How OTDR Technology Works

An OTDR operates by injecting short pulses of light into the fiber under test and analyzing the light that returns to the instrument.

Rayleigh Scattering occurs continuously along the fiber as light interacts with microscopic density variations, producing a gradual backscatter signal indicating fiber attenuation.

Fresnel Reflection occurs at discrete points where refractive index changes—connector interfaces, splice points, and fiber ends—producing sharp reflection peaks.

By measuring time between pulse transmission and return signal detection, the OTDR calculates distance to each event with high precision.

dB Distance Connector Splice Connector

Sample OTDR trace showing events

What OTDR Testing Reveals

Connector Loss & Reflectance

Connectors appear as both loss and reflection events. We evaluate against expected values and flag connectors exceeding normal levels.

Fusion Splice Loss

Well-made splices exhibit 0.05-0.10 dB loss. OTDR testing verifies splice quality by measuring loss at each location.

Fiber Breaks & Damage

Complete breaks appear as high-reflection events followed by total signal loss. OTDR precisely locates break points for targeted repair.

Macrobend Loss

Fiber bent tighter than minimum radius causes light to escape. OTDR traces show macrobends as non-reflective loss events.

Mechanical Splices

Mechanical splices typically exhibit 0.1-0.3 dB loss and some reflectance. OTDR identifies splices exceeding expected loss.

Distance Measurement

OTDR calculates distance to each event using light pulse time-of-flight. We report event distances for maintenance and troubleshooting.

OTDR Testing Procedures

  • Launch Cables: Move near-end connector beyond initial dead zone for accurate measurement
  • Bidirectional Testing: Testing from both ends allows accurate average loss calculation
  • Wavelength Selection: Multimode: 850nm/1300nm. Single-mode: 1310nm/1550nm
  • Event Documentation: Location, loss, and reflectance for every event
  • SOR Trace Files: Industry-standard format for cable management systems

OptiFiber Pro OTDR

Industry-leading fiber characterization

Need Detailed Fiber Characterization?

OTDR testing provides the diagnostic detail you need for troubleshooting and documentation.