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«WORKMANSHIP STANDARD FOR FIBER OPTIC TERMINATIONS, CABLE ASSEMBLIES, AND INSTALLATION Measurement System Identification: Metric (English) NASA-STD ...»

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Adhesive lot numbers and mix records shall be documented and traceable to the hardware.

Uncontrolled heat sources (e.g., heat guns or hotplates) to cure adhesives shall not be used.

Material Shelf Life Requirements Material storage shall be controlled by shelf life labels attached to each material container.

Records for manufacturing date, lot number, and receiving date of each material shipment shall be maintained.

Material shall not be used if the shelf life has expired.

Shelf life may be extended one time, for one-half of the original shelf life with prior NASA approval, based on test results that demonstrate material acceptability in accordance with the manufacturer’s specification and engineering documentation..

The working life of an adhesive shall be defined for the processes for which it will be used and recorded in the mix record.

Personnel Protection All necessary safety precautions shall be taken to protect personnel from injury while fabricating, inspecting, or testing fiber optic cable assemblies. The safety requirements of NASA-STD-8739.6 apply.

Protection from Bare Fibers Personnel who may come in contact with bare fibers shall wear wrap-around safety goggles for eye protection.

–  –  –

Slivers of bare fiber shall be wrapped in a heavy tape (e.g., duct tape) and placed in a specially marked container for later disposal.

Fiber waste is a personnel safety concern and shall be handled as such during disposal.

Incineration is the recommended method of safe disposal.

Protection from eye exposure to light sources shall be in accordance with ANSI Z136.1, American National Standard for the Safe Use of Lasers; and ANSI Z136.2, American National Standard for the Safe Use of Optical Fiber Communication Systems Utilizing Laser Diode and LED Sources.

WARNING: SOME LIGHT SOURCES USED IN TESTING AND

OPERATING FIBER OPTIC CABLE ASSEMBLIES MAY

CAUSE PERMANENT EYE DAMAGE.

–  –  –

OPTICAL FIBER END PREPARATION

General All parts, materials, tooling and equipment shall be verified for compliance with the engineering documentation prior to the start of fiber end preparation activities.

Safety Requirements The requirements of 6.9.2 apply for protection from bare fibers when preparing optical fiber ends.

Procedures Fiber optic cables shall be thermally preconditioned prior to preparation for termination to provide material stability in the final assembly.

Cables (see Figure 7-1 for a typical fiber optic cable) shall be prepared for termination in a fashion that will allow for the fiber to be exposed without sustaining damage or contamination.

All outer protective materials shall be removed to the dimensions defined in the engineering documentation.

The use of chemical strippers (e.g., acetone) for removal of certain buffer materials is acceptable. Chemically stripped fiber ends shall be thoroughly cleaned to remove any residual chemical stripping compounds and buffer materials immediately after stripping.

All parts that come in contact with the adhesives, including all dispenser parts and mixing pans, as well as the fiber and connector to be bonded, shall be thoroughly cleaned with appropriate solvents before bonding.

Procedures for collecting, controlling, and disposing of fiber optic waste shall be implemented.

The connector end-face may be finished either by polishing or cleaving provided that the process is compatible with the finished product quality and performance requirements.

The optical fiber shall be back-lit using an incoherent, low intensity light source from the opposite end of the cable, without touching the fiber, to inspect for cracks on or through the fiber end-face before and after polishing.

When the opposite end of the cable is not accessible, inspection techniques which produce core illumination shall be used.

–  –  –

CLEANING

General Cleaning procedures shall address the processes to be used for cleaning, drying parts, and visual inspection.

Fiber optic terminations to be cleaned shall be handled in a manner that will not degrade or damage the termination.

Terminations shall be cleaned within a time frame that permits removal of all contaminants.

Manual Cleaning Manual cleaning of fiber optic terminations shall be performed using a solvent and a wipe or swab.

The wipe or swab shall be non-abrasive, lint free, and either soxhlet extracted, or equivalent, to minimize residues.

Cleaning processes shall not degrade the optical characteristics of the termination.

Cleaning shall ensure removal of dirt, oil, grease, and particulate matter.

If not terminated immediately, prepared cable components shall be protected from contamination.

–  –  –

FIBER OPTIC SPLICING

Splice Assembly Prior to splicing, the fiber shall be examined to ensure there is no contamination, blockage of the internal fiber channel in parts or fixturing, unacceptable conditions as shown in Appendix A as applicable, or other nonconformances with specific requirements in the engineering documentation.





The prepared fiber shall not be used to check for blockage of the fiber channel in parts or fixturing.

Completed fusion splices shall be able to withstand a minimum 4.45 newton (1 pound) pull test, or as specified in the engineering documentation.

Mechanical splicing shall not be used for mission hardware assemblies.

Chemical splicing shall only be used for temporary joining of fiber optics (i.e., testing).

Completed Splices Splices shall not be located in flexure areas of the cable except when a splice is recoated and re-jacketed in accordance with the manufacturer's original specifications.

Splices shall be protected from inadvertent mechanical damage using an enclosure or an equivalent method.

Strength members shall be secured to splice enclosures, or other means of protection, to prevent mechanical stress on the optical fiber.

Finished splices shall be inspected visually and optically to verify that they meet physical quality and optical performance requirements. Optical Time Domain Reflectometry (OTDR), as well as other appropriate test procedures from Appendix B, may be applied.

Test records shall be maintained with the assembly/subassembly documentation.

–  –  –

FIBER OPTIC CABLE ASSEMBLIES

General A fiber optic cable assembly consists of a prepared fiber optic cable, connector, and associated hardware.

Cable Assembly Fiber optic cables shall be identified in such a way to distinguish these cables from wire or coaxial cables.

Cable connectors shall be permanently marked with mating connector designation within 15 cm (6 in) of connector body, or as stated in the engineering documentation.

Prior to assembly, compliance of all parts, materials, and tooling with critical dimensions, conditions, and quality controls and requirements, defined in the in the engineering documentation shall be verified.

Prior to assembly, prepared fiber optic cables shall be subject to documented in-process

visual inspection for the following:

Correct cable stripping dimensions.

Strength member damage.

Cracks, nicks, cuts, or other damage in the termination area to all cable components, including the optical fiber.

Chemical strip wicking or damage.

Cleanliness as per Chapter 8.

All other critical dimensions, conditions and quality criteria defined herein and in the engineering documentation.

Note: The requirement in NASA-STD-8739.6, Appendix A prohibiting operators from inspecting their own work, applies.

The prepared fiber shall not be used to check for blockage.

Prior to assembly, prepared fiber optic connector parts shall be examined for the

following:

–  –  –

Completed cable assemblies shall be inspected for the following:

Strength member, when visible, is uniformly distributed and securely attached to the connector.

Heat shrinkable sleeving and crimp sleeve is positioned properly.

Connector end-face geometry is compliant with engineering documentation.

Connector ferrule length is compliant with engineering documentation.

Connector end-face quality is in accordance with Appendix A or the engineering documentation.

Proper positioning and attachment of the strain relief device per the engineering documentation.

Cleanliness as per Chapter 8.

Cable axial alignment with the connector is within 5 cm (2 inches) of the termination or per the engineering documentation.

Freedom from nicks exposing underlying elements.

Freedom from kinks or twists.

Cable designation marking.

If cracks in a flight fiber optic cable end-face are found, the cable shall be re-terminated or scrapped. Re-polishing to fix cracks in flight hardware is prohibited.

Post Assembly Testing All completed flight cable assemblies shall be tested to ensure that measured optical performance (e.g., insertion loss or return loss) meets or exceeds the performance requirements in the engineering documentation.

Records of testing shall be maintained with the assembly or subassembly documentation.

Appendix B provides a list of standard test and verification methods.

Upon completion of the test(s) required in paragraph 10.3.1, the flight cable assemblies shall be subjected to workmanship temperature cycling or preconditioning as identified in the engineering documentation to ensure assembly geometries and conditions are stable.

Following temperature cycling or preconditioning per 10.3.2, the cable shall be retested per paragraph 10.3.1.

Following retesting per 10.3.3 the cable shall be visually inspected to verify conformance with the quality criteria and requirements defined in in the engineering documentation for

the following:

–  –  –

Cracks in fiber end-face.

Pistoning of the fiber in connector.

Cracks in epoxy bond line at the end-face.

Shrinkage of the cable components (e.g. buffer, strength members, jacket).

Crack in the fiber end-face of fiber optic assemblies shall use direct light, and back lighting with an incoherent, low intensity light source from the opposite end of the fiber, without touching the fiber as part of the examination.

–  –  –

FIBER OPTIC ASSEMBLIES

General Fiber optic assemblies include such devices as electro-optical components, star couplers, and splice enclosures. The optical fibers found in these devices consist of the fiber (core and cladding) and the coating surrounding the fiber. Optical fibers differ from fiber optic cables which may have a buffer, loose tube, strength members, and outer jacket as additional protective sheathing.

Fiber Optic Connector Termination Prior to assembly, compliance of all parts, materials, and tooling with critical dimensions, conditions, and quality controls and requirements, defined in the in the engineering documentation shall be verified.

Prior to assembly, prepared optical fibers shall be subject to documented in-process

visual inspection for the following:

–  –  –

Note: The requirement in NASA-STD-8739.6, Appendix A prohibiting operators from inspecting their own work, applies.

The prepared fiber shall not be used to check for blockage.

Prior to assembly, fiber optic connector parts shall be examined for the following:

–  –  –

Post Fiber Optic Connector Termination

Terminated fiber optics shall be inspected for the following:

Heat shrinkable sleeving and/or crimp sleeve is positioned properly.

Connector end-face geometry is compliant with engineering documentation.

–  –  –

Connector end-face requirements are in accordance with Appendix A or engineering documentation.

Proper positioning of the strain relief per the engineering documentation.



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