Jean-Paul Pellaux

Polarization mode dispersion of short and long single-mode fibers

Polarization mode dispersion (PMD) in short and long single-mode fibers was measured by a polarization-maintaining Michelson interferometer. A nonnegligible PMD was found in some standard fibers. The sensitivity enables PMD to measure the bend-induced PMD of a fiber rolled on a 28-cm diameter drum. A theoretical model for PMD with random mode coupling is developed, and an explicit equation for the time-of-flight distribution is presented. Comparison between measurements on short and long fibers with residual birefringence leads to an estimation of the coupling length on the order of 20-30 m. >

Polarization mode dispersion: time versus frequency domains

We present two ways of analyzing the polarization mode dispersion with random coupling in standard single-mode fibers. The first one is based on the concept of principal polarization states and is valid for highly coherent propagating light (analysis in the frequency domain). The second one is based on unpolarized short pulses split by the local birefringence (analysis in the time domain). The two approaches lead to different definitions of polarization mode dispersion, but we prove that the two definitions lead to the same values. For this purpose we derive the evolution equations for the principal states and for the pulse distribution for arbitrary concatenations of polarization maintaining fibers. Both models have a continuous limit.

All-fiber interferometer for chromatic dispersion measurements

An all-fiber interferometric method for chromatic dispersion measurements in meter-length single-mode fibers is presented. In a Michelson setup the physical length of a reference fiber was varied so as to obtain adjustable optical delay. Time resolution, ease of manipulation, and mechanical isolation are considerably improved with respect to conventional interferometers. Resolution of group delay measurement and chromatic dispersion over the full 1100-1700-nm spectral range are better than 5 fs and 0.1 ps/nm-km, respectively. >

Self-trapped exciton in caesium iodide. III. Polarisation of the emissions

For pt.II see ibid., vol.13, no.6, p.993 (1980). The radiative recombination of (100) oriented self-trapped holes and conduction electrons has been measured in CsI:Na between 1.4 and 50K. At the lowest temperatures, both intrinsic emissions (290 nm and 338 nm) exhibit a partial plane polarisation perpendicular to the (100) axis of the parent VK centres. The 338 nm emission polarisation remains independent of temperature but the 290 nm emission polarisation decreases with temperature and eventually reverses its sign near 11K. Calculations show that both emissions come from a split triplet state located slightly below a singlet state which has an allowed transition to the ground state for the 290 nm emission but is forbidden for the 338 nm emission. This model explains reasonably well all the previously measured properties of self-trapped exciton emissions in CsI such as intensities, polarisations and decay times.

Photoacoustical detection of trace gases with an optical microphone

An alternative to the electrical microphone for photoacoustical detection of trace gases is presented. This microphone is made of a monomode optical fiber wound and glued on a thin plate. This fiber is one arm of a Michelson interferometer. A Sagnac interferometer has also been used and has given better results.

Group delay measurement in single-mode fibers with true picosecond resolution using double optical modulation

Highly accurate group delay measurements in long single-mode fibers were achieved over the full 1200-1600 nm spectral range by measuring phase shifts of a modulated lightwave. The high modulation frequency is shifted down to the kilohertz range using a second optical modulation at the fiber output end, so that low-frequency, ultrasensitive detection and phase measurement can be performed with high-frequency resolution conserved. This results in extremely reliable measurements with a >

Interferometric Measurements Of Birefringence In Single Mode Fibers And Devices

A simple method for interferometric measurements of chromatic and polarization mode dispersion os single mode fibres and devices is presented. Accuracy of the method and resolution limits are discussed.

Modulation frequency-shift technique for dispersion measurements in optical fibers

An improved technique for chromatic dispersion measurements in single-mode fibers using phase-shift measurements is presented. The conventional experimental setup using a modulated light-emitting diode filtered by a monochromator as a light source, a fast receiver, and a vector voltmeter for the phase measurements suffers from inherent drawbacks such as strong phase fluctuations due to poor SNR and RF interference providing biased measurements. The improved method eliminates these drawbacks with optical signal processing by shifting the modulation frequency down to the kilohertz range and maintaining the phase resolution due to high-frequency modulation. The advantages inherent in low-frequency detection and signal processing, such as stability, low noise, and strong filtering capability, and the resolution achieved by using a high modulation frequency result in reliable and accurate group delay measurements, giving a measured standard deviation of <0.5 nm for the zero chromatic dispersion wavelength.