R. Calvani

Polarization measurements on single-mode fibers

An overview of current measurement techniques on conventional and polarization maintaining single-mode fibers is presented. The various methods are discussed and classified with respect to the relevant polarization parameters. Applicability ranges and resolution are pointed out for different types of fibers. >

Fiber birefringence measurements with an external stress method and heterodyne polarization detection

Precise birefringence measurements on polarization maintaining fibers have been obtained with external pressure scanning along the fiber axis. Output detection has been performed through heterodyne interferometric polarimetry, which allows the use of a simplified technique (avoiding pressure modulation and fiber eigenaxis search). Beat-length evaluation is achieved directly through multiple counting of periodical variations of the two radio-frequency output signals provided by the polarimeter. A theoretical model for the behavior of the fiber output polarization on the Poincare sphere, as a function of pressure scanning, has been developed and experimentally tested and the results are in good agreement with the theory.

Nonlinear absorption and refraction in strained InGaAs/InP multiple quantum wells for all-optical switching

Absorption spectra of strained InGaAs/InP quantum wells exhibit a single, unusually large exciton feature. 60% quenching is obtained for 4.3 mW Nd:YAG effective pump power at a wavelength of 1.064 mu m. A simple two-level formula fits well the behaviour at the exciton peak, and absorption spectra are reasonably approximated by a standard two-dimensional exciton model. Saturation intensities calculated with these techniques range around 200 W cm-2. Finally the Kramers-Kronig relations are used to calculate the associated refractive index change.

Ultra-stable polarization independent all-optical demultiplexer using four wave mixing in a dispersion shifted fiber

A novel polarization-independent all-optical demultiplexer using four-wave mixing in a dispersion-shifted fiber is demonstrated employing a 4/spl times/10 Gbit/s optical time-division multiplexing transmitter. The polarization dependency is lower than 0.5 dB and no bit-error-rate floor is present down to 10/sup -13/.

Real-Time Heterodyne Fibre Polarimetry by Means of Jones and Stokes Vector Detection

The study and measurement of the state of polarization (SOP) of the light propagating along a single-mode optical fibre, has been receiving particular attention in recent applications, such as coherent optical communications and fibre sensors [1, 2]. In both cases the polarization analysis requires a dynamical measurement of the SOP at the fiber output, which can be done on the basis of the Jones vector [3] (in terms of the amplitude ratio R and the relative phase Φ of the two components of the electric field) or of the Stokes vector [4] (in terms of the intensity parameters usually represented on the Poincare sphere to describe a fully polarized beam: s0, s1, s2, s3).

Mach-Zehnder Systems for Heterodyne Fibre Polarimetry in Different Coherence Conditions

In this contribution two distinct types of heterodyne systems are presented for the fast detection of polarization states at the output of a single -mode fibre. Based on the same measurement principle, the two versions differ as to source coherence properties, in order to cover a wider range of application conditions. Though devoted to fibre characterization purposes in the area of optical communications, the present work can be of considerable interest also for the development of new polarimetric fibre optic sensors.