Fast and broadband fiber dispersion measurement with dense wavelength sampling

Abstract

Abstract:We report on a method to obtain accurate dispersion measurements from spectral-domain low-coherence interferograms, which enables high accuracy (~ps/nm/km), broadband measurements and the determination of very dense (up to 20 points/nm over 500 nm) datasets for both dispersion and dispersion slope. The method exploits a novel phase extraction algorithm which allows the phase associated with each sampling point of the interferogram to be calculated and provides for very accurate results as well as a fast measurement capability, enabling close to real time measurements. The important issue of mitigating the measurement errors due to any residual dispersion of optical elements and to environmental fluctuations was also addressed. We performed systematic measurements on standard fibers which illustrate the accuracy and precision of the technique, and we demonstrated its general applicability to challenging problems by measuring a carefully selected set of fibres: a lead silicate microstructured fiber with a flat, near-zero dispersion profile; a hollow core photonic bandgap fiber with strongly wavelength-dependent dispersion and dispersion slope; a small core, highly birefringent index guiding microstructured fiber, for which polarization resolved measurements over an exceptionally wide (~1000 nm) wavelength interval were obtained. 2013 Optical Society of America

Dispersion measurement of ultra-high numerical aperture fibers covering thulium, holmium, and erbium emission wavelengths

“…For short fiber samples, where direct dispersion measurement methods like the phase shift technique [17] are not viable, spectral interferometry is widely used [18][19][20][21][22][23][24][25][26]. While interferometer-less schemes do exist [24], the method is usually based on employing a Mach-Zehnder interferometer, with the fiber under test placed in one arm and the other arm serving as the reference (Fig.…”

“…The interferometric measurement reveals the spectral phase difference between the two interferometer arms (which ideally is only due to the fiber under test), retrieved from the interferogram by i.e. observing equalization wavelength shift for various arm path length differences [19,21], Fourier filtering [22], fringe counting [20,25], nonlinear fit of the interferogram [23] or direct phase extraction [26]. Dispersion is subsequently obtainable by differentiation of the spectral phase.…”

“…For example, if the shortest equalization wavelength is in the normal dispersion region, then going towards longer wavelengths the fringe order should increase up to the first equalization wavelength, decrease until the second equalization wavelength, then increase once again in the direction of longer wavelengths and so on, depending on the number of equalization points visible in the interferogram. Subsequent operations enable to retrieve the dispersion parameter D either by direct numerical differentiation [26] or by approximating the refractive index with polynomials. Hlubina et al [25] used a modified Cauchy dispersion formula in the form (.…”

“…Additionally, the results calculated using the fitting parameters were cross-checked with the dispersion obtained by direct numerical differentiation of the spectral phase, in a similar way to Ponzo et al [26]. While our numerical differentiation operations led to unacceptably noisy curves (not shown), the visual comparison allowed to ensure that no major artifacts resulted from using approximating functions like the one in Eq.…”

Low‐Latency WDM Intensity‐Modulation and Direct‐Detection Transmission Over >100 km Distances in a Hollow Core Fiber

“…We note that CD characterization over a wider spectral range can be realized by using other characterization methods, such as the Mach-Zehnder interferometer method together with a super-continuum source. [34,35] To facilitate a direct comparison, our experiments were carried out on spools that were available in our labs, and which had as close a physical length to the NANF under test as possible (4.76 km). These fibers were a ≈4.53-km length of SSMF (Corning SMF-28e) and a ≈4.73-km length of NZ-DSF (Corning LEAF).…”