对现有放大自发辐射(ASE)光源与掺铒光纤放大器(EDFA)增益平坦的方法做了分析和讨论，采用双芯光纤和光纤波分复用(WDM)耦合器组合的方法设计了一种新的增益平坦滤波器。由于双芯光纤的传输谱特性可以通过弯曲、扭转以及拉伸等方式调节，从而这种全光纤的增益平坦滤波器具有实现简便、可调谐性好等优点，平坦化后的出射光谱在1527.36～1561.04 nm的带宽内只有±0.5 dB的起伏。结果表明，采用双芯光纤与其他器件一同制作的滤波器，在光通信与光纤传感领域有较大的应用前景。

Methods related to the design of gain flattening filters for amplified spontaneous emission (ASE) and erbium-doped fiber amplifier (EDFA) are reviewed. A novel scheme to realize the gain flattening filter by using a piece of twin-core fiber and a wavelength division multiplexing (WDM) coupler is proposed and verified experimentally. The spectrum of the twin-core fiber can be adjusted by bending, twisting and stretching to meet the filter requirement. The flexibility and tunable properties make the proposed all-fiber device a good candidate for gain flattening filter. The experimental results show that the ASE spectrum can be flattened in the wavelength region of 1527.36～1561.04 nm with ripples within ±0.5 dB. The results show the filters with twin-core fiber may offer great potential for optical communications and sensing applications.