SIST EN 3745-504:2004

Overview

SIST EN 3745-504:2004 is a European standard developed by CEN dedicated to aerospace-grade optical fibres and cables used in aircraft applications. It specifies the micro bending test method, which evaluates the ability of optical fibres or fibre optic cables to withstand microbending effects. Microbending refers to small-scale bends or distortions that may induce signal attenuation and degrade optical performance in fibre optics, critical in aerospace environments where mechanical stresses and vibrations are common.

This standard is part of the aerospace series for fibres and cables, emphasizing reliability and robustness under aircraft operating conditions. It functions in conjunction with EN 3745-100, the general test methods framework for aerospace optical fibres and cables.

Key Topics

• Microbending resistance assessment
  The standard defines a precise testing procedure to quantify how microbends affect attenuation in the fibre or cable under specified mechanical loads.

• Test apparatus specifications
  The required test fixture includes sets of cylinders with diameters tailored to the size of the fibre or cable under test-ensuring consistent application of microbending forces. Light launch and detection systems (LLS and LDS) conforming to EN 2591-100 are used for optical power measurements.

• Specimen preparation
  Specimens are prepared as 2-meter lengths with cable ends treated according to EN 2591-100. Testing conditions are standardized and include stabilization to defined environmental parameters.

• Measurement and evaluation
  Attenuation changes are continuously monitored during load application, maintenance, and removal phases. Limits for maximum variation and residual attenuation are specified to determine compliance. Visual inspections per EN 3745-201 verify the absence of physical damage post-test.

• Optional temperature cycling
  The method allows combining microbending tests with thermal cycling (EN 3745-402) to simulate aerospace temperature extremes and evaluate combined environmental effects.

Applications

• Aerospace optical systems
  EN 3745-504 ensures that optical fibres and cables installed in aircraft can maintain signal integrity despite microbending stresses caused by vibration, mechanical handling, routing restrictions, or structural movement.

• Quality assurance and certification
  Manufacturers and suppliers of aerospace fibre optic components apply this test method to certify product compliance, helping to meet stringent aerospace standards for safety and performance.

• Design validation
  Aerospace engineers use this standard during design and development phases to select materials and design cable assemblies resistant to microbending-induced signal loss.

• Maintenance and reliability testing
  Airlines and maintenance organizations may use the standard to periodically verify the continued mechanical and optical integrity of installed fibre optic systems, supporting aircraft reliability.

Related Standards

• EN 3745-100: Aerospace series – Fibres and cables, optical, aircraft use – Test methods – Part 100: General
  Provides foundational testing principles and apparatus definitions that complement the micro bending test.

• EN 3745-201: Test methods – Part 201: Visual examination
  Specifies inspection techniques for detecting physical damage to optical fibres and cables post-testing.

• EN 3745-301: Test methods – Part 301: Attenuation measurement
  Defines the measurement of signal attenuation in optical fibres, critical for assessing the impact of microbending.

• EN 3745-402: Test methods – Part 402: Temperature cycling
  Details temperature cycling procedures that can be combined with the micro bending test to reproduce aerospace temperature conditions.

• EN 2591-100: Aerospace series – Elements of electrical and optical connection – Test methods – Part 100: General
  Includes preparation and general requirements for fibre optic connections used in these tests.

Adhering to SIST EN 3745-504:2004 helps aerospace manufacturers and operators ensure their optical fibre systems are resistant to microbending, safeguarding communication and sensor systems vital for modern aircraft operation. For comprehensive fibre optic testing in aerospace, this micro bending test standard is an essential reference aligned with broader EN aerospace series standards.