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An Efficient and Low Noise L-band Erbium-Doped Fiber Amplifier

Introduction The use of the long-wavelength-band (Lband) is attractive for both increasing the capacity of wavelength division multiplexing (WDM) systems and has been used in WDM transmission experiments at over 1 Tb/s. Recently, a gain bandwidth of about 80nm has been achieved by integrating the L-band EDFA in parallel with conventional band (Cband) EDFA [1]. Moreover, the L-band EDFAs will make it possible to construct an effective WDM systems employing dispersion-shifted fiber (DSF) without the degradation caused by four-wave-mixing (FWM) [2]. The L-band erbium-doped fiber amplifier (EDFA) is studied because it can be constructed by silica-based erbium-doped fiber (EDF) and has a low linearity for WDM signals. However, L-band EDFAs have a low power conversion efficiency (PCE) compared to a C-band. Therefore, a double-pass L-band EDFA has been introduced to enhance the gain in this region [3]. Besides gain improvement, L-band EDFAs for WDM system must also be able to manage gain variation due to dynamic add/drop or abrupt failure in the system. To stabilize the gain, various techniques applying the ring laser have been investigated for single-pass EDFA [4-5]. In this letter, a novel and simple configuration of gain-clamped double-pass Lband EDFA is proposed and demonstrated using a ring resonator.