Interference Cancellation for Hollow-Core Fiber Reference Cells

• Published in: IEEE transactions on instrumentation and measurement Vol. 64; no. 6; pp. 1595 - 1599
• Main Authors: Seppa, Jeremias, Merimaa, Mikko, Manninen, Albert, Triches, Marco, Hald, Jan, Lassila, Antti
• Format: Journal Article
• Language: English
• Published: IEEE 01.06.2015
• Subjects: Absorption; Frequency measurement; Frequency measurement standards; Frequency modulation; infrared spectra; Interference; interference cancellation; Measurement by laser beam; measurement techniques; metrology; optical fiber; Optical pumping; spectroscopy; measurement techniques; spectroscopy; Frequency measurement standards; infrared spectra; optical fiber; metrology; interference cancellation
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2015.2408800

Doppler-free saturated absorption spectroscopy of gases in hollow-core fiber (HCF)-based cells can be used for realizing new compact, robust, and portable frequency standards. In this paper, methods for cancelling interferences resulting from the optical connections between standard fiber and HCF and other factors such as varying coupling to HCF modes are investigated. Laser power modulation with simultaneous detection of ac and dc signal is used to separate saturated absorption from interferences. In addition, a technique of two piezoelectric stack actuators stretching the fiber at different locations is described. The presented experimental results demonstrate that 99% interference attenuation is readily attainable with the techniques. Frequency comb-referenced measurement of saturated acetylene absorption features near 1.54 μm, with fiber length and power modulation, is presented. For comparison, measurements and results of the same acetylene fiber, using a system having pump and probe beams at mutually shifted frequencies, are also given.