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Subsea Cable Repeaters hit 100% Completion - SUBCO

Subsea Cable Repeaters hit 100% Completion

Manufacturing of SMAP’s 61 repeaters has been completed, signalling a major milestone in the production of the cable system.

During the manufacturing of the repeaters, over 25,000 tests/checks were carried out to ensure they meet specified performance criteria.

Each repeater is placed 90km apart over the length of the cable and extensive testing and qualification are carried out to ensure they can withstand life under the sea for 25-30 years without maintenance, at depths of up to 8000m.

What components make up Subsea Repeaters?

Repeater

 

The subsea repeater’s job is to provide amplification for the incoming optical signal in each direction on each fibre pair. In the case of SMAP, optical amplification is typically achieved using a type of optical device known as an “Erbium Doped Fibre Amplifier” or EDFA.

An EDFA consists of a section of fibre “doped” with a small amount of Erbium ions, a “pump” laser used to excite the Erbium ions, and an optical coupler to combine the incoming signal with the pump laser’s output.

The pump laser operates at a significantly different wavelength (usually at 980nm or 1480nm) to the repeater’s signal bandwidth (usually centred about 1550nm), so besides exciting the Erbium ions it doesn’t directly interact with the incoming signal.

However, when the incoming optical signal interacts with the excited Erbium ions it causes some of them to drop back to a lower energy state and release new photons with the same phase and direction of propagation as the incident signal, causing signal amplification.

A practical EDFA also includes components like isolators with a finely tuned distribution of Erbium ions and pump laser power to optimise the bandwidth, gain and noise of the amplifier.

Noise in an EDFA (also known as “Spontaneous Emission”) occurs when excited Erbium ions spontaneously drop to a lower excitation level, releasing photons with random direction and phase, rather than in sync with the incoming signal.

The rest of the repeater consists of:

  • the electronics required to power the pump laser
  • the “sea case” to protect the delicate optical and electrical equipment inside
  • the “coupling”, in which the repeater is jointed to the subsea cable along with the associated protective flexible armadillo, cable glands and joint housing

How is the rest of our manufacturing going?

  • Cables: 80%
  • Repeaters: 100%
  • Branching Units: 33%
  • Terminal Equipment: 100%
  • System Assembly: 60%