CFR > Title 7 - Agriculture > SUBTITLE B—Regulations of the Department of Agriculture > CHAPTER XVII—RURAL UTILITIES SERVICE, DEPARTMENT OF AGRICULTURE (parts 1700 to 1794) > PART 1755—TELECOMMUNICATIONS POLICIES ON SPECIFICATIONS, ACCEPTABLE MATERIALS, AND STANDARD CONTRACT FORMS > 1755.200—RUS standard for splicing copper and fiber optic cables.

1755.200—RUS standard for splicing copper and fiber optic cables.

(a) Scope. (1) This section describes approved methods for splicing plastic insulated copper and fiber optic cables. Typical applications of these methods include aerial, buried, and underground splices.
(2) American National Standard Institute/National Fire Protection Association (ANSI/NFPA) 70, 1993 National Electrical Code (NEC) referenced in this section is incorporated by reference by RUS. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. A copy of the ANSI/NFPA 1993 NEC standard is available for inspection during normal business hours at RUS, room 2845, U.S. Department of Agriculture, Washington, DC 20250-1500, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. Copies are available from NFPA, Batterymarch Park, Quincy, Massachusetts 02269, telephone number 1 (800) 344-3555.
(3) American National Standard Institute/Institute of Electrical and Electronics Engineers, Inc. (ANSI/IEEE), 1993 National Electrical Safety Code (NESC) referenced in this section is incorporated by reference by RUS. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. A copy of the ANSI/IEEE 1993 NESC standard is available for inspection during normal business hours at RUS, room 2845, U.S. Department of Agriculture, Washington, DC 20250-1500, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. Copies are available from IEEE Service Center, 455 Hoes Lane, Piscataway, New Jersey 08854, telephone number 1 (800) 678-4333.
(b) General. (1) Only Rural Utilities Service (RUS) accepted filled cable and splicing materials shall be used on outside plant projects financed by RUS.
(2) The installation instructions provided by the manufacturer of splicing materials shall be followed except where those instructions conflict with the procedures specified in this section.
(3) Precautions shall be taken to prevent the ingress of moisture and other contaminants during all phases of the splicing installation. When an uncompleted splice must be left unattended, it shall be sealed to prevent the ingress of moisture and other contaminants.
(4) Minor sheath damage during construction may be repaired if the repair is completed immediately and approved by the borrower's resident project representative. Minor damage is typically repaired by:
(i) Scuffing the cable sheath associated with the damaged area;
(ii) Applying several layers of DR tape over the scuffed and damaged area;
(iii) Applying several layers of plastic tape over the DR tape; and
(iv) If damage is severe enough to rupture the cable shield, a splice closure shall be installed.
(5) All splice cases installed on RUS toll trunk and feeder cables shall be filled, whether aerial, buried, or underground.
(c) Splicing considerations for copper cables— (1) Preconstruction testing. It is desirable that each reel of cable be tested for grounds, opens, shorts, crosses, and shield continuity before the cable is installed. However, manufacturer supplied test results are acceptable. All cable pairs shall be free from electrical defects.
(2) Handling precautions. The cable manufacturer's instructions concerning pulling tension and bending radius shall be observed. Unless the cable manufacturer's recommendation is more stringent, the minimum bending radius shall be 10 times the cable diameter for copper cables and 20 times the cable diameter for fiber optic cables.
(3) Cable sheath removal. (i) The length of cable sheath to be removed shall be governed by the type of splicing hardware used. Follow the splice case manufacturer's recommendations. For pedestals or large pair count splice housings, consider removing enough cable sheath to allow the conductors to extend to the top of the pedestal and then to hang downward to approximately 15 centimeters (cm) (6 inches (in.)) above the baseplate.
(ii) Caution shall be exercised to avoid damaging the conductor insulation when cutting through the cable shield and removing the shield. Sharp edges and burrs shall be removed from the cut end of the shield.
(4) Shield bonding and grounding. For personnel safety, the shields of the cables to be spliced shall be bonded together and grounded before splicing activities are started. (See paragraphs (g)(2), and (g)(5)(i) through (g)(5)(iii) of this section for final bonding and grounding provisions.)
(5) Binder group identification. (i) Color coded plastic tie wraps shall be placed loosely around each binder group of cables before splicing operations are attempted. The tie wraps shall be installed as near the cable sheath as practicable and shall conform to the same color designations as the binder ribbons. Twisted wire pigtails shall not be used to identify binder groups due to potential transmission degradation.
(ii) The standard insulation color code used to identify individual cable pairs within 25-pair binder groups shall be as shown in Table 1:
Table 1—Cable Pair Identification Within Binder Groups
Pair No. Color
Tip Ring
1 White Blue.
2 White Orange.
3 White Green.
4 White Brown.
5 White Slate.
6 Red Blue.
7 Red Orange.
8 Red Green.
9 Red Brown.
10 Red Slate.
11 Black Blue.
12 Black Orange.
13 Black Green.
14 Black Brown.
15 Black Slate.
16 Yellow Blue.
17 Yellow Orange.
18 Yellow Green.
19 Yellow Brown.
20 Yellow Slate.
21 Violet Blue.
22 Violet Orange.
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23 Violet Green.
24 Violet Brown.
25 Violet Slate.
(iii) The standard binder ribbon color code used to designate 25-pair binder groups within 600-pair super units shall be as shown in Table 2:
Table 2—Cable Binder Group Identification
Group No. Color of bindings Group pair count
1 White-Blue 1-25
2 White-Orange 26-50
3 White-Green 51-75
4 White-Brown 76-100
5 White-Slate 101-125
6 Red-Blue 126-150
7 Red-Orange 151-175
8 Red-Green 176-200
9 Red-Brown 201-225
10 Red-Slate 226-250
11 Black-Blue 251-275
12 Black-Orange 276-300
13 Black-Green 301-325
14 Black-Brown 326-350
15 Black-Slate 351-375
16 Yellow-Blue 376-400
17 Yellow-Orange 401-425
18 Yellow-Green 426-450
19 Yellow-Brown 451-475
20 Yellow-Slate 476-500
21 Violet-Blue 501-525
22 Violet-Orange 526-550
23 Violet-Green 551-575
24 Violet-Brown 576-600
(iv) Super-unit binder groups shall be identified in accordance with Table 3:
Table 3—Super-Unit Binder Colors
Pair numbers Binder color
1-600 White.
601-1200 Red.
1201-1800 Black.
1801-2400 Yellow.
2401-3000 Violet.
3001-3600 Blue.
3601-4200 Orange.
4201-4800 Green.
4801-5400 Brown.
5401-6000 Slate.
(v) Service pairs in screened cables shall be identified in accordance with Table 4:
Table 4—Screened Cable Service Pair Identification
Service pair No. Color
Tip Ring
1 White Red.
2 White Black.
3 White Yellow.
4 White Violet.
Red Black.
6 Red Yellow.
7 Red Violet.
8 Black Yellow.
9 Black Violet.
(6) Cleaning conductors. It is not necessary to remove the filling compound from cable conductors before splicing. However, it is permissible to wipe individual conductors with clean paper towels or clean cloth rags. No cleaning chemicals, etc., shall be used. Caution shall be exercised to maintain individual cable pair and binder group identity. Binder group identity shall be maintained by using color coded plastic tie wraps. Individual pair identification shall be maintained by carefully twisting together the two conductors of each pair.
(7) Expanded plastic insulated conductor (PIC) precautions. Solid PIC and expanded (foam or foam skin) PIC are spliced in the same manner, using the same tools and materials and, in general, should be treated the same. However, the insulation on expanded PIC is much more fragile than solid PIC. Twisting or forming expanded PIC into extremely compact splice bundles and applying excessive amounts of tension when tightening tie wraps causes shiners and, thus shall be avoided.
(8) Splice connectors. (i) Only RUS accepted filled splice connectors shall be used on outside plant projects financed by RUS.
(ii) Specialized connectors are available for splicing operations such as butt splices, in line splices, bridge taps, clearing and capping, and multiple pair splicing operations. The splice connector manufacturer's recommendations shall be followed concerning connector selection and use.
(iii) Caution shall be exercised to maintain conductor and pair association both during and after splicing operations.
(iv) Splicing operations that involve pairs containing working services shall utilize splice connectors that permit splicing without the interruption of service.
(9) Piecing out conductors. Conductors may be pieced-out to provide additional slack or to repair damaged conductors. However, the conductors shall be pieced-out with conductors having the same gauge and type and color of insulation. The conductors used for piecing-out shall be from cables having RUS acceptance.
(10) Splice organization. Spliced pair bundles shall be arranged in firm lay-ups with minimum conductor tension in accordance with the manufacturer's instructions.
(11) Binder tape. Perforated nonhygroscopic and nonwicking binder tape should be applied to splices housed in filled splice cases. The binder tape allows the flow of filling compound while holding the splice bundles near the center of the splice case to allow adequate coverage of filling compound.
(12) Cable tags. Cables shall be identified by a tag indicating the cable manufacturer's name, cable size, date of placement, and generic route information. Information susceptible to changes caused by future cable throws and rearrangements should not be included. Tags on load coil stubs shall include the serial number of the coil case, the manufacturer's name, and the inductance value.
(13) Screened cable. Screened PIC cable is spliced in the same manner as nonscreened PIC cable. However, special considerations are necessary due to differences in the cable design. The transmit and receive bundles of the cable shall be separated and one of the bundles shall be wrapped with shielding material in accordance with the cable manufacturer's recommendations. When acceptable to the cable manufacturer, it is permissible to use either the scrap screening tape removed from the cable during the sheath opening process provided the screening tape is edge coated or new pressure sensitive aluminum foil tape over polyethylene tape.
(14) Service wire connections. (i) Buried service wires may be spliced directly to cable conductors inside pedestals using the same techniques required for branch cables. Buried service wires may also be terminated on terminal blocks inside pedestals in areas where high service order activity or fixed count cable administration policies require terminal blocks. However, only RUS accepted terminal blocks equipped with grease or gel filled terminations to provide moisture and corrosion resistance shall be used.
(ii) Only filled terminal blocks having RUS acceptance shall be used on aerial service wire connections.
(15) Copper cable testing. Copper cable testing shall be performed in accordance with RUS Bulletin 345-63, “RUS Standard for Acceptance Tests and Measurements of Telephone Plant,” PC-4, (Incorporated by reference at § 1755.97 ).
(16) Cable acceptance. Installed cable shall be tested and pass the inventory and acceptance testing specified in the Telephone System Construction Contract (Labor and Materials), RUS Form 515. The tests and inspections shall be witnessed by the borrower's resident project representative. All conductors shall be free from grounds, shorts, crosses, splits, and opens.
(d) Splice arrangements for copper cables— (1) Service distribution closures. Ready access closures permit cable splicing activities and the installation of filled terminal blocks for service wire connections in the same closure. Ready access designs shall allow service technicians direct access to the cable core as well as the terminal block.
(ii) Fixed count terminals shall restrict service technician access to the cable core. Predetermined cable pairs shall be spliced to the terminal leads or stub cable in advance of service assignments.
(2) Aerial splices. Aerial splice cases accommodate straight splices, branch splices, load coils, and service distribution terminals. Aerial splicing arrangements having more than 4 cables spliced in the same splice case are not recommended. Stub cabling to a second splice case to avoid a congested splice is acceptable.
(3) Buried splices. (i) Direct buried splice cases accommodate straight splices, branch splices, and load coils. Direct buried splices shall be filled and shall be used only when above ground splicing in pedestals is not practicable.
(ii) A treated plank or equivalent shall be placed 15 cm (6 in.) above the buried splice case to prevent damage to the splice case from future digging. Where a firm base for burying a splice cannot be obtained, a treated plank or equivalent shall be placed beneath the splice case.
(iii) Each buried splice shall be identified for future locating. One method of marking the splice point is the use of a warning sign. Another method is the burying of an electronic locating device.
(4) BD-type pedestals. (i) BD-type pedestals are housings primarily intended to house, organize, and protect cable terminations incorporating splice connectors, ground lugs, and load coils. Activities typically performed in pedestals are cable splicing, shield bonding and grounding, loading, and connection of subscriber service drops.
(ii) The recommended splice capacities for BD-type pedestals are shown in Table 5. However, larger size pedestals are permissible if service requirements dictate their usefulness. Table 5 is as follows:
Table 5—Splice Capacities for BD-Type Pedestals
Pedestal type Maximum straight splice pair capacity using single pair connectors or multiple pair splice modules Maximum load splice pair capacity using single pair connectors or multiple pair splice modules (see note 1)
BD3, BD3A 100 Pair 50 Pair.
BD4, BD4A 200 Pair 100 Pair.
BD5, BD5A 600 Pair 300 Pair.
BD7 1200 Pair 600 Pair.
BD14, BD14A 100 Pair 50 Pair.
BD15, BD15A 400 Pair 200 Pair.
BD16, BD16A 600 Pair 300 Pair.
Note 1: This table refers to load coil cases that are to be direct buried with stub cables extending into the pedestal for splicing. Requirements involving individual coil arrangements inside the pedestal should be engineered on a case-by-case basis.
(iii) Special distribution pedestals having a divider plate for mounting filled terminal blocks are available. Distribution pedestals are also equipped with service wire channels for installation of buried service wires without disturbing the cabling and gravel inside the base of the pedestal. Distribution pedestals are recommended in locations where the connection of service wires is required.
(5) Large pair count splice housings. Large pair count splice housings are recommended for areas not suitable for man- holes. The recommended capacities are shown in Table 6:
Table 6—Splice Capacities for Large Count Housings
Housing type Maximum straight splice pair capacity using single pair connectors or multiple pair splice modules Maximum load splice pair capacity using single pair connectors or multiple pair splice modules (see note 1)
BD 6000 6,000 Pair 3,000 Pair.
BD 8000 8,000 Pair 4,000 Pair.
BD 10000 10,000 Pair 5,000 Pair.
(6) Pedestal restricted access inserts. Restricted access inserts may be used to protect splices susceptible to unnecessary handling where subsequent work activities are required or expected to occur after splices have been completed. Restricted access inserts also provide moisture protection in areas susceptible to temporary flooding. A typical restricted access insert is shown in Figure 1:

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(7) Serving Area Interface (SAI) Systems. SAI systems provide the cross-connect point between feeder and distribution cables. Connection of feeder to distribution pairs is accomplished by placing jumpers between connecting blocks. Only RUS accepted connecting blocks having grease or gel filled terminations to provide moisture and corrosion resistance shall be used.
(8) Buried cable splicing arrangements. Typical buried cable splicing arrangements are illustrated in Figures 2 through 5:

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(9) Underground splices (manholes). Underground splice cases accommodate straight splices, branch splices, and load coils. Underground splices shall be filled.
(10) Central office tip cable splices. (i) Filled cable or filled splices are not recommended for use inside central offices, except in cable vault locations. Outside plant cable sheath and cable filling compound are susceptible to fire and will support combustion. Fire, smoke, and gases generated by these materials during burning are detrimental to telephone switching equipment.
(ii) Tip cables should be spliced in a cable vault. However, as a last resort, tip cables may be spliced inside a central office if flame retardant splice cases or a noncombustible central office splice housing is used to contain the splice.
(iii) Splices inside the central office shall be made as close as practical to the point where the outside plant cables enter the building. Except in cable vault locations, outside plant cables within the central office shall be wrapped with fireproof tape or enclosed in noncombustible conduit.
(e) Splicing considerations for fiber optic cables— (1) Connection characteristics. Splicing efficiency between optical fibers is a function of light loss across the fiber junctions measured in decibels (dB). A loss of 0.2 dB in a splice corresponds to a light transmission efficiency of approximately 95.5 percent.
(2) Fiber core alignment. Fiber splicing techniques shall be conducted in such a manner that the cores of the fibers will be aligned as perfectly as possible to allow maximum light transmission from one fiber to the next. Without proper alignment, light will leave the fiber core and travel through the fiber cladding. Light outside the fiber core is not a usable light signal. Core misalignment is illustrated in Figure 6:

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(3) Splice loss. (i) Splice loss can also be caused by fiber defects such as nonidentical core diameters, cores not in center of the fiber, and noncircular cores. Such defects are depicted in Figure 7:

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(ii) Undesirable splice losses are caused by poor splicing techniques including splicing irregularities such as improper cleaves and dirty splices. Typical cleave problems are illustrated in Figure 8:

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(4) Handling precautions. The following precautions shall be observed:
(i) Avoid damaging the cable during handling operations prior to splicing. Minor damage may change the transmission characteristics of the fibers to the extent that the cable section will have to be replaced;
(ii) The cable manufacturer's recommendations concerning pulling tension shall be observed. The maximum pulling tension for most fiber optic cable is 2669 newtons (600 pound-force);
(iii) The cable manufacturer's recommendations concerning bending radius shall be observed. Unless the cable manufacturer's recommendation is more stringent, the minimum bending radius for fiber optic cable shall be 20 times the cable diameter;
(iv) The cable manufacturer's recommendations concerning buffer tube bending radius shall be observed. Unless the cable manufacturer's recommendation is more stringent, the minimum bending radius for buffer tubes is usually between 38 millimeters (mm) (1.5 in.) and 76 mm (3.0 in.). The bending limitations on buffer tubes are intended to prevent kinking. Buffer tube kinking may cause excessive optical loss or fiber breakage; and
(v) Handle unprotected glass fibers carefully to avoid introducing flaws such as scratched or broken fibers.
(5) Personnel safety. The following safety precautions shall be observed:
(i) Safety glasses shall be worn when handling glass fibers;
(ii) Never view open-ended fibers with the naked eye or a magnifying device. Improper viewing of a fiber end that is transmitting light may cause irreparable eye damage; and
(iii) Dispose of bare scrap fibers by using the sticky side of a piece of tape to pick up and discard loose fiber ends. Fiber scraps easily penetrate the skin and are difficult to remove.
(6) Equipment requirements. (i) Fiber optic splices shall be made in areas where temperature, humidity, and cleanliness can be controlled. Both fusion and mechanical splicing techniques may require a splicing vehicle equipped with a work station that will allow environmental control.
(ii) Both fusion and mechanical splicing techniques are permitted on RUS financed projects. When using the mechanical splicing technique, only RUS accepted mechanical fiber optic splice connectors can be used.
(iii) Fusion splicing machines shall be kept in proper working condition. Regular maintenance in accordance with the machine manufacturer's recommendations shall be observed.
(iv) Mechanical splicing tools shall be in conformance with the tool manufacturer's recommendations.
(v) An optical time domain reflectometer (OTDR) shall be used for testing splices. The OTDR shall be stationed at the central office or launch point for testing individual splices as they are made and for end-to-end signature tests for the fiber optic link.
(vi) An optical power meter shall be used for end-to-end cable acceptance tests.
(vii) A prerequisite for the successful completion of a fiber optic splicing endeavor is the presence of a talk circuit between the splicing technician in the splicing vehicle and the operator of the OTDR in the central office. The splicing technician and the OTDR operator shall have access to communications with each other in order to inform each other as to:
(A) Which splices meet the loss objectives;
(B) The sequence in which buffer tubes and fibers are to be selected for subsequent splicing operations; and
(C) The timing required for the performance of OTDR testing to prevent making an OTDR test at the same time a splice is being fused.
(7) Cable preparation. (i) Engineering work prints shall prescribe the cable slack needed at splice points to reach the work station inside the splicing vehicle. Consideration should be given to the slack required for future maintenance activity as well as initial construction activities. The required slack may be different for each splice point, depending on the site logistics. However, the required slack is seldom less than 15 meters (50 feet). The amount of slack actually used shall be recorded for each splice point to assist future maintenance and restoration efforts.
(ii) The splice case manufacturer's recommendations concerning the amount of cable sheath to be removed shall be followed to facilitate splicing operations. The length of the sheath opening shall be identified with a wrap of plastic tape.
(iii) If the cable contains a rip cord, the cable jacket shall be ring cut approximately 15 cm (6 in.) from the end and the 15 cm (6 in.) of cable jacket shall be removed to expose the rip cord. The rip cord shall be used to slit the jacket to the tape mark.
(iv) If the cable does not contain a rip cord, the cable jacket shall be slit using a sheath splitter. No cuts shall be made into the cable core nor shall the buffer tubes be damaged.
(v) If the cable contains an armor sheath, the outer jacket shall be opened along the slit and the jacket shall be removed exposing the armor sheath. The armor shall be separated at the seam and pulled from the cable exposing the inner jacket. The armor shall be removed making allowances for a shield bond connector. The inner sheath shall be slit using a sheath splitter or rip cord. The cable core shall not be damaged nor shall there be any damage to the buffer tubes. The jacket shall be peeled back and cut at the end of the slit. The exposed buffer tubes shall not be cut, kinked, or bent.
(vi) After the cable sheath has been removed, the binder tape shall be removed from the cable. The cable shall not be crushed or deformed.
(vii) The buffer tubes shall be unstranded one at a time. The buffer tubes shall not be kinked.
(viii) If the cable is equipped with a strength member, the strength member shall be cut to the length recommended by the splice case manufacturer.
(ix) Each buffer tube shall be inspected for kinks, cuts, and flat spots. If damage is detected, an additional length of cable jacket shall be removed and all of the buffer tubes shall be cut off at the point of damage.
(x) The cable preparation sequence shall be repeated for the other cable end.
(8) Shield bonding and grounding. For personnel safety, the shields and metallic strength members of the cables to be spliced shall be bonded together and grounded before splicing activities are started. (See paragraphs (g)(4), and (g)(5)(i) through (g)(5)(iii) of this section for final bonding and grounding provisions).
(9) Fiber optic color code. The standard fiber optic color code for buffer tubes and individual fibers shall be as shown in Table 7:
Table 7—Fiber and Buffer Tube Identification
Buffer tube and fiber No. Color
1 Blue.
2 Orange.
3 Green.
4 Brown.
5 Slate.
6 White.
7 Red.
8 Black.
9 Yellow.
10 Violet.
11 Rose.
12 Aqua.
13 Blue/Black Tracer.
14 Orange/Black Tracer.
15 Green/Black Tracer.
16 Brown/Black Tracer.
17 Slate/Black Tracer.
18 White/Black Tracer.
19 Red/Black Tracer.
20 Black/Yellow Tracer.
21 Yellow/Black Tracer.
22 Violet/Black Tracer.
23 Rose/Black Tracer.
24 Aqua/Black Tracer.
(10) Buffer tube removal. (i) The splice case manufacturer's recommendation shall be followed concerning the total length of buffer tube to be removed. Identify the length to be removed with plastic tape.
(ii) Experiment with a scrap buffer tube to determine the cutting tool adjustment required to ring cut a buffer tube without damaging the fibers.
(iii) Buffer tubes shall be removed by carefully ring cutting and removing approximately 15 to 46 cm (6 to 18 in.) of buffer tube at a time. The process shall be repeated until the required length of buffer tube has been removed, including the tape identification marker.