Feature Articles: All-Photonics Network for Enabling Innovative Optical and Wireless Network (IOWN)

Vol. 18, No. 5, pp. 24–29, May 2020. https://doi.org/10.53829/ntr202005fa4

Optical Full-mesh Network Technologies Supporting the All-Photonics Network

Hiroki Kawahara, Takeshi Seki, Sachio Suda,
Masahiro Nakagawa, Hideki Maeda, Yasuhiro Mochida,
Yukio Tsukishima, Daisuke Shirai, Takahiro Yamaguchi,
Mika Ishizuka, Yasuharu Kaneko, Kohjun Koshiji,
Kazuaki Honda, Takuya Kanai, Kazutaka Hara,
and Shin Kaneko

Abstract

This article introduces the concept of an optical full-mesh network for achieving ultra-low-latency transmission of diverse and large-capacity content in ultra-realistic services and the technologies underlying this network. It also introduces a demonstration of 8K uncompressed video transmission in a large-capacity optical transmission system as an embodiment of the optical full-mesh network concept.

Keywords: ultra-low latency, full-mesh network, large-capacity optical transmission

1. Introduction

NTT laboratories aim to provide ultra-realistic services [1] that break through the time-space wall by enabling the real-time sharing of not only ultra-high-definition video information but also diverse content that includes information conveyed through the five senses such as touch and hearing. However, providing such services to a large number of people will require a network that can transmit diverse and large-capacity content with low latency. To this end, our aim is to achieve the innovative All-Photonics Network (APN) based on photonics technology as a part of NTT’s Innovative Optical and Wireless Network (IOWN) [2]. Researchers at NTT Network Service Systems Laboratories, NTT Network Innovation Laboratories, NTT Network Technology Laboratories, and NTT Access Network Service Systems Laboratories are studying an optical full-mesh network as a means of achieving a large-capacity, low-latency transport function for the APN.

2. Concept of optical full-mesh network

In a conventional network, accommodating content to be transmitted requires data compression due to restrictions in the communication line capacity, conversion to Internet protocol (IP) packets for routing control by the IP protocol, and packaging of the data in Ethernet frames for multiplexing/switching control. These requirements generate latency due to data-compression processing, packet-queuing processing, etc., thus have been the dominant factors in communication latency between terminals.

In contrast, the optical full-mesh network shown in Fig. 1 provides end-to-end optical paths for each service by directly connecting the optical access network and optical backbone network through a photonic gateway (Ph-GW) that minimizes electronic processing for packet conversion, multiplexing/switching control, etc. This scheme eliminates the latency associated with data compression, packet-queueing processing, etc., which enables to provide a large-capacity and ultra-low-latency network.

Fig. 1. Overview of optical full-mesh network.

3. Key technologies for optical full-mesh network

The following three key technologies are being extensively studied for optical full-mesh network.

(1) Technologies for petabit-class ultra-large-capacity optical transmission system

With the aim of deploying a petabit-class ultra-large-capacity optical transmission system, optical system architecture is being studied based on high-speed optical signal technology, multi-band transmission technology for transmitting wavelength-multiplexed signals over multiple wavelength bands, and spatial multiplexing transmission technology for transmitting optical signals over new types of optical fiber such as multicore fiber. Please see the article “Ultra-high-capacity Optical Communication Technology” in this issue [3] for details on the device technologies supporting these ultra-large-optical transmission systems.

(2) IP-independent, protocol-free media transmission technology

We are studying the transmission technology of diverse types of media data including uncompressed video/audio, the five senses, and emotions as an elementary stream unconcerned with protocol, interface type, and format. Our goal is to achieve large-capacity and ultra-low-latency media transmission via end-to-end optical paths connected by IP-independent path control. Various types of signals, such as 4K/8K uncompressed video signals that flow through serial digital interface (SDI)/high-definition multimedia interface (HDMI) cables, audio signals that flow through multichannel audio digital interface (MADI)/Audio Engineering Society (AES) cables, and peripheral component interconnect (PCI) bus signals that flow among storage, memory, and network interfaces, will be directly accommodated in the all-photonic media transmission paths. To begin with, we have set out to develop interface technology to accommodate SDI signals on optical paths. Although SDI is used to connect video equipment within a broadcast station, our interface technology will enable users to make a connection with a remote location in the same manner as that within a broadcast station without considering transmission protocol, path control, etc. The real-time outside broadcasting of sporting events, concerts, etc. currently requires the dispatching of outside broadcasting vans carrying editing crews and editing equipment. IP-independent and protocol-free media transmission technology will provide an efficient production workflow (remote production) using uncompressed video/audio transmitted from the event venue via an end-to-end optical path. We can envision totally new applications as seen above.

(3) Topology-free access-network wavelength management/control technology

Achieving the APN that provides end-to-end optical paths with diverse user equipment requires remote management/control of wavelengths that user equipment transmits/receives for each optical path. In this regard, studies are underway on wavelength management and control in the access area as one of the main functions of the Ph-GW that connects the access area with a local full-mesh area. To prevent duplication of wavelengths among optical paths that share the same transmission medium, the Ph-GW interacts with the upper-level system that allocates wavelengths to assign wavelengths to each unit of user equipment. It also sends wavelength control instructions to user equipment and performs regular wavelength monitoring. User equipment, in turn, sets the optical transceiver wavelength according to the wavelength control instructions received from the Ph-GW. In this regard, a method is being studied for sending wavelength control instructions from the Ph-GW to user equipment by superposing the management/control signal on the same wavelength as the user signal but in a low-frequency band as an auxiliary management and control channel (AMCC) to prevent interference. The aim is to use an AMCC as a means of achieving an optical network that any type of user equipment can immediately connect to as long as the equipment can connect to optical fiber irrespective of any communications protocol, optical modulation scheme, or network topology.

4. Demonstration: 8K uncompressed video transmission in a large-capacity optical transmission system

We conducted a demonstration to show the effectiveness of an optical full-mesh network based on the key technologies described above. First, we constructed a prototype optical transmission system with a capacity of 0.24 Pbit/s per fiber (approximately 30 times the capacity of current commercial systems) as a large-capacity optical transmission system supporting an optical full-mesh network. In conjunction with this system, we developed a state-of-the-art real-time transponder capable of generating 600-Gbit/s/λ optical signal. As shown in Fig. 2, up to 100 wavelengths of the above 600-Gbit/s/λ optical signal was high-density wavelength-multiplexed over the C-band and L-band. We also applied spatial multiplexing technology based on a prototype multicore fiber with four cores to transmit wavelength-multiplexed signals using all four cores. We achieved a large-capacity optical transmission system by using these key technologies.

Fig. 2. Optical spectrum of large-capacity transmission system.

In the demonstration, we transmitted 8K video over a 600-Gbit/s/λ optical path using the optical transmission system. This large-capacity optical path enabled real-time transmission of 8K video without compression. We also transmitted 8K compressed video over the same optical path for comparison purposes. The 8K uncompressed video, which is shown on the right in Fig. 3, showed no degradation in image quality and achieved low latency about 1/30 that of the 8K compressed video. Further research of IP-independent media transmission technology will enable even further reduction in transmission latency.

Fig. 3. Transmission of 8K video content.

5. Future outlook

This article introduced the concept of an optical full-mesh network for ultra-low-latency transmission of diverse and large-capacity content and the technologies needed for deployment. An optical full-mesh network can be applied to networks requiring low latency such as those for financial and medical-care systems and can provide stress-free communications unconstrained by bandwidth and transmission delays. Going forward, our aim is to achieve early development of elemental technologies while taking into account network requirements in various application fields.

References

[1]	A. Akutsu, K. Minami, and K. Hidata, “Kirari! Ultra-realistic Communication Technology: Beyond 2020,” NTT Technical Review, Vol. 16, No. 12, 2018. https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr201812fa1.html
[2]	NTT Technology Report for Smart World, https://www.ntt.co.jp/RD/e/techtrend/index.html
[3]	K. Nakajima, Y. Miyamoto, H. Nosaka, and M. Ishikawa, “Ultra-high-capacity Optical Communication Technology,” NTT Technical Review, Vol. 18, No. 5, pp. 14–18, 2020. https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr202005fa2.html

	Hiroki Kawahara Research Engineer, Transport Network Innovation Project, NTT Network Service Systems Laboratories. He received a B.E. and M.E. in electrical, electronics, and information engineering from Osaka University in 2009 and 2011. He is currently with NTT Network Service Systems Laboratories and involved in the development of optical cross-connect and optical transmission systems. He is a member of the Institute of Electronics, Information and Communication Engineers (IEICE) of Japan.
	Takeshi Seki Senior Research Engineer, Transport Network Innovation Project, NTT Network Service Systems Laboratories. He received a B.S. and M.S. in electronics and applied physics from Tokyo Institute of Technology in 2002 and 2004. In 2004, he joined NTT Network Service Systems Laboratories, where he was engaged in research on optical cross-connect systems. He is currently developing wavelength division multiplexing (WDM) transmission systems. He is a member of IEICE.
	Sachio Suda Research Engineer, Transport Network Innovation Project, NTT Network Service Systems Laboratories. He received a B.S. and M.S. in electronics and optical science from Osaka University in 2005 and 2007. In 2007, he joined NTT Network Service Systems Laboratories, where he was involved in developing WDM transmission systems. He is currently developing optical cross-connect systems.
	Masahiro Nakagawa Research Engineer, Transport Network Innovation Project, NTT Network Service Systems Laboratories. He received a B.E. and M.E. in electrical engineering and computer science from Nagoya University, Aichi, in 2008 and 2010. In 2010, he joined NTT. Currently, he is with NTT Network Service Systems Laboratories, where he is engaged in research and development of transport network systems. His research interests include photonic network systems and dynamic network control. He is a member of IEICE.
	Hideki Maeda Senior Research Engineer, Supervisor, Transport Network Innovation Project, NTT Network Service Systems Laboratories. He received a B.S. and M.S. in electrical engineering from the Tokyo University of Science in 1992 and 1994. In 1994, he joined NTT Transmission Systems Laboratories and was engaged in research on long-haul large-capacity transmission systems. He is currently a senior research engineer and supervisor at NTT Network Service Systems Laboratories. He is a member of IEICE.
	Yasuhiro Mochida Research Engineer, Media Innovation Laboratory, NTT Network Innovation Laboratories. He received a B.E. and M.E. from the University of Tokyo in 2009 and 2011. Since he joined NTT laboratories in 2011, he has been engaged in research on video transmission over IP networks including transport protocol, presentation synchronization, and video conferencing. His current research interest is in low-latency video transmission over high-speed optical networks. He is a member of IEICE.
	Yukio Tsukishima Senior Research Engineer, Media Innovation Laboratory, NTT Network Innovation Laboratories. He received a B.E. in electronic engineering and an M.E. in physical electronics from Tokyo Institute of Technology in 1999 and 2001. He received the Best Paper Award from the 12th Optoelectronics and Communications Conference in 2007 and the IEICE Young Researchers’ Award in 2008.
	Daisuke Shirai Senior Research Engineer, Supervisor, Media Innovation Laboratory, NTT Network Innovation Laboratories. He received a B.E. in electronic engineering, M.E. in computer science, and Ph.D. in media design from Keio University, Kanagawa, in 1999, 2001, and 2014. He pioneered the world’s first 4K JPEG 2000 codec system, which enables low latency 4K60p video transmission on a Gigabit network. He is a veteran in the design and implementation of parallel processing architecture, hardware codec boards, codec control software, and high-performance forward error correction (FEC) technology. He also developed FireFort, a high-performance FEC technology, which is a part of the FEC standard in MPEG Media Transport. He has applied his expertise across multiple domains through his study of practical applications in digital audio and video broadcasting technology, image coding, information theory, networking, human-computer interaction, and software architecture. His current research topics include remote video production network and other applications using cutting-edge optical transport technology.
	Takahiro Yamaguchi Senior Research Engineer, Supervisor, Media Innovation Laboratory, NTT Network Innovation Laboratories. He received a B.E., M.E. and Ph.D. in electronic engineering from the University of Electro-Communications, Tokyo, in 1991, 1993, and 1998. He joined NTT in 1998 and has been researching super high definition image distribution systems. He is currently a group leader of media processing systems research group. He is a member of IEICE and the Institute of Image Information and Television Engineers.
	Mika Ishizuka Senior Research Engineer, Cognitive Foundation Network Project, NTT Network Technology Laboratories. She received a Ph.D. in engineering from Keio University, Kanagawa, in 2009. She has worked on the performance evaluation and optimization of communication networks. She is currently researching the All-Photonics Network. She is a member of IEICE.
	Yasuharu Kaneko Senior Research Engineer, Cognitive Foundation Network Project, NTT Network Technology Laboratories. He received a B.S. in mathematics from Waseda University, Tokyo, in 1999 and a Master of Mathematics from Kyushu University, Fukuoka, in 2001. He joined NTT Communications in 2001, where he worked as an optical transport network engineer. He moved to NTT Network Technology Laboratories in 2017, where he is currently researching and developing a network-architecture design strategy for the 5G era.
	Kohjun Koshiji Research Engineer, Cognitive Foundation Network Project, NTT Network Technology Laboratories. He received a B.E. and M.E. in management science from Tokyo University of Science in 2007 and 2009. He joined NTT in 2009 and worked on reliability evaluation/design/management of telecommunication networks. He is currently involved in the All-Photonics Network. He is a member of IEICE.
	Kazuaki Honda Engineer, Optical Access Systems Project, NTT Access Network Service Systems Laboratories. He received a B.S. from Kyoto University in 2013 and joined NTT Access Network Service Systems Laboratories the same year He has been involved in research on management and control of WDM passive optical network systems. He is a member of IEICE.
	Takuya Kanai Research Engineer, Optical Access Systems Project, NTT Access Network Service Systems Laboratories. He received a B.S. and M.S. in physics from Tokai University, Tokyo, in 2007 and 2009. In 2009, he joined NTT Access Network Service Systems Laboratories, where has been engaged in research on next generation optical access systems. Mr. Kanai is a member of IEICE.
	Kazutaka Hara Senior Research Engineer, Access Network Service Systems Project, NTT Access Network Service Systems Laboratories. He received a B.S. and M.E. in applied physics from Tokyo University of Science and Tokyo Institute of Technology in 2003 and 2005, and a Ph.D. in engineering from Tokyo Institute of Technology in 2011. In 2005, he joined NTT Access Network Service Systems Laboratories. His current interests are the next-generation optical access systems and an architectural design for the vision of future access networks. He is a member of IEICE.
	Shin Kaneko Senior Research Engineer, Optical Access Systems Project, NTT Access Network Service Systems Laboratories. He received a B.E. and M.E. in electronics engineering from the University of Tokyo in 2002 and 2004. He joined NTT Access Network Service Systems Laboratories in 2004. His current research interests include next-generation optical access networks and systems. He is a member of IEICE.

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