FIBER OPTICS<br>GENERAL REQUIREMENTS

FIBER OPTICS GENERAL REQUIREMENTS
	FIBER OPTICS The term Fiber Optics (FO) is uded to describe a technology which is based upon the use of a filament-shaped optical waveguide, made of a dielectric material (plastic or glass) having controlled optical reflection and refraction properties, to transmit information as light pulses rather than electrical pulses. Fiber Optics has benefits that the traditional copper-based system does not, including low weight, electromagnetic noise immunity and extremely high transmission speeds.

PREFERRED AXIAL ALIGNMENT Axial alignment of the cable to the connector shall be maintained within 5 cm (2 in.) of the entry/exit from the connector body. NASA-STD-8739.5 [10.2.7.h]	PREFERRED BARE FIBER AND FACE End face is smooth and free from cracks, scratches, edge chips, hackles, pits and/or other surface or sub-surface anomalies. The core is clearly discernable. Cleave angle is less than 2 degrees from perpendicular to the fiber axis. NASA-STD-8739.5 [App. A]

PREFERRED CHEMICAL SPLICE The fiber endfaces are perfectly aligned and in contact with each other. No bubbles or contamination. Note: Chemical splices are allowed for the temporary joining of fiber optics (i.e. test) only. NASA-STD-8739.5 [9.2.2.c]	PREFERRED CONNECTOR/CABLE CONFIGURATION Connector is properly assembled, clean and damage-free. Strain-relief is properly installed, straight, tight and damage-free. Axial alignment of the cable to the connector is maintained within 5 cm (2 in.) of the exit from the connector body. NASA-STD-8739.5 [11.3]

NASA WORKMANSHIP STANDARDS
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 10	Section: 10.01	Page: 1

FIBER OPTICS GENERAL REQUIREMENTS (cont.)

PREFERRED CONNECTOR/FIBER CONFIGURATION The connector is properly assembled, clean and damage-free. The connector and fier strain-relief device(s) are properly installed, straight, tight and damage-free. Axial alignment of the fiber to the connector is maintained within specifications. NASA-STD-8739.5 [11.3]	PREFERRED ENDFACE (MULTI-MODE) The endface is clean and free from cracks, scratches, edge chips, hackles, pits and other anomalies. The fiber is concentric in the ferrule, and the epoxy ring is even. Ferrule and connector are damage-free. NASA-STD-8739.5 [11.3.1.c]

PREFERRED ENDFACE (SINGLE-MODE) The endface is clean and free from cracks, scratches, edge chips, hackles, pits and other anomalies. The fiber is concentric in the ferrule, and the epoxy ring is even. Ferrule and connector are damage-free. NASA-STD-8739.5 [11.3.1.c]	PREFERRED FUSION SPLICE The splice is perfectly aligned. Fusion zone is of uniform diamter, with no bubbles, contamination or boundary layer evident. Splice closure is properly installed. NASA-STD-8739.5 [9.2.2.a]

PREFERRED MECHANICAL SPLICE The fibers are properly inserted, aligned and the endfaces are in contct with each other. Splice housing is properly assembled, and strain relief features are set. Mechanical splices are not for spaceflight applications. NASA-STD-8739.5 [9.2.2.b]	PREFERRED SPLICE CLOSURE Splices shall be protected. If an enclosure cannot be used for a specific application, engineering documentation shall provide for other means of protection. NASA-STD-8739.5 [9.2.3.b]

NASA WORKMANSHIP STANDARDS
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 10	Section: 10.01	Page: 2

FIBER OPTICS GENERAL REQUIREMENTS (cont.)

PREFERRED SPLICE LOCATION Splices shall not be located in flexure areas of the cable except when a splice is recoated and rejacketed in accordance with the manufacturer's specifications. NASA-STD-8739.5 [9.2.3.a]	PREFERRED SPLICE TRAY Splices shall be neatly organized and marked. Service loops shall be adequate, with bend radii within specifications. NASA-STD-8739.5 [9.3.9]

PREFERRED STRENGTH MEMBER Strength members shall be secured to prevent mechanical stress on the fiber. NASA-STD-8739.5 [9.2.3.c]	PREFERRED TIE DOWNS Optical fibers and cables shall be tied down per engineering documentation. Ties shall no pinch, deform or stress the fiber. NASA-STD-8739.5 [11.4.3], [12.2.3], [12.3.4]

MANDATORY DUST CAP Dust caps shall be installed on all connectors when not in use. Vinyl dust caps shall not be used. NASA-STD-8739.5 [12.2.4], [12.3.5]	MANDATORY IDENTIFICATION Fiber optic cables shall be identified in such a way to distinquish these cables from wire or coaxial cable. Identification methods typically used are color-coding, labeling/marking, etc. NASA-STD-8739.5 [10.2.2]

NASA WORKMANSHIP STANDARDS
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 10	Section: 10.01	Page: 3

FIBER OPTICS GENERAL REQUIREMENTS (cont.)

ACCEPTABLE ENDFACE ANOMALIES EDGE CHIPS Edge chips are acceptable if chip maximum dimension is <3% of fiber diameter and there are less than 3 chips total. May be fixable by repolishing if connectorized. NASA-STD-8739.5 [10.2.7.e]	UNACCEPTABLE ENDFACE ANOMALIES EDGE CHIPS Unacceptable if chip maximum dimension is >3% of fiber diameter and/or there are more than 3 chips. Reject and recleave for splice termination. May be fixable by repolishing if connectorized. NASA-STD-8739.5 [10.2.7.e]

ACCEPTABLE FUSION SPLICES Mating fubers are properly aligned, but fused section is slightly distorted. No bubbles or boundary layer/diffraction zone. Optical loss is within engineering requirements. Best Workmanship Practice	UNACCEPTABLE FUSION SPLICES ANGULAR MISALIGNMENT Caused by poor cleaves and/or misalignment of the mating fiber ends. High attenuation and poor mechanical properties. Scrap and reterminate. Best Workmanship Practice

UNACCEPTABLE FUSION SPLICES BOUNDARY LAYER/DIFFRACTION ZONE A boundary layer or diffraction zone in a fusion splice is an indicator of an incomplete fusion process, improper cleave and/or contamination. Scrap and reterminate. Best Workmanship Practice	UNACCEPTABLE FUSION SPLICES BUBBLES Bubbles in a fusion splice are an indicator of an incomplete fusion process, improper cleave, and/or contamination. Scrap and reterminate. Best Workmanship Practice

NASA WORKMANSHIP STANDARDS
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 10	Section: 10.01	Page: 4

FIBER OPTICS GENERAL REQUIREMENTS (cont.)

UNACCEPTABLE FUSION SPLICES LATERAL OFFSET Caused by a lateral misalignment during the fusion process. Very high attenuation and poor mechanical properties. Scrap and reterminate. Best Workmanship Practice	ACCEPTABLE MARKINGS Cable connectors shall be permanently marked with mating connector designation within 15 cm (6 in.) of the connector body, or as per engineering documentation. NASA-STD-8739.5 [10.2.3]

ACCEPTABLE SCUFF MARKS Minor scuff marks on the connector body, and/or cable jacket are acceptable, provided the damage does not impact form, fit or function. Scuffing on the ferrule is an indicator of improper handling or excessive use. Best Workmanship Practice	ACCEPTABLE SPLICE PROTECTOR BUTTERFLY Splice closure is properly installed, and strain relief features are set. NASA-STD-8739.5 [9.2.2.a]

ACCEPTABLE SPLICE PROTECTOR HEAT SHRINK Splice closure is properly located. Shrinkage is uniform and strain relief features are set. No evidence of scorching, burning or melting. NASA-STD-8739.5 [9.2.2.a]	UNACCEPTABLE CONFORMAL COATING/STAKING Conformal coating or staking shall not be applied to optical fiber unless specifically required in the engineering documentation. NASA-STD-8739.5 [11.4.5]

NASA WORKMANSHIP STANDARDS
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 10	Section: 10.01	Page: 5

FIBER OPTICS GENERAL REQUIREMENTS (cont.)

UNACCEPTABLE CONTAMINATION Contamination is the primary cause of splicing and connectorization problems. Fingerprints and cleaning residue on the endface can significantly degrade signal quality. Best Workmanship Practice	UNACCEPTABLE DAMAGE Damage to the buffer, outer jacket, or other cable components in excess of engineering specification shall be cause for rejection. Best Workmanship Practice

UNACCEPTABLE ENDFACE ANOMALIES BREAKDOWN/ROLLOFF A surface irregularity characterized by an angular shearing of a portion of the endface. Defect is non-repairable. The fiber/assembly shall be reterminated or scrapped. Best Workmanship Practice	UNACCEPTABLE ENDFACE ANOMALIES CONCAVE A surface irregularity caused by excessive polishing or an improper cleave. Defect is non-repairable. The assembly/fiber shall be reteerminated or scrapped. Best Workmanship Practice

UNACCEPTABLE ENDFACE ANOMALIES CONVEX A surface irregularity caused by incomplete polishing or an improper cleave. Reject and recleave for splice termination. May be fixable by repolishing if connectorized. Best Workmanship Practice	UNACCEPTABLE ENDFACE ANOMALIES HACKLE/MIST A surface irregularity characterized by a jagged, rippled or stepped break in the fiber face. Reject and recleave for spllice termination. May be fixable by repolishing if connectorized. NASA-STD-8739.5 [9.2.1]

NASA WORKMANSHIP STANDARDS
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 10	Section: 10.01	Page: 6

FIBER OPTICS GENERAL REQUIREMENTS (cont.)

UNACCEPTABLE ENDFACE ANOMALIES LIP A surface irregularity characterized by a raised fillet in the fiber edge. Reject and recleave for splice termination. May be fixable by repolishing if connectorized. Best Workmanship Practice	UNACCEPTABLE ENDFACE ANOMALIES NECKING Necking is the drawing (pulling) of the optical fiber to a smaller diameeeeeter during stripping. The fiber shall be trimmed and restripped. Best Workmanship Practice

UNACCEPTABLE ENDFACE ANOMALIES NOTCH A surface irregularity characterized by a radial chip in the fiber edge. Reject and recleave for splice termination. May be fixable by repolishing if connectorized. Best Workmanship Practice	UNACCEPTABLE ENDFACE ANOMALIES SCRATCHES Reject and recleave for splice termination. May be fixable by repolishing if connectorized. NASA-STD-8739.5 [10.2.7.e]

UNACCEPTABLE ENDFACE ANOMALIES SHATTERED A surface irregularity characterized by radial cracks in the core or cladding. Defect is non-repairable. The fiber/assembly shall be reterminated or scrapped. Best Workmanship Practice	UNACCEPTABLE ENDFACE ANOMALIES SPIRAL A surface irregularity characterized by a circular (screw-shaped) cleave. Defect is non-repairable. The fiber/assembly shall be reterminated or scrapped. Best Workmanship Practice

NASA WORKMANSHIP STANDARDS
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 10	Section: 10.01	Page: 7

FIBER OPTICS GENERAL REQUIREMENTS (CONT.)

UNACCEPTABLE ENDFACE ANOMALIES SUB-SURFACE CRACKS Sub-surface cracks are only visible with core illumination, and are non-repairable. The fiber/assembly shall be reterminated or scrapped. NASA-STD-8739.5 [10.2.7.e]	UNACCEPTABLE ENDFACE ANOMALIES SURFACE CRACKS-FLIGHT HARDWARE If cracks in a flight fiber optic assembly endface are found, the assembly shall be reterminated or scrapped. Re-polishing to fix cracks in flight hardware is prohibited. NASA-STD-8739.5 [11.3.2]

UNACCEPTABLE ENDFACE ANOMALIES SURFACE CRACKS-GROUND SUPPORT If cracks in a flight fiber optic assembly endface are found, the assembly shall be reterminated or scrapped. Re-polishing to fix cracks in flight hardware is prohibited. NASA-STD-8739.5 [11.3.2]	UNACCEPTABLE ENDFACE ANOMALIES SURFACE PITS Repolish if in core or cladding. NASA-STD-8739.5 [10.2.7.e]

UNACCEPTABLE EPOXY BOND LINE CRACKS Cracks in the epoxy bond line shall be cause for rejection. NASA-STD-8739.5 [10.3.3.c], [11.5.3.c]	UNACCEPTABLE FERRULE DAMAGE Cracks, damage or deformities on the ferrule shall be cause for rejection. NASA-STD-8739.5 [10.2.5.c], [11.2.3.c]

NASA WORKMANSHIP STANDARDS
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 10	Section: 10.01	Page: 8

FIBER OPTICS GENERAL REQUIREMENTS (CONT.)

UNACCEPTABLE IMPROPER SPLICE CLOSURE INSTALLATION Splice closures shall be installed to provide environmental and mechanical protection to the splice section. As depicted, the splice closure does not completely cover the exposed fiber. NASA-STD-8739.5 [9.2.3.b], [10.2.7.f]	UNACCEPTABLE IMPROPER STRIP LENGTH Fibers designated for splicing or connectorization shall exhibit the proper cable and fiber stripping dimensions. Improper stripping dimensions may reduce reliability or performance. NASA-STD-8739.5 [10.2.4.a], [11.2.2.a]

UNACCEPTABLE KINKING Kinking produces microbends in the fiber, increasing signal attenuation and may promote breakage of the fiber. Best Workmanship Practice	UNACCEPTABLE LEAKS Light leakage is the result of a macrobend event in the fiber (i.e. crack, ship, etc.), causing a disruption in the light's transmission path. Best Workmanship Practice

UNACCEPTABLE MECHANICAL SPLICES BUBBLES Bubbles in the matching gel cavity will result in a high attenuation termination. The assembly shall be reterminated or scrapped. Best Workmanship Practice	UNACCEPTABLE MECHANICAL SPLICES END SEPARATION Typically seen in mechanical splices where the fiber ends are not in intimate contact, or in splices in which the matching gel has been lost/removed. High attenuation/completely dark. Best Workmanship Practice

NASA WORKMANSHIP STANDARDS
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 10	Section: 10.01	Page: 9

FIBER OPTICS GENERAL REQUIREMENTS (CONT.)

UNACCEPTABLE PISTONING The axial movement of the fiber within the connector body/ferrule causes pistoning. Positive pistoning may be fixable by repolishing. Negative pistoning shall be cause for rejection. NASA-STD-8739.5 [10.3.3.b], [11.5.3.b]	UNACCEPTABLE ROUTING Optical fibers and cable assemblies shall not be routed over sharp edges or corners unless appropriate protection is provided. NASA-STD-8739.5 [11.4.1], [12.2.8], [12.3.8]

UNACCEPTABLE SPLICES, CORE MISMATCH Core mismatch is typically caused by the splicing of two differing fiber core sizes (i.e. 50/125 to 62.5/125). The splice can result in a power gain, or loss, depending on the direction of transmission. Best Workmanship Practice

NASA WORKMANSHIP STANDARDS
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 10	Section: 10.01	Page: 10


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