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EPON Network Fault Analysis and Treatment

In Electronic Infomation Category: E | on March 18,2011

In the country "triple play" policy in the context of promoting a comprehensive, two-way radio and XC2S100-6PQ208C datasheet and television operators, network construction and XC2S100-6PQ208C price and renovation work has been full speed, the current EPON + EOC and XC2S100-6PQ208C suppliers and EPON + LAN network construction has become a mainstream way, the paper mainly discusses the EPON optical network failure causes and analysis and processing.

1 EPON networks pose

EPON networks are typically includes OLT (Optical Line Term ina, l Optical Line Terminal), ONU (Optical Netw ork U ni, t optical network unit), passive optical splitter (Splitter) and central office fiber to the client link. OLT in the EPON system, the central office side of the EPON system is responsible for voice, data and video services with the end-user connections, external business together, coordinating remote ONU, in addition to these basic functions, OLT also has a high level of data routing, switching and voice gateways and other functions, ONU is responsible for the users access, business coverage.

EPON network transmission downstream direction (from OLT to ONU) by broadcasting way, every ONU will receive all the downstream information, based on their MAC addresses extract useful signals. Upstream direction (from ONU to OLT) using time-division method sharing system. In order to avoid data collisions and fairly share the channel, the use of OLT static or dynamic bandwidth allocation method to assign a time for each ONU is no overlap in the variable transmission window slot for data transmission ONU, as shown in Figure 1 .


Figure 1 EPON transmission network structure

2 EPON transmission index

EPON system ONU design to meet the OLT and the optical transmission characteristics. OLTs transmitter and receiver optical power range varies by model PON modules, 10 km of the launch optical power modules range from 2 ~ - 3 dBm, the received optical power range is - 1 ~ - 24 dBm; 20 km of the launch optical power range of modules for the 7 ~ 2 dBm, the received optical power range - 6 ~ - 27 dBm. ONU transmit optical power range of 4 ~ - 1 dBm, the received optical power range is - 3 ~ - 24 dBm. EPON burst mode in the uplink direction, the ordinary power meter can not measure, can only test down in the implementation of OLT and ONU transmit optical power of the received optical power, wavelength measurement 1 490 nm, if the 1 550 nm wavelength measurement, based on experience with 1 ~ 2 dB deviation.

Now commonly used to send optical power in general OLT + 7 ~ + 2 dBm between the ONU optical input optical power is greater than - 27 ~ - 24 dBm, so the project can take multi-level shunt control structure for transmission, can ensure ONU input optical power, but also can save resources and increase the number of users.

3 EPON Fault Classification and causes

EPON access network is the all-optical networks, optical and access equipment (OLT, ONU, etc.) proposed new requirements, coupled with sensitivity to light a substantial increase in road indicators, so the construction specifications have more stringent requirements, view of the above characteristics of the two types of fault current analysis.

(1) Equipment problems

OLT port: This often leads to failure of all or part of its following ONU is not working properly, and restart difficult to restore, this time in a normal optical fiber and the ONU Dengjun state, field staff are often difficult to judge and deal with the need and room network Controllers timely communication, the port where the device in the OLT find out the reasons.

optical network unit (ONU): ONU EPON access network is the key equipment, ONU By using time-division multiplexing principle, any one ONU light is not normal, can lead to OAM (operation and management of maintenance) confusion, so that under the ONU OLT port not working properly. The exclusion of the failure, also need to plug one by one under the port OLT ONU, while the command View ONUs FER / BER, to determine the exception and replace ONU, the OLT port to make all under the ONU to resume normal work.

client: client failure in addition the users computer, network card reasons, there are the more common loop, * attacks, can loop detection, traffic monitoring and other methods lock the user, be ruled out.

cable connecting devices: optical splitter, flanges and other connections are the key elements of optical power attenuation, and most of the residents in the corridor outside or in the chassis, dust poor conditions, such failure is not easy to determine, difficult to detect, so called for better protection measures.

(2) the construction type of problem

weld decay must be strictly controlled, or which ONU optical power in the normal work of the edge, after a period of aging equipment and lines, ONU may frequently UP / DOWN.

indoor optical fiber (eg, $ splitter pigtail part) disk fiber radius is too small (less than 6 cm) or by external forces involved, extrusion, can lead to optical attenuation.

reserved fiber dust cap does not cover, resulting in dust pollution, lead to optical fiber immersed in water and gas is not available, two optical fiber connection must be clean with alcohol cotton face.

flange or other means through the optical fiber connection, be sure to check the reliability of its connection, make sure to install bayonet in place; fiber is not inserted tight will lead to an unstable connection, end the dust, moisture intrusion lead optical path loss is too large not available.

ONU cabinet in the corridor is not well fixed, will lead to optical fiber, cable unnecessary force, occurred off the network cable, optical path interrupted.

ONU power adapter to ensure a fixed and can not fly, otherwise easily lead to power loss and business interruption.

outdoor lightning protection measures should be considered the alignment, network port Ethernet ports can be added mine, mine power supply can be added.

4 maintenance and improvements

First: (1) full use of network management features to speed up recovery. Some ONU subject to some interference, it may not work correctly within a short time, the use of network management issued the restart command can be restored; (2) Aggregate breakdown phenomenon, fast positioning backbone access network failure or malfunction, saving on-site staff time. A large number of users can not access the same area, they should first of all through the network management system, query OLT port status, followed by cable issues to consider; (3) to strengthen on-site maintenance personnel and network management personnel exchanges, quickly locate the problem.

Second: construction, installation, commissioning proposals should meet the design requirements, based on equipment, equipment manufacturers recommended parameters, methods, and to achieve the best network performance. Equipment, equipment installation point it is necessary to facilitate the installation, testing, maintenance, and also taking into account security. Construction quality of the implementation of strict accordance with the relevant industry standards to ensure that equipment installation and laying optical fiber, splice, and other construction details meet specifications, to avoid quality problems caused by network failures.

5 Typical Case Analysis

Case I: (1) identify problems: a ONU BER / FER frame error too; (2) field measurement: the actual test ONU input optical power: - 37. 2 dBm; (3) Check the problem: See optical fiber end, there is a very serious face dust pollution; (4) Troubleshooting: alcohol to clean the fiber end and re-insert the ONU port; (5) measurements: time observed BER / FER is 0, ONU is in normal operation; (6 ) Failure Analysis: ash layer fiber end face serious pollution, the lack of construction site cleaning equipment and cleaning fiber end awareness, resulting in excessive optical attenuation, ONU generating error.

Case II: (1) identify problems: a ONU BER / FER exception, there UP-DOWN; (2) field measurement: the actual test ONU input optical power: - 28. 4 dBm; (3) Check the problem: optical fiber cable tie too tight, causing permanent damage fiber, resulting in attenuation; (4) Troubleshooting: Re-weld replacement pigtail. Check the OLT to the ONUs cable link; (5) Failure Analysis: generate BER / FER exception because the optical power does not meet the requirements, fiber optic cable tied too tight is too much attenuation of one of the reasons, also need to check between the OLT to ONU The fiber optic cable link.

Case III: (1) identify problems: a ONU BER / FER exception (error frame too); (2) field measurement: the actual test ONU input optical power: - 20. 1 dBm; (3) Check the problem : a cloth fiber irregularities, but the basic normal control; (4) Troubleshooting: fiber optic connectors to re-insert the ONU, to ensure reliable connection; (5) measuring the results: long observed BER / FER is 0, ONU at work in; (6) failure analysis: optical path normal, but when the ONU optical plug is not fully inserted, resulting in bad light junction is too large, resulting in ONUBER / FER anomalies larger.

EPON is currently two-way television system in the application of more and more network construction, equipment performance is improving, continue to strengthen a variety of management applications, which gave an increase of fault handling of favorable conditions, I believe that with this the deepening of technology applications, EPON network failure will continue to simplify the maintenance of treatment efficiency is increasing.

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