1.84Pb/s, twice the total global Internet bandwidth: a single laser achieves the fastest data transmission record

Sometimes, people describe the efficiency of the network as "not as good as transporting hard drives by truck": Amazon AWS has a service called snowmobile, which actually uses container trucks and can transfer 100Pb at a time. The volume of data transmitted by this large USB flash drive is huge, but it also tells us from another aspect that there is a big bottleneck in network data transmission.

Recently, a research team from the Technical University of Denmark (DTU) and Chalmers University of Technology in Gothenburg, Sweden, achieved the highest data transmission efficiency to date, and It is the world's first research to achieve transmission of more than 1 petabit per second (Pbit/s) using only a single laser and a single optical chip.

In the experiment, the researchers achieved a transmission rate of 1.8 Pbit/s over a distance of 7.9 kilometers using only one light source - 1 Petabit is equivalent to 125,000 Gigabyte. According to some estimates, The average internet bandwidth used around the world is about 1 Pbit/s, so it's nearly twice as fast as global bandwidth.

It's hard to describe how fast 1.84 Pbit/s is - home internet connections are typically a few hundred megabits per second, and if you're lucky, 1 gigabit or even 10 gigabit bits, but a petabit is one million gigabits. This data transfer speed far exceeds the previous record of 1.02 Pbit/s set in May this year.

The light source is emitted by a custom-designed optical chip that can use light from a single infrared laser to output multiple colors of the rainbow spectrum, that is, multiple frequencies. Therefore, one frequency (color) from 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, and each color is isolated from each other - like the teeth on a comb - so it's called a frequency comb. Finally, all frequencies are sent over fiber optics, thereby transmitting data.

Replacing thousands with a single laser

Experimental demonstration shows that a single chip can easily carry a speed of 1.8Pbit/s, reaching a speed of 1.8Pbit/s according to the previous state-of-the-art commercial equipment. Such a level would require thousands of lasers.

Victor Torres, a professor at Chalmers University of Technology, is the leader of the research team that developed and manufactured the chip. What's special about this chip, says Victor Torres, is that it generates a frequency comb with the ideal properties for fiber optic communications - very high optical power and broad bandwidth coverage in the spectral region of interest for advanced optical communications.

Communication system modeling.

#Interestingly, the chip is not optimized for this specific application. "In fact, some characteristic parameters are achieved by coincidence rather than by design," Victor Torres said. "However, with the team's efforts, we now have the ability to reverse engineer it and achieve highly reproducible microcombs for targeted applications in the telecommunications field."

In addition, the researchers created A computational model was developed to theoretically investigate the underlying potential of data transmission using the same single chip used in the experiments. The calculation results show that the scaling solution has great potential.

Professor Leif Katsuo Oxenløwe, Head of DTU’s Silicon Photonics Center of Excellence for Optical Communications (SPOC), said: “Our calculations show that a single chip manufactured at Chalmers University of Technology and A laser capable of transmission speeds up to 100 Pbit/s. The reason for this is that our solution is scalable, both in terms of creating multiple frequencies, but also in terms of splitting the frequency comb into many spatial copies, then optically amplifying them, and Treat them as parallel sources for transmitted data. Although the copy of the frequency comb must be amplified, its quality is not lost, and we use it for spectrum-efficient data transmission."

Modulation method

The process of adding information to an electronic or optical carrier signal and converting the data into radio waves is called "modulation." In this process, the wave characteristics of light are utilized, such as:

• Amplitude (the height/strength of the wave);
• Phase (the "rhythm" of the wave, which may make the wave earlier or later than expected Arrival);
• Polarization (the direction of wave propagation).

By changing these properties, you can create signals. These signals can be converted to 1 or 0 and thus exploited as data signals.

In the study, the data stream was split into 37 lines, each sent along a different optical thread in the cable. Each of the 37 data lines is divided into 223 data blocks, corresponding to different regions in the "data comb" spectrum. In other words, the scientists created a "massively parallel spatial and wavelength multiplexed data transmission" system. This multiple splits greatly increases the potential data throughput supported by fiber optic cables.

Testing and validating 1.84 Pb/s of bandwidth is no easy task—no computers can yet process that much data instantly, and storage is unlikely. The research team used dummy data on individual channels to verify full bandwidth capacity, and each channel was tested individually to ensure data received matched data transmitted.

The photonic chip can split a single laser into many frequencies, and some processing is required to encode the optical data in each of the 37 data optical streams. According to the researchers, a compact, fully functional light-processing device could be built the size of a matchbox. This is similar in size to monochromatic laser transmission devices currently used in the telecommunications industry.

##Achieved data transfer rate (red triangle) vs. theory Throughput (blue dots).

Reduce Internet Energy Consumption

With this technology, we can use the same fiber optic cable infrastructure as today, using only the same volume of photons The chip device replaces the original optical data encoder/decoder, which is expected to increase the effective data bandwidth by 8251 times.

In addition to extremely high speeds, new research could help reduce the energy consumption of the Internet.

"Our solution has the potential to replace the hundreds of thousands of optical devices located at the heart of the Internet and in data centers, all of which consume large amounts of power and generate heat. We have the opportunity to help reduce the number of contribute to the industry's carbon footprint," said Leif Katsuo Oxenløwe, one of the authors of the paper.

Although the researchers broke the petabyte-scale milestone for a single laser source and a single chip in their demonstration, there is still some development work before the solution can be implemented in our current communications systems To do.

"Currently, the world is working hard to integrate laser sources into optical chips. The more components we can integrate into the chip, the more efficient the entire transmitter will be. The transmitter includes the laser, the comb frequency output chip, the data modulator and any amplifier components. It will be an extremely efficient optical transmitter of data signals," said Leif Katsuo Oxenløwe.

This research was published in the latest issue of Nature Optics.

##Paper link: https://www.nature.com/articles/s41566-022-01082-z

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