ROA (Raman Optical Amplifier)

What is of ROA (Raman Optical Amplifier)?

Raman amplifier was put forward as an advanced optical amplifier that enhances the signals by stimulated Raman scattering. To meet the future-proof network needs, it can provide gain at any wavelength. At present, two kinds of Raman amplifiers are available on the market. One is lumped Raman amplifier that always uses the DCF (Dispersion Compensation Fiber) or high nonlinear fiber as gain medium. Its gain fiber is relatively short, generally within 10 km. The other one is distributed Raman amplifier. Its gain medium is common fiber, which is much longer, generally dozens of kilometers.

 

When the Raman amplifier is working, the pump laser may be coupled into the transmission fiber in the same direction as the signal (co-directional pumping), in the opposite direction (contra-directional pumping) or in both directions. Then the signals and pump laser will be nonlinearly interacted within the optical fiber for signal amplification. In general, the contra-directional pumping is more common as the transfer of noise from the pump to the signal is reduced, as shown in the following figure.

Characteristics of ROA

Principle of ROA

The principle of ROA is based on the Stimulated Raman Scattering (SRS) effect. The gain medium is undoped optical fiber. Power is transferred to the optical signal by a nonlinear optical process known as the Raman effect. An incident photon excites an electron to the virtual state and the stimulated emission occurs when the electron de-excites down to the vibrational state of glass molecule. The Stokes shift corresponding to the eigen-energy of a phonon is approximately 13.2 THz for all optical fibers.

Advantages of ROA

– Variable wavelength amplification possible

– Compatible with installed SM fiber

– Can be used to extend EDFAs

– Can result in a lower average power over a span, good for lower crosstalk

– Very broadband operation may be possible

 

By Group 16 :

• DIMAS PRIHADI WALUYA (1101178309)
• LISNAWATI SILVIA BANGUN (1101178025)
• SOPHIE DWIVITA EVANS (1101178030)
• WAHYU HANGGORO (1101178004)