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Sensors 2014, 14(1), 1757-1770; doi:10.3390/s140101757
Article

Two-Stage System Based on a Software-Defined Radio for Stabilizing of Optical Frequency Combs in Long-Term Experiments

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Received: 30 October 2013; in revised form: 8 January 2014 / Accepted: 8 January 2014 / Published: 20 January 2014
(This article belongs to the Section Physical Sensors)
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Abstract: A passive optical resonator is a special sensor used for measurement of lengths on the nanometer and sub-nanometer scale. A stabilized optical frequency comb can provide an ultimate reference for measuring the wavelength of a tunable laser locked to the optical resonator. If we lock the repetition and offset frequencies of the comb to a high-grade radiofrequency (RF) oscillator its relative frequency stability is transferred from the RF to the optical frequency domain. Experiments in the field of precise length metrology of low-expansion materials are usually of long-term nature so it is required that the optical frequency comb stay in operation for an extended period of time. The optoelectronic closed-loop systems used for stabilization of combs are usually based on traditional analog electronic circuits processing signals from photodetectors. From an experimental point of view, these setups are very complicated and sensitive to ambient conditions, especially in the optical part, therefore maintaining long-time operation is not easy. The research presented in this paper deals with a novel approach based on digital signal processing and a software-defined radio. We describe digital signal processing algorithms intended for keeping the femtosecond optical comb in a long-time stable operation. This need arose during specialized experiments involving measurements of optical frequencies of tunable continuous-wave lasers. The resulting system is capable of keeping the comb in lock for an extensive period of time (8 days or more) with the relative stability better than 1.6 × 10−11.
Keywords: optical frequency combs; digital signal processing; software-defined radio; beat note; stabilization; long-term operation optical frequency combs; digital signal processing; software-defined radio; beat note; stabilization; long-term operation
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Čížek, M.; Hucl, V.; Hrabina, J.; Šmíd, R.; Mikel, B.; Lazar, J.; Číp, O. Two-Stage System Based on a Software-Defined Radio for Stabilizing of Optical Frequency Combs in Long-Term Experiments. Sensors 2014, 14, 1757-1770.

AMA Style

Čížek M, Hucl V, Hrabina J, Šmíd R, Mikel B, Lazar J, Číp O. Two-Stage System Based on a Software-Defined Radio for Stabilizing of Optical Frequency Combs in Long-Term Experiments. Sensors. 2014; 14(1):1757-1770.

Chicago/Turabian Style

Čížek, Martin; Hucl, Václav; Hrabina, Jan; Šmíd, Radek; Mikel, Břetislav; Lazar, Josef; Číp, Ondřej. 2014. "Two-Stage System Based on a Software-Defined Radio for Stabilizing of Optical Frequency Combs in Long-Term Experiments." Sensors 14, no. 1: 1757-1770.



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