Two types of novel organic materials have been specifically developed for the fabrication of optical-communications systems devices. One is a UV-curable durable epoxy adhesive featuring refractive index controllability, low shrinkage during curing, and a low heat-expansion coefficient. These optically transparent adhesives are refractive index controllable between 1.45 and 1.59, and have been successfully applied to many optical devices that require return losses of more than 40 dB. The precision adhesives show an extremely low volume shrinkage of less than 2% during curing. The submicron positioning accuracy of these adhesives allows the fabrication of highperformance laser-diode modules and optical modulators. The other type of material is a fluorinated polyimide (F-PI) for optical waveguides; it features high optical transparency from visible to near-infrared and good heat resistance. Buried optical waveguides fabricated from F-PI operate in a single mode. They also exhibit a low loss of less than 0.3 dB/cm at the wavelength of 1.3 μm, and are heat and moisture resistant: the increase in optical loss is less than 5% after heating at 300°C for lh or after exposure to 85% relative humidity at 85°C for 24h.