Which three technologies are used to reduce chromatic dispersion accumulation in fiber-optic transmission systems? ()(Choose three.)
A. PIN photodiodes
B. zero-chirped lasers
C. Erbium-doped fiber amplifiers
D. dispersion compensating fiber
E. dispersion compensating Bragg grating
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患者,男性,70岁,半年前外伤后,出现一下肢无力,查体出现如下图步态。请出此患者为什么步态()
A. 划圈样步态
B. 剪刀样步态
C. 慌张步态
D. 醉汉步态
E. 跨阈步态