94 The Open Optics Journal, 2008, 2, 94-99 1874-3285/08 2008 Bentham Open Open Access Fabrication of Integrated Optical Mode Field Adapters at the End of Single/Multimode Fibers Using Fiber Splicing Machine U.H.P. Fischer * , T. Windel, S. Hemrungrote and V. Giannoglou Harz University of Applied Sciences, Friedrichstr. 57, 38855 Wernigerode, Germany Abstract: In this paper we present the fabrication of optical mode field adaptors for fiber optical communications using fiber splicing machine in special newly developed modus. We developed mode field transformers with radii from 5 m to 80 m the end of standard singlemode and multimode glass fibers, characterized by far field and near field methods. Easy and reliable fabrication of the radii with low standard deviation  = 0.16-0.97 m or better than 3,2% relative to the mean radius has been achieved. Keywords: Fiber-chip coupling, fiber tapers, lensed fibers, optical mode field adaptation, integrated optical mode field trans- formers. 1. INTRODUCTION The demand for high-speed digital communication such as data, video, and the broadband internet increases, the re- quired throughput of the modules in communication systems will also increase [1]. Fast transmitter and receiver modules are basic elements of these systems, which should be able to transmit terabits/s of information via the fiber. Such tech- nologies in turn rely strongly on advanced opto- electronically technologies, and the progress made in inte- grated optics. With rapidly increasing market demand for the use of these technologies and access to the information highway, the next challenge in optical communications is to provide high coupling efficiency in stable modules at afford- able prices [2]. 2. OEIC-FIBER COUPLING One important item in all optical transmission systems is the necessity to couple a maximum amount of light from a *Address correspondence to this author at the Harz University of Applied Sciences, Friedrichstr. 57, D-38855 Wernigerode, Germany; Tel: +49 3943 659351; Fax: +49 3943 659399; E-mail: ufischerhirchert@hs-harz.de single mode laser diode into a standard monomode fiber (SMF). Additionally, the coupling from SMF into photo di- odes and the coupling of light from/into SMF to passive waveguides in InP or GaAs devices must be performed with high efficiency. For low cost coupling a butt fiber is normally used, which is fixed with glue in front of the opto-electronic inte- grated circuit (OEIC) facet. For lasers and passive waveguides this technique allows only 10-15% coupling efficiency because of the great mode field mismatch between butt ended cleaved standard SMF and integrated waveguides (Fig. 1). Saruwatari has shown the analytical calculation of the SMF to OEIC coupling problem in detail [3, 4]. The optical power distribution of the propagating lightwave can be ex- pressed nearly perfect by a Gaussian function. The normal- ized frequency V of the optical singlemode distributing wave in the SMF has therefore only small variety between 1.9 and 2.4. Using this Gaussian approximation [5] it can be shown that the coupling efficiency between two single mode waveguides is a function of the width of the propagating wave, called w 0 . Fig. (1). Optical far field of SMF and laser diodes.