Article Overview

Optical Return Loss (ORL) testers measure reflected light in fiber networks, while Optical Power Meters (OPMs) measure the absolute optical power transmitted through the fiber.

Optical Return Loss Tester

An Optical Return Loss (ORL) tester quantifies the amount of light reflected back toward the source in a fiber optic system, expressed in decibels (dB) . High return loss (larger dB values) indicates low reflection and better fiber performance, while low return loss (closer to 0 dB) indicates higher reflections, which can degrade signal quality . ORL testers are essential for:

  • Characterizing connectors, splices, and passive components like isolators .
  • Ensuring compliance with network standards and minimizing signal interference.
  • Measuring both total return loss and wavelength-dependent reflections when synchronized with tunable laser sources . Examples of ORL testers include the Keysight N7753C, which integrates power sensors and fiber couplers for fast, accurate measurements up to 70 dB, and the Santec RLM-100, capable of measuring single-mode return loss up to 85 dB with self-calibration features . The VIAVI SmartClass Fiber ORL-85 combines ORL measurement with optical power and connector inspection in a single compact device .

Optical Power Meter

An Optical Power Meter (OPM) measures the absolute optical power transmitted through a fiber, typically in milliwatts (mW) or dBm. It is used to:

  • Verify signal strength in fiber optic links.
  • Measure insertion loss and ensure proper network performance.
  • Calibrate light sources and test equipment for accurate measurements . OPMs are often paired with a light source in Optical Loss Test Sets (OLTS), such as EXFO's FPM-600 Power Meter combined with the FLS-600 Light Source, enabling fast, automated measurements of loss, length, and polarity across multiple wavelengths . These devices support simplex, duplex, and multi-fiber connectors, making them suitable for data center and enterprise network certification .

Key Differences

FeatureOptical Return Loss TesterOptical Power Meter
MeasuresReflected light (return loss)Transmitted optical power
UnitsdB (positive for ORL)dBm or mW
PurposeDetect reflections, ensure low signal interferenceVerify signal strength, measure insertion loss
Typical UseConnector and component characterizationNetwork link verification and calibration
IntegrationOften combined with tunable lasers or light sourcesOften paired with light sources in OLTS kits

Combined Instruments

Modern instruments, like the VIAVI SmartClass Fiber ORL-85, integrate ORL measurement, optical power metering, light sources, and connector inspection into a single device, streamlining testing workflows and reducing the need for multiple instruments . This integration is particularly useful for field technicians and network engineers performing Tier-1 fiber certification and maintenance. In summary, ORL testers focus on reflections and signal quality, while OPMs focus on transmitted power and link performance, and both are critical for ensuring reliable fiber optic networks.

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