OLT, ONT, ODN, Fiber, Divido
FTTH network consisting OLT, ONT / ONU, ODN, the ODN network fiber composite, dividers, etc.
Fiber
Installation of fiber optic cable is one of the most expensive items in the PON deployment and how to proceed depends on several factors, including cost, rights of way, legal standards, aesthetics, etc., and if the fiber is installed in new facilities (installation ‘greenfield’) or an existing development in active routes (overlap / overbuilding). Three basic cable installation methods are used:
> Direct-With this method Burial cable is placed underground, in direct contact with the ground; this is done by digging ditches, plowing or drilling.
> Installation duct-In this case, the optical cable is placed inside a network of underground passages. Although the initial installation of ducts is more expensive than a system under direct land use duct makes it much easier to add or remove cables.
> Air-Con Installing this approach, the cable is usually installed on poles or towers on the ground. This type of installation, normally used for overbuilding, is usually more affordable than installing underground and does not require heavy achinery. The optical cable can be secured to a suspension cable or optical cable can be used freestanding.
For densely populated areas struggling right of way, there are several alternative methods available. For example, the cable can be run slots are cut into the pavement or into drainage pipes, sewer pipes and gas pipes.
Dividers
branching optical device used in PONs bidirectional point-to-multipoint (P2MP) is called a divisor ópticoo just a splitter, which has an entrance from the F1 port and multiple output ports.Are considered passive splitters that do not require an external power except the incident light beam.They are broadband and only added loss, mainly due to the fact that divide the input power (in descending order).This loss, known as loss divisoro division ratio, is usually expressed in dB and depends mainly on the number of output ports, as shown in Table 3. The optical signal (low) input is divided equally in a cascade or on branches;for example, a 1×2 splitter has only two branches or split bearing a 3 dB loss (50% of light in each path).In a 1×4 splitter, two branches each path to the original 1×2 division, adding 3 dB other, to a total loss of 6 dB are added.In a 1×8 splitter, two or more branches each route 1×2 division of the original 1×4 division are added, adding another 3 dB loss to a total loss of 9 dB again.1×16 splitter then withstand a loss of 12 dB and 1×32 splitter shall have a minimum loss of 15 dB, without the additional losses due to connections and imperfections (typically adds 1 dB loss to the original division);therefore a 1×32 splitter will normally have a loss of 16 dB.
PONs use the equivalent of the output ports to F2, which allows multiple users to share a single optical fiber and therefore a shared bandwidth. In the upstream direction, the optical signals from different ONTs are combined in a single fiber (F1).
It should be noted that contrary to what one might expect, the splitter adds approximately the same amount of loss (even for light traveling upstream).
In an FTTx network, there may be a splitter or more cascaded splitters, depending on the topology. The G.984 recommendation ITU-T allows splitting ratios of up to 31, while the G.984.6 recommendation relationship extends to 64. Regardless of the topology, the divisor must satisfy the allowed optical loss budget.
The dividers can be packaged in various shapes and sizes depending on the basic technology used. The most common types are planar wave guide (usually for high split ratios) and fiber fused biconical conditioner (FBT) (usually for low counts). Both types are manufactured for mounting box-tray assemblies. The illustrations 1-5 and 1-6 show the two technologies.
Connectors
There are three different categories of connectors:
1. Simplex-connector with a finished fiber
2. Duplex-connector with two fibers terminated
in March. Multiple fiber-connector with more than two fibers (up to 72)
simplex connectors are currently the most popular FTTH deployments.Figure 1-7 shows the most common types of simplex connectors:
Another category of connector that charges popularity is the multifiber (or MT) connector. A single MT connector can have from 4-72 fibers. The type of multifiber connector used more widely in PONs is the MTP type. This connector is often repackaged and used to create a more robust, especially designed for tough environments typical FTTH deployments cable.
It should be noted, however, that the most common type of connector used in implantation FTTH at the moment is polished angled connector (APC), mainly due to the inclination of 8 in cap reduces reflections by more than 60 dB ( the typical loss is ≤0,5 dB). The APC connectors can be easily identified by their green color (Figure 1-7)
Joints
Joints may be mechanical or fused and protected from the environment by junction boxes. Mechanical splices are the least expensive but have insertion loss and back reflection higher than fused joints, which have a very low loss (0.02 dB) and virtually no retroreflection. However, fused joints require expensive and extensive fusion splicing equipment and well trained technicians. The number of splices in a link depends on the length of the cross-sections used (section lengths are typical ≤2 km 4 km and 6 km). The shorter is the length, simpler the aintenance, but the entire cable assembly requires more joints more time and more money. By contrast, the use of longer cable sections is less expensive, but the subsequent maintenance is more complicated and expensive.
When splicing different types of fiber and perform tests based on reflectometry (OTDR or iOLM) method, you may see a significant gain or loss due to the difference in diameters field-mode fibers. A good example of this would G625D fiber splicing fiber G657.
Unit Team Collective Housing Interior
Depending on the type of architecture collective housing (MDU) to be implemented (see Figure 1-9 and 1-10), the equipment used may be similar to that used in implementations OSP or be especially designed for indoor use (see Figure 1-9). The interior equipment is less subject to harsh environmental conditions and therefore does not require the same degree of robustness equipment outside plant (OSP). The following items are normally find in indoor deployments:
Fiber optic cables:
> The input cables form the segment between the CO and the fiber distribution hub (FDH) and are usually found
. in the basement
> Cables climb up the segment between the FDH and the terminal fiber distribution (FDT) and are found on each floor or in the collecting fiber (FC). Rise cables may consist of a single fiber or MTP port splitter cables.
> drop cables form the segment between the FDT and ONT and are located in the apartment. They are usually made of fiber which is insensitive to micro / macro bends.
Hubs fiber distribution (FDHs) include:
> Cabinets, junction boxes
> Divider (s)
> Panel (s) connections
> Elements fiber management Terminal fiber distribution FDT): > The FDT-located in each plant-serves as the connection between FDH and drop cable; You can connectorized or spliced. Collector fiber (FC): > The FC serves as a connection point between the FDH and a few FDTs (see Figure 1-9).
Source: EXFO.
