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Fibră optică

Transmisie video optică

Fiber optic system for cameras installed on poles.
The main problem faced by installers implementing a fiber-optic video surveillance system in open areas is to choose the right way to install and connect IP cameras. Since the most common questions concern systems where cameras are deployed on poles/light poles/masts, this article presents wiring methods for this type of installation and an example of implementing a camera point in a dedicated waterproof box.
CCTV – fiber type
When cabling and transmission equipment are selected in parallel, care should be taken to ensure mutual compatibility of these components (i.e., single-mode cabling for single-mode equipment and multimode cabling for multimode equipment). If the connections on the camera-switch line exceed 2 km, it is necessary to use single mode cabling. A similar situation is when the extensive monitoring system will transmit the signal from dozens or hundreds of IP cameras via a single bus. With such a wide bandwidth, the use of single-mode fibers will be a more favorable solution due to the larger range of single-mode cables (the ability to better match the cable to the installation and environmental conditions), as well as the greater range.
The price difference between multi-mode and single-mode devices, often used as an argument for the option of using the former, is already negligibly small (for LAN/CCTV transmission equipment). At present, all arguments favor single-mode systems (greater bandwidth, greater distance, lower price).
Advantages of choosing cables with single-mode fibers:
  • a wider range of different types of cables on the market,
  • the ability to transmit a signal over a distance of tens of kilometers using widely available equipment,
  • lower cable price resulting from a less complicated fiber core manufacturing process,
  • availability of fibers with a reduced bending radius.
Topology of fiber optic cabling for CCTV systems
Feeding a separate cable to each pole (mast, lantern), on which the cameras are to be installed, is the most universal and the least labor-consuming solution when it comes to attention welding and protection of optical fibers. However, this involves a greater amount of work when laying cables and the need to provide more space on the cable route.
Fiber optic CCTV system – star topology

In this topology, the structure of the cable is not a significant factor, as there are no branches along the paths. Of course, the cable must meet all the requirements necessary for the proper operation in the environmental conditions. An important parameter is the tensile strength, sufficient for operations connected with pulling in the cable to cable ducts. The most popular types of cables used in installations of this type include:
  • Direct access cables
ZTT DAC 2J 9/125 G.657A1 L79302 optical cable
    The possibility to bury the cable directly in the ground is a feature that is taken into account when time for installation is short or the lowest service cost is important. DAC (Direct Access Cable) underground cables have a sheath made of highly foamed polyethylene (HDPE). This makes them rigid and very strong against mechanical damage. Two 0.9 mm diameter FRP bars additionally protect the cable from breaking, which is crucial when the cable is buried directly in the ground (freezing and thawing of the ground, movements caused by cyclical shocks caused by passing cars, for example, infiltration of rainwater into the ground, etc.). These cables have so called Water Block (WB) design which blocks the internal flow of water along the cable.
  • Outdoor cables
Typical outdoor cable: DRAKA A-DQ(ZN)B2Y 8SM L79508
    For outdoor use only (PE sheath – flammability class F according to EN50575). These cables are resistant to weather conditions and UV radiation. In Dipol's range, this category includes Optix brand cables which remain the best choice for overhead lines (self-supporting cables) and A-DQ(ZN)B2Y brand Draka cables. The former can also be used as standard interconnection (non-suspended) cables. However, it should be borne in mind that they do not have hydrophobic gel which prevents the propagation of water/moisture inside the cable (to some extent, aramid fibers are responsible for this). Both cables have a high installation tension force. Optix cables are usually the choice when a small cable diameter (about 3 mm) and the resulting smaller minimum bending radius are important. DRAKA A-DQ(ZN)B2Y outdoor cables are the best choice in wide-area outdoor systems. These cables can be laid without additional conduits (the use of additional conduits is a good practice and is always recommended, regardless of the type of cable) on roofs, facades, telecom conduits and even in the ground.
  • Universal cables
Universal Cable: DRAKA U-DQ(ZN)BH 4E (4xG.657A1)
Typical universal cable: DRAKA U-DQ(ZN)BH 4E L76004
    DRAKA universal cables have most of the advantages of outdoor cables. These include a gel-filled central tube and glass fibers for reinforcement and basic anti-rodent protection. DRAKA universal cables have excellent strength in comparison with similar types of cables from other manufacturers. The maximum installation pulling force is 2000 N which makes them slightly less resistant than typical outdoor cables. The outer sheath is resistant to UV radiation, but in the long run the cables with PE sheath perform better in this respect. For this reason, when using the universal cable outdoors, it is recommended to use PVC or similar protective conduits. Cables of this type remain the most popular product in the fiber optic cable section of Dipol's offer. They are used for point-to-point connections in local LANs, all kinds of building network backbones, video surveillance networks including both indoor and outdoor cameras, etc.
Regardless of the number of cameras on a pole, the transmission is performed only via two optical fibers. However, we recommend at least the minimum redundancy level - the application of optical fibers with 4 fibers.
CCTV box
The choice of the star topology also allows you to save space on the pole itself – the fiber optic cable can be inserted directly into the box, in which devices including media converter, PoE switch, video converter, power supply etc., are installed. The fiber optic, of course has to be secured with a pigtail, and the connection (splice) itself should be secured on the splices box or a dedicated optical fiber box. Then the pigtail should be plugged into the fiber optic adapter, and the connection with the device responsible for signal conversion should be made using a patch cord. Do not plug the cable directly into the device! In the future, when performing any service or maintenance work, the installer will only risk damaging the patch cord, and not the cable, which would entail the need to splice the fiber again.
SIGNAL CCTV 210/230/145 mm sealed box is R90601 designed for mounting on a pole, mast or wall. Inside, there is a mounting plate which can be easily removed, and two DIN rails for easy installation of components such as switches, power supplies, media converters or mini fiber optic distribution frames. Additionally, the box has protective wires which can be connected to active devices.
Example of using SIGNAL CCTV box R90601
The box can easily accommodate, among others, an industrial switch, power supply, main switch and mini distribution frame in the case of systems based on fiber optic cabling. In this case we recommend to use ODF-DIN L5312 distribution frame. All these elements can be mounted on DIN rails or aluminum mounting plate. Thanks to adequate number and size of cable gland holes, it is possible to lead in and out the cabling for: power supply, fiber optic cable, twisted pair, for connecting up to 4 surveillance cameras.
A list of accessories for a pole-mounted sealed box, which can provide a ready-made solution for many systems, is shown below:
  • R90601 – CCTV sealed box 250/310/145 mm
  • R90610J – pole mount for waterproof boxes
  • N299714 – Industrial PoE switch ULTIPOWER 341SFP
  • E1412 – NETSET U/UTP Cat. 5 outdoor twisted-pair cable
  • N93326 – Switched-mode power supply MDR-60-48
  • L1415 SFP ULTIMODE SFP-203G insert
  • L76004 – Universal optical cable A-DQ(ZN)BH
  • L5312 – Mini distribution frame L5312
  • L32151R – Single-mode patch cable ULTIMODE PC-515S1
  • L35511A – SC/UPC pigtails
  • L4311 – Single-mode adapter ULTIMODE A-511D
  • L76004 – Universal optical cable ULTIMODE UNI-4SM-A
The cabinet has six cable gland holes (all are blanked but can be easily punched out, the set includes two PG13.5 glands and four PG9 glands). The box is fully sealed, it has no gaps in the connection of walls, so there is no possibility of water getting in. Additionally, the door is protected with a rubber seal. The box can be closed with a cylinder lock. IP66 environmental rating.
 
George Popescu
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