Abstract: This paper, the development of the global optical network situation is briefly introduced, then elaborated on some form next-generation optical networks and the corresponding key technologies.
Keywords: Metro optical networks; long-distance optical network; Multi-Service Transport Platform (MSTP); Resilient Packet Ring (RPR); Multi-protocol Label Switching (MPLS), wavelength division multiplexing (WDM); Raman amplifier ( RamanAmplifier); Automatic Switched Optical Network (ASON); Generalized Multi-Protocol Label Switching (GMPLS)
1. Overview End of last century, the new century, the global telecommunications market had a bubble, optical networking market was a serious recession, operators are no longer blind pursuit of high capacity and high bandwidth, but more emphasis on capital expenditure (CAPEX), operating expenses (OPEX) and return on investment (ROI) and other financial indicators, more value system equipment performance and low cost, multi-business solutions more attention, more attention can save labor costs of the intelligent configuration and scheduling function. After several years of sharpening and the shock, since 2004, signs optical networking market, particularly evident.
Optical network is a basic network, after all, once the business grew, the bearing pressure optical network will increase accordingly. If the pursuit of long-haul optical network with high bandwidth, large capacity, then the pursuit of metro optical networks are multi-service and flexibility. So far, the global long-distance optical network bandwidth becomes saturated or even excess carriers in long-distance optical network investment ratio decreased or remained stable. However, due to the urgent need for practical engineering, ultra-long distance transmission which has evoked strong concern about some of the technical bottlenecks have been resolved, the pace is accelerating business. In addition, including the storage network (SAN) business, including data services is rising, image and multimedia services rather potential, will amount to anything. Many operators are moving in multi-service operator (MSO) the direction of evolution, voice, data and image go hand in hand makes the “TriplePlay” the word is very compelling. Construction of metro operators in full swing, the real purpose is to achieve network optimization is aimed at long-distance backbone network and access network between the user remove the “fault” phenomenon. We know that Metro is the metro optical network business network carrier, if the optical network (such as the traditional SDH and WDM) is only “fool” to send a business signal, then the business layer of pressure would be enormous. Now, the incumbent operators are building networks to modify their thinking, new operators is one step, adopt a new generation of optical networking equipment with the joint network service layer equipment.
2. On the next-generation optical network
Not mentioned here, the next generation of optical networks is to allow everyone to think that is a long way off. In other words, a new generation of optical network seems more practical, more relevant.
As voice services and TDM services can not instantly disappear, “a new generation of SDH” despite being classified as transitional technology, but it does have the vitality, the kind of “SDH degraded from a system to an interface “too early to say, especially for the Third World and less developed regions have operators. Two features is the new generation SDH multi-service and intelligent, multi-service performance evolved from SDH MSTP, intelligent performance as the introduction of GMPLS / ASON control plane to realize flexible bandwidth allocation, the business end scheduling and dynamic protection and restoration of function.
Has been the requirements of the industry is high-capacity WDM and transparent transmission. But the new generation of WDM equipment, other than to provide large capacity, high bandwidth, long distance transmission, while also providing rapid multi-service access and its own optical layer protection.
3. On the next-generation WDM networks
Long distance transmission is the next generation WDM network one of the key technologies. At present, the worldwide well-known optical communication system vendors offer large capacity, ultra-long distance DWDM transmission systems to support SDH / SONET / GE and many other business interface, the capacity can be smoothly extended to the T-bit level, the wavelength range covering C + L band can be G.652, G.655 fiber to achieve thousands of kilometers of radio relay transmission. The key technologies include: Distributed Raman and EDFA hybrid amplifier technology, super-band FEC technology, NRZ and RZ modulation pattern, dynamic power balancing, distributed dispersion management technology. Among them, the distributed Raman amplifier with large gain bandwidth, gain flatness, the distribution can be adjusted according to signal characteristics of the gain spectrum. Currently, the new standard for the Raman amplifier has been G.665 ITU-TSG15 allowed to pass through.
One of the highlights next-generation WDM network that is unique for the metropolitan area has many designs, including multi-service OTU, T-MUX, optical layer protection. For example, Metro WDM can not rely on the client layer (eg SDH) protection switching facility, which has its own recovery to share with the section of the protection and optical channel shared protection. Some metro OADM equipment serial / parallel optical switch integrated design approach, using a unique “upgrade interface” real guarantee “online upgrade” will not interrupt existing business. In addition, for the metro access network applications, operators can choose a compact, cost-effective CWDM equipment, enabling rapid capacity expansion and network optimization.
4. On the next-generation SDH network
About next-generation SDH, we naturally think of MSTP equipment, it can be based on a variety of SDH line rates to achieve, including 155Mb / s, 622 Mb / s, 2.5 Gb / s and 10Gb / s and so on. On the one hand, MSTP retains the inherent cross-SDH capabilities and traditional SDH / PDH service interfaces, TDM services continue to meet the demand; the other hand, MSTP provides ATM processing, Ethernet transparent transmission, L2 Ethernet switching, RPR processing , MPLS processing capabilities to meet the convergence of data services, carding and integration needs. Currently, the most preferred GFP MSTP to provide excellent package of order, and virtual concatenation and LCAS are adapted to the different needs of bandwidth and can in some particles within the link capacity adjustment. In addition to Ethernet functions, MSTP the RPR feature the original Ethernet switching module to overcome the disadvantage of slow, can achieve quick within 50ms protection switching, in addition, RPR provides a fair method to ensure the link bandwidth rational use, to maximize the situation to prevent link congestion. The use of MPLS functionality can MSTP networking capability extends from the ring lattice network, you can pseudo-wire (PW) approach to multi-client services (including Ethernet, ATM and frame relay) to access and together, and through
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