Design And Performance Testing Of Wavelength Adapter In Metro CWDM System

Coarse Wavelength Division Multiplexing (CWDM) technology is getting more and more attention for its good characteristics such as low-cost, high-capacity, flexible application, and easy to increase the capacity. CWDM system is regarded as a new solution for broadband metropolitan access networks. Wavelength conversion unit is one of the most important parts in CWDM system. Although the O/E/O wavelength converter has "electronic bottleneck", the CWDM system is designed for metro network with short-haul transmission, and the Channel rate is not over 2.5Gbit/s. So the O/E/O wavelength converter is still very attractive for the low-cost CWDM system.Combining the short-haul transmission characteristics of CWDM system, a hardware and software scheme is presented in this paper. The role of each module and how to implement it are analyzed detailedly. The scheme is composed of two parts: transmission design and monitor design. Transmission design includes the whole hardware system, the implement of optical transceriver modules and the method of clock and data recover. The choice of center wavelength and the budget of optical power are analyzed in this part. Monitor design is implemented by two field programmable gate array (FPGA). The configuration of transmission unit and the read of data are completed by the control FPGA. Transmission signals are detected by the performance FPGA. The project is implemented by Alcatel R&D center in Chengdu.The testing ways of network function and performance guideline of the wavelength adapter (WLA) are presented, as well as analysis and test results are presented in this paper. The results show that the Synchronous Digital Hierarchy (SDH) and Gigabit Ethernet (GE) signal can be monitored by the WLA. The quality of optical signal is better after transport through the wavelength adpter. Each indicator is better than the requirement of optical interface paramenters. The transmission damage of signal is suppressed by the retiming function of clock and data recover. So the wavelength adapter can also be used as relay to extend the transmission distance.