Description: The Naval Research Laboratory (NRL) has developed an optical High Power Microwave (HPM) field sensor for test and evaluation (T&E). The device measures the real time amplitude, polarity and phase of the HPM field with 3-axis capability by analyzing the phase modulation of a laser beam through an electro-optical (EO) crystal sensor head. This analyzer is isolated from the sensor head by long, large core multimode (MM) optical fibers. The device has very broad band capability covering 10 GHz in frequency range. Unlike D-dot and B-dot sensors, or Mach-Zehnder interferometry, the NRL electro-optical sensor does not contain metal conducting parts and therefore the sensor head does not generate significant interference with the field it is measuring which is a major problem facing the HPM T&E community. The integrated sensor head design and the use of a MM output fiber greatly simplifies construction, reduces cost, improves robustness, reduces the noise level and therefore increases sensitivity, and improves the stability and reliability of the EO sensor. The sensor head is also quite small enabling its use in confined spaces.

Advantages/Features Include:

  • Measures real time amplitude, polarity and phase of the HPM field with 3-axis capability (Ability to measure electric field vectors)
  • Minimal perturbation; EO sensor does not perturb the field that it measures
  • Wideband measurement (DC- 10 GHz) capability
  • Relatively high sensitivity; sensitivity is better than 2 mV/m (Hz)1/2
  • Compact size, suitable for field measurements in a small confined space, smaller than 2 cm3
  • Survives an extreme field strength; Maximum field strength > 500 kV/m
  • Allows the use of long optical fibers (> 50 meters)
  • Inexpensive

Applications Include:

  • HPM test and evaluation
  • Microwave communications
  • Electronic warfare
  • Electromagnetic Compatibility (EMC) testing
  • Electric-field leakage testing for high power transmission lines

References:

  • "Optimal Electro-Optic Sensor Configuration for Phase Noise Limited, Remote Field Sensing Applications," Appl. Phys. Lett. 94 (2009) 221113.

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