Basic Fiber Cable Type for Optical Communication Network

October 14, 2021

Basic optical cables are the earliest fiber cable type which are widely used in communication networks. The regular fiber cable are duct fiber optic cables, overhead fiber optic cable, direct buried fiber optic cable, flame retardant fiber optic cable and FTTH drop cable.

Duct Fiber Optic Cable

The duct fiber optic cable is a multi loose tube stranded structure. Single mode optical fibre is put into the loose tube, and the loose tubes are filled with waterproof compound. The center of the duct fiber cable core is a metal steel wire reinforced core. For some fiber cable types, a layer of polyethylene (PE) needs to be squeezed outside the metal steel wire reinforced core.

All loose tubes (and filling rope) are twisted around the central reinforcing core to form a compact circular cable core, and the gaps in the cable core are filled with water blocking fillers.

Plastic-coated aluminum tape (APL) is longitudinally wrapped outside loose tubes and fillers. And then all materials are extruded into a cable with a polyethylene sheath. The structure and of this duct fiber optic cable is shown as below.

armored fiber cable GYTA

This duct fiber cable type has good waterproof performance and is suitable for occasions where pipe laying is the main method, and overhead laying can also be used.

Overhead Fiber Optic Cable

The core structure of overhead fiber optic cable is the same as that of duct fiber optic cable mentioned above. The difference is that its sheath is double-sided chrome-plated plastic coated steel tape (PSP) + polyethylene. The structure is shown in below. Compared with duct fiber optic cable, overhead fiber optic cable has better resistance to lateral pressure.

multi-tube steel tape light armored fiber optic cable

It is suitable for scenarios that require greater pressure on the side of the fiber optic cable. For example, in the section dominated by overhead laying, or for the access of home broadband, it can also be used for pipeline laying.

Direct Burial Fiber Optic Cable

Direct burial fiber optic cable can be understood as duct fiber optic cable being armored with double-sided chrome-plated plastic coated steel tape (PSP), and finally extruded into a cable with a polyethylene (PE) outer sheath. The structure of direct burial fiber cable is shown in below.

direct burial fiber optic cable gyta53 stranded loose tube armored fiber optic cable

Direct burial fiber optic cable has good waterproof, side pressure resistance and tensile resistance, and is suitable for direct buried laying. Due to the high cost of direct burial optical cables and the inability to expand the capacity, the direct-buried method is no longer used for newly-built optical cable lines. Directly buried optical cables are mainly used for the maintenance of the original directly buried optical cable lines.

Flame Retardant Fiber Optic Cable

The structure of flame retardant fiber optic cable is the same as duct fiber optic cable. The difference is that the sheath of duct fiber optic cable is made of polyethylene material, and the sheath of flame retardant fiber optic cable is made of flame-retardant material.

This fiber cable type is mainly used for core network and the incoming sections of important convergence point. Generally, the length of each incoming optical cable shall not be less than 500m.

FTTH Drop Cable

FTTH drop cable is mainly used in the drop-in section of FTTH (Fiber to the home). It connects optical communications from the fiber distribution box to the user’s home ONT equipment. Based on its structure and shape, FTTH cable is divided into bow type drop cable (or butterfly drop cable), self-supporting butterfly drop cable, and prefabricated end.

Bow Type Drop Fiber Cable
ftth fiber cable bow type drop cable 2 core distribution cable

In bow type drop fiber optic cable, optical fibre is placed in the center, which two parallel steel wires are placed on both sides as strengthening elements, and outside is extruded into cable with low-smoke halogen-free (LSZH) flame retardant sheath.

This fiber cable type has 1 or 2 cores in common use, the short and long axis dimensions of the sheath are 2mm and 3mm respectively. And the short-term allowable tensile force (minimum) is 200N. It should be laid along the wall or through pipes, rather than hanging in the air.

Self-Supporting Drop Fiber Cable

ftth drop cable self supporting bow type fiber optic cable with steel wire

It is a non-metallic bow type drop fiber optic cable with a reinforced member (a steel wire or steel wire rope) attached to the outside.

The common fiber count of this fiber cable type is 1 or 2 cores, and the allowable tensile force (minimum) is 600N. It can be suspended in a short distance of less than 50m, which is suitable for introduction from outdoor to indoor.

Pre-terminated Drop Optical Cable

The pre-terminated drop cable is a fixed length bow type optical cable with SC connector prefabricated at both ends to reduce the workload of on-site termination during installation.

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Tony Lau is technical manager and co-founder at HOC. He loves writing about content optical fiber communications, specializes in fiber optic cables, FTTH turnkey solutions, ADSS cable, and ODN networks.

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