Optical Single-Sideband Modulators and Their Applications

We review our recent work in the implementation of optical single-sideband (OSSB) modulation and in the application of this modulation format to microwave photonics and optical testing systems. We have developed an enhanced OSSB modulator for wide-band operation, the so-called bidirectional OSSB modulator, and a simplification of this scheme for narrow-band applications. These OSSB modulators are based on the use of a standard single-electrode Mach-Zehnder electro-optic modulator (MZ-EOM) and passive fiber-optic components. In both designs, the OSSB operation is shown to be independent of the MZ-EOM bias. Therefore, the optical modulation depth at the output of the device can be enhanced using minimum transmission biasing to provide suppression of the optical carrier. Finally, we demonstrate the application of OSSB modulators to the improvement of microwave/millimeter-wave subcarrier multiplexing fiber-optic links and to narrow-band fiber radio systems. In addition, we analyzed the feasibility and the limitations of an optical vector network analysis technique based on OSSB modulation that can provide sub-picometer wavelength resolution.     

INTERACTION BETWEEN UPOSOMES AND MONOLAYERS IN THE PRESENCE OF CALCIUM

Abstract

The interaction between phospholipid vesicles (phosphatidylcholine : phosphatide acid, 90:10 w/w) and phosphatidylcholine : cholesterol (70:30, molar ratio) monolayers at air/water interfscks has been studied at. several concentrations of calcium cation ( Ca²⁺). The liposome vesicles were SUVs and MLVS.

The vesicles interact with the monolayers, rapidly causing a large increase in surface pressure. Limiting values of surface pressure, 2.07-6.99 mN.m-1 for SUVs, and 7.01-11.11 mN.m^?1 for MLVs, were reached in less than 40?min.

Calcium ion concentration affects the liposome size in MLVs, producing an increase of gyration radius. The SUVs are little influenced. The change in size can be due to a variation of liposome composition induced by calcium: cholesterol molecules can migrate from monolayer to liposomes and the redistribution of exchanged lipids in the outer bilayer can also explain the size variation.