Công nghệ này tuy còn mới mẻ với khách hàng nhưng thực ra đã được sử dụng từ đầu thế kỷ 20, cho các mục đích truyền thông tin của nội bộ ngành Điện. Ví dụ như hệ thống CFS (Carrier Frequency System), sử dụng các máy phát 10W để truyền thông tin bảo vệ, đo đạc trên đường dây cao thế với khoảng cách lên tới 500km hay hệ thống RCS (Ripple Carrier Signalling) sử dụng trong quản lý tải của hệ thống truyền tải điện hạ thế và trung thế | I IEC NEC Corporation of America CWDM Technology Applications and Operations Abstract Wavelength Division Multiplexing WDM enables carriers to deliver more services over their existing optical fiber infrastructure by combining multiple wavelengths on a single fiber. Each service is carried over a separate wavelength thus increasing the capacity of the fiber by the number of wavelengths transmitted. Coarse Wavelength Division Multiplexing CWDM and Dense Wavelength Division Multiplexing DWDM are both mature WDM technologies using standardized ITU-T wavelengths. CWDM and DWDM differ in complexity offered capacity cost and the markets they address. Due to its low cost and simple deployment CWDM is a good fit for access networks and many metro regional networks. This paper focuses mainly on the CWDM technology and its applications and explains how carriers can use CWDM to cost-effectively maximize their optical network capacity. Introduction Wavelength Division Multiplexing WDM transports multiple signals on a single optical fiber by using different wavelengths to carry each signal. For a given transmission line rate WDM multiplies the amount of data that can be carried over the same optical fiber by the number of wavelengths transported. WDM technologies have been in use since the 1980s and gained popularity with carriers after Dense Wavelength Division Multiplexing DWDM became standardized in the mid-1990s. DWDM enabled carriers to extend the capacity of the SONET SDH rings in the network core without installing new fiber. To cope with increasing bandwidths demands a new generation of DWDM systems is being developed today. While DWDM dominates the long haul network segment a different WDM technology Coarse Wavelength Division Multiplexing CWDM is now well-positioned to help carriers maximize their network capacity in the access metro and regional network segments. CWDM supports fewer wavelengths than DWDM but is available at a fraction of the cost of DWDM. This makes
