Fiber Optic Cable and Assemblies

Lessons Learned for Quality Assurance Professionals Ensuring Compliance with NASA Workmanship Standard for Fiber Optic Cables and Assemblies, NASA-STD-8739.5

Adhesives:

1.       Accelerated cure schedules may not be successful for fiber optics (see NASA-STD-8739.5, para 6.10.2, 6.10.5, 6.10.8, 6.10.10).  Over-cure can create a brittle interface that will not be reliable in ground testing or use conditions.  A higher cure temperature may damage the hardware.  Fast cure may not provide enough time for volatiles to escape creating an outgassing or offgassing failure.

Bend Radius:

1.       Minimum bend radius is strongly dependent on the fiber and cable used and is best defined by the designer and process engineer in the engineering documentation.  NASA-STD-8739.5 requires use of a default minimum bend radii when it is not specified.  See para 9.3.10, 12.2.2 and 12.2.3.

2.       Minimum bend radius can be exceeded during integration operations that involve positioning of connectors pre-mate, installing connector backshells, and after assembly installation when the system level assembly is moved around.  Extreme care needs to be given to sustaining bend radius limits whenever repositioning hardware that contains installed optical fiber or fiber optic cables.  (see NASA-STD-8739.5, para 12.2.3)