Aleksandra Kaszubowska-Anandarajah

Electro-Optical Generation and Distribution of Ultrawideband Signals Based on the Gain Switching Technique

We demonstrate and compare the generation and distribution of pulse position modulation (PPM) ultrawideband (UWB) signals, based on two different techniques using a gain-switched laser (GSL). One uses a GSL followed by two external modulators, while the second technique employs two laser diodes gain switched (GS) using a combined signal from a pattern generator and an RF signal generator. Bit-error-rate (BER) measurements and eye diagrams for UWB signals have been measured experimentally by using the different GS transmitter configurations and various fiber transmission distances. The simulation of both systems also has been carried out to verify our obtained results, which show the suitability of employing gain switching in a UWB over fiber (UWBoF) system to develop a reliable, simple, and low-cost technique for distributing the impulse-radio UWB (IR-UWB) pulses to the receiver destination.

An IR-UWB Photonic Distribution System

Experimental results are presented for a novel distribution system for an impulse radio ultra-wideband (UWB) radio signals employing a gain-switched laser. The pulse position modulated short optical pulses with a bit rate of 1.25 Gb/s are transmitted over fiber to a remote antenna unit, where the signal is converted to the electrical domain and undergoes spectral shaping to remove unwanted components according to UWB requirements. An experimental radio terminal has also been constructed to enable bit-error-rate measurements to be carried out. These experiments show that the optical distribution system will be capable of supporting the radio part of the system.

Cross-Channel Interference Due to Wavelength Drift of Tunable Lasers in DWDM Networks

The authors present an investigation of the wavelength stability of a tunable laser (TL) transmitter and its impact on the performance of a 2.5-Gb/s dense wavelength-division-multiplexed (DWDM) system. Performance of a DWDM system, employing such a TL, is characterized by examining the cross-channel interference caused by this drift when the channel spacing is set to 12.5 and 25 GHz. Results obtained show that the wavelength drift affects the system performance by introducing an error floor in the case of 12.5-GHz spacing. This error floor can be mitigated by increasing the blanking time of the TL during the channel transition, in order to reduce the wavelength drift

Demonstration and optimization of an optical impulse radio ultrawideband distribution system using a gain-switched laser transmitter

What we believe to be a novel system for the distribution of high-definition video streams in a residential environment is demonstrated. The system utilizes impulse radio ultrawideband (IR-UWB) technology integrated with a fiber-based distribution network. The pulses are directly generated in the optical domain, and the receiver is implemented with a carrier recovery system for the demodulation. The system was built and tested to demonstrate error-free operation of the distribution network and the receiver. Spectrum shaping by varying the pulse position within the bit slot to optimize system performance is also examined.

Optical generation, fiber distribution and air transmission for Ultra Wide Band over fiber system

A system for all-optical generation and distribution of Impulse Radio UWB signals has been implemented and demonstrated experimentally. Bit error rate measurements at 1.625Gbps and “over the air” performance is presented.

Characterization of Frequency Drift of Sampled-Grating DBR Laser Module Under Direct Modulation

The authors demonstrate the drift in frequency of a static sampled-grating distributed Bragg reflector (SG DBR) laser module when it is subjected to direct modulation. The magnitude of drift and its settling time is characterized as a function of the index of modulation. Results show that when the directly modulated SG DBR is optically filtered, as in a dense wavelength-division-multiplexed system, a power penalty of 6.7 dB is incurred in comparison to the unfiltered case.

Cross Channel Interference due to Wavelength Drift of Tuneable Lasers in DWDM Networks

The authors present an investigation of wavelength stability of a tunable laser transmitter and its impact on the performance of a 2.5 Gb/s dense wavelength division multiplexed system. The wavelength drift of the laser after switching between channels is accurately measured by using a self-heterodyning technique and an optical filtering technique. Performance of a DWDM system, employing such a tunable laser, is characterised by examining the inter-channel interference caused by this drift when the channel spacing is set to 12.5 and 25 GHz. Results obtained show that the wavelength drift affects the system performance by introducing a power penalty in the case of 25 GHz spacing and an error floor in the case of 12.5 GHz spacing

Remote downconversion scheme for uplink configuration in radio/fiber systems

The authors present a novel technology for uplink transmission in radio over fiber (RoF) distribution systems. The technique employs remote downconversion of the uplink data to intermediate frequency (IF) in the base station (BS). The local oscillator (LO) signal for the downconversion is optically generated in the central station (CS) and sent to the BS via optical fiber. The IF uplink data is then modulated onto an optical carrier and sent to the CS, where the baseband conversion takes place. By employing this method of uplink connection simplicity and cost efficiency of the BS is achieved.

Demonstration of Wavelength Packet Switched Radio-Over-Fiber System

The authors present a novel concept of employing optical wavelength packet switching in radio-over-fiber access networks. In such a system, the tunable laser (TL) would be employed as a transmitter in the central station. The optical carrier generated by this device would be externally modulated with the data signal upconverted to an RF frequency before being sent to the appropriate base station (BS). If each of the BSs is assigned a unique wavelength, the addressing and routing of traffic could be performed on a packet-by-packet basis with the TL switching between the wavelength assigned to different BSs

EDFA transient suppression in optical burst switching systems

Authors demonstrate that a combination of feed-back control, feed-forward control, optical delay line and saturating channel can obtain the effective suppression of the transient effect in EDFA-based optical burst switched systems.