WDM Transponder 3R functions
WDM transponder is the element that sends and receives the optical signals over a single fiber. It performs an optical-electrical-optical operation. WDM transponders originally served to transmit wavelength of a client-layer signal into one of the DWDM system’s internal wavelengths in the 1550 nm band. However, they barely have the required frequency stability tolerances nor have the optical power necessary for the system’s EDFA (Erbium-doped Fiber Amplifier). In the mid-1990s, WDM transponders rapidly took on the additional function of signal regeneration. Signal regeneration in transponders quickly evolved through 1R to 2R to 3R and into overhead-monitoring multi-bitrate 3R regenerators. Now I will introduce 3R one by one.
1R
1R represents retransmission. The earliest transponders had little flexibility and are more like “garbage in garbage out”. Their output was nearly an analogue “copy” of the received optical received optical signal, nearly without signal cleanup occurring. Because the signal had to be handed off to a client-layer receiver (likely from a different vendor) before the signal deteriorated too far, the reach of early DWDM systems is limited. In addition, signal monitoring was basically confined to optical domain parameters such as received power.
2R
2R means re-time and re-transmit. Compared with 1R transponders, transponders of this type utilized a quasi-digital Schmitt-triggering method for signal clean-up before re-transmitting. Based on these analogue parameters, some rudimentary signal quality was done by such transmitters.
3R
3R is the combination of re-time, re-transmit and re-shape. 3R transponders can more closely monitor signal quality. Because many systems offer 2.5 Gbit/s transponders, the transponders are able to perform 3R regeneration to report signal health. Besides, full multi-rate 3R in both directions can be achieved.
Advantages of WDM Transponder
WDM transponders perform dual fiber to single fiber conversion and wavelength conversion within the WDM frequency domain to increase capacity. They provide an extended number of services for both CWDM (Coarse Wavelength Division Multiplexing) and DWDM (Dense Wavelength Division Multiplexing) with numerous advantages.
Multiprotocol Support
WDM transponders are designed for most of the equipment operating directly with
pluggable optics. They offer dedicated wavelength transport for a comprehensive mix of data, storage, TDM, video protocols including Ethernet, Fiber Channel and FICON (Fiber Connection), SONET (Synchronous Optical Networking), and SDH (Synchronous Digital Hierarchy). Thus, WDM transponders facilitate a wide variety of applications, such as broadcasters and cable operations, data networks, telecommunication room, and etc.
Performance Monitoring
WDM transponders provide efficient network monitoring and enhanced operations, because many performance metrics in of OAM (Administration and Maintenance) and SLAs (Service Level Agreements) are available.
Automatic Rate Detection
WDM transponders automatically detect incoming data rates so user provisioning is not required. In addition, they can supports 3R operation at all supported rates between 125 Mbps and 4.25 Gbps.
High Capacity and Low Cost
WDM transponders can not extend fiber optic links by hundreds of kilometers, but also provide high capacity. They are the cost-effective solution for a broad range of protocols.
Conclusion
From the above introduction of WDM transponders, you may gain a better understanding of their 3R functions and advantages. Besides, there are many other important devices in WDM systems, such as WDM filter, optical amplifier and dispersion compensation module and so on. All of them, including WDM transponders, are widely used in WDM networks.
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