Development of Frequency Transfer via Optical Fiber Link at Nict

NICT in Japan has developed a radio frequency (RF) dissemination system using an optical fiber link. The phase noise induced during the transmission through the optical fiber is actively cancelled by a compensation system. A proving test has been conducted on the 114-km urban telecom optical fiber link in Tokyo. The transfer stability in the 10 level at an averaging time of 1 day was achieved. INTRODUCTION In the last few years, optical frequency standards have improved significantly and attained high frequency stability [1,2]. Such significant improvements make it difficult to compare the optical clocks between distant laboratories without performance degradation by using conventional time transfer methods via a satellite link [3]. A low-noise frequency distribution system is demanded in the field of astronomy and particle accelerators, as well as time and frequency metrology [4,5]. Frequency distribution using an optical fiber link has attracted worldwide attention as one of the candidates to connect the distant sites in higher stability. In general, however, during a transmission through optical fiber, the transmitted frequency is exposed to the Doppler effect, which is attributed to fiber length variation caused from mechanical stress or temperature variation. The longer the transmission distance is, the larger the effect becomes. For stable dissemination via optical fiber link, active compensation to cancel the Doppler shift is required. Recently, various optical fiber dissemination systems have been demonstrated in several laboratories. Stable RF frequency distribution has been developed and has achieved a transfer stability level of 10 for an averaging time of 1 day in an 86-km optical fiber link [6,7]. Optical carrier transfer, which requires optical frequency combs to bridge to local references, has been developed and achieved ultra-stable transfer stability [8-10]. The National Institute of Information and Communications Technology (NICT) also has been developing a stable optical-fiber dissemination system. NICT has maintained highly stable and accurate frequency standards, such as the cesium atomic fountain NICT-CsF1 [11] and a Cryogenic Sapphire Oscillator (CSO) [12]. To distribute these frequency signals 125 Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 01 DEC 2008 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Development Of Frequency Transfer Via Optical Fiber Link At Nict 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) National Institute of Information and Communications Technology, 4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795, Japan 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release, distribution unlimited 13. SUPPLEMENTARY NOTES See also ADM002186. Annual Precise Time and Time Interval Systems and Applications Meeting (40th) Held in Reston, Virginia on 1-4 December 2008, The original document contains color images.