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LIANG Shuang-you1，LI Li-zhong2，ZHANG Jian-kang2
（1. National Time Service Center, Chinese Academy of Sciences, Xi’an, Shaanxi 710600, China；
2. Graduate University of Chinese Academy of Sciences, Beijing 100039, China）
Abstract: Some methods and experiences on time-frequency transfer via optic fiber are introduced. The methods for time-frequency transfer without phase compensation, two-way time-frequency transfer, temperature compensation via optic-mechanics and electronic conjugated phase compensation are described in detail. The time delay in optic fiber transfer changes mainly with temperature. Within a distance of 200 km, the changes of time delay are a few nanoseconds for one day and ten-odd nanoseconds for one month. If a 100 MHz signal is transferred via optical fiber within 50 km, the frequency stabilities are 3×10-14/s and 1×10-15/d for the case without compensation, and the frequency stabilities are 1.5×10-14/s and 1×10-17/d for the case with optical compensation. The electronic conjugated phase compensation can reduced the phase variations, which is caused by temperature change of 20℃, by a factor of 45. The effect of optic fiber transmission on the short term stability is smaller than that on the long term (day and longer than day) stability for time-frequency signal.
Key words: optic fiber；transfer methods；time-frequency；phase compensation
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