Fiber filter has important applications in fiber sensor and optical fiber communication system. Especially, filter with all-fiber structure and tunable wavelength spacing is worth studying due to its unique characteristics. A polarization-independent all-fiber birefringent filter with adjustable wavelength spacing is proposed. The apparatus consists of a polarization beam splitter (PBS) , two sections of polarization-maintaining fiber (PMF), and four half-wave plates (HWPs). The theoretical analysis shows that it operates as a polarization-independent multi-wavelength filter with good channel isolation and adjustable wavelength spacing by controlling the four HWPs in the loop. This filter is applicable for flexible multi-wavelength fiber laser and other optical fiber systems.%设计了一种新的便于调谐且波长间隔可调的全光纤双折射滤波器.该滤波器由一个偏振分束器(PBS),2段保偏光纤(PMFs)和4个二分之一波片(HWPs)连接而成.计算并分析了它的理论结果,发现在合理调节环中4个二分之一波片的情况下,该滤波器除了可以获得有很好的滤波光谱输出之外,还具有波长间隔可调的作用.这种滤波器在设计可灵活改变波长间隔的多波长光纤激光器及光纤系统等方面具有巨大的应用前景.
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