Technology review 2010: Scientists and engineers: A vital alliance

Suspended-core fibers have a small solid core with a large gas-filled region; if the core is small enough, it becomes a suspended nanowire, opening the door for interesting nonlinear optical effects. Scientists at Toyota Technological Institute (Nagoya, Japan) used a gas-pressure inflation technique to fabricate a suspended lead-silicate-glass-core nanofiber that has a diameter ratio of holey region to core of at least 62, a core diameter of 480 nm, and a length of several hundred meters (see Fig. 4). Optical loss at 1557 nm was 8 ±2 dB/m; single-mode third-harmonic generation (THG) was achieved when pumped with a 1557 nm femtosecond laser.

In fiber-optic communications, systems are now being designed to encode not just the light signal's amplitude but its phase as well, to reach higher data transmission rates. But, as a result, nonlinear phase noise—formerly a nonissue—will become the prime limitation to performance. In response, a team of researchers from the University of Southampton, Chalmers Institute of Technology (Gotebörg, Sweden), University College Cork (Cork, Ireland), OFS (Brøndby, Denmark), Eblana Photonics (Dublin, Ireland), and the University of Athens (Athens, Greece) have developed the first practical all-optical regenerator that can remove both phase and amplitude noise from binary phase-encoded optical signals. The device, which takes advantage of the phase-squeezing ability of phase-sensitive amplifiers, operates on 40 Gbit/s signals and has the potential to operate at much higher rates, say the researchers.

FIGURE 4. A suspended-core fiber with a core diameter of 480 nm is imaged via optical microscope (a) and scanning-electron microscope at various magnifications (b-d). (Courtesy of the Toyota Technological Institute)