We developed the bidirectional optical transceiver module that combined the two LED light sources of different wavelength and three-dimensional (3-D) optical waveguides. By using a light-induced self-written (LISW) technique, we fabricated and tested 3-D optical waveguide circuits for a plastic optical fiber (POF) WDM full-duplex communication module. Because of the large diameter of the POF, an optical waveguide has the advantages, as compared to conventional lens based modules, of a small size and optical low-loss features. The LISW waveguide enables optical components to connect automatically even if the circuit in the module is complex. In this paper, we demonstrate newly developed bidirectional WDM optical module containing 3-D optical circuits, i.e. a branching waveguide and a reflection waveguide, and their optical properties. The module using commercially available green and red LED was constructed and the two-way communication on IEEE1394-S100 (125Mbps) protocol was verified through 10m-length of POF.
Data links incorporating a green light source at 520nm are required for use with polymethyl methacrylate (PMMA) plastic optical fiber (POF) systems because they have a lower attenuation coefficient compared with conventional red light sources at 650nm. Recently, green LEDs have been developed based on Gallium Nitride (GaN) materials, and high optical output power GaN green LED lamps are now commercially available for general use in display applications. In this paper, we describe in detail the fundamental characteristics of these GaN green LEDs that are due to be employed in POF data links. We evaluate the temperature coefficients of the optical output power and the center wavelength shift and also demonstrate a green LED POF data link that complies with IEEE 1394 S100 operation. GaN green LEDs seem to be promising candidates as light sources for the next generation of POF data links for automotive applications or for long distance In-house multimedia networks. This is because, as we will show, they can operate both at high temperatures and with reduced temperature sensitivity compared with red LEDs fabricated from AlGaInP materials.
We developed a novel fiber laser Doppler velocimeter (FLDV) using an integrated optical frequency shifter on LiNbO3 substrate. The FLDV system consists of a small probe-head (diameter of 17 mm and length of 60 mm) with two polarization maintaining fibers for projection and one single mode fiber for detection. The FLDV system can measure the line velocity of two-dimensional vectorial flow by only one probe tilted against the direction of the flow. We will describe the construction of the measurement system and the measurements of actual velocities. Two vectorial components of the line velocity were obtained from the calculations between the interference signals detected on a photo-detector.
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