Low-Loss and Low-Nonlinearity Pure-Silica-Core Fiber for Large Capacity Transmission

To keep up with the exponential growth of data network traffic, large transmission capacity per a fiber is strongly needed for optical communication systems. Recent progress in the transmission capacity mainly relies on multi-level modulation techniques with digital coherent detection. However, the larger capacity transmission over long distance requires higher optical signal-to-noise ratio (OSNR)(1). Although there would be several techniques to improve the OSNR, the use of low-loss and low-nonlinearity fiber would be one of the most effective solutions to improve the OSNR(2). Pure-silica-core fiber (PSCF), which has been known to have inherently low attenuation(3), would be a promising candidate for the low-loss and low-nonlinearity fiber. Since 1980’s(4), Sumitomo Electric Industries, Ltd. has continuously developed and proposed several types of PSCFs(5)-(9), including a record-low attenuation PSCF(5). In fact, Sumitomo Electric has supplied PSCF products, Z Fiber and ZPLUS Fiber for many years to submarine optical fiber cable industries by virtue of the low attenuation. However, there is a continuous need for lower attenuation and lower nonlinearity of fiber to realize further large capacity transmission over long distance. This is by no means a particular requirement for submarine applications. With the growing demand for the large volume of data traffic, OSNR improvement with low-loss and low-nonlinearity fiber would become increasingly important for terrestrial long haul applications as well. In this paper, we first show that requirement for optical fibers have been dramatically changed to low loss and low nonlinearity. Then, we introduce Z-PLUS Fiber LL with lower attenuation and Z-PLUS Fiber 130 with lower nonlinearity as improved submarine PSCFs. Terrestrial PSCFs, PureAdvance-80 and PureAdvance-110 are also newly developed to support terrestrial long haul systems. In addition, we quantitatively discuss the impact on OSNR improvement of the low-loss and low-nonlinearity PSCFs, and present possible benefits for terrestrial long haul systems in views of the increase of span length or transmission distances. 2. OSNR Improvement with Low-Loss and Low-Nonlinearity Fiber