«WORKMANSHIP STANDARD FOR FIBER OPTIC TERMINATIONS, CABLE ASSEMBLIES, AND INSTALLATION Measurement System Identification: Metric (English) NASA-STD ...»
The inspection of terminated fiber optics shall use 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.
When the opposite end of the fiber is not accessible, inspection of terminated fiber optics shall use techniques which produce core illumination.
If cracks in a flight fiber optic assembly end-face are found, the assembly shall be reterminated or scrapped. Re-polishing to fix cracks in flight hardware is prohibited.
Fiber Optic Routing The optical fiber shall not be routed over sharp edges or corners unless appropriate protection is provided.
The minimum bend radius of the routed optical fiber shall be in accordance with the engineering documentation.
The optical fiber shall be tied down (e.g., lacing cord) per the engineering documentation to prevent subsequent damage due to processing, handling and operational environments.
The ties shall not pinch, deform or otherwise stress the optical fiber.
The ties shall be loose enough to allow the fibers to move slightly due to thermal expansion and contraction. Overly tight ties can cause microbending of the fiber and affect performance or reliability. Conduits should be used to route optical fibers through areas where access is limited or restricted.
Staking or conformal coating shall only be applied to optical fiber when specified in the engineering documentation. See NASA-STD-8739.1 for Workmanship requirements for staking.
Fiber Optic Assembly Testing All finished flight fiber optic assemblies shall be tested to ensure that measured optical performance meets the performance requirements in the engineering documentation.
Records of testing shall be maintained with the assembly or subassembly documentation (Requirements). Appendix B provides a list of available test and verification methods.
Upon completion of the test(s) required in paragraph 11.5.1 the flight fiber optic assemblies shall be subjected to temperature cycling or preconditioning as identified in
the engineering documentation to demonstrate the assembly’s mechanical and optical stability following exposure to mission-relevant temperatures.
Upon completion of the environmental test in 11.5.3, retest the flight fiber optic assembly per paragraph 11.5.1.
Following the optical retest in 11.5.4, the flight fiber optic assembly shall be examined
for the following:
Cracks in fiber end-face.
Pistoning of the fiber in connector or termination.
Cracks in epoxy bond line at the end-face.
Shrinkage of buffer or outer jacket.
The examination of the flight fiber optic assembly in 11.5.5 shall use direct 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.
When the opposite end of the fiber is not accessible, the examination of the flight fiber optic assembly in 11.5.5 shall use inspection techniques that produce core illumination.
FIBER OPTIC CABLE ASSEMBLY INSTALLATIONGeneral Care is necessary to prevent damage to fiber optic cable assemblies during the installation process. Fiber optic cables shall only be installed and inspected by trained fiber optic operators and inspectors.
This section applies for both mission hardware as well as for fiber optic assemblies used in critical ground support equipment with the exception described in 12.3.6.
Design Requirements and Considerations for Fiber Optic Assembly Installation Fiber optic cable assemblies should not be combined in the same wiring bundle as wire or coaxial cable assemblies to ensure they are not exposed to handling practices that are acceptable for electrical cables but can damage optical cables.
The engineering documentation shall specify the maximum installation tensile load and the maximum use tensile load.
For fiber optic assemblies used in ground support equipment, the engineering documentation shall specify the maximum vertical rise for cable assemblies installed in raceways, trays, ducts or conduits.
The minimum short term and long term bend radii applicable to all operations during installation and use of the fiber optic assembly or cable shall be specified in the engineering documentation. A bend radius of not less than 10 times the cable diameter is recommended for long term bend radius.
The minimum bend radius shall not be violated at connector backshells (Requirement).
Protection Constraints for Fiber Optic Cable Assemblies When installed, fiber optic cable assemblies shall be constrained to protect them from damage during operations on the ground, from movement during launch, and from movement in the mission as applicable.
The method of constraint (e.g. cable ties, staking) shall be specified in the engineering documentation. A spacing of at least once every 20cm (8 in) is recommended when using cable ties. Conduits should be used to route optical fibers where access is limited or restricted.
Tie downs shall be tight enough to capture the fiber optic cable but shall not deform the cable outer jacket.
The ties shall not pinch, deform, kink, or otherwise stress the cable assembly.
Dust caps shall be installed on all connectors when not in use.
Vinyl dust caps shall not be used.
Fiber optic cable connector or termination end-faces shall be examined before each mate and cleaned if necessary in accordance with Chapter 8.
For payload installation operations in certified aircraft where Technical Order 1-1A-14, Installation and Repair Practices, Aircraft Electric and Electronic Wiring, is the baseline or primary design and quality standard, all requirements in this chapter shall be flowed to the work orders, procedures or other applicable engineering documentation used when installing optical cable and harness assemblies in NASA mission aircraft.
Partial operator training is recommended for individuals whose interactions with fiber optic assemblies is limited to assembly installation. Partial Level B Instructor training is recommended for instructors who will only teach operators who perform fiber optic installations in accordance with this chapter but will not terminate fiber or cable or repair terminations.
QUALITY ASSURANCE PROVISIONSGeneral Workmanship shall be of sufficient quality to assure that the products meet the performance requirements of the engineering documentation and criteria delineated herein.
Inspection for acceptability shall be performed on all fiber optic terminations and cable assemblies to the requirements specified in this Standard.
If any elements of the fiber optic components are moved to aid inspection, they shall not be disturbed in a fashion that will cause damage.
X-ray or other means of automated inspection techniques are permissible provided that it has been determined that the x-ray emission level is not detrimental to the product being inspected.
Quality Assurance. The following functions shall be performed:
Product Verification. Witness or verify that all tests, examinations, peer verifications, inspections, and measurements specified by this Standard and the engineering documentation have been performed.
Personnel Qualifications. Verify that all personnel who assemble or inspect hardware in accordance with this Standard have been trained in accordance with NASA-STDProcesses and Procedures. Verify, through manufacturing readiness reviews and inprocess surveillance of all assembly operations that all processes and procedures implementing the requirements of this Standard are current, approved, adequate, and are being accurately used.
Part Cleanliness. Verify that all parts were cleaned and undamaged prior to being assembled.
Facility Control. Verify that the facility cleanliness, environmental conditions, and lighting requirements of NASA-STD-8739.6 and Chapter 6 herein are met.
APPENDIX B TEST METHODS FOR THE VERIFICATION OF
OPTICAL FIBER FABRICATION PROCESSESThe following fiber optic test procedures should be considered for all optical fiber cable
assemblies, splices, and/or connectors, as applicable:
EIA-455-1 (FOTP 1) Cable Flexing for Fiber Optic Interconnection Devices EIA-455-3 (FOTP 3) Procedure to Measure Temperature Cycling Effects on Optical Fibers, Optical Cable, and Other Passive Fiber Optic Components.
EIA-455-4 (FOTP 4) Fiber Optic Connector/Component Temperature Life.
EIA-455-5 (FOTP 5) Humidity Test Procedure for Fiber Optic Connecting Devices EIA-455-6 (FOTP 6) Cable Retention Test Procedure for Fiber Optic Cable Interconnecting Devices EIA-455-11 (FOTP 11) Vibration Test Procedure for Fiber Optic Connecting Devices and Cable EIA-455-12 (FOTP 12) Fluid Immersion Test for Fiber Optic Components EIA-455-13 (FOTP 13) Visual and Mechanical Inspection of Fiber, Cables, Connectors etc.
EIA-455-14 (FOTP 14) Fiber Optic Shock Test (Specified Pulse) EIA-455-15 (FOTP 15) Altitude Immersion EIA-455-16 (FOTP 16) Salt Spray EIA-455-17 (FOTP 17) Maintenance Aging of Fiber Optic Connectors and Terminated Cable Assemblies EIA-455-21 (FOTP 21) Mating Durability for Fiber Optic Interconnecting Devices EIA-455-25 (FOTP 25) Repeated Impact Testing of Fiber Optic Cables and Cable Assemblies EIA-455-26 (FOTP 26) Crush Resistance of Fiber Optic Interconnecting Devices EIA-455-33 (FOTP 33) Fiber Optic Cable Tensile Loading and Bending Test EIA-455-34 (FOTP 34) Interconnection Device Insertion Loss Test EIA-455-36 (FOTP 36) Twist Test for Fiber Optic Connecting Devices EIA-455-37 (FOTP 37) Low or High Temperature Bend Test for Fiber Optic Cable EIA-455-39 (FOTP 39) Fiber Optic Cable Water Wicking Test EIA-455-41 (FOTP 41) Compressive Loading Resistance of Fiber Optic Cables EIA-455-42 (FOTP 42) Optical Crosstalk in Fiber Optic Components Page 42 of 43 NASA-STD 8739.5A – September 14, 2015 EIA-455-53 (FOTP 53) Attenuation by Substitution Measurement for Multi-mode GradedIndex Optical Fibers or Fiber Assemblies Used in Long Length Communication Systems EIA-455-57 (FOTP 57) Optical Fiber End Preparation and Examination EIA-455-59 (FOTP 59) Measurement of Fiber Point Defects using an Optical Time Domain Reflectometer EIA-455-60 (FOTP 60) Measurement of Fiber or Cable Length Using an OTDR EIA-455-61 (FOTP 61) Measurement of Fiber or Cable Attenuation Using an OTDR EIA-455-62 (FOTP 62) Measurement of Optical Fiber Macrobend Attenuation EIA-455-69 FOTP 69) Test Procedure for Evaluation of the Effect of Minimum and Maximum Exposure Temperatures on the Optical Fiber EIA-455-85 (FOTP 85) Fiber Optic Cable Twist Test EIA-455-88 (FOTP 88) Fiber Optic Cable Bend Test EIA-455-91 (FOTP 91) Fiber Optic Cable Twist-Bend Test EIA-455-95 (FOTP 95) Absolute Optical Power Test for Optical Fibers and Cables EIA-455-96 (FOTP 96) Fiber Optic Cable Long-Term Storage Temperature Test for Extreme Environments EIA-455-98 (FOTP 98) Fiber Optic Cable External Freezing Test EIA-455-171 (FOTP 171) Attenuation by Substitution Measurement for Short-Length Multimode Graded-Index and Single-Mode Optical Fiber Cable Assemblies NRL/MR/6505-92-6963 Procedure for Measuring Radiation-Induced Attenuation in Optical Fibers and Optical Cables