Terahertz time domain spectroscopic imaging (THz-TDSI) is a non-ionizing, non-contact and non-destructive measurement technique that has been recently utilized to study cultural heritage artifacts. We will present this technique and the results of non-contact measurements of papyrus texts, including images of hidden papyri. Inks for modern papyrus specimens were prepared using the historical binder, Arabic gum, and two common pigments used to write ancient texts, carbon black and red ochre. The samples were scanned in reflection at normal incidence with a pulse with a spectral range between 0.1 and 1.5 THz. Temporal analysis of the signals provides the depths of the layers, and their frequency spectra give information about the inks.

Terahertz (THz) imaging is an emerging technique for non-invasive analysis. Since THz waves can penetrate opaque materials, various imaging systems that use THz waves have been developed to detect, for instance, concealed weapons, illegal drugs, and defects in polymer products. The absorption of THz waves by water is extremely strong, and hence, THz waves can be used to monitor the water content in various objects.THz imaging can be performed either by transmission or by reflection of THz waves. In particular, time domain reflection imaging uses THz pulses that propagate in specimens, and in this technique, pulses reflected from the surface and from the internal boundaries of the specimen are detected. In general, the internal structure is observed in cross-sectional images obtained using micro-specimens taken from the work that is being analysed. On the other hand, in THz time-domain imaging, a map of the layer of interest can be easily obtained without collecting any samples. When real-time imaging is required, for example, in the investigation of the effect of a solvent or during the monitoring of water content, a THz camera can be used.The first application of THz time-domain imaging in the analysis of a historical tempera masterpiece was performed on the panel painting Polittico di Badia by Giotto, of the permanent collection of the Uffizi Gallery. The results of that analysis revealed that the work is composed of two layers of gypsum, with a canvas between these layers. In the paint layer, gold foils covered by paint were clearly observed, and the consumption or ageing of gold could be estimated by noting the amount of reflection.These results prove that THz imaging can yield useful information for conservation and restoration purposes.

Time-domain terahertz reflection imaging is presented as a novel method of measuring otherwise inaccessible tree rings in wooden cultural heritage for the purpose of tree-ring crossdating. Axial and lateral two-dimensional terahertz images of obscured ring patterns are statistically validated with respect to their corresponding optical photographs via adapted dendrochronological methods. Results are compared to similar analysis of x-ray images of a wood specimen.

The feasibility of applying time-domain, terahertz spectroscopic imaging to the evaluation of underdrawings and paint layers embedded within wall paintings is demonstrated. Metallic and dielectric paint patterns and a graphite drawing are resolved through both paint and plaster overlayers using a pulsed-terahertz reflectometer and imaging system. We calculated the bulk refractive indices of four common pigments and used them to confirm color domains in a terahertz-beam spectral image of a painting.

Gigabit Ethernet’s adoption as the cable industry’s transport protocol of choice has been swift. Recent technological developments have made GigE the ideal solution for converged networks, enabling the reliable delivery of broadcast and narrowcast video, data and VoIP voice traffic with an economic attractiveness never before possible. The current industry trend is to design high-capacity GigE networks that can handle various types of traffic on a single, converged platform. VoD and other services such as HDTV, high-speed data and VoIP are driving the network design requirements. Successfully delivering these bandwidth-heavy services to the end-user requires effective GigE transport system design, solution implementation at the operator head-end, and post-deployment maintenance.

We demonstrate full demultiplexing of a single 100-Gb/s optical time-division multiplexed data stream into eight parallel 12.5-Gb/s streams. This is performed using a photonic serial-to-parallel converter based on lithium niobate intensity modulators, and requires no nonlinear optical elements. Error-free operation is obtained for each of the eight output channels.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text M. L. Dennis, W. I. Kaechele, T. F. Carruthers, and I. N. Duling, "Timing tolerance for electro-optic demultiplexing of 100 Gb/s OTDM data," in Integrated Photonics Research, T. Li, ed., Vol. 45 of OSA Trends in Optics and Photonics (Optical Society of America, 2000), paper IThH3. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

In an experimental demonstration of four-channel, wavelength-division-multiplexed repeaterless transmission over 235 km, adiabatic soliton propagation allows for precise spectral characterization of cross-phase modulation effects during initial soliton collisions. Theoretical predictions of the spectral shifts that occur are verified for ultrashort solitons. The relationship between the frequency shift and the initial pulse separation is confirmed by measurement of the bit-error ratio as the pulse spacing is varied at the fiber input. Adiabatic expansion of narrow solitons may help to alleviate the channel restrictions that are required for prevention of soliton collisions at the fiber input.

Describes the development of components and subsystems for dispersion managed soliton transmission of optical time division multiplexed data at rates up to 100 Gb/s.

Broadband, polarisation-independent intensity modulation based on a lithium niobate phase modulator in a fibre Sagnac interferometer configuration is demonstrated. Residual polarisation dependence is found to be as low as < 0.25 dB for low frequency operation, and < 2 dB to frequencies of > 20 GHz.

Get PDF Email Share Share with Facebook Share on X Post on reddit Share with LinkedIn Add to Mendeley Add to BibSonomy Share with WeChat Get Citation Copy Citation Text M. L. Dennis and I. N. Duling, "Polarization independent electro-optic intensity modulator," in Integrated Photonics Research, T. Li, ed., Vol. 45 of OSA Trends in Optics and Photonics (Optica Publishing Group, 2000), paper IFG4. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

We study theoretically and experimentally actively modelocked fiber lasers that are used in high repetition rate optical communication systems. Using an innovative numerical technique and a reduced model, we have found that the laser can operate in four different operating regimes when the laser intensity was changed; three of the regimes were experimentally observed in a laser with a sigma configuration. An excellent quantitative agreement between the theoretical and the experimental results was obtained. The use of dispersion management in the sigma laser was found to significantly improve the laser performance.