Digital Phase Generated Carrier Research Articles

Proposal for eliminating the external disturbance via digital PGC technique in a multiplexed fiber interferometer measurement system

We demonstrate a multiplexed fiber interferometer measurement system for eliminating the external disturbance using the digital phase generated carrier (PGC) demodulation technique. By applying two fiber Bragg gratings (FBG) and two fiber interferometers that share the reference arm and part of the sensing arm in this measurement system, we find that the system can be used for detecting the useful signal and the external disturbances is reduced by 26dB. Thus, our work may provide some new possibilities for technological applications in vibration measurement.

Realization of 16-channel digital PGC demodulator for fiber laser sensor array

This paper describes a 16-element DFB FL (distributed feedback fiber laser) sensor array system interrogated by NI-PXI-based (PCI extensions for Instrumentation) digital PGC (phase generated carrier) technique. The lasing wavelengths of the DFB FLs are changed by the external strains or temperatures, and hence they can be used as sensors by detecting the wavelength shifts. An unbalanced MI (Michelson interferometer) is employed in the sensor array system to amplify the wavelength shifts of DFB FL sensors to detectable phase shifts. The output phase signals of the MI are separated into different channels by a DWDM, and then detected by a low-noise photodiode array. The digital PGC algorithm is realized on a PXI platform (NI, National Instruments), which consists of three FPGA (Field Programmable Gate Array) modules and a high performance system controller. The normalization of the interference fringe is proposed and realized in this paper to reduce the influence of the light intensity fluctuations, and a trigger mechanism is introduced into the digital multi-channel PGC demodulation scheme to synchronize the date among different channels. A 16-element DFB fiber laser sensor array system has been set up in the experiment and the demodulated results have demonstrated a minimum detectable wavelength shift of 1×10−6 pmA/√Hz, a linearity of as high as 0.9994, and a dynamic range of 110dB@100Hz.

Investigation of polarization-induced fading in fiber-optic interferometers with polarizer-based polarization diversity receivers

A technique is described to eliminate polarization-induced fading in fiber-optic interferometers with two or three polarizers. Modeling and simulation show that two polarizers should be angularly spaced by 90 degrees to alleviate polarization-induced fading. A test system is set up with two 6.5 km fiber coils to link the data. A bistate polarization diversity receiver is tested for reducing polarization-induced fading. The signal is demodulated using a digital phase-generated carrier and the system demonstrates self-noise up to 7.7 microrad/square root Hz (at 1 kHz).