目前大部分光缆工程测试都采用OTDR（光时域反射计）进行光纤衰减的测试，OTDR通过检测来自光纤的背向散射光进行测试。这种情况下采用（ ）方法比较合适。
- A.双向测试
- B.单向测试
- C.环形测试
- D.水平测试
正确答案及解析
正确答案
解析
本题考查利用 OTDR（光时域反射计）进行光缆测试的方法。目前大部分工程测试都采用OTDR （光时域反射计）来进行光纤衰减的测试的，而 OTDR 是通过测试来自光纤的背向散射光实现测试的。这样，因为两个方向的散射光往往是不同的，从而导致两个方向测试的结果不同。严格地说，两个方向测试结果都与实际衰减值不同。将两个方向的测试结果取代数和，再除2（这个方法也适合接头衰减的测试）的结果比较接近实际指标，因此就规定双向测试方法。
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