About RYU Laboratory

Ryu Laboratory (Ryu Lab) has just started research on April 2016 immediately after S. Ryu joined Meiji University.
Ryu Lab is aiming at research on optical communication systems, communication networking, and related optical measurement techbnology.
Ryu Lab is located at Nakano Campus, Meiji University near JR Nakano station in central Tokyo.

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Research fields

We are doing research on the following topics.
1. Optical wireless communication systems
２. Long-haul coherent optical fiber communication systems
３．SDN（Software-Defined Network）
４．Optical measurement techbnology

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1. Optical Wilreless Communication Systems

Mobile communication operators are facing heavy traffic demand, which has forced the use of the Wi-Fi systems to provide mobile operators with additional traffic capacities.
However, traffic demand is still increasing day by day. Even if we use the Wi-Fi systems, we frequently experience shortage of traffic capacity in the mobile communication systems in large traffic areas.
Optical wilreless communication (OWC) systems are attractiing much attention recently since the systems have possibilities to provide us with much traffic capacities by virtue of inherent high frequency of light. Recently, the OWC is sometimes referred to "Li-Fi" that is a new word coming from "Wi-Fi".
However, the OWC systems have essential problems; the systems are sensitive to the obstacles between a light source and a receiver since the OWC systems uses lightwave. To solve the above mentioned problem, we are now doing research on diversity systems in which multiple transmitters and receivers cooperate to establish stable communication channel. Diversity systems will play an important role in realization of the OWC systems.

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2. Long-haul coherent optical fiber communication systems

Research on long-haul high capacity systems has been improved significantly recetly. Using the present state-of-the-art digital coherent optical communication systems technology, 100-Gbit/s per wavelength using QPSK format and 200-Gbit/s per wavelength using 16QAM format have been commercialized. Coherent optical communication systems use optical phase of light to carry data streams.
Coherent optical communication systems using optical phase modulation is essentially susceptible to optical phase noise caused by, e.g., optical fiber nonlinearities. Optical phase noise have not been paid so much attention in traditional optical communication systems since the systems just used 'intensity modulation' of light.
We are doing research on optical phase noise caused in the fibers to clarify the effect of the phase noise characteristics on the transmission performance.

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3. Software-Difined Network (SDN)

In present communication networks, devices, i.e., routers, switches, and transmission equipment are controlled by the built-in software for operation. Such networks have the following problems,
(1) difficulties to view entire network operation,
(2) difficulties to identify the cause of the fault and/or instabilities inside the networks.
Software-defied network (SDN) technology is attracting attention recently since in the SDN network all the equipment inside the network can be supervised and controlled by a SDN controller. The SDN controller can also be used to program all the equipment in the network, so value-added network services can be created by the SDN technology.
We are doing research on SDN technology from a viewpoint of creating new network services.