Bicell-photodetector in the Fourier plane as a fiber optic homodyne phase demodulator: theoretical model and experimental results

Abstract

A concept of the Young interference experiment has been applied in the design of a fiber optic homodyne phase demodulator. The system is based on a bicell-photodetector in the Fourier plane. The above system has been designed, described, and verified together with an estimation of the minimization of phase measurement error in connection with the distance between photodetectors, wavelength, and focal length of the Fourier lens. The fundamental investigation concerning the choice of a distance between photodetectors and its influence on the demodulator's linearity has been presented and discussed as well.

The Young Interferometer as Optical System for Variable Depolarizer Characterization

“…The treatment of problems involving depolarization of incident polarized light beam passing through a variable depolarizing medium and general physical phenomena associated with it is the main element of our investigation. A suitable tool for this treatment is previously reported Young's interferometer [25] constructed with a new principle including the possibility to control the fringe pattern in real time with the objective to study the dynamics of polarization fluctuation.…”

“…The information about an error of the phase difference, induced by this system was analysed and described in reference and had the following expression [25]:…”

The Young Interferometer as an Optical System for a Variable Depolarizer Characterization

“…The adequate tool for studying the dynamic effects of the spatial distribution of birefringence upon switching a VAN cell by an electric field was a modified Young’s interferometer proposed in our previous works [15,16,17]. This interferometer was constructed in free space with the possibility of controlling the fringe pattern in real time to study polarization dynamics and their fluctuations in the time domain.…”

“…Interference between two beams with the same linear polarization that emerges from two single mode optical fibers can be analyzed by means of a bicell photodetector as used in [15]. In the present work, it is intended that an equivalent experimental configuration was appropriate to study the phase shift when the polarization state between two beams is different.…”

“…Furthermore, this device had a time-varying birefringence. In our proposal, we used a modified Young’s interferometer to enable simple and automatic measurements of the time-varying phase with high sensitivity [15]. Our interferometer was adapted to include a half-wave plate (HP) and a quarter-wave plate (QP) in the interferometer’s object arm to generate an arbitrary polarization state in the input of the depolarizer cell, while the reference beam is kept linearly polarized.…”