New Fiber Optic Signal Processing Technique Doubles Communication Distance

hypnosec writes: Researchers at University College London (UCL) have demonstrated a new technique for fiber optic signal processing that doubles the distance at which data travels error-free through transatlantic sub-marine cables. The UCL research, published in Scientific Reports, has the potential to reduce the costs of long-distance optical fiber communications as signals wouldn't need to be electronically boosted during their journey, which is important when the cables are buried underground or at the bottom of the ocean. The study reports a new way of improving the transmission distance, by undoing the interactions that occur between different optical channels as they travel side-by-side over an optical cable. By eliminating the interactions between the optical channels, researchers increase distance signals can be transmitted error-free from 3190km to 5890km, which is the largest increase ever reported for this system architecture.

Comments

Re:how do they do it today?

[msauve]

EDFA.

Re:how do they do it today?

[silas_moeckel]

Anything modern is running EDFA's where fiber is doped with Erbium and a pump laser is mixed in they get about 40db of amplification with a 100ma laser. Great part is it's not signal speed dependent as it's an all optical all analog method. The old way was to put a receiver and transmitter coupled back to back used a lot of power and was specific to a speed.

Re:how do they do it today?

[Shatrat]

But there are still going to be amplifiers. They are referring to eliminating transponders, which we already don't use for modern sub-sea links. This is basically just 16QAM, but instead of using 4 symbols over 1 frequency, it's 2 symbols over 2 frequencies tightly spaced together. It's been understood for a while that widening the channels was probably the only way to go beyond 100gbps for a transmitter/receiver.

Re:how do they do it today?

[Shatrat]

This sort of thing is measured in dBm to make the math easier. Decibel Milliwatts, where 0 dBm = 1 mw and it's a logarithmic scale up and down from there.
Individual channels are on the order of 0 to 5 dBm, or 1 to 3 mw. The composite signal coming out of an amplifier, which consists of multiple channels, is on the order of 20 dBm depending on how many channels are active and what the reach of the amplifier is. That's about 100 mw. Definitely a laser safety concern, but not military style death ray.