实验验证了一种结构简单、变换效率高的可调谐偏振不敏感全光波长变换器。光子晶体光纤由于其特殊的纤芯结构，能够保有较高的双折射效应。通过调节抽运光的偏振态,使之与光子晶体光纤的双折射轴成45°夹角入射,则此时信号光与抽运光在光子晶体光纤中进行简并四波混频过程时，其变换效率对信号光偏振态的随机变化不敏感,闲频光输出功率几乎保持不变。实验结果表明,所搭建的全光波长变换器在25 nm变换范围内,闲频光偏振敏感度低于0.6 dB,变换效率优于-15 dB(峰值可达-7.6 dB), 输出闲频光的光信噪比优于40 dB，长时间工作性能稳定，可实现开机自启动，是一种实用性强的偏振不敏感全光波长变换器。

A high-efficiency tunable polarization-insensitive all-optical wavelength convertor for 10 Gb/s return-to-zero on-off keying (RZ-OOK) signals using degenerate four-wave mixing (FWM) in a highly nonlinear photonic crystal fiber (PCF) is demonstrated. The residual birefringence in the 50 m dispersion-flattened PCF with 11 W-1·km-1 nonlinear coefficient guarantees the FWM-based wavelength conversion to be polarization-insensitive when the pump polarization is exactly at 45°to the birefringent axes of the PCF. Experimental results show that with 45°pump launch, the polarization dependence of FWM in the PCF can be decreased to less than 0.6 dB over the entire 25 nm conversion bandwidth. The optical signal-to-noise ratios (OSNR) of the converted signals are better than 40 dB and the conversion efficiencies are better than -15 dB over the conversion range with 10 Gb/s signal polarization-scrambled.