NTT Reports Increase in Optical Transmission Capacity, Reduced Power Consumption

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Tokyo – Oct. 12, 2023 – NTT Corporation (NTT) said it successfully demonstrated technology that expands transmission capacity while reducing energy use by 67 percent in optical communications platforms; specifically, the C band (near the wavelength of 1550 nm—a major communication wavelength band).

To demonstrate this expansion in capacity reduction in power consumption, NTT utilized multi-core fiber (MCF) and a multi-core amplification system using a core structure consisting of 12 cores arranged densely in an optical fiber for amplification. NTT aims to establish this technology by 2030 with over 10 channels of a space division multiplexing transmission line as part of its Innovative Optical and Wireless Network (IOWN) initiative, a communications infrastructure designed to enable a smarter world through the application of cutting-edge fields of study including photonics and advanced computing.

As demand for data continues to increase with the introduction and expansion of 6G wireless communication, video viewing, autonomous driving, generative artificial intelligence and more, the transmission capacity required for optical communication platforms is expected to increase exponentially. However, with current optical amplification systems, the power consumption of optical amplifiers, which are vital for long-distance optical communications, also increases alongside capacity.

The conventional optical amplifier utilizes the core excitation method, which amplifies the signal light propagating in the core by injecting excitation light in the core unit. In this study, however, the optical amplifier used the clad excitation method, which applies excitation light to the entire cross-section of the optical fiber and amplifies all the signal light propagating in multiple cores in the cross-section.

The amplification optical fiber used in this study maximized the area ratio of the core to the cladding by reducing and enlarging the outer diameter (cladding diameter) and core diameter of the fiber for optical amplification, while maintaining the same multi-core arrangement (number of cores and core spacing) as the optical fiber transmission line, thereby maximizing the efficiency of use of excitation light.

Since the cladding diameter is reduced to increase the area ratio of the core of the amplifying optical fiber, the cladding diameter does not match at the connection point between the transmission line optical fiber and the amplifying optical fiber and a part of the exciting light is lost. In addition, both conventional and proposed technologies generate excitation light that is not used for optical amplification but remains after propagation of the optical fiber for amplification and is removed. By adopting a tapered structure and a reflective device, NTT succeeded in reducing excitation light loss and residual excitation light and further increasing the efficiency of light amplification.

NTT presented this research on Oct. 4, 2023, in Scotland at the 49th European Conference on Optical Communications (ECOC), the world’s largest international conference on optical communication technology.

For more information and a diagrammatic breakdown of these research results, please visit: