Optical Amplifier
The transmission loss of the light that passes through optical switch fiber is the very small value of less than 0.2 dB per km with a light wavelength in the 1,550 nm band.
An optical amplifier is an extremely important device that supports the long-distance optical communication networks of today and it amplifies light as it is without converting the optical signal to an electrical signal. The main type of optical amplifiers includes an EDFA(Erbium-Doped Fiber Amplifier), FRA(Fiber Raman Amplifier), and SOA(Semiconductor Optical Amplifier).
FRA (Fiber Raman Amplifier)
An FRA is a type of OFA. When strong excitation light enters the optical attenuator fiber it causes stimulated emission based on SRS. In a wavelength range about 100 nm longer than the excitation light wavelength, the light is then amplified. It has a wide amplification wavelength region, and it can be freely set by the wavelength of the excitation light.
DFA (Erbium-Doped Fiber Amplifier)
An EDFA is 1 type of OFA and is an optical amplifier that consists of erbium ions added to the core of the optical fiber. It can amplify optical signals in the 1.55 μm band or 1.58 μm bands, features high gain and low noise, and is polarization independent.
Previously it was important to use an optical repeater to temporarily convert attenuated light into an electrical signal, then electrically amplify it and regenerate the waveform, then convert back to light and resend it.
SOA (Semiconductor Optical Amplifier)
An SOA is a semiconductor element. On the cleavage plane of a semiconductor laser by performing antireflective processing and eliminating the resonator structure, light can easily enter from outside the semiconductor and amplify light via stimulated emission.
In a compact size, you can make an SOA, and compared to an EDFA its lower running costs mean it is more economically efficient. Till recent years, the input light of an SOA was highly polarization-dependent but in recent years research into low polarization, dependency has proceeded. Furthermore, at data centers, optical amplifier EDFA is being replaced by SOAs, and their use is expected to expand in future optical communication.
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