Demodulator of phase signal for singlemode fiber-optics

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

“…The most important conclusion from the simulation results presented in Fig. 4 is that for specific values of q∕2 (i.e., q∕2 30.2 μm), every value of the phase difference from the range −π, π, has a unique corresponding combination of Sum and Diff signals [9,10,16,17]. For other values of q∕2, this explicitness is much less pronounced.…”

“…To avoid the above-mentioned inconveniencies one should, first, apply on the Fourier plane a B-PD with the gap q [10,16] to monitor the changes in the distribution of the field intensity. Second, modify the geometry of the light sources on the front Fourier plane so the ratio 2b∕d should be contained within the range of 1.5-3.0.…”

“…Commonly used phase modulators are commercially available integrated optical modulators or all-fiber piezoelectric optical modulators [1]. Optical demodulation, however, is difficult for technological realization; hence it is still arousing a lot of interest within the area of optical sensors [3] and in photonic links for the linear transport of analog radio-frequency (RF) signals [3][4][5][6][7][8], as well as in the systems for automatic identification and decoding of digitally modulated signals [9,10]. To this end, the detection systems employing a single photodiode (PD) have been designed and applied, among others the bicell and quadrant PDs (two or four PDs separated by a narrow gap).…”