A triangular, common-path interferometric rf spectrum analyzer arrangement has been demonstrated which has the property of high immunity to ambient vibration. Calculations show the TCPI arrangement, with two counter-propagating laser beams, is highly angle compensated and alignment stable when components are disturbed in position or orientation. Proper light polarization and Bragg cell geometry allows one Bragg cell to diffract primarily the clockwise beam and the other Bragg cell the counterclockwise beam. A birefringent quartz wedge shifts the heterodyne signal to a nonzero IF carrier frequency. Measured ambient phase noise is less than two degrees and calculated values indicate that further improvement may be possible.

© 1989 Optical Society of America

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  1. J. P. Lindley, “Applications of Acousto-Optic Techniques to RF Spectrum Analysis,” in Acousto-Optic Signal Processing, N. J. Berg, J. N. Lee, Eds., (Marcel Dekker, New York, 1983), Chap. 4.
  2. M. King, W. R. Bennett, L. B. Lambert, M. Arm, “Real-Time Electrooptical Signal Processors with Coherent Detection,” Appl. Opt. 6, 1367–1375 (1967).
    [CrossRef] [PubMed]
  3. A. VanderLugt, “Interferometric Spectrum Analyzer,” Appl. Opt. 20, 2770–2779 (1981).
  4. P. Hariharan, “Sagnac or Michelson-Sagnac Interferometer?,” Appl. Opt. 14, 2319–2321 (1975).

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Figures (2)

Fig. 1
Fig. 1

Independent-path interferometric (heterodyne) spectrum analyzer (Mach-Zehnder).

Fig. 2
Fig. 2

Triangular common-path interferometric (TCPI) heterodyne spectrum analyzer. (Bragg cell diffraction is normal to the plane of the figure and the various beams have been separated for clarity. The preferred beam splitter type is a symmetrical cube.)

Tables (1)

Tables Icon

Table I Calculated Relative Immunity to Vibration for Simple, Symmetric, Interferometers with Cube or Pellicle Beam Splitters