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World Record Optical Fiber Transmission Capacity Doubles to 22.9 Petabits per Second

- Significant increase achieved with combination of cutting-edge technologies -

November 30, 2023
(Japanese version released on October 5, 2023)

National Institute of Information and Communications Technology

Highlights

  • A record-breaking transmission capacity of 22.9 petabits per second in a single optical fiber was demonstrated.
  • Large-scale space-division multiplexing technology was successfully combined with multi-band wavelength-division multiplexing technology with 18.8 THz transmission bandwidth.
  • Demo is a major step toward the realization of future ultra-large capacity optical communication networks.
Researchers from the National Institute of Information and Communications Technology (NICT, President: TOKUDA Hideyuki, Ph.D.), in collaboration with the Eindhoven University of Technology and University of L’Aquila demonstrated a record-breaking data-rate of 22.9 petabits per second using only a single optical fiber, which was more than double our previous world record of 10.66 petabits per second.
In this research, researchers succeeded in combining the latest research technologies such as large-scale Space Division Multiplexing (SDM) and multi-band Wavelength Division Multiplexing (WDM), to demonstrate a path to future ultra-large capacity optical communication networks.
The results of this experiment were accepted as a post-deadline paper presentation at the 49th European Conference on Optical Communications (ECOC 2023) presented by Ben Puttnam on Thursday, October 5, 2023.

Background

To cope with the ever-increasing data traffic demands, multiplexing technologies using space and wavelength for high data-rate optical fiber communications have been investigated. The former uses advanced optical fibers containing multiple optical paths (channels) within a common cladding, whereas the latter enhances the total transmission capacity by increasing the transmission bandwidth to accommodate many independent Wavelength Division Multiplexed (WDM) data channels.
To date, NICT has realized Space Division Multiplexing (SDM) with over 100 spatial channels by combining multicore fiber (MCF) and multimode fiber transmission technologies as well as multi-band WDM with a total bandwidth of 20 THz by using the S-, C-, and L-bands (see Table 1). However, except for very short-distance cases (1 km), the combined use of multi-band WDM and SDM has only been demonstrated for uncoupled four-core MCFs. To combine multi-band WDM and SDM with large spatial channel count fibers (e.g., 114 channels with a 38-core 3-mode fiber), a multi-band-compatible MIMO receiver is required.

Table 1: Summary of recent results
Figure 1: Conceptual image of the ultralarge-capacity optical fiber transmission in this study

Achievements

Figure 2: Number of spatial channels and frequency bandwidth of recent experimental results on SDM transmission over >1 km distance

NICT demonstrated the possibility of fiber-optic data communication at 22.9 petabits per second, which is more than double the previous record of 10.66 petabits per second. Using a multi-band-compatible MIMO receiver, we successfully combined multi-band WDM and multi-core, multi-mode SDM for the first time. The details of the experimental system are shown in Figure 5 in the Appendix. 293 wavelength channels were used in S-band with 457 in the C-and L-bands giving a total of 750 WDM channels covering a frequency bandwidth of 18.8 THz. Polarization-multiplexed 256 QAM was used for signal modulation. As shown in Table 1 and Figure 2, the number of spatial channels in multi-band WDM transmission demonstration increased by a factor of 28.5.
The measured transmission capacity for each core ranged from ~0.3 to 0.7 petabits per second leading to a total transmission capacity of 22.9 petabits per second. The achieved data-rate includes an overhead for an implemented forward-error correction code with the demonstration showing up to 24.7 Pb/s can be achieved with better optimized coding. This is more than 1,000 times the data-rate of currently deployed optical fiber communication systems.
While uncoupled four-core MCF is suitable for early adaptation, further improvement of the telecommunication infrastructure using ultra-large-capacity optical fibers will be needed in the future, where the data traffic demand is expected to increase by 3 orders of magnitude (x1,000 times). This study demonstrates the first successful combination of multi-band WDM and SDM employing a multicore multimode fiber, which is key to the realization of future ultra-large-capacity optical fiber communication networks.

Future prospects

NICT will continue to explore multi-band WDM over large SDM fibers including randomly coupled MCFs or multimode fibers that require massive multi-band MIMO receivers. The results of this experiment were accepted as a post-deadline paper presentation at the 49th European Conference on Optical Communication (ECOC 2023, in Glasgow, UK, 1st to 5th October 2023) and presented on Thursday, October 5, 2023.

References

International Conference: European Conference on Optical Communication (ECOC 2023) Post-deadline Paper
Title: 22.9 Pb/s Data-Rate by Extreme Space-Wavelength Multiplexing
Authors: B. J. Puttnam, M. van den Hout, G. Di Sciullo, R. S. Luis, G. Rademacher, J. Sakaguchi, C. Antonelli, C. Okonkwo, and H. Furukawa

Previous NICT Press Releases

Appendix

1. Ultralarge-capacity optical fiber transmission system

Figure 5: Schematic of the optical transmission system in this study
Figure 5 shows a schematic of the optical transmission system.
① Multi-band optical signals (750 wavelength channels in the S-, C-, and L-bands) were generated, and 256 QAM modulations with polarization multiplexing were applied to the measurement signal channel.
② A set of optical amplifiers was used to amplify the multi-band optical signals.
③ An optical path switch was used to launch optical signals to the measurement and adjacent cores selectively.
④ Thirty-eight sets of commercially available 3-mode multiplexers were used to connect 114 SMF inputs to 38 sets of 3-mode fiber outputs.
⑤ The 38 sets of 3-mode fibers were connected to a 38-core 3-mode fiber using a free-space 38-core multiplexer.
⑥ The optical signals propagated through the measurement core and adjacent cores over 13 km of the 38-core 3-mode fiber.
⑦ The output of the 38-core 3-mode fiber was connected to 38 sets of 3-mode fibers using a free-space 38-core demultiplexer.
⑧ Thirty-eight sets of 3-mode demultiplexers connected 3-mode fibers to 114 SMF outputs.
⑨ The 3-mode signals that propagated through the measurement core were selected from 114 SMF outputs using an optical path switch.
⑩ The received multi-band 3-mode signals were amplified using optical amplifiers, before tunable filters selected the channel to be measured before simultaneous reception at three parallel coherent receivers. The optical signals were then converted into electrical signals and stored using a multichannel high-speed digital storage oscilloscope.
⑪ Offline MIMO signal processing was applied to the stored data to recover the transmitted signals. Finally, the signal quality was evaluated to obtain the data-rate. 

2. Results of this experiment

In the experimental system shown in Figure 5, optimal error correction was applied to each core and wavelength channel to maximize the transmission capacity (data-rate) of the system. Each symbol in the plot of Figure 6 represents the 3-mode combined data-rate after an implemeted error correction scheme, and the sum of all data-rates amounts to 22.9 petabits per second. Analysis of the received channels also revealed that a data-rate up to 24.7 Pb/s could be achieved by using better optimized forward error correction coding.

Figure 6: Measured data-rate ncluding error correction overhead for each wavelength channel and core

Glossary

Figure 3: Image of optical fiber communication using a single core, single mode fiber

Space Division Multiplexing (SDM)

Single-core, single-mode fibers (SMF; see Figure 3), which are widely used commercially, have a transmission capacity limit of several hundred Tb/s. To overcome this problem, optical fibers with an increased number of optical paths (spatial channels) using multiple cores or modes have been studied (see Figure 4). Fiber-optic communication technology that uses such optical fibers is collectively called space-division multiplexing (SDM). This study used a 38-core 3-mode optical fiber (Sumitomo Electric Industries, Ltd.).

Figure 4: Image of SDM using a multicore multimode fiber, multiband WDM, and multilevel modulation


Wavelength Division Multiplexing (WDM)

WDM is used to transmit optical signals of different wavelengths within a single optical path. The optical signals are assigned to carrier frequency slots within the wavelength band. The total frequency bandwidth is then determined by the spacing and number of wavelength channels. Hence, the transmission capacity can be increased by increasing the number of wavelength channels.
However, the wavelength band suitable for telecommunication applications is limited. The C-band (wavelength of 1,530-1,565 nm) is mainly used in current optical communication systems, and the number of wavelength channels for the 100 GHz frequency grid is ~50. L-band (1,565-1,625 nm) has recently been used in the commercial systems for additional capacity. By contrast, the T-band (1,000-1,260 nm), O-band (1,260-1,360 nm), E-band (1,360-1,460 nm), S-band (1,460-1,530 nm), and U-band (1,625-1,675 nm) have not yet been commercialized. WDM that includes these bands is commonly called multi-band WDM. The widest frequency bandwidth used in previous multi-band WDM experiments was 20 THz in the S-, C-, and L-bands. Recently, we also demonstrated multi-band WDM transmission with 27.4 THz total bandwidth using the E-, S-, C-, and L-bands, to be presented in another press release.


Multicore fiber (MCF)

An MCF has many cores (physical optical paths) in a common cladding region, and its total transmission capacity can be increased by transmitting different data through each core. Two types of MCFs are commonly investigated: uncoupled and randomly coupled. Uncoupled MCFs that confine each signal to a corresponding core are suitable for early adaptation. Randomly coupled MCFs with numerous cores are under research as candidates for next-generation transmission media.


Multimode fiber

A multimode fiber has a large core diameter that can support multiple modes within the same core. Intermodal signal interference occurs at the fiber connections, inputs/outputs, and during multimode fiber propagation. Therefore, MIMO receivers that undo the interference through MIMO digital signal processing are required to recover transmitted signals. Multimode fiber transmission with a maximum of 55 modes has been realized. This study used a multicore multimode optical fiber containing 38 cores, each supporting 3-mode propagation and an addition core supporting single-mode propagation unused (see Figure 4).


MIMO receiver

MIMO is a signal processing technique used to eliminate multipath interference in wireless communications. It is also used in SDM optical communication systems to eliminate the signal interference between different cores (in the case of randomly coupled MCFs) and different modes (in the case of multimode fibers).


Polarization-multiplexed 256 QAM
Multi-level modulation is a technique that encodes multiple bits on a lightwave by precisely controlling its amplitude and/or phase. Multi-level modulation, in which the amplitude and phase are used simultaneously, is called Quadrature Amplitude Modulation (QAM). Because 256 QAM uses 256 different points in the complex phase space, it can encode eight bits of information (28 = 256) in each transmitted symbol. Thus, the spectral density of 256 QAM is eight times higher than that of a simple modulation format, such as on-off keying. The data-rate can be further doubled by polarization multiplexing, in which different data signals are transmitted in two orthogonal polarization states.

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