Gain Equalization of Erbium Doped Fibre Amplifiers with Long Period Gratings
Gain Equalization of Erbium Doped Fibre Amplifiers with Tuneable Long-Period Gratings
Thabiso J. Nhlapo, Pieter L. Swart, and Anatoli A. Chtcherbakov Centre for Optical Communications and Sensors Faculty of Engineering, Rand Afrikaans University PO Box 524, Auckland Park 2006, South Africa
Abstract-This paper presents an adaptive gain equalization technique of the gain spectrum for an Erbium Doped Fibre Amplifier (EDFA) by using a tuneable Long-Period Grating ) (LPG). The gain spectrum of an EDFA at a wavelength of ) 1530nm was equalized from 5.2dB peak-to-peak to 2.3dB peak-to-peak. The LPG was fabricated by using an excimer laser and a metal mask. By means of a novel technique that enables one to tune the peak attenuation of the LPG, the gain equalizer can operate over a wide range of pump power. Index Terms-Erbium Doped Fiber Amplifier, Long-Period Grating, Gain Equalization, Wavelength-Division Multiplexing.
II. EDFA CHARACTERIZATION A. Optical Amplification by Erbium-Doped Fibres
I. INTRODUCTION
G
ain equalization of EDFAs has been a research topic in recent years with the development of high capacity WDM optical communication systems. The EDFA has been considered to be a key device in WDM transmission systems for fiber loss compensation and for the provision of an optical network with almost unlimited coverage [1]. However, the EDFA has a non-uniform gain spectrum that restricts its usable amplifier bandwidth. The amplification of a WDM signal by a non-equalized EDFA may result in signal distortion and poor signal-to-noise ratio performance. Several methods, either intrinsic or extrinsic, have been proposed to equalize the EDFA gain spectrum. Intrinsic methods constitute changing the spectroscopic properties of the erbium-doped glass absorption and emission crosssection by co-doping with other ions, or by using different glass matrices or special fibre designs. Alumino-silicate [2] or fluoride based glass [3] are known to improve the flatness of
Thabiso J. Nhlapo, Pieter L. Swart, and Anatoli A. Chtcherbakov Centre for Optical Communications and Sensors Faculty of Engineering, Rand Afrikaans University PO Box 524, Auckland Park 2006, South Africa
Abstract-This paper presents an adaptive gain equalization technique of the gain spectrum for an Erbium Doped Fibre Amplifier (EDFA) by using a tuneable Long-Period Grating ) (LPG). The gain spectrum of an EDFA at a wavelength of ) 1530nm was equalized from 5.2dB peak-to-peak to 2.3dB peak-to-peak. The LPG was fabricated by using an excimer laser and a metal mask. By means of a novel technique that enables one to tune the peak attenuation of the LPG, the gain equalizer can operate over a wide range of pump power. Index Terms-Erbium Doped Fiber Amplifier, Long-Period Grating, Gain Equalization, Wavelength-Division Multiplexing.
II. EDFA CHARACTERIZATION A. Optical Amplification by Erbium-Doped Fibres
I. INTRODUCTION
G
ain equalization of EDFAs has been a research topic in recent years with the development of high capacity WDM optical communication systems. The EDFA has been considered to be a key device in WDM transmission systems for fiber loss compensation and for the provision of an optical network with almost unlimited coverage [1]. However, the EDFA has a non-uniform gain spectrum that restricts its usable amplifier bandwidth. The amplification of a WDM signal by a non-equalized EDFA may result in signal distortion and poor signal-to-noise ratio performance. Several methods, either intrinsic or extrinsic, have been proposed to equalize the EDFA gain spectrum. Intrinsic methods constitute changing the spectroscopic properties of the erbium-doped glass absorption and emission crosssection by co-doping with other ions, or by using different glass matrices or special fibre designs. Alumino-silicate [2] or fluoride based glass [3] are known to improve the flatness of
References: [1] [2] J. M. P. Delavaux and J. A. Nagel, ”Multistage erbium-doped fiber amplifier designs,” J. Lightwave Technol., vol. 13, pp703-720, 1995. T. Tehara, T. Naito, N. Shimojoh, T. Tanaka, T. Chikama, and M. Suyama, “0.7 Tbists/s(66x10.66Gbits/s) WDM transmission over 2212km using broadband, high-power EDFA’s with pump reflector,” Electron. Lett., vol. 34, no. 10, pp. 1001-1002, 1998. M. Yamada, O. Hirotaka, T. Kanamori, T. Sakamoto, Y. Ohishi, and S. Sudo, “A low noise and gain-flattened amplifier composed of a silica-based and a fluoride-based Er3+ doped fiber amplifier in a cascade configuration,” IEEE Photon. Technol. Lett., vol. 8, pp. 620622, May 1996. [3] Thabiso J. Nhlapo received his National Diploma in Mechanical Engineering from Peninsula Technikon in 1996. He received his B.Ing degree in Electrical and Electronic Engineering from Rand Afrikaans University in 2001. He is now doing a research towards his M. Ing degree at the Centre for Optical Communications and Sensors in the Faculty of Engineering at RAU. His interests are in the areas of optical communication, optical fiber technology, and fabrication of optical devices and components.