A fiber optic tester works by measuring the amount of light that passes through a fiber optic cable. Specifically, an OLTS (Optical Loss Test Set) is the most accurate tool for this measurement.
The Basics of Fiber Optic Testing
Fiber optic testing is crucial to ensure that fiber optic cables are installed correctly and functioning as expected. These tests help identify issues that might degrade performance or cause failures.
How an OLTS Works
The core principle of an OLTS is comparing the power of light injected into one end of a fiber with the power of light received at the other end. This process involves the following key steps:
- Light Injection: A light source within the OLTS injects a controlled level of light at a specific wavelength into one end of the fiber optic cable.
- Light Measurement: At the other end of the cable, another part of the OLTS measures the power of the light received.
- Loss Calculation: The difference between the injected light power and the received light power represents the optical loss within the fiber optic cable.
The formula used to calculate the loss is:
Loss (dB) = Injected Power (dBm) - Received Power (dBm)
* **dBm** stands for decibels relative to one milliwatt, a unit used to measure optical power.Types of Fiber Optic Testers
While an OLTS is the most accurate method for measuring overall optical loss, several types of fiber optic testers are used for different purposes:
- Optical Power Meter: Measures the absolute power of a light signal.
- Light Source: Generates a light signal at a specific wavelength. Used in conjunction with an optical power meter.
- Visual Fault Locator (VFL): Uses a visible red laser light to find breaks, connectors, or bends in the fiber cable. Useful for short distances.
- Optical Time Domain Reflectometer (OTDR): Sends light pulses down the fiber, and analyzes the light reflected back, identifying the location and characteristics of events along the fiber, such as splices, connectors, and fiber breaks.
- Fiber Inspection Probe Used to inspect and clean fiber optic connector end faces.
Practical Insights
- Importance of Calibration: It is essential that fiber optic testers are regularly calibrated to ensure accurate readings.
- Wavelength Matters: Testing is typically done at the operating wavelengths of the fiber, which may vary from 850nm, 1310nm, and 1550nm. Using the correct wavelength for testing is vital.
- Connector Quality: High quality connections are critical, and improperly terminated connectors may introduce losses that can be detected with an OLTS.
- Fiber Length: Longer fiber lengths will typically have greater loss compared to shorter lengths.
Benefits of Using a Fiber Optic Tester
Fiber optic testers are indispensable for:
- Installation Verification: Ensuring that newly installed fiber optic links meet specified performance requirements.
- Troubleshooting: Identifying and locating faults such as breaks, bends, or dirty connections that could degrade performance.
- Maintenance: Monitoring the health of existing fiber optic networks and performing regular checks.
Table of Fiber Optic Testers and Their Uses
| Tester Type | Purpose |
|---|---|
| OLTS (Optical Loss Test Set) | Measures overall optical loss by comparing injected and received power levels. |
| Optical Power Meter | Measures absolute power levels of a light signal. |
| Light Source | Generates a controlled light signal used for testing. |
| Visual Fault Locator (VFL) | Finds faults (breaks, bends) by injecting visible red light. |
| OTDR (Optical Time Domain Reflectometer) | Analyzes light reflections to identify and locate events along the fiber. |
| Fiber Inspection Probe | Inspects and cleans fiber optic connector end faces. |
By utilizing these testers correctly, professionals can ensure the reliability and optimal performance of fiber optic networks.
