An electromagnetic field sensing apparatus includes an optical modulator,
a miniature antenna for sensing the electromagnetic field, a light
source, a first optical fiber, an optical detector and a second fiber.
The optical modulator can vary the amplitude of a light beam propagating
therethrough in response to an electric field intensity. The miniature
antenna for sensing the electromagnetic field can sense both the electric
field intensity and the magnetic field intensity of an electromagnetic
field and apply an electric voltage to the optical modulator in response
to the sensed electromagnetic field intensity. The light source is used
to generate a light beam, the first optical fiber is used for
transmitting the light beam to the modulator, and the second fiber is
used for transmitting the light beam from the modulator to the optical
detector.