Raman/EDFA hybrid bidirectional amplifier for fiber-optic time and frequency synchronization

Abstract

Herein, we verify that a Raman/EDFA hybrid amplifier can improve the stability of fiber-optic time and frequency synchronization systems compared to the Er3+-doped fiber amplifier (EDFA), owing to its higher gain and lower noise figure (NF) performance. We studied the variation law of Raman gain efficiency for a fiber Raman amplifier (FRA) as a function of pump power and input signal power, designed a bidirectional Raman/EDFA hybrid amplifier, and proved that equivalent NF below 0 dB can be obtained. Finally, hybrid amplifiers were compared to EDFAs in a free-running frequency synchronization system. The transfer stabilities reached 1.9678 × 10−13/1 s and 2.0248 × 10−13/1 s when FRA + EDFA and EDFA + FRA configurations were used, respectively, both exhibiting better performance than the stability of 3.0905 × 10−13/1 s obtained by EDFA.

Raman and erbium-doped fiber amplifiers hybrid bidirectional optical amplifier with low noise figure for fiber-optic radio frequency synchronization

“…At different input signal power, the highest gain is always obtained at a Raman pumping power of 500 mW. The reason that the gain increases for different Raman gain efficiencies is that the Raman gain efficiency increases with the decreasing input signal power and the larger efficiencies make output and hence cause more gain saturation 23 . Furthermore, the gain of the HBOA is higher at lower input signal power (−35 to −45 dBm) than at higher input signal power (−25 dBm).…”

“…The FRA amplification part is an FRA composed of 20 km DCF and a 1455 nm Raman pump for amplifying the λ1 and λ2 signals. Using fiber types with a smaller effective area can result in better pumping efficiencies 23 . With its effective area being approximately a quarter of many transmission fibers, DCF can maximize power concentration and achieve higher Raman gain.…”

“…Using fiber types with a smaller effective area can result in better pumping efficiencies. 23 With its effective area being approximately a quarter of many transmission fibers, DCF can maximize power concentration and achieve higher Raman gain. EDFAs amplification part is two identical EDFAs composed of 4.5 m Fibercore I-12 HC Er 3þ doped fiber, EDFA pump with a wavelength of 980 nm and isolator (ISO) for amplifying the λ 1 and λ 2 signals, respectively.…”