设计并实现了一种双向掺铒光纤放大器(BEDFA)。采用完全对称的结构设计，消除了来回波长的增益竞争问题。为了克服双向自发辐射(ASE)噪声，将两个光滤波器通过光环形器插入到了掺铒光纤(EDF)中。同时结合了级联掺铒光纤放大器(EDFA)的优点，使增益得到了有效的提高。通过对比发现，该设计比市场上同成本的商用EDFA增益要高5 dB。经过测试，该EDFA的有效增益达到了38 dB，噪声系数在5 dB左右，适合当前的密集型光波复用(DWDM)应用。如采用外接光滤波器，则其灵活性更适合实验室使用。

A bidirectional erbium-doped optical fiber amplifier (BEDFA) has been designed and realized. The symmetrical structure avoids the competition of signals come-and-go. Two optical filters have been inserted into the erbium-doped optical fiber (EDF) by optical circulars to eliminate the amplified spontaneous emission (ASE). So the two-stage structure was adopted and the gain was improved by 5 dB higher than the erbium-doped optical fiber amplifier (EDFA) in the market with same component. It was indicated by measurement that the signal gain achieved 30 dB with noise coefficient of 5 dB, which was appropriate for the dense wavelength division multiplexing (DWDM). If the optical fiber was out-placed, the flexibility was very suitable to the laboratory applications.