EN 3745-305:2002

Overview

EN 3745-305:2002 is a European Standard developed by the European Committee for Standardization (CEN) under the aerospace series focusing on optical fibers and cables for aircraft use. This standard specifies a precise test method to measure the immunity of optical fibers and cables against ambient light coupling-an essential factor affecting the performance and reliability of optical systems in aerospace applications. Developed in collaboration with the European Association of Aerospace Manufacturers (AECMA), this standard ensures that optical cables used in aircraft environments sustain operational integrity even when exposed to external light sources.

Key Topics

• Scope and Purpose
    This standard outlines a method to evaluate how well an optical fiber or cable resists the intrusion of power from external ambient light sources that can couple into the fiber, potentially causing signal degradation or errors.

• Test Specimen Preparation
    Specimens must be prepared under standardized conditions as defined in EN 3745-100 to ensure consistency. This includes stabilization at standard test conditions for 24 hours and establishing the specimen’s length, bend radius, and other properties.

• Test Apparatus
    The testing system includes:
    - A light source with defined spectral characteristics
    - A Ca modulator (set to a frequency avoiding multiples of 50 or 60 Hz to reduce interference)
    - Detector and a locking amplifier for precision measurement
    - An integration sphere to collect and measure power coupled from ambient light
    - Light-proof elements to isolate specimens during testing
    - Apparatus to maintain the minimum long-term bend radius of the fiber

• Measurement Method
    The method involves placing the specimen inside an integration sphere, measuring the optical power level with and without light-proof shielding, then calculating the ambient light coupling coefficient per unit length. The coupling coefficient quantifies the fiber’s or cable’s immunity level.

Applications

EN 3745-305:2002 is critical for aerospace manufacturers and designers who require reliable optical fiber systems in harsh aircraft environments. The standard helps ensure:

• Signal Integrity in Aircraft Optical Networks
    Minimizing interference from ambient light sources enhances communication accuracy and safety systems.

• Qualification of Optical Fibers and Cables for Aircraft Use
    By following this standard, manufacturers can certify that their products meet rigorous aerospace requirements for immunity against stray external light.

• Design of Flight-Certified Optical Systems
    Incorporating tested cables reduces risk in avionics, flight control communication, and onboard sensor networks.

• Standardized Testing Across Aerospace Industry
    Consistent methodologies encourage interoperability and help suppliers meet uniform performance specifications.

Related Standards

• EN 3745-100: Aerospace series – Fibres and cables, optical, aircraft use – Test Methods – Part 100: General
    Provides general testing protocols referenced for specimen preparation and standard conditions.

• Other Parts of EN 3745 Series
    These include tests for mechanical, environmental, and electrical robustness of aircraft optical fibers and cables, complementing the immunity assessment defined in Part 305.

• AECMA Aerospace Specifications
    Integrate EN 3745-305 as part of broader aerospace certification frameworks to ensure compliance with international quality and safety standards.

Keywords: EN 3745-305:2002, aerospace optical fiber testing, immunity to ambient light coupling, optical cables aircraft use, integration sphere measurement, fiber optic test methods, ambient light interference, aerospace standards, CEN aerospace standards, aircraft optical communication reliability.