Fibre Channel SAN Extension over Optical Networks DWDM Concepts
Other DWDM components that might be required are: Erbium-Doped Fibre Amplifier (EDFA) optical amplifiers are optical repeaters that can be used to boost the signal on longer spans, or to preamplify the signal before it leaves the local site. An optical fibre is doped with the rare earth element erbium, which allows the fibre to absorb light at one frequency and emit light at another frequency. A second laser couples light into the fibre at infrared wavelengths, which excites the erbium atoms. When the DWDM optical signal enters the fibre, it stimulates the already-excited erbium atoms to emit photons at the same wavelength as the incoming DWDM signal. This action amplifies a weak optical signal to a higher power at the same wavelength. Optical Add/Drop Multiplexers (OADMs) can de-multiplex (drop) and/or re-multiplex (add) specific
wavelengths while allowing all other
wavelengths to pass through unaffected. If you want to amplify this then it is recommended to amplify after 80km.