由组合波导理论出发，分析了超长耦合器耦合区内光纤间的功率耦合特性以及器件的偏振特性，并提出了研制二波段窄波分单模光纤波分复用器的新方法。在研制常规耦合器的工艺基础上，先后研制成功1310 nm或1550 nm单窗口窄带波分复用器及1310 nm和1550 nm双窗口等三种复用间隔约14 nm的窄带波分复用器，其波长隔离度大于20 dB，具有2～3 nm的带宽。偏振灵敏度小于0.1 dB，附加损耗小于0.5 dB。这些参数是迄今为止所报道的有关窄带波分复用器的最好结果。

On the base of the composited waveguide theory, the characteristics of coupled optical power and poarization in the coupling region of a overlong coupler have been analyzed, and a new mothed to fabricate single mode optical fiber dual window narrowband wavelength division multiplexers(NWDM) is proposed and demonstrated experimentlly. Three fabricated devices, operating at 1300 nm, 1550 nm mono window, and 1300 nm/1550 nm dual window, respectively, show spacing channel of 14 nm, channel bandwidth of 2～3 nm, adjacent channel isolation 20 dB, <0.1 dB polrization sensitivity, and <0.5 dB optical loss. These specifications are the best performances reported to-date for the NWDMs.