Radio-frequency low-coherence interferometry

Abstract

A method for retrieving low-coherence interferograms, based on the use of a microwave photonics filter, is proposed and demonstrated. The method is equivalent to the double-interferometer technique, with the scanning interferometer replaced by an analog fiber-optics link and the visibility recorded as the amplitude of its radio-frequency (RF) response. As a low-coherence interferometry system, it shows a decrease of resolution induced by the fiber's third-order dispersion (β3). As a displacement sensor, it provides highly linear and slope-scalable readouts of the interferometer's optical path difference in terms of RF, even in the presence of third-order dispersion. In a proof-of-concept experiment, we demonstrate 20-μm displacement readouts using C-band EDFA sources and standard single-mode fiber.

SCM Adaptation to Improve Scanning Rate in RF Interferometry Applications

“…4(b). A quasiinvariant resolution behaviour implies that third-order dispersion can be considered as negligible in our operation range [9]. Therefore, we demonstrate a great control of the parameters in the whole experiment in comparison to previous MWP-LCI results.…”

“…Comparing with previous MWP-LCI approaches [9][10][11], our proposal highly reduces the baseband contribution located at low RF frequencies due to the BPD as shown Fig. 2(a).…”

“…Combination of MWP and LCI (MWP-LCI) has become an attractive solution as can be seen in some recent publications [9][10][11][12][13]. Different proposals can be found where the slicing of an incoherent source and its analysis through a dispersive element has been demonstrated to retrieve the visibility of low-coherence interferograms by measuring the electrical transfer function in the RF domain [9][10][11].…”

“…Different proposals can be found where the slicing of an incoherent source and its analysis through a dispersive element has been demonstrated to retrieve the visibility of low-coherence interferograms by measuring the electrical transfer function in the RF domain [9][10][11]. Nevertheless, the scanning rate of these proposals is restricted to the sweep speed of commercial equipments [13].…”

Broadband Linearization of Dispersive Delay Line Using a Chirped Fiber Bragg Grating

“…This estimate also precludes the use of a SMF dispersive line, for which a = −2.7. The passband distortion induced by SMF in a similar range of parameters can be observed in [15].…”