Research on Design and Measurement Techniques for Optical Fiber Cables

Relationship between optical loss and parameter A (= outer diameter/core diameter) for graded-index multimode optical fiber

Fig.1 Relationship between optical loss and parameter A (= outer diameter/core diameter) for graded-index multimode optical fiber

Examples of optical fiber and optical fiber cable structure

Fig.2 Examples of optical fiber and optical fiber cable structure

Equi-loss curve of one repeater section for single-mode optical fiber

Fig.3 Equi-loss curve of one repeater section for single-mode optical fiber

    Since optical transmission systems had been developed for practical use, they were introduced rapidly into many public communication networks. Beginning with the long-haul trunk optical transmission system between Asahikawa and Kagoshima, which was completed in February 1985, these systems have been deployed in many major transmission lines in Japan.

    For the practical application of optical transmission systems, developments of various types of equipment and devices were required, such as optical fiber cables, light sources, optical receivers and repeaters. As for the optical fiber cables, it was essential to develop low loss optical fiber fabrication technologies, as well as an optical fiber cable design and manufacturing techniques that provided high reliability and high quality while maintaining the transmission characteristics of the optical fiber itself.

    Organized research and development aimed at the practical application of optical transmission systems started in around 1975, and the key technologies progressed considerably since then. Such technologies were integrated to the practical systems, and the systems were introduced into public telecommunication networks started in 1981.

    As for optical fiber cable technology, research on the transmission characteristics of multimode optical fiber, cable design and related measurement techniques started in around 1975. At that time, considerably low loss optical fiber had already been obtainable as a result of the progress in fabrication technology of optical fiber with a low OH content. Thus, it was essential to establish cable structural design technologies that would maintain the optical fiber low loss characteristics against bending and lateral pressure occurring during cable manufacture, installation, and long-term use. To achieve the above, it was necessary to determine the optimum optical fiber parameters and thus to avoid any loss increase, despite the presence of the bending and the lateral pressure. In addition, it was required to establish the structural design of the cable, in which the fiber suffered the minimal extent of bending, lateral pressure and tension.

    The optimum fiber parameters were determined after the investigations of the transmission, mechanical and connection characteristics and fiber productivity. The optimum graded-index multimode fiber parameters thus determined were recognized as the standard values in Japan. Furthermore, they were accepted as international standard by CCITT (the former name of ITU-T). In addition, the standard optical fiber cable structure was determined based on mechanical structure analysis and long-term reliability theory, and was used in the initial stage for public transmission lines.

    Techniques for measuring optical fiber transmission characteristics in the laboratory and factory, and also in the field were significant in terms of practical use. The basic transmission characteristics, i.e. optical loss and baseband frequency response of graded-index multimode fiber, depend strongly on the modal distribution excited in fiber. Therefore, the specification for the mode launching condition was essential and various mode launching conditions were investigated both theoretically and experimentally. As a result, a steady state launching method using a G-S-G exciter for loss measurements, and a uniform mode power distribution launching method using an S-G-S exciter for baseband frequency response measurements were developed. Furthermore, the cut back method was established as a standard method for measuring optical loss, and the optical time domain reflectometer was developed, which was the powerful equipment for fiber fault location and optical loss measurement along the fiber.

    In around 1979, research and development started on single-mode optical fiber cable for practical use, following the development of graded-index multimode optical fiber cable. The necessary condition for the single-mode optical fiber is that only the fundamental mode propagates regardless of the refractive index profile of the core. This led to the proposal of a specification that consisted of the mode field diameter and effective cutoff wavelength instead of the conventional specification, represented by the core diameter and relative refractive index difference. Specific parameter values were then determined, and were accepted as international standard values. In addition, techniques for measuring the mode field diameter and effective cutoff wavelength were developed and standardized, and an optical time domain reflectometer for single-mode optical fiber was also developed in 1982. These technologies were immediately introduced in the NTT’s long-haul trunk optical transmission systems of 400 Mbit/s, including that installed between Asahikawa and Kagoshima.

    In 1985, the Institute of Electronics, Information and Communication Engineers presented their Achievement Award to Naoya Uchida, Masamitsu Tokuda and Shigeyuki Seikai for the practical application of optical fiber cable and the related measurement technologies.



Publications

[1] M. Tateda, T. Horiguchi, M. Tokuda, N. Uchida、Optical loss measurement in graded-index fiber using a dummy fiber、1979、Appl. Opt., Vol.18, No.19
[2] S. Seikai, M. Tateda, K. Kitayama, N. Uchida、Optimaization of multimode graded-index fiber paramaters: design considerations、1980、Appl. Opt., Vol.19, No.16
[3] T. Nakahara, N. Uchida、Optical cable design and characterization in Japan、1980、Proc. IEEE, Vol.68, No.10
[4] Y. Kato, K. Kitayama, S. Seikai, N. Uchida、Effective cutoff wavelength of the LP11 mode in single-mode fiber cables、1981、IEEE J. Quantum Electron., Vol.QE-17, No.1
[5] M. Nakazawa, T. Tanifuji, M. Tokuda, N. Uchida、Photon probe fault locator for single-mode optical fiber using an acoustooptical light deflector、1981、IEEE J. Quantum Electron., Vol.QE-17, No.7
[6] Y. Mitsunaga,Y. Katsuyama,H. Kobayashi,Y. Ishida、Failure prediction for long length optical fiber based on proof testing、1982、J. Appl. Phys., vol.53, No.7
[7] K. Kitayama, Y. Kato, M. Ohashi, Y. Ishida,N. Uchida、Design cinsiderations for the structural optimaization of a single-mode fiber、1983、J. Lightwave Technol., Vol.LT-1, No.2
[8] M. Ohashi, K. Kitayama, Y. Koyamada, N. Uchida,S. Seikai、Design of multimode graded-index fiber parameters in the long-wavelength region、1984、Appl. Opt., Vol.23, No.11
[9] N. Uchida、Development and future prospect of optical fiber、2002、IEICE Trans. Electron., Vol.E85-C, No.4

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Communication
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1986
Big nuclear accident occurred in Chernobyl nuclear power plant. (USSR)
1986
Law on equal jop opportunities for men and women was enforced.
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