What Is Fiber Optic Cable

Fiber optic cable is an assembly similar to an electrical cable, but containing one or more optical fibers to carry light.

Fiber optic cable is an assembly similar to an electrical cable, but containing one or more optical fibers to carry light. The carrier of optical fiber communication is infrared light.
This blog will introduce some basic knowledge about fiber optic cable and helps you realize it.

The Advantages Of Using Fiber Optic Cable

  • Wide frequency band, large communication capacity. 
  • No crosstalk interference.
  • Low loss, long relay distance. 
  • Small size, light weight. 

Working Principle Of Optical Fiber

Optical fiber transmission is carried out by the mechanism of total reflection of light.
Light in the same medium is transmitted in a straight line when the two media refractive index is not equal to the phenomenon of total reflection.
If the light refraction, it will cause signal loss.

Classification of optical cables

According to the application environment

It can divided into outdoor, indoor and drop cable mainly depending on the application environment.
Indoor cables can be defined as those suitable for indoor use, which are generally softer to fit around corners.
Outdoor cables are harder.
Leather drop cables (black and white) Black cables are generally used for the interior wiring of houses (similar to water mains with dark lines), while white cables are mainly used for the renovation of old residential areas.

According to the structure

We can divide it into those types:

①Center tube type
②Layer twisted type
③Frame groove type

The main structure includes:

Fiber core (single-mode and multi-mode core) has a high refractive index, used for transmission sightseeing, generally 9~ 10um (single-mode) 50 or 62.5 (multi-mode)
Cladding: Low refractive index to provide total reflection conditions, diameter is generally 125um.
Coating layer: Protect the fiber core and cladding, enhance the mechanical strength, the diameter is generally 245um, the coating layer is generally two layers,

the inner layer with soft coating, outer layer with more hard material. Also known as coated fiber, it is generally bare when bought.

Bare fiber: Including fiber core and cladding, Our customers generally refer to the cable without coloring.

Optical Fiber Cable Machine
Optical Fiber Cable Machine

According to the construction method

This classification method is mainly used in outdoor optical cables.

① Overhead (pole connection) self-supporting [8-figure cable, ADSS OPGW] non-self-supporting [GYTS (steel belt, side pressure resistance),53]
② Underground is divided into pipeline and direct burial
The pipe (below the well) is GYTA construction, with more emphasis on moisture resistance and aluminum tape .
The GYTA53, with a steel sheath, is directly buried (the cable is placed in the ground and buried)
③ Submarine cable
According to the number of fiber cores, it can be divided into single core, double core, multi-core and large core.

Fiber Optic Cable Structure

Fiber is easy to break not because its tensile resistance is small, but the resistance to bending performance is poor.

Indoor optical cables can be interspersed with the core to connect the interface, peel the coating layer, wipe with alcohol, and then interspersed with the core. (It needs stable size and better quality, so that it can be carried out normally when interspersed, and there will be no problem of too big or too small)

  • indoor vertical use branch internal single core fiber optical cable, because the vertical wiring for pushing for more.
  • single-core twin-core fiber optic cable, such as 0.9 mm to 2.0 mm to 3.0 mm for jumper cables indoor shipment is more, indoor optical cable typically require joint.
  • tight set of coating layer is 0.9 mm.

Outdoor optical cable is generally fused with the process, the same need to peel the coating layer, the sub-fiber box has a card slot for welding, known as the fusion disk.

Colored fiber is generally arranged by spectrum, in Brazil and other mixed arrangement.

The purpose of coloring is to protect the optical fiber, and to identify it in the case of multi-core number, so as to facilitate the docking construction.

SM single mode

We can divide G652D into B1,3, which mainly use for indoor single/double and outdoor main line construction. Compatible with the G657A optical fiber, but incompatible with the G657B optical fiber, which means we cannot mix them.

The main difference of optical fiber G657 series is that the bending performance (the smaller the radius, the better) is different, from A1.2 B3 prices are higher. A1,2 is mainly used for butterfly cable and leather cable.

Butterfly cable divide into optical fiber A1A2, strengthening parts (metal wire phosphating and galvanized, non-metallic FRP, aramidon yarn) and sheath (Low Smoke Zero Halogen).

Circular lead-in cable: Optical fiber (B3 more than four times more expensive than A12), reinforcement (aramid), sheath (LSZH or TPU — 3 to 4 times more expensive)

B3 cable uses TPU material (hydrolysis resistance, friction resistance, chemical resistance, good bending performance, but very expensive, generally used in military, field, etc.), mainly used for circular indoor and outdoor introduction.

Aramid yarn (originally imported, such as DuPont in the United States, but now mainly domestic, a 1100D usually provides 10N tension, the final purpose of aramid yarn design is to meet the acceptance standard, that is the strain size).

Strain divide into fiber strain and cable strain, and the test has specific national and domestic standards, such as GB/T.

  1. The tension is strong and the strain is small (it is difficult to stretch the length), which is less than the strain of the optical fiber, so it plays the role of protecting the optical fiber.
  2. The price is high, about ten times more.
  3. Flame-retardant (it burns itself out) and turns to dust when burned.

Polyester yarn:

1. Does not provide tension, used for filling, the strain is very large, so in the stretch of the fiber stress, transmission performance will be poor, the main role is to avoid sheath and fiber stick off

2.Low price

3. Non-flame retardant, will shrink when burned and continue to burn.

MM multi-mode optical fiber

OM1~5 (mainly used for indoor cable).The jacket color of multi-mode fiber has a certain standard. OM12 is orange, OM3 is aqua/light blue, and OM4 is aqua or hidden red. OM5 is dark green.

Reinforcement piece


  1. steel wire (single), divided into phosphating (commonly used is 0.4,0.45, 1.0, 1.2) and galvanized (1.2, self-supporting [can withstand their own tension] steel wire), the difference is whether the need for corrosion resistance.The role of steel wire glue is to prevent slipping, only coated on the steel wire, and the outer sheath is easy to glue together, equivalent to adhesive, increase the cost is high, is generally not needed.
  2. Steel strand (multiple strands, generally greater than 1.2 need to be used, because it is soft and convenient for construction), generally galvanized (the role is to prevent corrosion, the price will be higher)

Non metal

  1. FRP, the default is GFRP white, QFRP KFRP is generally yellow, the material is arnylon yarn + adhesive curing, the price will be higher in turn.
  2. Aramid yarn
  3. Glass yarn, low cost, more rigid, internal glass fiber, can be called non-metallic armor.

Anti-rat bite function is divided into ① mixed chemical substances, volatile, not environmental protection, so this process was abandoned. (2) Glass yarn, glass belt (very high requirements for equipment), after biting will tie the mouth, symbolic anti-rat ③ sheath is hard, steel/nylon material.

Optical fiber models and raw materials

fiber optic cable

GY: It means outside, also called the field.

GJ: refers to indoor or intra-office.

GJY: indoor and outdoor, that is, the introduction cable, divided into butterfly cable, circular cable, figure 8 cable (upper and lower two circular structure, the upper layer is used for tensile, generally with steel strand, known as reinforcement member).

Center reinforcement (placed in the center) : Metal is generally omitted, non-metal will add F

Waterproof material: dry type generally omitted, refers to the water blocking yarn, water blocking belt (wrapped up) and water blocking powder, T refers to the oil paste filling, divided into fiber paste (and direct contact with optical fiber, quality to be more delicate, the price is higher) and cable paste

Sheath material:

PE (jacket for outdoor cable),

PVC (for tight packaging or tight sleeve, outer sheath 2.0 3.0 cable, especially a mining cable, mainly with its flame retardant performance),

LSZH (outer sheath for indoor or outdoor cable),

Nylon (generally used for tight or rat-proof outer sheath (a layer of PE sheath outside, 0.5mm, high price),

TPU (polyester type [cheap price, poor hydrolysis performance, easy to crack in the outdoor, is not recommended to use on the cable], and polyether type [mainly used for cable]),

PP(filler rope, indoor cable commonly referred to as false cable).

PBT: Loose casing, generally used outside.


Tight pack: LSZH PVC nylon

Outer sheath:


[Outdoor] PE PVC nylon

Filling material: PP

Loose casing: PBT or PP(the performance of loose casing is not very good, PBT material is recommended).

The cable has a service life of more than 20 years (or more than 30 years in static state) and a warranty period of 12 to 18 months.

Fibconet provide best quality fiber optic cable, contact us for more informations!

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