An international group of researchers from Technical
University of Denmark (DTU) and Chalmers University of Technology in
Gothenburg, Sweden have achieved dizzying data transmission speeds and are the
first in the world to transmit more than 1 petabit per second (Pbit/s) using
only a single laser and a single optical chip.
1 petabit corresponds to 1 million gigabits.
In the experiment, the researchers succeeded in
transmitting 1.8 Pbit/s, which corresponds to twice the total global Internet
traffic. And only carried by the light from one optical source. The light
source is a custom-designed optical chip, which can use the light from a single
infrared laser to create a rainbow spectrum of many colors, i.e., many
frequencies. Thus, the one frequency (color) of a single laser can be
multiplied into hundreds of frequencies (colors) in a single chip.
All the colors are fixed at a specific frequency
distance from each other—just like the teeth on a comb—which is why it is
called a frequency comb. Each color (or frequency) can then be isolated and
used to imprint data. The frequencies can then be reassembled and sent over an
optical fiber, thus transmitting data. Even a huge volume of data, as the
researchers have discovered.
One single laser can replace thousands
The experimental demonstration showed that a single
chip could easily carry 1.8 Pbit/s, which—with contemporary state-of-the-art
commercial equipment—would otherwise require more than 1,000 lasers.
Victor Torres Company, professor at Chalmers
University of Technology, is head of the research group that has developed and
manufactured the chip.
"What is special about this chip is that it
produces a frequency comb with ideal characteristics for fiber-optical
communications—it has high optical power and covers a broad bandwidth within
the spectral region that is interesting for advanced optical
communications," says Victor Torres Company.
Interestingly enough, the chip was not optimized for
this particular application.
"In fact, some of the characteristic parameters
were achieved by coincidence and not by design," says Victor Torres
Company. "However, with efforts in my team, we are now capable to reverse
engineer the process and achieve with high reproducibility microcombs for
target applications in telecommunications."
Enormous potential for scaling
In addition, the researchers created a computational
model to examine theoretically the fundamental potential for data transmission
with a single chip identical to the one used in the experiment. The
calculations showed enormous potential for scaling up the solution.
Professor Leif Katsuo Oxenløwe, Head of the Center
of Excellence for Silicon Photonics for Optical Communications (SPOC) at DTU,
says:
"Our calculations show that—with the single
chip made by Chalmers University of Technology, and a single laser—we will be
able to transmit up to 100 Pbit/s. The reason for this is that our solution is
scalable—both in terms of creating many frequencies and in terms of splitting
the frequency comb into many spatial copies and then optically amplifying them,
and using them as parallel sources with which we can transmit data. Although
the comb copies must be amplified, we do not lose the qualities of the comb,
which we utilize for spectrally efficient data transmission."
This is how you pack light with data
Packing light with data is known as modulation. Here, the wave properties of light are utilized such as:
Amplitude (the height/strength of the waves)
Phase (the "rhythm" of the waves, where it
is possible to make a shift so that a wave arrives either a little earlier or a
little later than expected)
Polarization (the directions in which the waves
spread).
By changing these properties, you create signals.
The signals can be translated into either ones or zeros—and thus utilized as
data signals.
Reduces Internet power consumption
"In other words, our solution provides a
potential for replacing hundreds of thousands of the lasers located at Internet
hubs and data centers, all of which guzzle power and generate heat. We have an
opportunity to contribute to achieving an Internet that leaves a smaller
climate footprint," says Leif Katsuo Oxenløwe.
Even though the researchers have broken the petabit
barrier for a single laser source and a single chip in their demonstration,
there is still some development work ahead before the solution can be
implemented in our current communication systems, according to Leif Katsuo
Oxenløwe.
"All over the world, work is being done to
integrate the laser source in the optical chip, and we're working on that as
well. The more components we can integrate in the chip, the more efficient the
whole transmitter will be, i.e., laser, comb-creating chip, data modulators,
and any amplifier elements. It will be an extremely efficient optical
transmitter of data signals," says Leif Katsuo Oxenløwe.
The research is published in Nature Photonics.
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