损耗是传统光纤和光子晶体光纤得以实用化的重要参量之一，降低损耗是光子晶体光纤制备的首要问题。折射率引导型光子晶体光纤的损耗由1999年的240 dB/km降至0.28 dB/km(1550 nm波长处)，光子带隙型光子晶体光纤的损耗也降低到1.2 dB/km(1620 nm波长处)。在对比传统石英光纤损耗来源基础上，阐述了光子晶体光纤的损耗机理，并说明了损耗降低的主要途径。

It is well known that loss is an important parameter for both conventional fiber and photonic crystal fiber(PCF). The loss of index-guiding PCF was 240 dB/km in 1999, with the development of fabrication technology, the loss has been reduced rapidly. It is only 0.28 dB/km at 1550 nm wavelength for index-guiding PCFs, while it is only 1.2 dB/km at 1620 nm wavelength for photonic bandgap PCF. Based on the analysis of loss origin of conventional optical fibers, the loss mechanism of PCFs has been introduced. After analysis of the parameters of conventional fiber and PCF, several ways to reduce the loss are proposed.