An all-fibre and integrated optics electric field sensing scheme using matched optical delays and coherence modulation of light

Abstract

Sensing electric fields occupying large bandwidths are interesting in practical applications related to natural phenomena and also in man-made hard electromagnetic industrial environments. In this work, an electric field sensor scheme, using coherence modulation of light, in an all-fibre configuration is described. The scheme uses lithium niobate (LiNbO3), integrated optics sensors. In a coherence modulation scheme, the LiNbO3 sensor detects the electric field and imprints it around an optical delay. The optical delay, acting as an information carrier, is transmitted through an optical fibre channel. At the receiver, light is demodulated by using a two-wave interferometer, introducing a second optical delay which is matched to the sensor's one. The demodulator can be implemented using either a second LiNbO3 crystal or an all-fibre optical retarder. Both alternatives are studied in this paper. The optical demodulator measures the optical autocorrelation around the optical delay and the electric field is recovered as a linear variation of the received optical power. Matching of the sensor and demodulator allows direct detection of the electric field, giving an unequal feature of an all-fibre scheme. The bandwidth of the sensing scheme is between 0 and 20 kHz.

Modeling and experimental electro-optic response of dielectric lithium niobate waveguides used as electric field sensors

“…A dynamic 0-100 kHz electric field is generated by a video high-voltage amplifier. In a previous work, a 20 kHz 'wide-band' electric field sensing scheme has been reported [21]. Sensing wide-band electric fields, at frequencies higher than 1 MHz, is an attractive application in industrial and commercial environments where high-intensity fields are present.…”

Electric field sensors based on optical retarders in lithium niobate (LiNbO3) integrated optics technology

“…An optical retarder introduces an optical delay, which can be used as information carrier if it is longer than the coherence time of the optical source. In the perspective of using optical retarders as electric field sensors, the optical delay can be modulated by a sensed electric field and transmitted through an optical channel; at the receiver, the electric field can be recuperated by introducing a second optical delay which is optically matched to the sensor's delay [1]. Electrooptic waveguides used simultaneously as optical retarders and electric filed sensors are of two types: birefringent slabs and Mach-Zehnder interferometers.…”

“…This is the only condition for recuperating the sensed electric field. The optical demodulator can be easily implemented by a passive optical retarder using polarizationmaintaining optical fiber (PMF) or a second electrooptic retarder [1]. In a practical scheme, the sensor retarder introduces an optical path-difference, which should be longer than the optical coherence length.…”