OTDR Analysis Calculator

Calculate OTDR parameters and analyze fiber test requirements.

OTDR Specifications

Typical: 35-50 dB

Fiber Under Test

Event Analysis

Typical: UPC -55 dB, APC -65 dB, PC -40 dB

OTDR Pulse Width Selection

Pulse Width Dead Zone Max Range Use Case
5-10 ns~1 m5 kmShort links, FTTX
30-100 ns5-10 m20 kmMetro, campus
275 ns-1 us25-100 m80 kmLong haul
2.5-20 us250-2000 m250 kmSubmarine, ultra-long

OTDR Measurement Principles

Dynamic Range

Dynamic Range = Backscatter level at start - Noise floor
Required DR = 2 x Total Loss + 5-8 dB margin

The OTDR must see the fiber end clearly. Two-way path (out and back) doubles the loss. Add margin for noise averaging.

Dead Zone Factors

  • Event DZ: Min distance to detect next event
  • Attenuation DZ: Min distance to measure loss
  • Pulse width: Longer = more range, worse resolution
  • Launch cable: Use to clear initial dead zone
  • Reflectance: Higher reflection = larger dead zone