Long-Wavelength-Band Optical Amplifiers Employing Silica-Based Erbium Doped Fibers Designed for Wavelength Division Multiplexing Systems and Networks

Motoki KAKUI  Shinji ISHIKAWA  

IEICE TRANSACTIONS on Electronics   Vol.E83-C   No.6   pp.799-815
Publication Date: 2000/06/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: INVITED PAPER (Special Issue on Advanced Optical Devices for Next Generation High-Speed Communication Systems and Photonic Networks)
Category: Fibers
wavelength-division-multiplexing,  optical amplification,  erbium-doped fiber,  1580 nm,  L-band,  

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Wavelength-division multiplexing (WDM) technique employing broadband erbium-doped fiber amplifiers (EDFAs) is considered to be the most effective solution to respond to the increasing demand for transmission capacity. As a means to extend the optical bandwidth outside the conventional band (C-band) ranging from 1530 to 1565 nm, silica-based EDFAs (EDSFAs) operating within the long-wavelength band (L-band) ranging form 1570 to 1600 nm seem to be the most attractive candidate because they can be composed of the same material as C-band EDSFAs, i. e. silica-based Al codoped EDF. However, there exist several discrepancies between C-band and L-band EDSFAs which originate inevitably from the difference in the inversion level and the band location. This paper reviews the basic characteristics of L-band EDSFAs, which have been a controversial issue for practical application of the L-band EDSFAs, such as required EDSF lengths, power conversion efficiency, noise performances, and optical bandwidth. We will also describe L-band EDSFAs' behavior under circumstantial changes, such as the variation of the span-loss, the temperature of the EDSF, and the number of wavelengths, which are expected in the field WDM systems. The dynamic-gain-tilt and temperature-induced change in the gain spectra of L-band EDSFAs are more significant than those of C-band EDSFAs are. Moreover, L-band EDSFAs exhibit a greater apparent inhomogeneous broadening effect, which may hinder the precise gain control when the number of wavelengths is dynamically changed. All of these characteristics must be considered for future designs of broadband WDM networks.