Quantum-dot lasers have shown remarkable properties, such as temperature-insensitive operation, low loss, efficient
carrier recombination, ultrafast gain recovery time, suppression of beam filamentation, reduced sensitivity to optical
feedback, etc. These excellent performances will contribute to open new cost effective and improved lightwave
communication systems. We exploit the performance of mode-locking of quantum-dot lasers for ultrashort, high power,
and low noise optical pulse generation using two-section mode-locked laser diodes and a semiconductor optical
amplifier (SOA)-based ring laser cavity.
KEYWORDS: Homodyne detection, Signal to noise ratio, Semiconductor lasers, Receivers, Signal detection, Laser optics, Systems modeling, Mode locking, Laser systems engineering, Transmitters
High detection sensitivity and large multi-user interference rejection are key requirements to accommodate a higher
number of users in an optical coherent CDMA system. In this work, we propose efficient coherent homodyne receiver
system configurations, as well as, demonstrate experimentally the performance of coherent homodyne pulse detection
using a synchronized modelocked semiconductor laser system. We present the significant improvement of coherent gain
and signal-to-noise ratio of the NRZ ASK format modulated PRBS data detection compared with direct detection.
We study the characteristics of wavelength tunable quantum-dot mode-locked lasers using a curved two-section device, external grating, and optical bandpass filter. Wide wavelength tunability is demonstrated due to the fact that the center wavelength of mode-locking is extended to excited state transitions as well as ground state transitions of the quantum-dot gain media.
This paper discusses use of optical frequency combs generated by modelocked semiconductor lasers for coherent photonic signal processing applications. Key in our approach is a high Q cavity, supermode suppression and low spontaneous emission. Targeted applications of the stabilized optical frequency combs lie in areas of metrology, optical sampling, arbitrary waveform generation and communications using coherent detection.
We have demonstrated coherent heterodyne detection for an arrayed coherent receiver system based on synchronized modelocked semiconductor lasers. Dual-mode injection locking technique is employed to achieve excellent oscillator synchronization between two independent modelocked semiconductor laser systems.
KEYWORDS: Heterodyning, Semiconductor lasers, Oscillators, Channel projecting optics, Analog electronics, Data modeling, Signal to noise ratio, Signal detection, Optical filters, Bandpass filters
The optical heterodyne detection for an extremely densely channelized coherent communication systems using phase coherent optical combs is demonstrated by using a passively modelocked semiconductor laser injection locked to a master laser oscillator. The single sideband noise of the heterodyne beat tone at 13.160 GHz was reduced to -123 dBc/Hz at 100 kHz offset from the carrier by exploiting the excellent noise rejection performance of a commercially available microwave bandpass filter. A signal-to-noise ratio of over 65 dB/Hz has been achieved in a single channel filtered from two analog RF signals detuned by only 200 MHz. These results show improved signal-to-noise ratio and superior crosstalk reduction between densely packed neighboring channels via electrical manipulation of the optical heterodyne detection signal.
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