Walter Nowak

Simultaneous electro-optical upconversion, remote oscillator generation and air transmission of multiple optical WDM channels for a 60 GHz high capacity indoor system

Bidirectional transmission experiments have been carried out by advantageous use of WDM for simultaneous remote millimeter wave generation in a 60 GHz wireless LAN. Low bit error rates have been obtained under realistic conditions.

A wireless LAN at 60 GHz-novel system design and transmission experiments

A novel system design for a wireless LAN simplifying the base station and transponder complexity is proposed. It advantageously uses the WDM technology for simultaneous modulation of optical carriers with a master oscillator signal. Transmission experiments under realistic conditions prove the concept by achieving BER<10/sup -9/ at 50 MBit/s.

Simultaneous electro-optical upconversion to 60 GHz of uncoded OFDM signals

The transmission of 46 MBit/s DQPSK-OFDM signals by simultaneous electro-optical upconversion to 60 GHz has been successfully demonstrated. Bit error rates <10/sup -7/ were obtained for each of two optical channels.

Radio-Optical System Design and Transmission Experiments for a Mobile Broadband Communications System at 60 GHz

The paper presents the system designconcept for a mobile broadband communications systemat 60 GHz. A dense WDM system is used for the opticalbackbone employing novel add/drop multiplexers. Forsimplicity, there is no signal processing andfrequency generation at the base station and a masteroscillator signal are used for millimetric carriergeneration. The master oscillator signal is modulatedonto the optical carriers by a novel concept ofsimultaneous external modulation, simplifying systemdesign significantly. Transmission experiments over acomplete downlink path using uncoded 2-FSK have beencarried out and a BER of 10-9at 50 MBit/s hasbeen obtained. Furthermore, 512-carrier DQPSK-OFDMtransmission at 45.8 MBit/s using 35 MHz bandwidth at60 GHz has been demonstrated.

Simultaneous Upconversion Of Several Channels In MM-Wave Subearrier Transmission Systems for Wireless LANs at 60 GHz

Simultaneous upconversion of several channels in nzm-wave subcarrier transmission systems is proposed. The technique is advanta,geous for optical backbones of wireless LANs at 60 GHz with numerous base stations. Low cross-talk was obtained in experiments. Introduction For future mobile broadband communiication systems or wireless LANs millimeter-wave (mm-wave) fiber links are increasingly considered as attractive solutions for signal distribution to the base stations. In recent years, different concepts have been proposed. Heterodyne techniques using two lasers need complex circuitry for suppressing phase noise. Resonantly modulated [ 11 or mode-locked [2] lasers are other solutions for optical generation of mm-waves, where dual-mode devices [3] are preferable. In [4] two correlated subcarriers were generated by externally modulating a single laser diode and suppressing the carrier, resulting in detection of twice the modulation frequency. Furthermore, direct signal modulation of a laser diode and upconversion of the signal by an external modulator has been demonstrated 151. All techniques discussed so far concentrate on the generation of mm-wave subcarriers of a single channel. However, for a coinmunication system at 60 GHz 161 we propose upconversion of many baseband signals simultaneously with a single external modulator using a dense wavelength division mulliplex (WDM) system. The upconverted signals can easily have different subcarrier frequencies being required for a frequency division multiplexed (FDM) communication system. Furthermore, we propose the use of a phase inodulator and simple dispersion management instead of a IClach-Zehnder intensity modulator. This results in a 6-dB-imlprovement of the signal dletected [7]. Hence, the system proposed is well-suited for efficient upconversion of many downlink signals in a communication system at mm-wave frequencies. System Concept The concept for simultaneous upconversion of many subcarriers with a single external modulator is shown in Fig. 1. Basically, a dense wavelength division multiplexed (WDM) system is used for multiplexing many carriers at different waveliengths into a fiber bus. These signals are generated by laser diodes being available at well-defined emission wavelengths for dense WDM systems. Each laser with its emission wavelength is assigned to a certain base station and is modulat.ed with the corresponding datas in the baseband or at an intermediate frequency. By choosing different intermediate frequencies for different

RF-front end and optical feeding system for a millimeter-wave broadband communications system at 60 GHz

The paper presents the integration of microwave and millimeter-wave techniques as well as the RF-front end and optical feeding system of a wireless broadband integrated services communications system at 60 GHz. The system is intended for indoor use and integrates applications ranging from low data rate mobiles to high rate portable or fixed stations. Antennas, microwave and MM-wave circuits and new optical components are being developed. A hardware demonstrator for proof of concept is currently being built and will incorporate several features of the entire system.

Simultaneous upconversion by phase modulation for dispersion-independent optical MM-wave transmission

For dispersion-independent optical mm wave transmission systems simultaneous upconversion of IF signals in WDM channels by electro-optical phase modulation and direct detection is proposed. Transmission experiments using this technique demonstrate the feasibility of the concept.

Novel compact dual-channel all-fiber Bragg grating multiplexer

Due to the excellent spectral characteristics, fiber Bragg gratings are widely considered as filters for wavelength-division multiplexed (WDM) systems. Because Bragg gratings are stopband filters they have to be combined with other components such as circulators or couplers in order to work as optical multiplexers. Recently, we analyzed the characteristics of an all-fiber add-drop multiplexer with a Bragg grating within the coupling zone of a fiber coupler. We have shown that the position of the grating has to be chosen carefully for proper device operation. Here we demonstrate a novel dual-channel all-fiber Bragg grating multiplexer. The device is based on a polished fiber coupler. Two 2.8-mm-long Bragg gratings at different wavelengths of 1531.6 nm and 1535.3 nm were written at the same position identically into both fibers of the coupler. This was done easily by using a phase mask and stretching the fibers before writing the gratings. After embedding the fibers in separate glass substrates using an epoxy resin, the fiber claddings were polished off. Because we improved the polishing process, a long and homogenous coupling length of /spl sim/14 mm could be reached. Thus, the actual grating position within the coupling zone is less critical, which makes manufacturing easier. The dependency of the grating position on the Bragg wavelength can be neglected.