Splicing
Overview
Splicing can be defined as the joining of two conductors or fibers together to restore the conductor continuity between two points. Since most cables are constructed of more than one or two conductors or fibers, splicing generally involves more than one or two pairs, and generally involves restoring the integrity of the cable sheath, armour and shield.
Splicing begins with the joining of the conductors with a single splice. In copper splicing one of the types of splices used is the 3M Scotchlok. Once all of the conductors have been spliced they will be inserted into the splice enclosure which is selected by the location of the splice enclosure. In a fiber optic splice, the fibers are joined by a mechanical or fusion splice and then inserted into a splice tray.
For the purpose of this Standard, the term splice closure shall include bonding hardware, sealing materials and the closure housing.
COPPER SPLICING
General
Copper splice connectors:
-
generally use IDC technology
-
can be single wire connectors (discrete), or modular to splice up to 25 pairs
-
can be used with 26 throuhg 19 AWG wire
-
shall be moisture resistant in OSP environments
Splicing connectors for OSP:
- have low connection resistance
- have high insulation resistance
- are robust
- resistant to moisture and corrosion
- are easy to installation
Due to the variety of
connectors, manufacturers shall provide all of the necessary tooling required
to terminate their connectors.
Materials
Metal components shall:
- resist corroision, cracking and pitting
- not produce significant galvanic corrosion effects on other metals likely to be present in their use environment
Insulating materials:
- shall be resistant to fungi, heat, and cable cleaning solvents.
- must be compatible with metals and other materials such as conductor insulation and filling compounds used in the manufacture of cable.
Plastic materials shall:
- be non-corrosive to metals
- resist deterioration when exposed to chemical pollutants and sunlight.
Connector filling compounds shall:
- be compatible with other connector and cable materials
- be resistant to fungi
- conform to safety and toxicology requirements at the time of manufacture.
Transmission Performance Markings
If the manufacturer so desires it may mark its splicing hardware with its level of transmission performance and these markings shall be visible during installation. It is suggested that the markings consist of:
"Cat 3" for category
3 components
"Cat 4" for category 4 components
"Cat 5" for category 5 components
Tensile Strength
The tensile strenght of
a splice is the force required to pull the wire in the opposite direction
of entry to the splice. The pull out strength is expressed as a percentage
of the strength required to break an unspliced wire. The minimum breaking
strength for a 19 AWG wire is 60% of 19 AWG wire breaking strength. The breaking
strength for smaller gauge splices is 75% of the wire breaking strength.
Insulation Resistance
Splicing connectors that
are to be used in severe service conditons shall be tested for moisture resistance.
This test involves immersing the moisture filled or resistant connector tap
water for a period of one week. The insulation resistance shall then be measured
between each conductor and the water bath with 250 Vdc applied. No more than
10 percent of the conductors shall be less than 10 6 ohms, not more than 25
percent shall be less than 10 8 ohms, and the remainder shall be greater than
10 9 ohms. After drying, the test units shall be restored to greater than
10 9 ohms. Those that fall below 10 8 ohms shall be inspected for corrosion.
If there is evidence of corroision, the unit shall be deemed to have failed
the test. It should be noted that this is a criteria for the manufacturer
to follow and not the installation contractor.
Salt Fog Exposure
Terminated (or spliced)
filled samples shall be exposed to salt fog per ASTM B 117 for a period of
48 hours. The resistance though each splice shall not increase by more than
2 milli-ohms as a result of this exposure.
OSP Twisted-Pair Cross-Connect Jumpers
Cross-connect jumper wire shall be wire of the same or higher transmission category as the cross-connect block so as to maintain the overall performance of the system. The twist shall be maintained to within 13 mm (0.5 in) of the entry into the cross-connect block.
INSTALLATION REQUIREMENTS
Cable Splices for BBOSP
There are two type of splices, the butt splice (preferred) and the inline splice. An in-line splice method can also be used if the conductors are spaced close together, i.e., no open loops. The amount of untwisting of the conductor pairs shall be kept at 13 mm (0.5 in) maximum. Pair splices should be staggered within the splice closure to help maximize performance.
Bridge-Taps
Bridge taps may be used
for low-frequency analog circuits, but are not recommended for OSP circuits
or high frequency digital circuits.
Binder group integrity
25-pair binder groups should not be split between termination points.
OSP Twisted-Pair Testing
OSP twisted pair cables are not subject to the same tests as horizontal UTP cables are. The primary field test parameters for OSP twisted-pair cabling are:
- DC loop resistance
- Wire map
- Continuity to remote end
- Shorts between two or more conductors
- Crossed pairs
- Reversed pairs
- Split pairs
- Any other mis-wiring.
S PLICE ENCLOSURES
General
Splice cases, splice closures or splice enclosures are the more common names used to describe the devices used to house splices. These names may refer to devices for both copper and fiber.
Materials
In copper and fiber optic splice enclosures the materials used in shall exhibit the following properties:
Metal components shall:
- be corrosion resistant
- resist cracking and pitting
- not produce significant galvanic corrosion effects on other metals used in pedestal terminal closures or aerial cable terminals
Non-metallic components shall:
- resist fungi, heat, solvents
- resit stress cracking agents
- be compatible with metals and other materials used in the manufacture of cable
- be non-corrosive to metals
- resist deterioration when exposed to chemical pollutants and sunlight.
COPPER TWISTED-PAIR COPPER ENCLOSURES
General
Outdoor closures may be installed:
- on pedestals
- in maintenance and man holes
- on poles and cable messenger strands
The splice enclosures are should be expected to operate at temperatures between -40ºC and 65ºC (-40ºF and 150ºF) without degradation in performance. The enclosure is also expected to function normally if subjected to other forms of environmental factors such as ice, submersion in water and heat sources.
A splice closure is used restore integrity of the cable sheath's electrical and mechanincal properties following a sheath opening to:
- join wires
- install an isolation gap, capacitor, or pressure dam
- repair a damaged sheath
- close initial gaps between sheaths at splice points.
Aerial Copper Closures/Terminals
- are constructed of either metallic or nonmetallic materials
- provide access to terminated cable pairs for the purpose of connecting service wires
- accommodate splicing, connecting service wires for residential and business customers
- provide bonding and grounding hardware and terminal block mounting arrangements
- allows for the appropriate entry of the cables from either or both ends
- can be used on strand, pole or wall mount
Strand Mount
There are a variety of design configurations available for strand mounted enclosures, depending on the application. Regardless of the overall design, strand mount devices:
- are designed for in-line installation
- may include a terminal block with a fusible-link stub cable for splicing to distribution cable splice chamber
- may have a separate chamber for the terminal blocks where service drop wires may be connected
- may contain electrical protection
- are supported by the suspension strand
- shall have all metal supporting members and all electrical shields and ground wires electrically bonded to provide a current carrying capacity at least equivalent to that of #6 AWG wire
- shall have shield openings bridged with proper bonding devices
Some terminals designed
for strand mounting may also be pole mounted, eg: at a dead end, or where
a transition from aerial to buried cable is required.
Special Testing
Special tests for aerial copper closures/terminals can be found in Bellcore document TR-NWT-00014
Buried Service Wire Closures
- are used to join underground service wire
- shall be compatible with the wires
- shall have a 40 year life span
Application
Buried service wire closures:
- shall provide adequate moisture protection without the use of secondary encapsulants
- be compatible with all types of encapsulant compounds (if used)
Special Tests
Special tests for buried service wire copper closures are found in Bellcore document TR-NWT-000251.
BURIED/UNDERGROUND/VAULT SPLICE CLOSURES
Closure Housing
The closure housing shall
be compatible with all materials used in the construction of cable, filling
compounds, bonding and grounding devices, chemicals, and sealants which the
closure would contact under normal use. Secondary corrosion protection should
not be required.
Installation Requirements
The closure:
- shall be suitable for handling by one craftsperson
- minimize on-site assembly or disassembly of the closure
- should have factory assembled bonding, grounding and other sub-assemblies
- should be re-enterable without destroying the housing unless it is more economical to do so
- reuseable components should be immediately reusable, without factory or service center refurbishing and with minimum field work
- avoid using specialized tools or equipment not normally at craftsperson's disposal unless used for protection from tampering.
- should be suitable for installation over cut or through (uncut) cable
- should be usable on 254 mm to 533 mm (10 in to 21 in) sheath openings (but not necessary limited to these openings)
- should accept cables of 15 mm to 86 mm (0.6 in to 3.4 in) OD
- should have splice cavity diameters from 25 mm to 228 mm (1 in to 9 in) (or equivalent cross-sectional areas if not round).
- should have replacement and special application parts shall be readily available
- should avoid the use of specially-ordered non-catalog stock parts
- the encapsulant must not generate any exothermic (heat) condition that will damage the housing, cable insulation or connectors.
- housing shall be sealed to prevent encapsulant leakage
- shall have provisions which will indicate that the closure is properly filled with encapsulant after the encapsulant has cured.
Special Tests
Special tests for buried/underground/vault copper splice closures can be found in Bellcore documents TR-NWT-000014, TR-NWT-000251 and PUB 55004