NTT Corporation announced has succeeded in the world’s fastest1 optical transmission experiment of digital coherent2 optical signals exceeding 2 Tbits/s per wavelength.
In its experiment demonstrating the breakthrough transmission speed, as recounted in a footnoted press release, NTT developed an ultra-wideband baseband amplifier IC3 module and digital signal processing technology that can compensate for distortion in the optical transceiver circuit with extremely high accuracy.
The company then demonstrated the transmission and reception of digital coherent optical signals exceeding 2 Tbits/s per wavelength and succeeded in a 240 km optical amplification repeater transmission experiment of an optical signal of 2.02 Tbits/s.
The company contends this result suggests that further scalability of digital coherent optical transmission technology can achieve both a large capacity per wavelength―which is more than double the conventional level―and a long transmission distance.
Communication traffic is predicted to increase in the future due to the proliferation of 5G services that will address various social issues and the development of IOWN and 6G services. The All-Photonics Network, which is IOWN's backbone optical communication network, must cost-efficiently achieve even greater capacity.
In the future, to economically transmit ultra-high-speed Ethernet signals of 1.6 terabits per second or more over long distances, NTT's experts said they hope to achieve long-distance optical transmission of more than 2 Tbits/s per wavelength by expanding the transmission capacity per optical signal wavelength and the signal symbol rate6, optimizing the amount of information per symbol.
As further explained by NTT's statement:
To expand the transmission capacity per wavelength, it is necessary to overcome the speed limit of silicon CMOS7 semiconductor circuits. To date, NTT has been researching and developing optical transmission systems and integrated devices using band doubler technology that overcomes the speed limit of silicon CMOS using AMUX and has succeeded in generating optical signals with a symbol rate exceeding 100 gigabaud8. However, to realize optical transmission of multi-terabits per second or more, it is necessary to achieve both a wider bandwidth and higher output of the electrical amplifier (driver amplifier for driving the optical modulator) in the optical transceiver. In addition, as speeds continue to increase, there is a demand for technology that can compensate for deviations from the ideal optical transmission/reception circuit (differences in signal path length, loss variations due to signal paths, etc.) with extremely high accuracy.
Now, for the first time in the world, we have demonstrated the transmission and reception of a digital coherent optical signal exceeding 2 Tbits/s per wavelength (Fig. 1, left) and successfully conducted an optical amplification repeater transmission experiment of 2.02 Tbits/s over 240 km (Fig. 1, right). Our team achieved this feat through the advanced fusion of NTT's original ultra-wideband baseband amplifier IC module and ultra-high-precision digital signal processing technology.
Ultra-wideband baseband amplifier IC module
NTT stated that it has been researching and developing an ultra-wideband baseband amplifier IC3 based on InP-based heterojunction bipolar transistor (InP HBT) technology9 and equipped with a 1mm coaxial connector that supports frequencies up to 110 GHz.
The new technology is expected to enable highly reliable transmission of large-capacity signals by multiplexing optical signals exceeding 2 Tbits/s per wavelength. In particular, the company noted that its technology for increasing the modulation speed of optical signals not only contributes to increasing the capacity per wavelength, but also can generate large-capacity signals when combined with wavelength resource expansion technology 10.
The company said the demonstrated technology is also expected enable long-distance transmission. NTT said it will promote research and development by continuing the integration of its own device technology, digital signal processing technology, and optical transmission technology toward the realization of an All-Photonics Network of the IOWN and 6G initiatives.