Simultaneous dispersion measurements of multiple fiber modes using virtual reference interferometry

Abstract

We present the simultaneous measurement of first and second order dispersion in short length (< 1 m) few mode fibers (polarization and transverse) using virtual reference interferometry. This technique generates results equivalent to balanced spectral interferometry, without the complexity associated with physical balancing. This is achieved by simulating a virtual reference with a group delay equal to that of the physical interferometer. The amplitude modulation that results from mixing the interferograms, generated in both the unbalanced interferometer and the virtual reference, is equivalent to the first order interference that would be produced by physical balancing. The advantages of the technique include speed, simplicity, convenience and the capability for simultaneous measurement of multiple modes. The theoretical framework is first developed and then verified experimentally.

Full-set mode analysis of three-mode fibers calculated from polarization components of near-field pattern

“…There have been several mode analysis methods, which can be categorized into two types, i.e., one includes methods of analysis of the modes of output light based on the information on the modal pattern of an electromagnetic field, such as the prism-coupled mode analysis using an oblique section of an optical fiber 6) and a tapered fiber, 7) m-line observation from fiber Bragg gratings, 8) low-coherence interferometry, [9][10][11][12][13][14] eigen-mode expansion technique, 15) spatial and spectral (S 2 ) imaging, [16][17][18][19][20] and swept wavelength interferometry. 21) The other type includes methods based on longitudinal information like propagation constant and group velocity, such as optical frequency domain reflectometry, [22][23][24] resonator, 25,26) time of flight (ToF) method, 27,28) and optical time domain reflectometry (OTDR) method, 29,30) which can measure the dispersion characteristics and the longitudinal distribution of coupling coefficient. There has been no mode analysis method, however, that can provide a full set of amplitudes, phases, and polarization states of transmitted modes including degenerate modes.…”