26 terabits per second by fiber with one laser
In the journal Nature Photonics published a description of the new technology of data transmission over fiber at speeds up to 26 Tbit / s instead of the current maximum 1.6 Tbit / s.
A group of German engineers led by Professor Wolfgang Freude from the University of Karlsruhe used OFDM (orthogonal frequency division multiplexing) technology in optical fiber, which is widely used in wireless communication (802.11 and LTE), digital television (DVB-T) and ADSL .
In fiber, using OFDM is more difficult, because here you need to divide the luminous flux into subcarriers. Previously, the only way to do this was to use a separate laser for each subcarrier.
Comparison of different types of multiplexing
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For broadcasting at each frequency, a separate laser and a separate receiver are used, so that hundreds of lasers can transmit a signal simultaneously in a single fiber-optic channel. According to Professor Freude, the total bandwidth of the channel is limited only by the number of lasers. “An experiment has already been conducted and a speed of 100 terabits per second has been demonstrated, ” he said in an interview with the BBC. But for this it was necessary to use about 500 lasers, which in itself is very expensive.
Freude and his colleagues developed a technology for transmitting over 300 fiber optic fibers of different colors using a single laser using short pulses. This is an interesting phenomenon called optical frequency comb . Each small pulse is “smeared” in frequency and time, so that the receiver of the signal with the help of good timing can theoretically process each frequency separately.
After several years of work, the German researchers still managed to find the right timing, select suitable materials, and put into practice the processing of each subcarrier using the Fast Fourier Transform (FFT). A Fourier transform is an operation that associates the functions of a real variable with another function of a real variable. This new function describes the coefficients in the decomposition of the original function into elementary components - harmonic oscillations with different frequencies.
FFT is ideal for decomposing light into subcarriers. It turned out that a total of about 350 colors (frequencies) can be extracted from a conventional pulse, and each of them is used as a separate subcarrier, as in the traditional OFDM technique. Last year, Freude and his colleagues conducted an experiment and in practice showed a speed of 10.8 terabits / s , and now they have further improved the accuracy of frequency recognition.
According to Freude, the technology of timing and FFT developed by him may well be implemented in a microchip and find commercial application.
A group of German engineers led by Professor Wolfgang Freude from the University of Karlsruhe used OFDM (orthogonal frequency division multiplexing) technology in optical fiber, which is widely used in wireless communication (802.11 and LTE), digital television (DVB-T) and ADSL .
In fiber, using OFDM is more difficult, because here you need to divide the luminous flux into subcarriers. Previously, the only way to do this was to use a separate laser for each subcarrier.
Comparison of different types of multiplexing
')
For broadcasting at each frequency, a separate laser and a separate receiver are used, so that hundreds of lasers can transmit a signal simultaneously in a single fiber-optic channel. According to Professor Freude, the total bandwidth of the channel is limited only by the number of lasers. “An experiment has already been conducted and a speed of 100 terabits per second has been demonstrated, ” he said in an interview with the BBC. But for this it was necessary to use about 500 lasers, which in itself is very expensive.
Freude and his colleagues developed a technology for transmitting over 300 fiber optic fibers of different colors using a single laser using short pulses. This is an interesting phenomenon called optical frequency comb . Each small pulse is “smeared” in frequency and time, so that the receiver of the signal with the help of good timing can theoretically process each frequency separately.
After several years of work, the German researchers still managed to find the right timing, select suitable materials, and put into practice the processing of each subcarrier using the Fast Fourier Transform (FFT). A Fourier transform is an operation that associates the functions of a real variable with another function of a real variable. This new function describes the coefficients in the decomposition of the original function into elementary components - harmonic oscillations with different frequencies.
FFT is ideal for decomposing light into subcarriers. It turned out that a total of about 350 colors (frequencies) can be extracted from a conventional pulse, and each of them is used as a separate subcarrier, as in the traditional OFDM technique. Last year, Freude and his colleagues conducted an experiment and in practice showed a speed of 10.8 terabits / s , and now they have further improved the accuracy of frequency recognition.
According to Freude, the technology of timing and FFT developed by him may well be implemented in a microchip and find commercial application.
Source: https://habr.com/ru/post/119803/
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