FINAL REPORT For Japan-Korea Joint Research Project AREA

Transcription

1 FINAL REPORT For Japan-Korea Joint Research Project AREA 1. Mathematics & Physics 2. Chemistry & Material Science 3. Biology 4. Informatics & Mechatronics 5. Geo-Science & Space Science 6. Medical Science 7. Humanities & Social Sciences 1. Research Title: Research on next generation FTTH system with high security using optical CDMA 2. Term of Research: From July 1, 2008 To June 30, Total Budget a. Financial Support by JSPS: Total amount: 2,400 thousand yen 1 st Year 1,200 thousand yen 2 nd Year 1,200 thousand yen 3 rd Year 0 thousand yen b. Other Financial Support : Total amount: 0 thousand yen 4. Project Organization a. Japanese Principal Researcher Name Masanori Hanawa Institution / Department Position Interdisciplinary Graduate School of Medicine and Engineering University of Yamanashi Associate Professor b. Korean Principal Researcher Name Chang-Soo Park Institution / Department Position Department of Information and Communication systems Gwangju Institute of Science and Technology Professor 1

2 c. List of Japanese-side Participants (Except for Principal Researcher) Name Institution/Department Position Kenta Hosoya Interdisciplinary Graduate School of Medicine Ph.D. candidate and Engineering / National University Corporation, University of Yamanashi Wang Xiaoyang (until March 2010) Deng Yiquiang (until March 2010) Nguyen Van Minh Kohei Mori Kazuhiko Nakamura Research Associate d. List of Korean-side Participants (Except for Principal Researcher) Name Institution/Department Position Siewook Jeon Young Bok Kim Baek-Sang Han Soo Yong Jung Seung Heon Han Yongkyu Choi 2

3 5. Number of Exchanges during the Final Fiscal Year* a. from Japan to Korea *Japanese fiscal year begins April 1. Name Home Institution Duration Host Institution Masanori Hanawa University Yamanashi of From April 13 to April 14 Gwangju Institute of Science and Technology (Did not use this fund) Total: 1 persons Total: 2 man-days Numbers of Exchanges during the past fiscal years FY2008: Total 6 persons FY2009: Total 1 persons b. from Korea to Japan Name Home Institution Duration Host Institution Total: 0 persons Total: 0 man-days Numbers of Exchanges during the past fiscal years FY2008: Total 0 persons FY2009: Total 4 persons 3

4 6. Objective of Research In this project, we intended to develop a novel PON (Passive Optical Network) test bed for next generation high-speed/high-security FTTH (Fiber-To-The-Home) systems. It is intended to be based on WDM (Wavelength Division Multiplexing) and OCDM (Optical Code Division Multiplexing) technologies and also intended to have no expensive laser diodes in remote terminals (ONU: Optical Network Unit), which are placed in homes. There were several technical issues to realize such the WDM/OCDM hybrid PON system; the en/decoders for OCDM, transmission characteristics of WDM/OCDM hybrid signal, a cost-effective ONU configuration to be placed in homes, and so on. In the first proposal of this joint research project, the two research groups had agreed to develop a loopback system, which distributes source lights for uplink connection for ONUs from a center station (OLT: Optical Line Terminal); however it had to be changed later because of big losses of the optical encoders based on FBGs (Fiber Bragg Gratings). So we had rearranged our technical objectives of this joint research project as follows: 1) Develop OCDM en/decoders, which may be used in ONUs of a PON system 2) Develop cost effective ONU configuration, which does not requires any high cost optical devices 3) Test the transmission characteristics of WDM/OCDM hybrid signal through experiments The Japanese principle researcher and the Japanese-side participants were mainly responsible for development of the OCDM en/decoders, and partially took on development of the cost effective ONU configuration. On the other hand, the Korean-side team was mainly responsible for testing the WDM/OCDM hybrid transmission characteristics. Another and the most important objective of this joint research project was to form a tight and sustainable relationship between two research teams in both Japan and Korea through the division of roles. 4

5 7. Methodology The OCDM-PON systems need to have a pair of OCDM encoder and decoder in every ONU. The OCDM en/decoders are required to be compact, cost-effective and easily adapted into any codewords in the orthogonal code-set used. One of the most important and practical implementation method of the OCDM en/decoders are the use of FBGs. However, the conventional FBG based OCDM en/decoders have fabricated to implement the orthogonal codes used in the wireless CDMA systems, e.g. the maximum length sequences the Gold sequences, and the family A sequences, which require very long code length; therefore it is hard to make the encoders and decoders compact. In addition, because those orthogonal codes are not systematic, it is impossible to be adapted into different codewords after the fabrication. The well-known binary Hadamard sequences of length N give N orthogonal codewords, and allow us to realize compact encoders or decoders. Unfortunately, their aperiodic cross-correlation property is not preferable for OCDM systems. Therefore, we firstly proposed a novel multi-phase optical orthogonal code suitable for OCDM-PON systems, the Fourier code, which is based on the generalized Hadamard matrix. The Fourier code requires N phases for N orthogonal codes, but it allows us to realize compact, cost-effective and easy to be adapted en/decoders, while having better cross-correlation properties than the binary Hadamard codes. The Japanese team firstly investigated the correlation characteristics of the Fourier code numerically, then tested it experimentally with the lab-made FBG-based OCDM en/decoders. For the purpose we also developed a novel FBG fabrication technique by computing the phase structure of the fabricated FBGs using an adaptive algorithm, then tune the phase shifts between individual FBGs in the en/decoders as a batch process. In fact, we had proposed such a scheme before staring the joint research project, we had upgrade the phase structure estimation algorithm and developed a LabVIEW based easy-to-use FBG fabrication system. Secondly, we developed the PFVOC (programmable FBG-based variable optical correlator), which can be used as adaptable OCDM en/decoders. A N-chip PFVOC is possible to be adapted into any N-chip codeword just by clicking a button on the microcontroller board. The developed 4-chip PFVOC for the Fourier code were tested in the experimental room in the Japanese team with the two-channel OCDM setup. In our first plan, we intended to test the 4-chip en/decoders firstly, and then the 8-chip en/decoders. However, with the Fourier code, the longer the code length, the severer the phase error margin. Thus we proposed another novel orthogonal code, the concatenate code. With the concatenate coding, it is possible to suppress the number of phases required to configure longer codewords; thus we tested a 16-chip OCDM As a bonus, we also proposed and tested a simple and cost effective optical short pulse laser based on the RSOA (reflective semiconductor optical amplifier) and a FBG. It would be reported from the Korean team. 5