Stable Frequency Unrepeatered Transmission Using Distributed Raman Amplifier Over 200 km Fiber Link

We demonstrate stable frequency transmission over a 200 km repeaterless fiber link. Raman amplifiers are placed at the transmitter and the receiver to offset optical fiber attenuation. The frequency stability of the transmission system is 3.1×10
⁻¹⁴
@1s, 1.8×10
⁻¹⁷
@10000s.