What is field tactical optical cable? Is it a must to connect RRU/AAU?

Field Cable Structure and Features

Tactical Fiber Cable is a kind of military optical cable. It is a metal-free optical cable specially designed for rapid wiring or repeated use in field operations and complex environments. The number of cores in field optical cables is mostly 1, 2, or 4 cores. The figure below shows the cross-sectional structure of a field optical cable.

The single core fiber unit in the cross-section above is the light yellow cable between the two movable connectors in our commonly used single-core fiber optic patch cord. Many people call it soft optical fiber, but its standard name is ” Single core indoor optical cable”.

Since single core optical cables are very suitable for use as fiber jumpers (with movable connectors at both ends) or pigtails (with movable connector at one end), field optical cables are often equipped with movable fiber optic connectors when used.

To facilitate rapid deployment, tactical fiber optic cable usually appear as tactical Fiber Optic Cable Assemblies, including: field optical cables, optical cable connectors and retractable cable racks. To facilitate portability, field optical cables have a thinner outer diameter and are lighter in weight.

In order to adapt to the requirements of rapid wiring and repeated retraction in field operations and complex environments, field optical cables also have: tensile resistance, pressure resistance, high strength-to-weight ratio; good flexibility, easy to bend; oil resistance, wear resistance, flame retardant; applicable temperature Wide range and other characteristics.

Current Connecting Status Of RRU/AAU Cable

The BBU/DU and RRU/AAU of the base station need to be connected through optical cables. RRU/AAU are mostly installed outdoors, such as on iron towers, which requires that the optical cable connecting to BBU/DU has the characteristics of easy connection, outdoor use, safety and reliability.

The tactical fiber cable meets the above requirements very well, so the field optical cable is widely used for the connection between the BBU/DU and RRU/AAU of the base station.

The connection between the field optical cable antenna end and the 5G base station AAU is shown in the figure below.

Open the outdoor quick-lock connector and you can see the movable connector on the field optical cable. The movable connector is plugged into the optical module (optical transceivers) on the AAU.

The connectors with field fiber optic cable which is far away from the antenna end is usually usually directly plugged into the optical module of the (e) CPRI interface of the BBU/DU equipment base band board.

In CRAN mode, it may be plugged into the ODF unit of the base station / outdoor cabinet or the multiplexer / demultiplexer port of the passive wavelength division, and then connected to the BBU/DU equipment through ordinary access optical cables.

Chaos in the use of RRU/AAU Cable

Although the mechanical and protective performance of field optical cables when used for RRU/AAU connections far exceeds actual needs, operators still feel that it is not enough, so they add a metal armor layer (flexible steel pipe in the picture below) to the field optical cables. , making its compression resistance as high as 3000N/100mm; this performance exceeds that of directly buried optical cables, reaches the standard of underwater optical cables, and can withstand being crushed by cars.

The tensile strength of the single core optical fiber unit in the field optical cable is relatively low (40N), and it is not resistant to ultraviolet rays. Therefore, when the field optical cable is connected to the AAU, an outdoor quick-lock connector should be used to fix the sheath of the field optical cable to prevent the single-core optical fiber unit from being damaged by direct force. However, the height of the outdoor quick-lock connector is less than 10cm, if the length of the single-core optical fiber unit branched at both ends exceeds the height of the outdoor quick-lock connector, the outdoor quick-lock connector cannot be fixed on the sheath of the field optical cable, which will cause the single-core optical fiber unit at the AAU end to be stressed and exposed outdoors.

Since the purchase length of a single base station cable is certain, the commonly are: 40 meters, 50 meters, 60 meters, 70 meters, and 80 meters. During construction, each optical cable has an excess length of less than 10 meters. Usually a base station (physical site) contains multiple logical stations, and each logical station needs to lay at least three field optical cables. In this way, the total length of the remaining field optical cables for a base station may be more than 100 meters.

The common steel tube towers on the roadside are basically filled with entangled field optical cables.

What kind of optical fiber cable is required for RRU/AAU connection?

The RRU/AAU connection optical cable customized by the operator is not suitable for field use because it contains metal components. It is actually an armored fiber patch cord for outdoor use, but everyone is still accustomed to calling it a field optical cable. The Ministry of Industry and Information Technology’s standard for RRU/AAU connecting optical cables is YDT 2289 released in 2011. According to this standard, the name of the RRU/AAU connecting optical cable should be “RRU/AAU optical cable (Wireless radio frequency remote unit=RRU) )”.

The optical cables for RRU/AAU specified in YDT 2289 do not have the characteristics of field optical cables such as wear resistance, impact resistance, bending resistance, oil resistance, and high temperature adaptability. Its allowable tensile force and flattening force are even higher than those of ordinary field communication optical cables. The requirements are much lower, but flame retardant is required.

The excess length of the optical cable for RRU/AAU can be controlled by terminating  on-site at the equipment-side (that is to add a movable optical connector). The RRU/AAU-side optical cable is still prefabricated in the factory, and the equipment-side cable will be cut according to the actual required length like the FTTH drop cable, fusion splice with a pigtail  on site for termination, and protect the welding point with e protective box. See below photo

It may be more appropriate to purchase and name optical cables according to product industry standards, and to cut and lay optical cables according to the actual required length.

FAQ?

Do you have 4 cores field tactical cable?

Yes, field tactical cable mostly use is 2 cores, but 4 cores is the same structure, only change the 2pcs filling rope in the cable into optical fiber unit, it is 4 cores.

What kind of connectors can you add on field cable?

All types of optical connectors can be used for field fiber optic cable, such as SC LC FC ST, etc. It is depend on your project requirements.

Meanwhile, we can add steel armored tape or metal braided mesh for higher performance request.

How long of the breakout kits when pre terminated in factory?

Normally it is 3cm, and 34cm at both sides of the cable, like below photo, but it can be custom.

How do you pack the tactical optical cable?

If you only buy cable, it is delivered with wooden drum, 2km/km or 3km/drum; if you need short length to pre connected at factory, we will use plastic film to wrap, or with cardboard reel like below to protect for better operate during field construction.

What is the dimension of the tactical cable?

The cable is about 7.0mm diameter and 42.3kg/km, it can be 2 cores or 4 cores. it is widely used in base station field, details like below:

Can I add pulling eye for workers to pull but protect the cable from damage？

Yes,we can add pulling eyes at both sides of the connector, which will be made of corrugated pipe or woven nets. All the length from the breakout kits to the connectors will be wrapped inside the the pulling eye, when pulling, will not hurt the connector, and we will make a hook or hole at end of the pulling for handling.

What color of the fiber unit inside of the field fiber optic cable?

If customer not specify, the standard color is blue orange green brown, the same as the Industrial chromatography.