Testing Instruments & Measurement
Optical power meters, light sources, OTDRs, visual fault locators - how each tool works and when to use it.
- Explain how optical power meters and light sources measure loss
- Define insertion loss and return loss and their measurement units
- Describe OTDR operation including traces, events, and dead zones
- Explain the purpose of launch cables and receive cables in OTDR testing
- Identify visual fault locator and video microscope applications
Lesson 1
Optical Power Meters & Light Sources
Optical Power Meter
An optical power meter measures the absolute power of light in a fiber, displayed in dBm (decibels referenced to 1 milliwatt). It is the most fundamental fiber optic test instrument. The power meter connects to a fiber via a connector adapter and reads the optical signal level.
Power meters are used to:
- Measure absolute power from a transmitter or light source
- Measure insertion loss when used with a calibrated light source
- Verify system power budget by checking levels at each point in a link
- Troubleshoot low signal conditions
Light Source
A light source generates a stable, calibrated optical signal at a specific wavelength. When paired with a power meter, the two instruments form a loss test set - the standard method for measuring fiber link insertion loss.
The light source connects to one end of the fiber under test, and the power meter connects to the other end. The difference between the reference power (measured through the reference test jumper) and the received power equals the insertion loss of the link.
An optical power meter measures light power in dBm. Paired with a calibrated light source, it forms a loss test set for measuring insertion loss in dB. This is the fundamental test method for fiber optic link certification.