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Dive into the research topics where Dalma Novak is active.

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Featured researches published by Dalma Novak.


IEEE Transactions on Microwave Theory and Techniques | 1997

Overcoming chromatic-dispersion effects in fiber-wireless systems incorporating external modulators

G.H. Smith; Dalma Novak; Z. Ahmed

We demonstrate two techniques to reduce the effects of fiber chromatic dispersion in fiber-wireless systems incorporating external modulators. We theoretically and experimentally show that the achievable link distance can be increased by varying the chirp parameter of the modulator to give large negative chirp using a dual-electrode Mach-Zehnder modulator (MZM) biased at quadrature. In addition, we show that dispersion can be almost totally overcome by implementing a simple method using the dual-electrode MZM to generate an optical carrier with single sideband (SSB) modulation. We demonstrate the transmission of a 51.8-Mb/s pseudorandom bit sequence (PRBS) at 12 GHz over 80 km of standard single-mode fiber using the SSB generator and measure a bit-error-rate (BER) power penalty due to fiber dispersion of less than 0.5 dB for a BER equal to 10/sup -9/.


Journal of Lightwave Technology | 2010

Fiber-Wireless Networks and Subsystem Technologies

Christina Lim; Ampalavanapillai Nirmalathas; Masuduzzaman Bakaul; Prasanna A. Gamage; Ka-Lun Lee; Yizhuo Yang; Dalma Novak; Rod Waterhouse

Hybrid fiber-wireless networks incorporating WDM technology for fixed wireless access operating in the sub-millimeter-wave and millimeter-wave (mm-wave) frequency regions are being actively pursued to provide untethered connectivity for ultrahigh bandwidth communications. The architecture of such radio networks requires a large number of antenna base-stations with high throughput to be deployed to maximize the geographical coverage with the main switching and routing functionalities located in a centralized location. The transportation of mm-wave wireless signals within the hybrid network is subject to several impairments including low opto-electronic conversion efficiency, fiber chromatic dispersion and also degradation due to nonlinearities along the link. One of the major technical challenges in implementing such networks lies in the mitigation of these various optical impairments that the wireless signals experience within the hybrid network. In this paper, we present an overview of different techniques to optically transport mm-wave wireless signals and to overcome impairments associated with the transport of the wireless signals. We also review the different designs of subsystems for integrating fiber-wireless technology onto existing optical infrastructure.


IEEE Transactions on Microwave Theory and Techniques | 2006

Analysis of optical carrier-to-sideband ratio for improving transmission performance in fiber-radio links

Christina Lim; Manik Attygalle; Ampalavanapillai Nirmalathas; Dalma Novak; Rod Waterhouse

In this paper, we investigate the optimum carrier-to-sideband ratio (CSR) for maximizing the transmission performance of an optically modulated millimeter-wave signal in a fiber-wireless system via experiment, theory, and simulation. We present a simple analytical model to assess the performance enhancement resulting from optical CSR variations. The model is capable of analyzing systems incorporating binary phase-shift keyed and quaternary phase-shift keyed modulation formats. We quantify the optical CSR of a point-to-point fiber-radio link and establish that the performance of the fiber-wireless links can be significantly improved when the optical signal is transmitted at the optimum CSR of 0 dB. The analysis further shows that the optimum optical CSR is independent of transmission bit rates.


IEEE Photonics Technology Letters | 1998

A millimeter-wave full-duplex fiber-radio star-tree architecture incorporating WDM and SCM

G.H. Smith; Dalma Novak; Christina Lim

We propose a full-duplex millimeter-wave fiber-radio network for providing wireless customer access to broadband services. It consists of a hybrid star-tree architecture connecting remote antenna base stations to a central control office (CO) by incorporating wavelength-division multiplexing (WDM) of the optical signals and subcarrier multiplexing (SCM) of the radio signals. These multiplexing schemes allow the sharing of equipment at the CO and therefore enable a simple radio distribution architecture to be implemented. We also demonstrate a 35.5-39.5-GHz full-duplex fiber-radio star-tree network, featuring three WDM carriers in the downstream and a single carrier in the upstream. Each downstream wavelength carries three 155-Mb/s BPSK SCM channels between 35.8-39.3 GHz, while a 37-GHz carrier transports 51.8 Mb/s upstream.


IEEE Transactions on Microwave Theory and Techniques | 1995

Signal generation using pulsed semiconductor lasers for application in millimeter-wave wireless links

Dalma Novak; Z. Ahmed; R.B. Waterhouse; Rodney S. Tucker

We investigate the generation of signals using pulsed semiconductor lasers for application in millimeter-wave (mm-wave) wireless links. The generation of mm wave harmonic frequencies in both mode-locked and gain-switched lasers is considered and a method to generate mm-wave modulated optical signals with modulation depths approaching 100% is implemented. The technique uses optical filtering to select only two optical modes in the pulsed laser spectrum that beat together in a highspeed photodiode. The application of this method to the feeding of mm-wave wireless links incorporating microstrip patch antennas is demonstrated. These optically fed links have application in indoor wireless LANs and optical fiber microcellular systems. >


Journal of Lightwave Technology | 2007

Intermodulation Distortion Improvement for Fiber–Radio Applications Incorporating OSSB+C Modulation in an Optical Integrated-Access Environment

Christina Lim; Ampalavanapillai Nirmalathas; Ka-Lun Lee; Dalma Novak; Rod Waterhouse

In this paper, we investigate the reduction of intermodulation distortion (IMD) in fiber-radio systems incorporating a dispersion-tolerant optical single sideband with carrier modulation. We present a systematic analysis and quantification of the third-order IMD generated due to optical components in the nonlinear optical front-end. Our proposed technique to improve the optical front-end linearity is by the removal of the optical components that contribute most to the third-order IMD in the RF domain. We experimentally demonstrated the proposed technique with two- and three-tone tests and showed more than 9-dB improvement in the overall carrier-to-IMD ratio. The proposed technique was also investigated via simulation analysis for a larger number of radio channels and showed an IMD suppression of >10 dB. In addition, the proposed technique is not only able to improve the carrier-to-interference of the radio signals but also to enable simultaneous baseband transmission, thereby facilitating the merging of millimeter-wave fiber-radio systems with other wired-access infrastructure. We present a detailed investigation and characterization of this technique.


Journal of Lightwave Technology | 2000

Millimeter-wave broad-band fiber-wireless system incorporating baseband data transmission over fiber and remote LO delivery

Christina Lim; Ampalavanapillai Nirmalathas; Dalma Novak; Rod Waterhouse; Gideon Yoffe

We present the first demonstration of a millimeter-wave (mm-wave) broadband fiber-wireless system which incorporates baseband data transmission in both the downstream (622 Mb/s) and upstream (155 Mb/s) directions. The local oscillator (LO) required at the remote antenna base station for up- and downconversion to/from the mm-wave radio frequency (RF) is delivered remotely via a modulation scheme that is tolerant to the effects of fiber chromatic dispersion on the detected LO carrier power. The technique employs a single dual electrode modulator located at the central office (CO) and the data and an RF signal at a frequency equal to half the LO frequency, are applied simultaneously to the device. The modulation scheme was optimized as a function of the modulator operating conditions. Simultaneous bidirectional radio transmission in the mm-wave fiber-wireless network was implemented using specially designed mm-wave diplexers located at the base station (BS) and customer unit, and a single Ka-band printed antenna array at the BS operating simultaneously in transmit and receive mode. Error-free data transmission was demonstrated for both down(34.8 GHz) and uplinks (37.5 GHz) after 20 km of single-mode optical fiber and a bit error rate (BER) of 10/sup -6/ was achieved after the inclusion of a 2-m radio link.


IEEE Photonics Technology Letters | 2005

Efficient multiplexing scheme for wavelength-interleaved DWDM millimeter-wave fiber-radio systems

Masuduzzaman Bakaul; Ampalavanapillai Nirmalathas; Christina Lim; Dalma Novak; R.B. Waterhouse

A simple multiplexing scheme is proposed and demonstrated with the capability to interleave optically modulated 37.5-GHz radio channels in a dense-wavelength-division-multiplexed fiber-radio system with 25-GHz wavelength spacing, and also enable a carrier subtraction technique that improves the overall link performance by reducing the carrier-to-sideband ratio of the multiplexed channels. The proposed scheme is realized by the use of an arrayed waveguide grating having multiple optical loop-backs between the input and the output ports.


IEEE Transactions on Microwave Theory and Techniques | 2001

Wavelength reuse in the WDM optical interface of a millimeter-wave fiber-wireless antenna base station

Ampalavanapillai Nirmalathas; Dalma Novak; Christina Lim; R.B. Waterhouse

A novel technique for wavelength reuse has been proposed to simplify the upstream optical interface of an antenna base station in a millimeter-wave fiber-wireless system incorporating wavelength division multiplexing. This technique is based on recovering the optical carrier used in downstream signal transmission and reusing the same wavelength for upstream signal transmission. Two novel configurations for optical carrier recovery and wavelength reuse are proposed and demonstrated experimentally.


IEEE Journal of Selected Topics in Quantum Electronics | 1995

A time-domain model for high-speed quantum-well lasers including carrier transport effects

Linh V. T. Nguyen; Arthur J. Lowery; Phillip C. R. Gurney; Dalma Novak

Carrier transport plays an important role and can significantly affect the ultra-fast properties of quantum-well (QW) lasers. We present a detailed multi-mode time-domain large-signal dynamic model including the effects of carrier transport, suitable for the high-speed QW lasers. It is based on the well-proven transmission-line laser modelling technique with the addition of a multilevel system of coupled rate equations. Simulated results from studies of both the static and small-signal properties are compared with measurements from another laboratory. Our model can accurately predict the modulation-bandwidth discontinuity in QW laser structures with large separate-confinement-heterostructure (SCH) regions. We use large-signal simulations to predict increased damping of transient responses and larger turn-on delays caused by the effects of carrier transport. Our large-signal simulations also show that an increase in the turn-on delay times is expected in QW structures with large carrier transport times across the SCH region, whereas the inter-well transport times do not affect the turn-on delay times significantly. >

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H.F. Liu

University of Melbourne

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Z. Ahmed

University of Melbourne

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G.H. Smith

University of Melbourne

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Thomas R. Clark

Johns Hopkins University Applied Physics Laboratory

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