Gain- and noise-figure improvement of a reflective L-band EDFA by using a short length of preamplification EDF

Abstract

[2,5]. The advantage of the SA techniques is the ability to provide variations to the CLS method for differing sidelobe topographies. The edge brightening that appeared in the amplitude distributions obtained using the SA approach can be reduced by adding a corresponding term in the cost function of Eq. (3), thus penalizing that behavior. Nevertheless, this is of concern with regard to the implementation of other kinds of excitation distributions analogous to Taylor's (such as, for example, the one in a work elaborated upon by Rhodes [6]). In that case, the amplitude distributions behave very similarly to those obtained using the CLS implementation, with a central segment and flanking monotonic decaying curves, as was verified by the authors via inspection of some the results not shown here for brevity. As straightforward extensions of the methods, circular continuous sources and -symmetrical arrays are under consideration by some of the authors in a recent paper [7]. ACKNOWLEDGMENTSThis work was supported in part by the National Science Foundation NSF Grant ECS-0098547 and by the Spanish Ministry of Science and Technology under project no. TIC2002-04084-C03-02. As the natural extension for increasing the transmission capacity of a wavelength division multiplexing (WDM) system, long-wavelength-band erbium-doped fiber amplifiers (L-band EDFAs) has become the subject of extensive studies [1,2]. Nevertheless, since the L-band is far from the gain peak of silica-based erbium-doped fiber (EDF), the gain coefficient of the L-band is much lower than that of the conventional C-band by a factor of 10, approximately [3]. In recent years, much effort has been made to enhance the amplification characteristics in the L-band [4 -8]. One of the most promising amplifier schemes to realize high gain in the L-band is the double-pass configuration [6]. The double-pass L-band EDFA provides significant enhancement to the amplifier gain. And a reflective L-band EDFA with a simpler and economized structure was also proposed in [8]. However, in such a scheme the amplified spontaneous emission (ASE) is reflected back into the EDF together with the signal light, which leads to relatively high noise figure. GAIN-AND NOISE-FIGURE IMPROVEMENT OF A REFLECTIVE L-BAND EDFA BY USING A SHORT LENGTH OF PREAMPLIFICATION EDFIn this paper, a reflective L-band EDFA with improved noise figure is achieved by utilizing a section of forward-pumped shortlength EDF to increase the Er 3ϩ inversion level at the input part of the amplifier. The experimental results show that the L-band EDFA with preamplification EDF has much higher gain and lower noise figure than the conventional design without the first stage. Moreover, the saturation output power under different prestage pump powers is also investigated. CONFIGURATION AND OPERATION PRINCIPLEThe basic configuration of our novel L-band EDFA structure is shown in Figure 1. This amplifier is composed of two stages. In the first stage, a 980-nm laser diode (LD) is used as the pump source and EDF1 has an absor...

Gain improvement in L-band double-pass EDFA with incorporated CFBG

“…It is viewed as a natural extension for conventional band (C-Band) EDFA as it increases the overall capacity of wavelength division multiplexing (WDM) communication system [1][2][3][4][5]. Chirped fiber Bragg grating (CFBG) has been used as a reflector to create C band double-pass EDFAs [6,7].…”