What is a "dynamic fatigue test" for a fiber optic patch cord?

OFSCN Global Technical Center OFSCN Technical Knowledge Base
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How can the “limit” of a jumper be tested by continuously increasing the tensile force?

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In optical engineering and material mechanics, the Dynamic Tensile/Fatigue Test is commonly employed to assess the ultimate performance of fiber optic patch cords or materials by progressively increasing the axial tensile force. This method, based on standardized rate loading, precisely determines their limit tensile strength and fatigue failure characteristics by recording the relationship between the applied tension and the fiber’s optical performance and structural deformation.

Here are the standard principles, implementation procedures, and limit determination methods for this test:

I. Basic Principles and System Composition

The dynamic fatigue and ultimate tensile testing adheres to international standards such as IEC 60794-1-21 (Method E1, Cable Tensile Test) and IEC 60793-1-33 (Fiber Fatigue Test).

  1. Test Equipment:
    • Universal Tensile Testing Machine:
      Equipped with a high-precision load cell and a displacement acquisition system.
    • In-situ Optical Monitoring System:
      Composed of a highly stable light source (SLD/laser) and an optical power meter or OTDR for real-time monitoring of optical power attenuation.
    • Specialized Fixtures (Capstan / Connector Clamps):
      Since quartz glass fibers are extremely sensitive to shear stress, the cable body ends typically use Capstan clamps to dissipate local compressive stress. The connector ends employ locking clamps matching standard sockets to evaluate the connector’s pull-out strength.

II. Specific Test Implementation Steps

  1. Sample Installation and Optical Path Connection:
    Secure the connectors or cable body of the fiber optic patch cord to be tested onto the tensile machine’s fixtures. Simultaneously, connect the fiber core to the in-situ optical monitoring system, calibrating for initial tension F = 0\ \text{N} and initial optical power loss \alpha_0.
  2. Setting Constant Strain/Loading Rate:
    Configure the testing machine’s crosshead to move at a constant rate (e.g., 5\ \text{mm/min}, 10\ \text{mm/min}, or 50\ \text{mm/min}).
  3. Linear Loading and Synchronous Data Acquisition:
    The tensile machine continuously increases the axial load F at a constant rate. The sensors synchronously record:
    • Instantaneous tensile force F(t)
    • Specimen elongation \Delta L(t) and strain \varepsilon(t)
    • Additional optical power loss \Delta \alpha(t)
  4. Stretching Until Complete Failure:
    Continue applying tensile force until the specimen undergoes mechanical fracture (e.g., brittle fracture of the core, rupture of aramid yarn or metallic sheath, connector pull-out) or the signal is completely interrupted.

III. Definition and Classification of Limit Criteria

On the test data curve, the