Douglas A. Reid

Optimized pulse source employing an externally injected gain-switched laser diode in conjunction with a nonlinearly chirped grating

In this paper, we demonstrate the generation of transform-limited short optical pulses, which display excellent spectral and temporal qualities by employing a novel technology, based on an externally injected gain-switched laser in conjunction with a nonlinearly chirped grating. Using this technique, 3.5-ps optical pulses exhibiting a time-bandwidth product (TBP) of 0.45 are generated, which are suitable for use in high-speed 80 Gb/s optical time-division multiplexing (OTDM) communications systems. The numerical integration of a set of rate equations using suitable parameters for the devices used in the experiments were carried out to further confirm the feasibility of the proposed method for developing an optimized pulse source for high-speed photonic systems.

Quantum-Dot Mode-Locked Lasers With Dual-Mode Optical Injection

Quantum-dot mode-locked lasers are injection-locked by coherent two-tone master sources. Spectral tuning, significantly improved time-bandwidth product, and low jitter are demonstrated without deterioration of the pulse properties.

In-band OSNR monitoring using a pair of Michelson fiber interferometers

Two polarization-independent Michelson fiber interferometers with different optical delays were used to measure the in-band OSNR of an optical signal from 5 to 30 dB within an accuracy of 0.5 dB. Using an expansion of the amplitude autocorrelation function of the signal around zero delay, it was possible to perform measurements without any prior knowledge of the signal. The system is shown to be immune to the effects of modulation frequency (up to 10G), partially and fully polarized noise, chromatic dispersion and poorly biased modulators.

Stepped-heterodyne optical complex spectrum analyzer.

We present a heterodyne measurement of the spectral amplitude and phase of periodic optical signals. In contrast to previous techniques this measurement requires no optical modulation of either the signal or the local oscillator, places much relaxed tunability requirements on the optical local oscillator, and requires no electronic clock to be passed to the receiver. We present measurements of the spectral amplitude and phase of 20 GHz 33% return-to-zero, and 66% carrier-suppressed return-to-zero optical signals, as well as a passively modelocked optical source with in excess of 100 modes.

Optimization of optical data transmitters for 40-Gb/s lightwave systems using frequency resolved optical gating

The measurement technique of frequency resolved optical gating has been used to optimize the phase of a 40-GHz train of optical pulses generated using a continuous-wave laser gated with an external modulator. This technique will be vital for optimization of optical transmitters to be used in systems operating at 40 Gb/s and beyond, as standard measurement techniques will not suffice to optimize such high-speed systems.

Phase shift keyed systems based on a gain switched laser transmitter

Return-to-Zero (RZ) and Non-Return-to-Zero (NRZ) Differential Phase Shift Keyed (DPSK) systems require cheap and optimal transmitters for widespread implementation. The authors report on a gain switched Discrete Mode (DM) laser that can be employed as a cost efficient transmitter in a 10.7 Gb/s RZ DPSK system and compare its performance to that of a gain switched Distributed Feed-Back (DFB) laser. Experimental results show that the gain switched DM laser readily provides error free performance and a receiver sensitivity of -33.1 dBm in the 10.7 Gbit/s RZ DPSK system. The standard DFB laser on the other hand displays an error floor at 10(-1) in the same RZ DPSK system. The difference in performance, between the two types of gain switched transmitters, is analysed by investigating their linewidths. We also demonstrate, for the first time, the generation of a highly coherent gain switched pulse train which displays a spectral comb of approximately 13 sidebands spaced by the 10.7 GHz modulation frequency. The filtered side-bands are then employed as narrow linewidth Continuous Wave (CW) sources in a 10.7 Gb/s NRZ DPSK system.

Linear Spectrograms Using Electrooptic Modulators

Accurate intensity and phase measurement of high-speed optical pulses is becoming more important with the ever increasing data rates of fiber links. Linear spectrograms employing electroabsorption modulators have proven to be useful in making these measurements. In this letter, we investigate and compare the use of electrooptic Mach-Zehnder and phase modulators in linear spectrograms

Optimized pulse source for 40-Gb/s systems based on a gain-switched laser diode in conjunction with a nonlinearly chirped grating

The authors demonstrate the generation of short optical pulses, which display spectral sidemode suppression ratio, and temporal pedestal suppression ratio, well in excess of 30 dB. The exceptional spectral and temporal characteristics exhibited by these pulses are attained by employing a novel technology, based on an externally injected gain-switched laser in conjunction with a nonlinearly chirped grating. Using this technique, near transform limited 7-ps optical pulses, exhibiting a time bandwidth product of 0.49, are generated.

Characterization of 40-Gbit/s pulses generated using a lithium niobate modulator at 1550 nm using frequency resolved optical gating

The characteristics of 40-Gbit/s pulses generated by exploiting the nonlinear characteristics of a Mach-Zender Lithium Niobate modulator are presented. A high spectral resolution frequency resolved optical gating apparatus has been developed to allow for the complete characterization of the intensity and phase of these pulses. The use of these measurements to simplify the design and optimization of an 80-Gbit/s pulse source, based on this 40-Gbit/s source followed by a nonlinear fiber compressor and multiplexer, is also demonstrated.

Characterization of a Turbo-Switch SOA Wavelength Converter Using Spectrographic Pulse Measurement

We use the frequency-resolved optical gating (FROG) technique to determine the pulsewidth and chirp characteristics of wavelength-converted pulses from a turbo-switch and asymmetrical Mach-Zehnder filter combination under a variety of operating conditions. The output pulses were found to be near transform limited and had a high tolerance to line rate and input power variations.