Creation of a broadband network based on gpon technology qualification work of bachelor

Direct Stream The direct stream at the optical signal level is broadcast. Each ONT subscriber node, reading the address fields, extracts from this general stream a part of the information intended only for it. In fact, we are dealing with a distributed demultiplexer.
Reverse flow All ONT subscriber nodes transmit in a reverse stream on the same wavelength, usingthe time division multiple access ( TDMA division) conceptmultiple access. In order, to exclude the possibility of crossing signals from different ONTs, each of them sets its own individual schedule for data transmission, taking into account the correction for the delay associated with the removal of this ONT from the OLT.
3.2. "Passive" technology
The main element of the PON system is a passive splitter. This is a small and fairly simple device that distributes the incoming light stream over several fibers.
Splitters are rated as passive devices because they do not contain electronics that analyze and redirect the input signal. These devices do not use optical transmitters (the same lasers) and do not require power supply.
Accordingly, the signal strength at the outputs will be lower, so developers should take into account the power budget when determining the number of output lines and communication range. These limits are currently set at 32 lines and 20 km. Thus, it is possible to perform optical wiring from access nodes that are sufficiently remote from subscribers. However, you don't need a switchboard to connect the subscriber.
The subscriber device in the PON access system is called ONU (Optical Network Unit), and another name for the subscriber terminal is used-ONT (Optical Network Terminal).
An Optical Line Terminal (OLT) is installed in the access node. This device communicates with the ONU. The OLT and ONU have WDM multiplexers that separate the downstream and upstream streams.
All terminals receive a broadcast downstream stream from the access node. Each ONU extracts information from this common stream that is addressed to the corresponding subscriber. The upstream stream is built on the principle of multiple access with temporary multiplexing. Each ONU is assigned its own time interval (time slot), when transmission can be carried out in the direction of the access node.- theseare rather complex and quite expensive devices, since they use different principles for processing incoming and outgoing streams. According to IEEE estimates, approximately 70-80% of the cost of purchasing equipment falls on these subscriber devices. But compared to access solutions based on other technologies, implementing PON requires much lower infrastructure costs. In particular, the access node is connected to the splitter by only one fiber.
There are four main topologies for building optical access networks: "ring", "point-to-point", "tree with active nodes", "tree with passive nodes".
"The ring"
The SDH-based ring topology has proven itself well in urban telecommunications networks. However, access networks are not doing as well. If when building an urban highway, the location of nodes is planned at the design stage, then in access networks it is impossible to know in advance where, when and how many subscriber nodes will be installed.

Picture 3.2-Ring topology
In case of accidental territorial and temporary connection of users, the ring topology can turn into a very broken ring with many branches. Connecting new subscribers is carried out by breaking the ring and inserting additional segments. In practice, such loops are often combined in one cable, which leads to the appearance of rings that look more like a polyline - ” compressed " rings (collapsed rings), which significantly reduces the reliability of the network. In fact, the main advantage of a ring topology is minimized.
Point-to-point" (P2P)
The P2P topology does not impose restrictions on the network technology used. P2P can be implemented for any network standard, as well as for non-standard ones (proprietary ) solutions that use optical modems, for example.
Picture 3.3-P2P Topology
From the point of view of security and protection of transmitted information, when connecting P2P, the maximum security of subscriber nodes is ensured. Since the OK needs to be laid individually to the subscriber, this approach is the most expensive and attractive mainly for large subscribers.
Tree with active nodes
A tree with active nodes is a fiber-efficient solution.
Picture 3.4-Tree with active nodes
This solution fits well into the scope of the Ethernet standard with a speed hierarchy from the central node to subscribers of 1000/100/10 Mbit / s (1000Base-LX, 100Base-FX, 10Base-FL). However, each node in the tree must contain an active device (for IP networks, a switch or router). Optical Ethernet access Ethernetnetworks that primarily use this topology are relatively inexpensive. The main disadvantage is the presence of active devices on intermediate nodes that require individual power supply.
A tree with passive branching
Solutions based on the PON architecture useмноготочка" P2MP (the P2MP ( point - to-multipoint) logical topology, which is the basis of PON technology. An entire fiber-optic segment of the tree architecture covering dozens of subscribers can be connected to a single port of a central node, Picture 8.
Picture 3.5-Passive branching tree
At the same time, compact, fully passive optical splitters (splitters) that do not require power and maintenance are installed in the intermediate nodes of the tree.It is well known that PON allows you to save on cable infrastructure by reducing the total length of optical fibers, since only one fiber is used in the section from the central node to the splitter. To a lesser extent, they pay attention to another source of savings - reducing the number of optical transmitters and receivers in the central node. Meanwhile, the savings from the second factor in some cases are even more significant. Thus, according to NTT estimates, a PON configuration with a splitter in the central office in close proximity to the central node is more economical than a point-to-point network, although there is practically no reduction in the length of optical fiber! Moreover, if the distances to subscribers are not large, taking into account the operating costs (in Japan, this is a significant factor), it turns out that a PON with a splitter in the central office is more economical than a PON with a splitter close to the subscriber nodes.
3.3. Ways to implement PON technology
The first implemented PON technology, dating back to 1998, was called APON (ATM-PON). It was based on ATM transport technology, which at that time was widely used in telecommunications. The idea was to bring the ATM directly to the subscriber, for example, to the office of a large company. Thus, a single technological basis for the backbone network and access network was implemented.
APON technology allows symmetric connection, in which the speed of the descending and ascending streams is 155
PON technology is the most cost-effective solution for implementing optical access. Connection options are shown in Picture 9.
The reference to ATM in the name of the APON technology after some time turned out to be not entirely justified, because passive optical networks can be used to deliver other types of traffic. Therefore, the improved version of the access technology is called BPON (Broadband PON, that is, broadband PON). This implementation increased the speed of the downstream stream, which, according to the developers, was supposed to provide performance for applications such as video loading.
The spread of Ethernet as a transport technology in telecommunications resulted in the emergence of EPON (Ethernet PON). This access technology is one of the areas of development of Ethernetcarrier-class Ethernet solutions, which was initially developed by IEEE and the EFMA (Ethernet in the First Mile Alliance) industry alliance. These organizations offered to increase the speed to 1.25 Gbit /s in both directions. In addition, EPON offers a number of network management and troubleshooting capabilities that are based on the generally accepted and fairly simple concept of building EPON networks.
The ability to choose can be a hindrance to improving technology. In particular, the recent stagnation in the PON market was largely due to the uncertainty caused by the presence of several standards and the lack of a clear idea of the future development of the market. As a way out of this situation, GPON (Gigabit PON) technology was proposed, which provides voice and data support for network traffic that comes from ATM, SONET / SDH and Ethernet. This technology provides even faster speeds, up to 2.5 Gbpsс. КромеIn addition, it provides extensive data management and protection capabilities.
There are several other PON implementations that, unlike those listed, are not widely used. An example is CPON (CDMA PON) technology, which is designed to separate optical interconnects in CDMA. This is also WPON (Wavelength-Division-Multiplexing-PON).
As for the uncertainty about the generally accepted standard, even today it is difficult to name a leading technology. It is necessary to compare proven and proven BPON solutions with EPON, which are becoming more and more popular as Ethernetcarrier-class Ethernet technologies are widely implemented.
The main attractive characteristics of PON deployment by telecom operators, as a mass-market technology, are:
passive optics only in the entire subscriber access network;
significant reduction of wiring and occupied space at the telephone exchange;
reduced operating costs of the subscriber access network, in particular, reduced power supply costs due to the lack of active equipment in the distribution network, as well as maintenance costs due to built-in operation, administration and maintenance tools;
easy upgrades and long service life of the subscriber access network.
The introduction of GPON to the market has shown that this technology is also gaining popularity as even more productive and versatile. At the same time, EPON processes packets according to the same principles as in other Ethernetsystems, which makes it easier for all network sections to interact and, consequently, requires lower costs for its construction and operation. So the question of which of the technology options is better - improved EPON or GPON - remains open. We can trace the dynamics of lower prices for connecting a subscriber to the PON network in Picture 10.

Costs of connecting one subscriber equipment and work

Picture 3.7-Connection costs per subscriber

3.4. Calculation of the attenuation of a section of the Fergana-Motrudiy st.
To calculate line attenuation, you need to know the following parameters: Fiber attenuation coefficient, dB / km; number of welded joints and attenuation coefficient on them; number and type of optical splitters and attenuation on them.

Picture 3.8-section of the route Motrudiy St.
The OMZKGM-10A optical cable was used during the construction of the highway-01-0,22-64-(7.0) with an attenuation of 0.22 dB / km.
To calculate the attenuation, we took the longest section of the highway - up to letter 2.
Formula for calculating attenuation:
∑α =αk×L1+αk×L1+αk×L2+αk×L3+αk×L4+∆αpc +∆αcb +α1×2 +α1×32
Where αk is the attenuation of the cable
L1, L2, L3 - lengths between couplings
L4 - length from coupling to splitter
∆αα α kn connectors
∆αα α sv-welded joints
α1 × 2 - сплиттер1x2 splitter
α1×32 - сплиттер1x32 splitter
Attenuation:

• 
  Connector - 0.5 dB
  
• 
  Welding point-0.2 dB
  
• 
  Сплиттер1x2 - 3.5 dB Splitter
  
• 
  Сплиттер1x4 Splitter - 7.2 dB
  
• 
  Сплиттер1x8 Splitter - 10.7 dB
  
• 
  Сплиттер1x16 - 14.4 dB Splitter
  
• 
  1x32 Splitter - 18.2 dB
  

Substituting the numerical attenuation values, we get α α=23.8dB. For correct operation, it is necessary that the energy reserve of the system
W=Pper-Ppr >>∑α,
Where Pper is the power of the transmitting device, and Ppr is the attenuation. At the PBX adjacent to this section of the highway, equipment with an optical power budget of at least 29 dB per 10 km is installed. Thus, we obtain the energy reserve of the system: W=29-23. 8=5.2 dB. An example of the equipment installed on the PBX and subscribers, as well as the parameters of this equipment, are presented by me in Pictures 14 and 15.
The active OLT hardware is installed in the access node.

Picture 3.9-ZyXEL OLT-1308H