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How to identify OTDR curve?

2017-12-20

Correct Curve: A is dead zone, B is reflection peak of testing end

Appearance: No Fresnel Reflection, curve slope and attenuation is normal, cannot specify fiber length

Problem: Fiber end face is dirty or fiber quality is bad 

Solution: Clean fiber end face or reform end face

Appearance: Curve appears obvious arched, attenuation is serious larger or smaller, no Fresnel Reflection

Problem: Wrong measurement range 

Solution: Increase measurement range

Appearance: 'A small peak ' on the curve with constant curve slope

Problem: a) Fiber quality (crack)

         b) Secondary reflection produce reflection at anterior face

Solution: Change measuring range, pulse width, reform end face , then re-test. If small peak disappears,reason b), otherwise, reason a)

 

Appearance: Obvious increase at the point of fiber connector, splicing, coupler

Problem: Diameter does not match

Solution: Test attenuation and connector loss must two-way test, and take the average

Appearance: 1310nm curve: smooth, attenuation slope and index is normal

             1550nm curve: attenuation slope is bad, index is seriously high

Problem: Bending radius is too small

Solution: Increase rest length of fiber tube

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