A Novel Approach to Raman Distributed Temperature-Sensing System for Short-Range Applications.

A novel approach to the development of Distributed Temperature-Sensing (DTS) systems based on Raman Scattering in Multimode optical fibers operating at around 800 nm is presented, focusing on applications requiring temperature profile measurement in the range of a few hundreds of meters. In contrast to the standard Raman DTS systems, which aim to shorten the pulse space width as much as possible to improve the precision of measurement, the novel approach studied in this work is based on the use of pulses with a space width that is approximately equal to the distance covered by the fiber under test. The proposed technique relies on numerical post-processing to obtain the temperature profile measurement with a precision of about ±3 °C and a spatial resolution of 8 m, due to the transaction phases of the optical pulses.

Reduction of modal noise due to fiber/photodetector misalignment in SSMF links based on 850 nm VCSELs through a low-cost polymer coupling structure.

A low-cost polymer-based structure is proposed to improve the coupling between a fiber end section and photodetector active surface in optical links based on standard single-mode fiber (SSMF), which employs vertical cavity surface emitting lasers operating at 850 nm, i.e., below the SSMF cutoff wavelength.

Chirp evaluation of semiconductor DFB lasers through a simple Interferometry-Based (IB) technique.

Direct modulation of a laser source is often utilized in realizing optical fiber connections where the cost of the entire system must be kept at a low level. An undesired consequence of this choice is the onset of the laser frequency chirp effect, which is detrimental in the case of either digital or analog links, and must be evaluated with precision in order to perform an accurate design of the whole system. Various methods of evaluation of the chirp parameters have been proposed, and the choice among them is typically made on the basis of the laboratory equipment available at the moment.

Effects of laser frequency chirp on modal noise in short-range radio over multimode fiber links.

An important effect of the frequency chirp of the optical transmitter in radio over multimode fiber links is put into evidence experimentally and modeled theoretically for the first time, to our knowledge. This effect can have an important impact in short-range connections, where, although intermodal dispersion does not generally cause unacceptable limitations to the transmittable bandwidth, the presence of modal noise must be accurately kept under control, since it determines undesired real-time fluctuations of the link.

Avoided-crossing-based liquid-crystal photonic-bandgap notch filter.

We demonstrate a highly tunable deep notch filter realized in a liquid-crystal photonic-bandgap (LCPBG) fiber. The filter is realized without inducing a long-period grating in the fiber but simply by filling a solid-core photonic-crystal fiber with a liquid crystal and exploiting avoided crossings within the bandgap of the LCPBG fiber. The filter is demonstrated experimentally and investigated using numerical simulations.