subject: Optical Network Development And Market Needs [print this page] The basic concept of optical network The basic concept of optical network
Itself from the optical fiber communication technology development, the optical network is most active in the field. However, the so-called "optical network" is not a strictly technical terms, it is a popular term. Historically, optical networks can be divided into three generations. The first generation of optical networks is used to achieve high-capacity transmission, all the switching, routing and other intelligent power levels are achieved, SDH is this the first generation of optical networks, and is currently developing optical transmission network (OTN) and all-optical networks can be considered a second generation, respectively, and third-generation optical network optical network. OTN are functionally similar to SDH, OTN regulated only in the rate and format to achieve it, while the all-optical network is different, this time transmission, multiplexing, routing, monitoring, and some level of intelligence will be realized in the light. From a broader perspective, the optical network should also cover areas of metro and access networks, both in the field of optical networking is not only a more varied choice of technology, and technical features are also very different.
Advantages and disadvantages of OTN In terms of relatively traditional SDH, ITU-T OTN defined the main advantages:
- Have a stronger ability to forward error correction FEC. OTN's band than SDH in-band FEC FEC error correction ability can be improved 3-7dB;
- With TCM Tandem Connection monitoring function. Monitor connections can be nested, overlapping type and / or cascade, which allows only single-stage SDH;
- Support for transparent transmission of client signals. SDH SDH can only support a single client signal, and transparently support all customers OTN signal;
- The expansion of exchange capacity. SDH levels in two main exchange, the 2Mbit / s and 155Mbit / s. The OTN line rates can be increased with the increase of any level of the exchange rate, and the specific wavelength of the signal bit rate for each independent.
However, OTN's main shortcomings is the lack of fine granularity bandwidth, the performance monitoring and fault management capabilities, network applications do not ask for rate poor economy. In addition, because the existing SDH optical network has been able to basically meet the application needs, manufacturers developing next-generation optical networking products, lack of driving force, There is no mature product is available, the market window is narrow.
The development of all-optical OXC All bare cross-connect device (OXC) is the core of future optical network, transmission network in the main function: to provide wavelength-based connectivity, optical-drop wavelength channel function of wavelength to ease access to the fiber infrastructure in order to achieve maximum efficiency, to achieve the wavelength, wavelength and fiber-level group on the protection and restoration. OXC can be achieved when the dynamic wavelength routing function is often referred to as the wavelength router.
From achieving technically, OXC can be divided into two categories, namely, cross-matrix by electro OXC (sometimes referred to as OEO form or call OXC) and optical cross-matrix of pure OXC (sometimes referred to as OOO or in all-optical OXC). By OEO approach may be easier to achieve signal transmission quality control and eliminate injury, more mature network management, capacity is not large when the lower cost technology compatible with existing lines, more importantly, can be smaller than the wavelength bandwidth processing and deployment to meet the capacity needs of the recent market. However, its expansion mainly through the continuous semiconductor chip density and performance improvements to achieve because of the complexity of the system can not keep up with the network transmission link capacity growth rate. Finally, such systems are usually bulky, power-hungry, large-capacity when the high cost.
Other hand, the use of optical cross-matrix OXC save the photoelectric conversion part, not just save a lot of the photoelectric conversion interface, and because of pure light to eliminate bandwidth bottlenecks, capacity is expected to significantly expand, along with to the transparency can make it support a variety of client layer signal, power, smaller, more efficient multi-port switching capability, the technology has more long-term life. From the port cost and power consumption of view, than the use of such equipment, the OXC OEO lower. However, such equipment can be exchanged at least the bandwidth granularity is the wavelength, so even a small amount of additional bandwidth requirements must also provide the entire wavelength uneconomical. Secondly, in order to introduce all-optical switches, may have to update the transformation of existing track systems. Third, in the optical domain performance monitoring is difficult to achieve. Fourth, with the all-optical switch connected to a balanced line is formed over the optical amplifier, while the balance of all current methods are dedicated lines, involving many factors, these factors highly correlated and interdependent, so that a balanced work very difficult and takes time to stabilize. If the attempt to balance a good mesh of fast dynamic wavelength routing implemented, will result in the re-combination of many factors, the need for rapid implementation of the new wavelength channel re-balanced. The current optical line system also can not be in a standardized way to achieve fast dynamic network equilibrium.
