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4 Factors You Should Consider When Test Optical Fiber

In this blog post, we have outlined the critical considerations for testing the quality of optical fibers. If you require further information or assistance in ensuring the integrity of your optical fiber infrastructure, please reach out us for expert support.
optical fiber test
Table of Contents

When selecting optical fiber cables, it is crucial to consider not only the quantity and type required for your application but also the inherent quality of the fibers.

To accurately assess the quality of optical fibers, there are four key performance aspects to test:

  • Environmental performance
  • Mechanical properties
  • Geometric dimensions
  • Transmission performance.

1. Environmental Performance of Optical Fibers

Optical fiber cables must be tested for adaptability and endurance under various environmental conditions, including exposure to temperature and moisture.

These evaluations help ensure the fiber meets practical application standards, enhance product quality, and provide data for failure analysis.

Based on IEC standards, typical environmental tests include:

  • Temperature Humidity Bias (THB) Test: Subjecting the fiber to 85±2°C at a relative humidity of at least 85% for 30 days.
  • Dry Heat Test: Exposing the fiber to 85±2°C with a relative humidity not exceeding 50% at 35°C or below for 30 days.
  • Temperature Cycling Test: Cycling the fiber between -60°C to 85°C for a minimum of two cycles.
  • Water Immersion Test: Soaking the fiber at 23±5°C for 30 days.

After testing, the maximum permissible additional attenuation is ≤0.05 dB/km for single-mode fibers and ≤0.2 dB/km for multimode fibers to be considered acceptable.

Vacuum high and low temperature test machine

2. Mechanical Properties

The mechanical characteristics of optical fibers include resistance to lateral pressure, tensile strength, and resistance to bending and twisting. Fibers must withstand mechanical testing, such as screening tests, tensile strength tests, strippability tests, stress corrosion sensitivity tests, and twist tests, to ensure they can bear sufficient stress without breaking during installation.

Testing standards should refer to GB/T 15972.30.

3. Geometric Dimensions

Standards for the geometric dimensions of optical fibers include core diameter, cladding, and core-cladding concentricity. Products must meet the general requirements as outlined in GB/T 7610.1-2010. The diameters of the fiber core and cladding directly affect transmission loss, bandwidth, and the fiber’s bend radius, impacting performance and durability in practical use.

4. Transmission Performance

Transmission performance includes bandwidth, attenuation and dispersion:

fiber optic cable
  • Bandwidth: The bandwidth coefficient of a kilometer-long fiber is determined by the modulation frequency at which the power of the output optical signal drops to half its maximum value.
  • Attenuation Coefficient: One of the most critical parameters for both multimode and single-mode fibers, attenuation largely determines the relay distance for fiber optic communication.
  • Dispersion: This occurs when an input optical pulse broadens after transmission through the fiber, potentially causing significant distortion. Fiber dispersion narrows the bandwidth, limiting transmission capacity and signal distance. It can categorize into modal dispersion (relevant for multimode fibers), material dispersion, and waveguide dispersion.

Commonly used devices for testing the transmission performance of optical fibers include optical power meters, stable light sources, optical multimeters, Optical Time-Domain Reflectometers (OTDRs), and optical fault locators.

OTDR

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