Abstract
We report an absolute interferometer configured with a 1 GHz microwave source photonically synthesized from a fiber mode-locked laser of a 100 MHz pulse repetition rate. Special attention is paid to the identification of the repeatable systematic error with its subsequent suppression by means of passive compensation as well as active correction. Experimental results show that passive compensation permits the measurement error to be less than 7.8 μm (1 σ) over a 2 m range, which further reduces to 3.5 μm (1 σ) by active correction as it is limited ultimately by the phase-resolving power of the phasemeter employed in this study. With precise absolute distance ranging capability, the proposed scheme of the photonic microwave interferometer is expected to replace conventional incremental-type interferometers in diverse long-distance measurement applications, particularly for large machine axis control, precision geodetic surveying and inter-satellite ranging in space.
Highlights
Distance interferometry employing lasers has long been used for precision ranging and positioning in diverse industrial applications [1,2]
We have demonstrated a photonic scheme of an absolute distance interferometer using a 1 GHz microwave synthesized by the 10th harmonic of the pulse repetition rate of a fiber mode-locked laser
The measured interferometric phase phase is disturbed by optical and radio frequency (RF) electrical components comprising the interferometer system, is disturbed by optical and RF electrical components comprising the interferometer system, which were which were identified by measurements and subsequently corrected by passive and active schemes of identified by measurements and subsequently corrected by passive and active schemes of systematic systematic error suppression
Summary
Distance interferometry employing lasers has long been used for precision ranging and positioning in diverse industrial applications [1,2]. Continuous-wave monochromatic sources such as He–Ne gas lasers or semiconductor diode lasers are preferably used to attain sub-wavelength resolutions by performing phase-measuring interferometry based on homodyne or heterodyne principles [3,4]. Efforts are being made to apply photonic microwaves to large-scale industrial metrology [21] and space missions such as multiple satellite formation flying [22,23] In this investigation, we describe a 1 GHz microwave distance interferometer based on the 10th inter-mode harmonic of a 100 MHz pulse repetition rate of a fiber mode-locked laser. Experimental results reveal that absolute positioning can be achieved within a residual error of 3.5 μm (1 σ) over a 2.0 m distance, which corresponds to a phase resolution of ~0.0084◦ , which is comparable to the phase resolving power of the phasemeter configured in this study using a lock-in amplifier
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