We have developed a flying-spot scanner for fluorescence imaging of rheumatoid arthritis in the near infrared (NIR)
spectral range following intravenous administration of contrast agents. The new imaging system has been characterized
with respect to linearity, dynamic range and spatial resolution with the help of fluorescent phantoms. In vivo experiments
were performed on an animal model of rheumatoid arthritis. Finally, NIR-fluorescence images of early stages of joint
inflammation have been compared with findings from contrast enhanced MR imaging and histology.
Today, commercial fiber optical transmission systems are operated at a data rate of 10 or 40 Gbit/s per wavelength channel. The optical time division multiplexing (OTDM) technique allows for the investigation of the next generation TDM data rate of 160 Gbit/s while electrical signal processing at 160 Gbit/s is not yet available. In an OTDM transmission system, the key functions of the transmission system are realized using ultrafast all-optical or electro-optical network elements. In this paper, the recent progress in ultrafast technologies for 160 Gbit/s OTDM transmission systems is reviewed. The focus will be on techniques to realize optical pulse sources and ultrafast optical gates which operate on a time scale of a few picoseconds to a few hundred femtoseconds. They are the key elements of a 160 Gbit/s OTDM transmission system and are applied for various functions in the system. The paper focuses in particular on the application of ultrafast optical technologies for measurement purposes. In an optical communication system the quality of the data signal can be inferred from the optical eye diagram of the data signal. Presently, the measurement of optical eye diagrams at a data rate of 160 Gbit/s is inhibited by the limited bandwidth of photodetectors and electrical sampling oscilloscopes. By realizing an all-optical sampling system using the ultrafast technologies discussed before, the bandwidth of such an optical sampling system exceeds 400 GHz and allows for eye diagram measurements up to 320 Gbit/s.
Error-free all-optical demultiplexing is demonstrated with a monolithically integrated switch for 160 Gbit/s data stream. The switch comprises 'band gap shifted' semiconductor optical amplifiers, monolithically integrated within a symmetric Mach-Zehnder interferometer.
Flip-chip-mounting of integrated circuits has been shown as an effective way to connect integrated circuits with substrates providing highest bandwidths. This technique also has been used to connect chips directly without causing significant parasitics. In this paper, hybrid integrated photoreceivers with large bandwidths for fiber-optic data transmission will be discussed. Several photoreceivers with bandwidths of more than 60 GHz have been fabricated by combining photodiodes and amplifiers, which have been optimised in separated wafer runs. Key features of this type of photoreceivers are a waveguide photodiode with a high responsivity (0.8 A/W) and a traveling wave amplifier with low input impedance as well as high amplification to a 50 Ω output termination up to 65 GHz. Further improvement of bandwidth is expected by using metamorphic HEMTs instead of pseudomorphic ones in the amplifier.