Tunable Range Investigation at Different EDFA Locations on Single-wavelength Brillouin- Erbium Fiber Laser Nor Azura Malini A. Hambali*, Mohd Adzir Mahdi**, Mohammed Hayder Al-Mansoori, Mohammed Ajiya, Shee Yu Gang, Photonics Laboratory, Department of Computer and Communication Systems Engineering, Faculty of Engineering, University Putra Malaysia, 43400 UPM Serdang, Selangor, MALAYSIA. *norazura_malini@yahoo.com **e-mail: adzir@ieee.org ABSTRACT We have investigated the effect of the self-lasing cavity modes on the tuning range of a single wavelength Brillouin- erbium fiber laser (BEFL) at three different Erbium-doped fiber amplifier (EDFA) locations. The experimental results show that the location of EDFA before the Brillouin gain medium where by the Brillouin pump power is pre- amplified by the EDFA has greatest tuning range with absence of the self-lasing cavity modes. By fixing the Brillouin pump at 6.0 dBm, the tuning range of 34.08 nm was obtained with wavelength tunability from 1530.50 nm to 1564.50 nm. Keyword: Brillouin fiber laser, stimulated Brillouin scattering, EDFA, Ring cavity. INTRODUCTION Brillouin fiber laser (BFL) with narrow linewidth property has been useful for many applications. However, with small coefficient of the Brillioun gain, it is difficult to achieve efficient operation of BFL with its own cavity [1]. Thus, the Brillouin gain must be integrated with other amplifying medium to allow large output powers and to avoid the requirement for critically coupled resonator. Brillouin-erbium fiber laser (BEFL) operated in a ring cavity resonator with combination the two gain medium, Brillouin gain as used in the BFL with gain from erbium-doped fiber (EDF) to create fiber laser with reasonable output powers [2-3]. The linear gain of the EDF contributes the majority of the output power [4]. On the other hand, the nonlinear Brillouin gain in optical fiber (SMF) provided additional gain requirement to the BEFL. With Brillouin pump (BP) power injected into the fiber, the Brillouin Stokes are generated in the opposite direction to the BP propagation at a wavelength downshifted by 0.08 nm (10 GHz) form the BP wavelength [4]. In order to increase the efficiency in the BEFL, the elimination of the self-lasing cavity modes becomes an important issue. Owing to the self-lasing cavity mode, the tuning range of BEFL is limited. The tuning range in the BELF is defined as the range of BP wavelength which produces the Stoke signal in the absence of the self-lasing cavity modes [5-6]. The wide tuning range without appearances of the self-lasing cavity modes in the laser system has potential in dense wavelength division multiplexing communication systems [7]. In this paper, we propose and experimentally demonstrated the effect of EDFA location on the tuning range of a single wavelength ring cavity BEFL configurations. Based on the experimental findings, the tuning range of BEFL depends on the external BP power and the locations of the EDFA within the laser cavity. High external BP power with pre-amplification by EDFA before entering the Brillouin gain medium suppresses the self-lasing cavity modes and improves the laser tunability.