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| 2. |
- Ebenhag, Sven-Christian, 1976, et al.
(författare)
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Measurements and Error Sources in Time Transfer Using Asynchronous Fiber Network
- 2010
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - 1557-9662 .- 0018-9456. ; 59:7, s. 1918-1924
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Tidskriftsartikel (refereegranskat)abstract
- We have performed time transfer experiments basedon passive listening in fiber optical networks using Packet over synchronous optical networking (SONET)/synchronous digital hierarchy(SDH). The experiments have been performed with differentcomplexity and over different distances. For assessmentof the results, we have used a GPS link based on carrier-phase observations. On a 560-km link, precision that is relative to the GPS link of
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| 3. |
- Ebenhag, Sven-Christian, 1976, et al.
(författare)
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Time Transfer between UTC(SP) and UTC(MIKE) Using Frame Detection in Fiber-Optical Communication networks
- 2011
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Ingår i: 43rd Precise Time and Time Interval (PTTI) Systems and Applications Meeting. - 9781622767953 ; , s. 431-441
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Konferensbidrag (refereegranskat)abstract
- This paper presents recent results from a time transfer method using passive listening and detection of SDH frame headers in fiber-optical networks. The results are based on an experimental fiber-link that is implemented between the national time and frequency laboratories at SP in Borås, Sweden and at MIKES in Espoo, Finland with an intermediate connection at STUPI time and frequency facility in Stockholm, Sweden. The total fiber length exceeds 1129 km and is implemented in SUNET (Swedish University Network) and FUNET (Finnish University and Research Network). The two networks are connected via NORDUnet (Nordic Infrastructure for Research & Education) and the links are DWDM-based (Dense Wavelength Division Multiplexing).Both SP and MIKES maintains local representations of UTC and contributes with clock data to TAI, which gives the opportunity to compare the fiber-based method with those independent methods that are used regularly by the laboratories for the links to UTC. Preliminary results show that a time transfer stability of less than 10 picoseconds is obtained for averaging times of a few hundred seconds. The results also show that the method suffers from daily variations of a few nanoseconds, presumable due to temperature sensitive network equipment and asymmetric fiber paths. Nevertheless, a comparison to GPS carrier phase time transfer over three months shows an rms-agreement of less than 1 nanosecond.
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| 4. |
- Ebenhag, Sven-Christian, 1976, et al.
(författare)
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Time Transfer over a 560 km Fiber Link
- 2008
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Ingår i: EFTF 2008 - 22nd European Frequency and Time Forum. ; , s. Paper E5A04 -
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Konferensbidrag (refereegranskat)
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| 5. |
- Ebenhag, Sven-Christian, 1976, et al.
(författare)
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TIME TRANSFER USING AN ASYNCHRONOUS COMPUTER NETWORK: RESULTS FROM A 500 KM BASELINE EXPERIMENT
- 2007
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Ingår i: Topical Meeting on Precise Time and Time Interval, 27-30/11, Long Beach, CA.
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Konferensbidrag (refereegranskat)abstract
- SP Technical Research Institute of Sweden and STUPI have performed a time transferexperiment over a 500km long baseline between Borås and Stockholm. The time transfertechnique passively utilizes the data bit stream generated in an optical fiber computer networkbased on the packet over SONET/SDH technique. A small fraction of the optical signal ismonitored both at the transmitter and at the receiver. When an occurrence of a unique bitsequence of the SDH frames is detected, an electrical pulse is generated and compared with aresolution of 100 ps to a local clock. With data from all four positions of an optical bidirectionallink, two-way time-transfer can be achieved and any symmetrical variations in delay canpotentially be cancelled. The results presented here have been obtained over OptoSUNET, thenew Swedish University Network. In the experiment, 10 Gbit/s traffic from SP over OptoSUNETis extended in Stockholm to STUPI, a clock laboratory which is the second node in this setup.This reconnection enables that a communication channel is established between two nodes,with no intermediate jump. The time-transfer experiment includes more than 500 km of fibertransmission, of which several km is via air-lines. By comparing the results from a GPS carrierphaselink, a precision better than ± 1 ns is achieved over several months of measurementsbetween two Hydrogen-masers.
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| 6. |
- Ebenhag, Sven-Christian, 1976, et al.
(författare)
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Time transfer using an asynchronous computer network: Results from three weeks of measurements
- 2007
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Ingår i: European Frequency and Time Forum, 29/5 - 1/6, Geneva, CH.
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Konferensbidrag (refereegranskat)abstract
- We have performed a time transfer experimentbetween two atomic clocks, over a distance of approximately 75km using an 10 Gbit/s asynchronous fiber-optic computernetwork. The time transfer was accomplished through passivelistening on existing data traffic and a pilot sequence in the SDHbit stream. In order to assess the fiber-link clock comparison, wesimultaneously compared the clocks using a GPS carrier phaselink. The standard deviation of the difference between the twotime transfer links over the three-week time period was 243 ps.
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| 10. |
- Hedekvist, Per Olof E, 1967, et al.
(författare)
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Accurate time transfer utilizing the synchronization in an SDH-network
- 2006
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Ingår i: 2006 Optical Fiber Communication Conference, and the 2006 National Fiber Optic Engineers Conference; Anaheim, CA; United States; 5 March 2006 through 10 March 2006. - 9781557528032
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Konferensbidrag (refereegranskat)abstract
- A nationwide system for accurate time distribution is being developed, utilizing synchronization in an SDH-network. The first experimental results based on this technique are presented, performed on, but not limited to, STM-64.
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