Frequency noise reduction performance of a feed-forward heterodyne technique: application to an actively mode-locked laser diode.

We report on the frequency noise reduction performance of a feed-forward technique. The Letter is based on frequency noise measurements that allow the spectral response of the feed-forward phase noise correction to be determined. The main limitation to the noise compensation is attributed to the local oscillator flicker noise and the noise added by the optoelectronic loop elements.

Simple dispersion estimate for single-section quantum-dash and quantum-dot mode-locked laser diodes.

The optical outputs of single-section quantum-dash and quantum-dot mode-locked lasers (MLLs) are well known to exhibit strong group velocity dispersion. Based on careful measurements of the spectral phase of the pulses from these MLLs, we confirm that the difference in group delay between the modes at either end of the MLL spectrum equals the cavity round-trip time. This observation allows us to deduce an empirical formula relating the accumulated dispersion of the output pulse to the spectral extent and free-spectral range of the MLL.

Format-independent polarization-demultiplexing technique for dual-polarization intensity modulated signals.

We show through simulations how polarization demultiplexing of dual-polarization, intensity modulated signals of arbitrary format can be performed by only using the information in Stokes space. The technique would be applicable for short-range communications within data centers.

Numerical generation of laser-resonance phase noise for optical communication simulators.

We generate random numerical waveforms that mimic laser phase noise incorporating laser-resonance enhanced phase noise. The phase noise waveforms are employed in system simulators to estimate the resulting bit error rate penalties for differential quadrature phase shift keying signals. The results show that baudrate dependence of the bit error rate performance arises from laser-resonance phase noise.

Simple analytical model for low-frequency frequency-modulation noise of monolithic tunable lasers.

We employ simple analytical models to construct the entire frequency-modulation (FM)-noise spectrum of tunable semiconductor lasers. Many contributions to the laser FM noise can be clearly identified from the FM-noise spectrum, such as standard Weiner FM noise incorporating laser relaxation oscillation, excess FM noise due to thermal fluctuations, and carrier-induced refractive index fluctuations from stochastic carrier generation in the passive tuning sections. The contribution of the latter effect is identified by noting a correlation between part of the FM-noise spectrum with the FM-modulation response of the passive sections.