When the transmission distance is too long (more than 100 km), the optical signal will have a great loss. In the past, people usually used optical repeaters to amplify the optical signal. This kind of equipment has certain limitations in practical applications. Replaced by optical fiber amplifier. The working principle of optical fiber amplifier is shown in the figure below. It can directly amplify the optical signal without going through the process of optical-electrical-optical conversion.
How does the fiber amplifier work?
When the transmission distance is too long (more than 100 km), the optical signal will have a great loss. In the past, people usually used optical repeaters to amplify the optical signal. This kind of equipment has certain limitations in practical applications. Replaced by optical fiber amplifier. The working principle of optical fiber amplifier is shown in the figure below. It can directly amplify the optical signal without going through the process of optical-electrical-optical conversion.
What kinds of fiber amplifiers are there?
1. Erbium-doped fiber amplifier (EDFA)
Erbium-doped fiber amplifier (EDFA) is mainly composed of erbium-doped fiber, pump light source, optical coupler, optical isolator, and optical filter. Among them, erbium-doped fiber is an important part of optical signal amplification, which is mainly used to achieve 1550 nm Band optical signal amplification, therefore, the erbium-doped fiber amplifier (EDFA) works best in the wavelength range of 1530 nm to 1565 nm.
Advantage:
The highest pump power utilization (greater than 50%)
It can directly and simultaneously amplify the optical signal in the 1550 nm band
Gain over 50 dB
Low noise in long-distance transmission
shortcoming
Erbium-doped fiber amplifier (EDFA) is larger
This equipment cannot work in coordination with other semiconductor equipment
2. Raman amplifier
The Raman amplifier is the only device that can amplify optical signals in the 1292 nm~1660 nm band. Its working principle is based on the stimulated Raman scattering effect in the quartz fiber. As shown in the figure below, when the pump light is pulled When the weak light signal in the Mann gain bandwidth and the strong pump light wave are simultaneously transmitted in the optical fiber, the weak light signal will be amplified due to the Raman scattering effect.
Advantage:
Wide range of applicable bands
Can be used in installed single-mode fiber cabling applications
Can supplement the deficiencies of erbium-doped fiber amplifier (EDFA)
Low power consumption, low crosstalk
shortcoming:
High pump power
Complex gain control system
Noisy
3. Semiconductor optical fiber amplifier (SOA)
Semiconductor optical fiber amplifiers (SOA) use semiconductor materials as gain media, and their optical signal input and output have anti-reflection coatings to prevent reflection on the end face of the amplifier and eliminate the effect of the resonator.
Advantage:
small volume
Low output power
The gain bandwidth is small, but it can be used in many different bands
It is cheaper than erbium-doped fiber amplifier (EDFA) and can be used with semiconductor equipment
Four non-linear operations of cross-gain modulation, cross-phase modulation, wavelength conversion and four-wave mixing can be realized
shortcoming:
Performance is not as high as erbium-doped fiber amplifier (EDFA)
High noise and low gain
Post time: Sep-17-2021