Definition, meaning, and measurement of the polarization extinction ratio of fiber-based devices

Abstract

We clarify the definition of the polarization extinction ratio-also called polarization cross talk--of fiber-based devices. Its strong wavelength dependence, even for simple devices such as a single-fiber patchcord, is highlighted. Thus white sources may not be used for most measurements. We also explain the weakness of measurements with a rotating polarizer and a monochromatic source. Only a polarimeter may be used if accuracy is required. We report measurements of connections (including two connectors and one mating sleeve) and show the importance of the mating sleeve in the result. Finally, we define the validity domain of the standardized method, which uses both a white source and a rotating polarizer.

Alignment-free characterization of polarizing beamsplitters

“…Two 3-port and one 4-port PBS's were characterized with the proposed method, and the results are presented in Table I. Even though all extinction ratios measured comply with those described in the devices' data sheets (¿ 20 dB), for a more accurate comparison, the extinction ratios were also measured with the conventional method described in literature [4], [5], [6], [7]. For this, a polarized light source comprised of a laser was used and had its polarization aligned with one axis of the tested PBS.…”

“…In a realistic scenario where DOP 1, a first-order approximation shows that the error in the measurement, in dB, would correspond to approximately 10 · log 10 (1 + 3 · DOP); for instance, if DOP = 0.1, the error introduced in the measurement would be ∼ 1 dB. This is in contrast with the usage of highly polarized probe lights, where the sensitivity to the DOP variation is much higher [6].…”

“…Traditionally, this measurement is performed using a highly coherent light source, such as a laser [4], [5], [6], [7], [8], [9], [10], [11]. The polarization state of a test light signal is matched with both axes -horizontal and vertical polarizations -of the device under test (DUT), using birefringent elements such as half-waveplates or fiber polarization controllers, depending on whether the DUT is a bulk or fiber-optical PBS, respectively.…”

“…By a clever arrangement of a Faraday Mirror, a 2x2 optical switch, two power meters and an optical circulator, it is possible to obtain the insertion losses and extinction ratios in a single-sweep, three-step measurement. The method is validated, a fully automated characterization unit is assembled and the results are compared to the literature method [4], [5], [6], [7] with good correspondence.…”

Measurement of local polarization for multi-mode photonic crystal fibers

“…To quantify this property, the polarization extinction ratio PER = 10 log 10 P max P min dB (15) can be measured, where P max is the maximum power in a linear polarization state obtained by a polarizer and P min is the minimum power of the emerging light in the perpendicular polarization state. 19 The maximum achieved polarization extinction ratio after 2 m fiber length is PER = 24.3 dB for the multi-mode PCF. This excellent polarization extinction ratio agrees with PER > 20 dB stated by the manufacturer.…”