D. Jäger

Slow-Wave Propagation Along Variable Schottky-Contact Microstrip Line

Schottky-contact microstrip lines (SCML) are a special type of transmission line on the semiconducting substrate: the metallic-strip conductor is specially selected to form a rectifying metal-semiconductor transition while the ground plane exhibits an ohmic metallization. Thus the cross section of SCML is similar to that of a Schottky-barrier diode. The resulting voltage-dependent capacitance per unit length causes the nonlinear behavior of such lines. In this paper a detailed analysis of the, slow-wave propagation on SCML is presented, including the effect of metallic losses. Formulas for the propagation constant and characteristic impedance are derived and an equivalent circuit is presented. Conditions for slow-mode behavior are given, particularly taking into account the influence of imperfect conductors and defining the range of many interesting applications. Experimental results performed on Si-SCML are compared with theory.

High-efficiency fiber-to-chip coupling using low-loss tapered single-mode fiber

We report on the wet chemical fabrication of tapered step-index single-mode fibers and the low-loss coupling between these fibers and III-V semiconductor waveguide structures. Nearly adiabatic tapered fibers with an average transformation loss of 0.13 dB and mode field diameters ranging between 10.6 /spl mu/m and 0.8 /spl mu/m have been fabricated. Experimentally, tapered fibers have been coupled to 1.55-/spl mu/m InGaAsP-InP waveguide electroabsorption modulators with a minimum coupling loss of only 1.1 dB.

60-GHz Photonic Millimeter-Wave Link for Short- to Medium-Range Wireless Transmission Up to 12.5 Gb/s

In this paper, a 60-GHz photonic millimeter-wave link system for short- to medium-range broadband wireless data transmission is investigated. The system employs advanced mm-wave photonic components and radio-over-fiber (RoF) techniques for the generation of a DSB-SC optical mm-wave carrier and its subsequent on-off-keying modulation and transmission. For short-range applications, we have constructed a compact wireless RoF transmitter consisting of a high-frequency photodiode and a mm-wave antenna only. This system achieved error-free (BER=10-9, 231-1 PRBS, NRZ) in-door transmission of 12.5-Gb/s signals over wireless distances up to 3.1 m with a receiver sensitivity as low as - 45.4 dBm . For fixed wireless access (FWA) requiring a bit error rate of 10-4, the maximum transmission distance for 12.5 Gb/s is increased up to 5.8 m. For medium-range broadband wireless transmission an electrical radio-frequency (RF) amplifier was employed in the RoF transmitter. Here we achieved 7.5-Gb/s error-free transmission in out-door line-of-sight experiments over wireless distances of up to 36 m. Based upon the experimental results, we expect that the maximum wireless distance the system could accommodate for 12.5 Gb/s is in the kilometer range when using high-gain antennas and an RF transmitter amplifier with a sufficient bandwidth.

60 GHz radio-over-fiber technologies for broadband wireless services [Invited]

Some of the work carried out within the European integrated project Integrated Photonic mm-Wave Functions for Broadband Connectivity (IPHOBAC) on the development of photonic components and radio-over-fiber technologies for broadband wireless communication is reviewed. In detail, 60 GHz outdoor radio systems for >10 Gbits/s and 60 GHz indoor wireless systems offering >1 Gbit/s wireless transmission speeds are reported. The wireless transmission of uncompressed high-definition TV signals using the 60 GHz band is also demonstrated.

Plastic optical fiber technology for reliable home networking: overview and results of the EU project pof-all

The rising performance of broadband connections for residential users, particularly in conjunction with fiber to the home, will present a new challenge for telecom operators in the short and medium terms: how to deliver the high bit rate digital signals with high quality-of-service to all consumer devices scattered inside the building of final users? Among the many different solutions for the home network, we review in this article the use of polymer optical fibers for short-reach and high-capacity optical communications for residential customer premises. POF is an easy-to-install, low-cost, and eye-safe solution for these networks, with the potential of being future-proof. In this article the state of the art in POF technology is presented by summarizing significant results achieved in the European project POF-ALL. Data transmission rates of more than 1 Gb/s over 50+ m and 100 Mb/s over 200+ m of standard step-index POF have been shown.

Ultra-wide-band traveling-wave photodetectors for photonic local oscillators

This paper reviews recent advances in the development of high-speed 1.55-/spl mu/m traveling-wave p-i-n photodetectors (TWPD) for photonic millimeter-wave and submillimeter-wave local oscillators. We first discuss the basic physics and performances of high-speed 1.55-/spl mu/m TWPD. Next, we present a frequency-domain optical-heterodyne measurement technique for ultra-wide-band characterization of the TWPD and photonic transmitter modules within the frequency range from almost dc up to more than 1 THz. We further demonstrate ultra-wide-band (0.02-0.7 THz) photonic transmitter modules consisting of a high-speed TWPD coupled to a broad-band bow-tie antenna as well as a narrow-band 0.46-THz photonic transmitter module producing output power levels sufficient to operate a superconductor-insulator-superconductor (SIS) astronomical receiver under optimum conditions. Finally, we will report on ultra-wide-band (0.06-1 THz) photonic transmitter modules consisting of high-speed TWPDs coupled to various rectangular metallic waveguides (WR10, WR8, and WR5).

An approach to single optical component antenna base stations for broad-band millimeter-wave fiber-radio access systems

To realize a cost-effective and practical antenna base station (BS) for 60-GHz-band millimeter-wave fiber-radio access systems, an approach to a single optical component BS is presented in this paper. The external modulation technique will allow to replace the pair of a photodetector (PD) and a laser diode with an external modulator at the BS by an optical transceiver. Two system architectures using different types of optical transceivers are studied in detail: one employs an electroabsorption transceiver (EAT), and the other employs an electroabsorption transceiver/mixer (EATX). The EAT serves simultaneously as a PD and an external light modulator in 60-GHz-band millimeter-wave region. The EATX furthermore acts as an IF-to-RF upconverter and an RF-to-IF downconverter. It is shown that both system architectures have good prospects to realize cost-effective fiber-radio access systems.

Full-duplex fiber-optic RF subcarrier transmission using a dual-function modulator/photodetector

An electroabsorption waveguide device is presented as a dual-function modulator/photodetector for application as a cost-effective full-duplex transceiver in radio-frequency (RF) fiber-optic links. The spectral modulation and detection properties of the dual-function transceiver are characterized experimentally. Extinction ratio, insertion loss, and responsivity are 12 dB, 7 dB, and 0.8 A/W, respectively. Modulation and detection bandwidths are both in excess of 17 GHz. By employing a dual-lightwave technique, optimum modulation and detection performance is simultaneously achieved. Furthermore, full-duplex error-free optical transmission of RF subcarrier-multiplexed signals over 10 km nondispersion shifted single-mode fiber is demonstrated and a point-to-multipoint optical ring architecture is proposed.

Generation and optimum control of picosecond optical pulses from gain-switched semiconductor lasers

The generation of picosecond pulses from gain-switched semiconductor laser diodes is studied. Theoretically, common-rate equations are used to give pulse width and amplitude as a function of external parameters. The numerical predictions are compared with experimental results. It is found that optimum conditions can be achieved by an appropriate choice of the bias current. >

Perspective in next-generation home networks: Toward optical solutions?

The meaning of broadband connection is in continuous evolution. FTTH and ever-improving ADSL technologies are capable of offering to the final residential user a very-high-performance access network connection to the main door of our homes. At the same time, high-definition and interactive video will require higher and higher bit rates inside the home. Both drivers lead to the requirement for high-quality networking also inside homes, to avoid a somehow ironic, but indeed possible situation in which the home area network becomes the actual bottleneck of the full system. In this article we review the requirements for next-generation HANs and show that this environment may end up taking advantage of optical cabling solutions as an alternative to more traditional copper or pure wireless approaches.