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Amplifier (Booster), to increase the output power at the beginning of the link
Pre-Amplifier (PreAmp), high input sensitivity. Increasing the power level at the end of the transmission line according to receiver sensitivity
Inline-Amplifier, to compensate the attenuation of the link
RAMAN-Amplifier, increasing of the power level, at the end of the link by using the Raman scattering. Amplification is achieved with improved OSNR behavior and reduction of nonlinear effects.
EDFA (Erbium Doped Fiber Amplifier) principle
EDFAs use a pump laser (980 nm or 1480 nm) to bring up electrons to a higher energy level. If signal amplification is achieved by emitted photons of the same signal wavelength with the help of stimulated emission.
Wavelength: C-Band and L-Band
Amplification 20 – 40 dB
Output power: 14 – 23 dBm
RAMAN-amplifier principle
A Raman amplifier is using the effect of Raman scattering. For this purpose, light with high power and a corresponding wavelength is pumped into the fiber. Is the incoming wavelength within the Raman gain spectrum an amplification of light is enabled.
Wavelength area: 1300 – 1600 nm
Amplification: 10 – 15 dB
− Neodymium and Ytterbium Fiber Amplifiers
Fiber amplifiers based on ytterbium- or neodymium-doped double-clad fibers can be used to boost the output power of 1-μm laser sources to very high levels of up to several kilowatts (→ high-power fiber lasers and amplifiers). The broad gain bandwidth is also suitable for the amplification of ultrashort pulses (→ ultrafast amplifiers); limitations arise from fiber nonlinearities such as the Kerr effect and Raman effect (see below). Single-frequency signals can also be amplified to high powers; in this case, stimulated Brillouin scattering usually sets the limits.
Neodymium-based amplifiers can also be used in the 1.3-μm spectral region, but with less favorable performance
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