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.

FIBER OPTIC SPLICING

Splicing Methods

The two splicing methods generally used are fusion and mechanical. Fusion splices provide low loss compared to mechanical splices, but are more difficult to complete. Splices may be found virtually anywhere within a cable route, but are usually found in manholes, maintenance holes or other convenient points.

Fusion Splicing

Fusion splicing is the recommended method of fusing two fibers together. In a fusion splice, the two fibers are "welded" together with an electric arc. Because this method of splicing is much more accurate there may be no loss across the splice. Fusion splicing is the only type of splicing recommended for singlemode fiber.

Mechanical Splicing

A typical mechanical splice uses a gripping mechanism to prevent fiber separation, a means for fiber alignment, and includes index matching gel to reduce signal loss.

Insertion Loss (Attenuation) and Return Loss

ANSI/TIA/EIA-455-8 (OTDR Testing) defines acceptable results for splice insertion loss and splice return loss. Splice insertion loss shall not exceed 0.1 dB mean (0.3 dB maximum) and splice return loss shall have a return loss greater than or equal to 45.0 dB mean (40.0 dB minimum) for singlemode fiber.

Mechanical protection

Each fusion or mechanical splice shall be protected in a splice tray or similar protective device that will mount inside a closure or an enclosure.

The tray shall:

INDOOR SPLICING

General

Optical fiber inside terminals shall meet the requirements of the ANSI/TIA/EIA-568-B.3 standard. This portion of the standard refers to and governs fiber optic splicing enclosures located on a rack or a wall.

Fiber Storage and Organizing Housings

Fiber storage and organizing housings typically involve fiber and fiber splice storage, as well as fiber distribution and fiber cross connection. These housings may be rack or wall mounted depending on the size of the incoming fiber.

The following should be considered when selecting fiber storage and housings:

Fiber Distribution Units

A Fiber Distribution Unit (FDU) house and organize groups of fibers. Fibers are typically spliced to connector pigtails. The pigtail splices are housed in the FDU and may be then terminated on a connector panel within the FDU, or routed to another patch panel usually located directly above the FDU. Connections between cables are typically accomplished using connectorized patch cords.

SPLICE 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:

Non-metallic components shall:

OPTICAL FIBER CLOSURES

General

Splice closures for fiber optic cable are used in an outdoor environment to store and protect from:

Closures may be located in underground installations such as manholes and maintenance holes, direct burial, above ground pedestals, on poles, strands or racks. Closures should accommodate various cable constructions and splice capacities for discrete and mass, mechanical and fusion optical fiber splices.

Optical Fiber Splice Closure

Fiber optic splice closures:

Application

Fiber optic splice enclosures should:

Criteria

Optical fiber closures shall meet the following criteria.

Common tests

Common tests for optical fiber closures can be found in Bellcore document GR-771-CORE.

Installation Requirements

Splicing fiber optic cable can be time consuming and requires precise operation in a clean environment. Therefore fiber optic splice enclosures:

Free-Breathing Closures

Free-breathing closures:

Special Testing

Special tests for free-breathing optical fiber splice closures can be found in Bellcore document GR-771-CORE.

Sealed Aerial Closures

Vented Aerial Closures

Underground Closures

Direct-buried closures

Hermetically sealed closures (HSCs)

Special Tests


Special tests for direct-buried optical fiber splice closures can be found in Bellcore document GR-771-CORE.

Shield Isolation/Grounding Closure

Pedestal Closure

Special Tests

Special tests for direct-buried optical fiber splice closures are described in Bellcore document GR-771-CORE.