We present a laser-based system to measure the refractive index of air over a long path length. In optical distance measurements, it is essential to know the refractive index of air with high accuracy. Commonly, the refractive index of air is calculated from the properties of the ambient air using either Ciddor or Edlén equations, where the dominant uncertainty component is in most cases the air temperature. The method developed in this work utilizes direct absorption spectroscopy of oxygen to measure the average temperature of air and of water vapor to measure relative humidity. The method allows measurement of temperature and humidity over the same beam path as in optical distance measurement, providing spatially well-matching data. Indoor and outdoor measurements demonstrate the effectiveness of the method. In particular, we demonstrate an effective compensation of the refractive index of air in an interferometric length measurement at a time-variant and spatially nonhomogeneous temperature over a long time period. Further, we were able to demonstrate $7\mathrm{mK}$ RMS noise over a $67\mathrm{m}$ path length using a $120\mathrm{s}$ sample time. To our knowledge, this is the best temperature precision reported for a spectroscopic temperature measurement.

© 2011 Optical Society of America

You do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Log in to access OSA Member Subscription

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Log in to access OSA Member Subscription

You do not have subscription access to this journal. Figure files are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Log in to access OSA Member Subscription

You do not have subscription access to this journal. Article level metrics are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Log in to access OSA Member Subscription

Related Journal Articles

• Phase-Shift-Locked Interferometer with a Wavelength-Modulated Laser Diode (AO)
• Simultaneous In Situ Measurement of CO, H₂O, and Gas Temperatures in a Full-Sized Coal-Fired Power Plant by Near-Infrared Diode Lasers (AO)
• Analysis of Thermal Decay and Prediction of Operational Lifetime for a Type I Boron–Germanium Codoped Fiber Bragg Grating (AO)
• Application of Schlieren Interferometry to Temperature Measurements During Laser Welding of High-Density Polyethylene Films (AO)
• High-repetition-rate combustion thermometry with two-line atomic fluorescence excited by diode lasers (OL)

Related Conference Papers

• New room-temperature 2.3µm DFB-diode lasers: first spectroscopic characterization and CO-detection
• Using Thermal Profiling to Quantify Optical Feedback into Semiconductor Lasers
• Using Thermal Profiling to Quantify Optical Feedback into Semiconductor Lasers
• Complete characterization of fiber laser pulses using real-time spectral interferometry
• Ring laser measurement of magnetochiral interaction : Application to Pasteur's tartrates