THE MANUFACTURING OF AN OPTICAL-FIBER COUPLER BY THE FUSION ELONGATION METHOD

An optical fiber coupler is used for joining or splitting optical sign als at optical fiber branch points. It is an essential component for o ptical communication systems. Nowadays, telecommunication systems prov iders such as AT&T in America and NTT in Japan are in the process of i mplementing Fiber To The Home and Fiber To The Curb and therefore opti cal coupler will be in high demand in the near future. Special optical fibers such as polarization maintaining (PM) fiber also enjoy ever in creasing popularity as communication systems and fiber sensor become m ore sophisticated. Consequently optical fiber couplers made of PM fibe r will be in great demand. The fabrication of Phl fiber couplers is ei ther by the polishing method or by the fusion and elongation method. T he fabrication technique for the polishing type PM fiber coupler has w ell been developed. However, the properties of the epoxy resin used in a polishing type PM fiber coupler change with temperature and humidit y. Consequently, the characteristics of such coupler are also dependen t on temperature. This undesired characteristics has imposed severe li mitations of the use of the PM polishing type coupler. It is believed that Phl couplers made by the fusion and elongation method have a stea dy characteristics over a wide temperature range. This paper reports a method for the fabrication of Polarization-Maintaining (PM) Optical F iber Couplers using the fusion and elongation method and confirms that the characteristics of such PM couplers are stable over a temperature range of 110 degrees C. Moreover, the manufacturing time for the fusi on and elongation type coupler is reduced tremendously compared with t hat for the polishing type coupler. As the manufacturing time is reduc ed, the cost of production should proportionally be decreased. By appl ying this method, the manufacturing process could be fully automated a nd a high reliability product would be produced.