New approach for high reliability, low loss splicing between silica and ZBLAN fibers

摘要

In the past decade, ZBLAN(ZrF4-BaF2-LaF3-NaF)fibers have drawn increasing interest for laser operations at wavelengths where Fused Silica-based(SiO_2)fibers do not perform well. One limitation to the expansion of ZBLAN fiber lasers today is the difficulty to efficiently inject and extract light in/from the guiding medium using SiO_2 fibers. Although free space and butt coupling have provided acceptable results, consistent and long lasting physical joints between SiO_2 and ZBLAN fibers will allow smaller, cheaper, and more robust component manufacturing. While low loss splices have been reported using a traditional splicing approach, the very low mechanical strength of the joint makes it difficult to scale. Difficulties in achieving a strong bond are mainly due to the large difference of transition temperature between ZBLAN and SiO_2 fibers(~260°CC vs~1175°C). This paper presents results obtained by using the high thermal expansion coefficient of the ZBLAN fiber to encapsulate a smaller SiO_2 fiber. A CO2 laser glass processing system was used to control the expansion and contraction of the ZBLAN material during the splicing process for optimum reliability. This method produced splices between 125μm ZBLAN to 80μm SiO_2 fibers with average transmission loss of 0.225dB (measured at 1550nm)and average ultimate tension strength of 121.4gf. The Resulting splices can be durably packaged without excessive care. Other combinations using 125μm SiO_2 fibers tapered to 80μm are also discussed.