction and recycling in areas with a water depth of 20 meters or more and at least 1500 meters deep. If it is not buried but only laid on the seabed, it can be applied It is deployed, constructed and recycled in areas reaching a water depth of 2000 meters.
  • Submarine single armour optical cable (SA): generally suitable for deployment, burial, construction and recycling in areas with a water depth of more than 20 meters and at least 1500 meters deep.
  • Submarine double armour optical cable (DA): generally suitable for deployment, burial, construction and recycling in areas reaching a depth of 500 meters, and provides the protection required within this depth, and should have a certain weight to prevent tides waves from moving submarine cables.

Optical cable type

Typical applicable environment

Features

(LW) Submarine light-weight optical cable

1000m-8000m water depth, good and stable sandy seabed

Lightly protected, the center is a loose tube structure, surrounded by metal reinforced steel wires, and the outermost layer of medium density polyethylene sheath structure

(LWP) Submarine light-weight protected optical cable

1000m-8000m water depth, rough seabed, moderately abrasive environments or environments that may be bitten by marine food

Compared with subsea light optical cable, it adds metal tape and a second layer of polyethylene sheath to increase abrasion resistance and hydrogen sulfide corrosion resistance

(LWA) Submarine light-weight armour optical cable

20m-1500m water depth, rocky terrain, moderate tugboat hazardous area, suitable for 2000m water depth when not buried

Add light armored steel wire than submarine light fiber optic cable

(SA) Submarine single armour optical cable

20m-1500m water depth, complex rocky terrain, high-risk tugboat hazard area

Adds a layer of heavy-duty armored steel wire over submarine light-duty cables

(DA) Submarine double armour optical cable

0m-500m water depth, complex rocky terrain, high-risk tugboat hazard areas and high-wear areas

Adds two layers of heavy-duty armored steel wire to subsea light-duty cables

Submarine cable features:

  • Low loss, high strength, long manufacturing length, long relay distance of optical cable, generally more than 50 kilometers, and the transmission performance of optical fiber will not change within 25 years.
  • It requires firm structure and light material. However, light metal aluminum cannot be used as a reinforcing armor, because the electrochemical reaction between aluminum and seawater will produce hydrogen, and the hydrogen molecules will diffuse into the glass material of the optical fiber, which will increase the loss of the optical fiber. Therefore, the submarine optical cable should not only prevent hydrogen from being generated inside, but also prevent hydrogen from penetrating into the cable from the outside.
  • It is required to withstand strong pressure and tension. Submarine optical cables are basically laid by means of on-board operation, especially deep-sea optical cables (optical cables laid on the seabed above 1,000 meters in water depth). Under such a large load condition, the strain of the optical cable should be limited to 0.7-0.8%.

Application of submarine optical cables

Outdoor optical cables are mainly suitable for interconnection between buildings and between remote networks.

Coastal cities and island markets

Submarine cables are an important means of transmission of electricity and communication between coastal islands and cities, including mainland and islands, islands and islands, etc.

Submarine cable market for offshore oil platforms

It is understood that the amount of cables used on each offshore oil platform is: 150km for jack-up platforms, 180km for semi-submersible platforms, 200km for oil production platforms, 200km for production platforms, and 100km for living platforms.

Underwater cable market such as rivers and lakes

Due to the need to transform rivers, lakes and reservoir dams, underwater cables are more and more widely used.

Submarine cables for offshore wind power generation and power transmission

For submarine cables, their applications in offshore wind power generation and power transmission have broad market prospects.

Physical structure of submarine cable

  • Optical fibers for submarine optical cables. There are three types of optical fibers for submarine optical cables according to system requirements: G.652 non-dispersion-shifted single-mode fiber, G.653 dispersion-shifted single-mode fiber, and G.654 low-attenuation single-mode fiber . In general, the fiber strength should reach 2%, and the fiber diameter should be 125±2.4%μm. G.652 non-dispersion-shifted single-mode fiber is mostly used in the 1310nm region. When it is used in the 1550nm area, it should be adjusted according to the link length and bit rate, using a dispersion compensation fiber. G.653 dispersion-shifted single-mode fiber, when used for single-channel transmission in the 1550nm region, has less loss and less dispersion. G.654 single-mode fiber has the lowest fiber attenuation in the 1550nm region, which is very suitable for long-distance submarine communication systems.
  • The submarine cable structure design should realize the most comprehensive, reliable and safe protection of the optical fibers in the cable. The laying of submarine optical cables of different depths has different technical requirements. The structural design of submarine optical cables must meet these requirements including long length, high water pressure resistance, strong tensile strength, and good corrosion resistance of the sheath. In addition, it must be resistant to hydrogen, because hydrogen will increase the loss of optical fibers. At present, according to the different laying depths, the structure of submarine optical cables is divided into two categories. One type is a submarine optical cable with an outer armored structure suitable for shallow sea areas. The other type is the optical cable without the outer armor structure, and its strength member is placed inside the optical cable, which can be applied to the submarine optical cable in the deep sea area.
    The optical cable is on the seabed and looks like an oil pipeline, but only a small part of the core actually functions, and the rest are all protective layers. Generally speaking, the optical fiber bundle is surrounded by a paraffin protective layer, followed by copper tube, polycarbonate, aluminum waterproof, steel strand, asphalt and polyethylene, and seven lines of defense protect the optical fiber. The outermost polyethylene is mainly used to deal with seawater, so as to avoid the reaction between seawater and steel strands, causing the optical cable to be corroded one after another, while the steel strands are mainly used to deal with the unpredictable underwater world, such as large fish such as sharks, and deep-sea fishing nets.

 

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