NTT Programmable Optical Circuit Cuts Signal Temporal Spread by About 60 Percent in 1,300 km Transmission Experiment Announced November 13
NTT announced on November 13 a programmable optical circuit technology that can flexibly control optical signals partway along an optical network. In a 1,300 kilometer long-haul optical transmission experiment, the technology reduced the temporal spread of the signal by about 60 percent. Temporal spread is one of the causes of heavier digital signal processing load on the receiver side, so reducing it lowers the correction work the receiver must perform.
The results were published earlier in Nature Photonics on September 25, 2026. The paper reported a parameterized spatial division multiplexed transmission scheme that installs programmable photonic unitary processors at intermediate nodes along the line, compensating for modal dispersion in the optical domain instead of leaving all correction to digital processing at the receiver.
The photonic processor used in the experiment was built on a silica-based planar lightwave circuit platform. The chip measures 50 by 25 millimeters and implements an 8-by-8 Clements-type mesh of Mach-Zehnder interferometers. The experimental signal used 12-gigabaud polarization-multiplexed quadrature phase-shift keying, circulated through a recirculating loop with 51.2 kilometers of graded-index three-mode fiber per span.
After 1,331 kilometers of transmission, the paper reported, the normalized generalized mutual information of every spatial and polarization mode remained above the 0.836 error-free threshold, with cleanly clustered constellations. The team said this showed the low-loss, polarization-insensitive processor preserved signal quality end to end.
NTT said it will pursue research and development with applications such as data center interconnects and submarine cables in mind. The work is a long-haul transmission experiment, and the announcement materials gave no timetable for deployment in commercial networks.
Source: NTT
Published by GSM · USA (original Chinese edition)
Photo: 图：可编程光电路传输实验的论文图示。来源：NTT 官方发布。 / Photo: Figure from the programmable optical circuit transmission study. Credit: NTT.
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