DWDM system in the trunk and local fiber optic transmission network has a large number of applications. Due to the amount of traffic carried by focus on the importance of safety more and more attention in the event of full resistance will affect all business network hosted. The DWDM network security has always been the most important in the transmission maintenance work.
But DWDM protection technology by its own limitations, there is not flexible, large investment, the effect is not ideal problem, and therefore has played a very important role in light switch protection technology introducing. This article describes the basic principles of optical switching technology and protection technology trends, in practical application, large-scale use in the current network to improve network security.
The DWDM network protection: protection optical channel 1 +1 or 1: n protection OLP protection, dual-selective receiving and sending and receiving two-way selection protection. These methods can effectively improve the security of the network, but the cost is relatively high, relative to other levels of protection is not flexible enough. In practical systems, optical fiber, optical cable reliability than the reliability of the device differential protection system only, rather than for line protection, the practical utility is not too large. Therefore, a convenient, flexible, small investment light automatic protection technology came into being, it can effectively solve the protection issues, economic, practical, safe and protect the network.
Optical switch protection system for the security of communication network provides a set of economic, practical solutions, the formation of a non-blocking, high reliability, flexible, anti-disaster ability of the optical communication network. Optical switch protection system by the automatic switching and network management stations, you can achieve light switch protection, monitoring and the optical path of the optical power emergency dispatch three main functions.
The Optical switch protection system switching control module is a set of optical switches, optical power monitoring, stable light source monitoring in one of the high level of integration modules. Optical power monitoring module and optical switch control module coordination, selection of splitting ratio of 97:3 is more appropriate on the trunk, the equivalent of approximately 0.2dB attenuation on the transmission line; optical switching module contains 1x2 or 2x2 Optical switch, controlled by the switch between the main and backup light routing operation.
Real-time monitoring of the optical power monitoring module communication optical fiber optical power value reported to the main control module; analysis and comparison of the main control module, found that the change in value of the optical power exceeds a preset threshold switching immediately issued instructions to the optical switch module; optical switch module by the Directive instantly switching action has occurred. In order to achieve a switching operation.
The optical path automatically switch protective equipment involved in trunk transmission system did not affect the transmission characteristics. In fact, switching equipment involved in the optical switch and splitter only two passive optical devices.
One end of the switching unit is connected to the transceiver of the transmission system, the main fiber optic cable and the spare cable, respectively connected to two output terminals of the 2x2 optical switch. When the optical path occurs when the optical power is abnormal, the optical switch is automatically switched to the alternate route.
It is understood that the optical switch protection system has the following advantages. Fast switching speed, the optical switch switching speed ships 5ms, plus system analysis, the response time of a single-ended switching time of less than 20ms, the switching time of less than 50ms for the entire system, the basic switching operation can be done without interrupting the communication, to achieve business grade level of protection.
Switching, high reliability, implemented through the optical power monitoring, to avoid false alarm of the optical frame, ensure switched judgment is correct. The spare fiber routing monitoring, to ensure the validity of the switch, and continue to be monitored after switching optical path.
Emergency dispatch function, simply switching command issued from the program, you can deploy routing to facilitate the realization of the non-blocking cutover and line maintenance work. The switch device for a transmission system is transparent, i.e. the switching device does not require the type of transmission system can use either SDH or DWDM.
The optical switch protection DWDM is an economical and safe a line protection method, but the the light automatic protection system intervention to DWDM systems, there are many issues to consider. Splitter 97:3 spectral, optical switching device insertion loss is about 2 dB intervention light switching device, the system has an additional two light jump fiber insertion loss is estimated as 1 dB, so the whole switching device Interventional theoretically maximum will bring 3dB attenuation, and many cases of practical use only in 1.5-2.5dB. Primary and backup routes throughout the uniform attenuation, the attenuation of the primary and backup routing line difference is very small, the system standby line without consideration. If the attenuation of the alternate route is too large, you need to consider alternate route EDFA, to zoom in the standby line. Larger principle is that the alternate route than the main line of the route attenuation how much, the EDFA on compensation. Of course, EDFA generally leave a margin adjustable.
Signal-to-noise ratio OSNR values. 2.5G system, for example, if there is no FEC function, OSNR> 20dB; FEC function, OSNR> 16dB. 10G system if there is the the FEC function OSNR> 20dB. Intervention light switching equipment, the full attenuation will be reduced by 3 dB OSNR value of the system will also be reduced by 3 dB when the DWDM system is still able to meet the opening requirements, you do not need to intervene EDFA. If you can not meet the demand of the opening of the DWDM system, the need to intervene in the EDFA optical amplifier EDFA intervention, although the increase NFEDFA (Usually take 5.5dB), but also reduces the full attenuation of the line and to improve the light emitting power of a single wave, the overall increased slightly on the OSNR value than before the intervention.
Fiber dispersion coefficient to measure the dispersion coefficient is two wavelength interval of 1 km of the a 1nm two lightwave transmission length of the optical fiber to reach the time difference, in units of ps/nm·km. G.652 fiber dispersion coefficient to 17 ps/nm·km G.655 fiber dispersion coefficient of 6.5ps/nm·km, the 2.5G signal generally does not require compensation. 10G signal is relatively small due to chromatic dispersion tolerance, 10G rate signal on G.652 fiber transmission distance of more than 30km on the need for dispersion compensation, the G.655 fiber transmission distance of more than 100km may be compensated. The principle of dispersion compensation is necessary to leave after 10 to 30km margin dispersion compensation, the best dispersion compensation dispersion tolerance of alternating positive and negative, the best results.
Break placed currently used made of a dispersion-compensating fiber (DCF), dispersion compensating module (DCM) periodically so that the accumulated dispersion close to zero dispersion compensation fiber link. In general, the amount of dispersion of the preparation route should be considerable and the main route. Need to pay attention to the DCF fiber insertion loss is generally relatively large, it is generally DCM modules used together with the EDFA.
Optical automatic switching system for the DWDM line protection is both safe and economical means of protection. The future, as the size of the network continues to expand, light switch protection systems will play a more important role to meet the requirements of the assessment indicators, to improve the safety of operation of the transmission network.
The actual situation, DWDM is bound to play an important role in the optical transmission network, EDFA and fiber optic technology continues to evolve, the optical transmission system to overcome the obstacles of the optical signal attenuation and dispersion, to achieve the long-distance non-renewable transmission. New technologies continue to emerge, will promote the DWDM transmission lines applied to the development of all-optical network applications.
For more informaion on DWDM, please visit http://www.optoroute.com.cn/
No comments:
Post a Comment