Recent progress on optical fiber amplifiers and their applications

Abstract

I review recent progress on optical fiber amplifiers and their applications in fiber-optic communication systems. This study focuses on rare-earth doped fiber amplifiers (RDFAs) and fiber Raman amplifiers (FRAs). There are three types of RDFA, namely erbium, thulium, and praseodymium doped fiber amplifiers (EDFAs, TDFAs, and PDFAs, respectively) and EDFAs have been widely deployed in trunk networks for about a decade. EDFAs have wideband, low noise, and high pumping efficiency characteristics, and are key components of high-capacity and cost-effective wavelength-division-multiplexing (WDM) transmission systems in the low loss 1.5 μm band. In contrast, distributed Raman amplification (DRA) has been recognized as a powerful and practical technology in long-haul trunk networks in recent years. DRA/EDFA or DRA/lumped FRA hybrid-amplification systems yield significantly higher signal-to-noise ratios than lumped optical amplification systems that use EDFAs or FRAs. The latter are hybrid systems called all-Raman systems. As regards the bandwidth enhancement of optical fiber amplifiers, which is indispensable for cost-effectively realizing a rapid increase in communication traffic, silica Raman amplifiers have seamless single band bandwidths (Δλ) up to ~100 nm wider than those of RDFAs (~30 to ~80 nm). Further bandwidth enhancement can be achieved by using tellurite-based Raman amplifiers with Δλ up to ~160 nm or multi-band amplifiers. Each multi-band amplifier uses plural single-band RDFAs and/or FRAs in the parallel configuration in the low loss wavelength region (1.3-1.6 μm band) of silica transmission fibers.