High power dual-wavelength tunable fiber laser in linear and ring cavity configurations

Abstract

We describe and compare the performances of two crucial configurations for a tunable dual-wavelength fiber laser, namely, the linear and ring configurations. The performances of these two cavities and the tunability in the dual-wavelength output varied from 0.8 to 11.9 nm are characterized. The ring cavity provides a better performance, achieving an average output power of 0.5 dBm, with a power fluctuation of only 1.1 dB and a signal-to-noise ratio (SNR) of 66 dB. Moreover, the ring cavity has minimal or no background amplified spontaneous emission (ASE).OCIS codes: 060.2320060. , 060.2410 Dual-wavelength tunable fiber lasers (DWTFLs) are relevant to the provision of a stable and tunable dual wavelength output that can be used in many applications, such as the study of high-bit-rate soliton pulses [1] , differential absorption measurement of trace gases [2] , photonic generation of microwave carriers [3] , and microwave photonic filters [4] . Initial research into the development of dualwavelength fiber lasers has been limited by the inability to generate a high power lasing output. This limitation was caused by the effect of mode competition between the closely spaced wavelengths; resulting in the domination of the longer wavelength over the shorter wavelength. The mode competition itself is largely caused by the homogenous broadening effect in erbium-doped fibers (EDFs), which are normally used as the gain media for fiber-based dual-wavelength sources. To overcome the effect of the homogenous broadening in EDF-based dual-wavelength fiber laser sources, various methods have been proposed, including the cooling of the EDF in liquid nitrogen [5,6] by using elliptical EDFs [7] or by incorporating polarization maintaining fiber Bragg gratings (FBGs) for wavelength selection [8] , utilizing frequency shifter in the cavity [9] , and many other methods [10−13] . The key ability which is sought after in the development of a DWFTL is repeatability. Generally, multiwavelength output generated using FBGs as filters to select specific wavelengths provide tunabilty by adjusting the strain or compression that the FBG contends with because of the repeatability issue. The reason is the difficulty to revert to the original position to produce the previous wavelength once the FBG has been modified to select a new wavelength. This problem can be overcome using a filter mechanism with a series of pre-determined wavelengths, such as an arrayed waveguide grating (AWG), as proposed in this letter.In addition, the cavity configuration plays an important role in the generation of a high-powered output with a good signal-to-noise ratio (SNR). Numerous configurations have been proposed to generate DWFLs, such as linear cavities [14,15] , ring cavities [16,17] , and sigma cavity configuration [18] . This is in line with the growing research interest in the generation of high-powered DWFLs for applications such as wavelength conversion using four wave mixing (FWM) [19] , generation of microwave signals [20] , and generation of terahertz w...

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