Figure 1.3 shows the electric and magnetic fields distribution of a traveling RF wave with a normal probe shown in typical orientation. To detect the maximum electric field in this configuration, the propagation direction of the optical beam of the probe should be parallel to the E-field direction. In general, a normal EO probe is only sensitive to the electric field component parallel to the probe handle, whereas a tangential probe is sensitive to the electric field component perpendicular to the probe handle. Yet, the E-field sensitivity of a tangential probe depends on its crystal orientation sitting on its tip.
[[Image:neoscanfig_1_4.png|thumb|right|480px|<i><b>Figure 1.4</b>: An example of a real time measurement of a 6.6 nsec pulse with 10 kV/m peak field strength. The upper trace shown on the oscilloscope is the input signal, and the lower trace is the measured signal.</i>]] A low noise 1550 nm laser diode is used as optical beam source. The optical connections are fiber-based. The beam is delivered to an optical probe. The polarization of the beam is modulated through an electro-optic crystal on the probe tip. The modulated beam is reflected back into the fiber, and back to the mainframe for analysis. An optical analyzer converts the polarization change of the beam into an amplitude change. The amplitude is linearly proportional to the strength of the external electric field at the probe-crystal location. The equation E=αV is used to calculate the electric field, where α is the calibration factor, or the slope between the electric field E (in V/m) and the measured EO signal V (in V/m/uV). For instance, for a calibration factor of 1.082 V/m/uV. a measured EO signal of 1000 uV (0.001 V), corresponds to and electric field of 1.082 V/m/uV x 1000 V = 1082 V/m.
Due to the fast response of the EO crystal, it is possible to measure extremely high-bandwidth signals with the normal SNR limitations of wideband signal detection. Using this capability, EMAG Technologies Inc. has developed the worldâs first fiber-based real-time polarimetric electric field sensor system â [[NeoScan]] â for the measurement of high-power microwave signals. Figure 1.4 is an example of a real time measurement of a 6.6 nsec pulse with 10 kV/m peak field strength. The upper trace shown on the oscilloscope is the received signal, and the lower trace is the detected signal.