Evolution from 10G to 100G for a Metro Network Figure 2 Coherent detection using optical 90° hybrid and balanced photodiodes A direct detection technique, on the other hand, requires only a delay interferometer and two single photodiode translating into a device of much lower cost and complexity. The advantage of longer transmission distances (in the range of several 1000 km) enabled using a coherent approach is overkill for deployments of much shorter reaches - ranges of several 100 km. The direct detection technique is thus seen as an attractive alternative for metro networks, enterprise and datacenters where economic viability plays a vital role. Taking the minimalist approach, direct detection works without additional equipment in most cases. When the application range approaches the limit of direct detection technology, the simple addition of dispersion compensation and amplification may be used to augment signal detection and extend reach. Technological Requirements Similar to 10G multiplexed networks, 100G networks begin with the use of 100G transceivers and dense wavelength division multiplexing (DWDM) multiplexers or demultiplexers. Depending on the application scenario, 100G networks may require optical amplifier, dispersion compensation modules and FEC enabled transponder cards. In this section, we delve deeper into the details of these components. The 100G DWDM-CFP transceiver is currently specified for applications associated with distances of up to 20 km. The 100G CFP uses four lasers, each tunable over the DWDM grid, such that the resulting link realizes 4 x 25 Gb/s with each 25 Gb/s travelling in a separate single mode duplex fiber. • Transports 4 x 25 Gb/s • Four single mode duplex fibers • Employs tunable lasers in the 50 GHz or 100 GHz ITU-T channel grid (DWDM) with four receivers D-5116 Rev.A.2 Figure 3 100G DWDM CFP 3
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