Aldário C. Bordonalli

High-performance phase locking of wide linewidth semiconductor lasers by combined use of optical injection locking and optical phase-lock loop

The requirement for narrow linewidth lasers or short-loop propagation delay makes the realization of optical phase-lock loops using semiconductor lasers difficult. Although optical injection locking can provide low phase error variance for wide linewidth lasers, the locking range is restricted by stability considerations. Theoretical and experimental results for a system which combines both techniques so as to overcome these limitations, the optical injection phase-lock loop (OIPLL), are reported. Phase error variance values as low as 0.006 rad/sup 2/ (500 MHz bandwidth) and locking ranges exceeding 26 GHz were achieved in homodyne OIPLL systems using DFB lasers of summed linewidth 36 MHz, loop propagation delay of 15 ns and injection ratio less than -30 dB. Phase error variance values as low as 0.003 rad/sup 2/ in a bandwidth of 100 MHz, a mean time to cycle slip of 3/spl times/10/sup 10/ s and SSB noise density of -94 dBc/Hz at 10 kHz offset were obtained for the same lasers in an heterodyne OIPLL configuration with loop propagation delay of 20 ns and injection ratio of -30 dB.

High-performance heterodyne optical injection phase-lock loop using wide linewidth semiconductor lasers

The requirements for narrow linewidth lasers and short loop propagation delay limit optical phase-lock loop realizability with semiconductor lasers is presented. Although optical injection locking can provide low-phase-error variance, its locking range is limited by stability considerations. The first experimental results for a new architecture combining both techniques, the optical injection phase-lock loop (OIPLL), are reported. Phase error variance values as low as 0.006 rad/sup 2/ (500 MHz bandwidth) and locking ranges exceeding 26 GHz are achieved using DFB lasers of summed linewidth 36 MHz with loop delay of 15 ns and injection ratio less than -30 dB.

Optical injection locking and phase-lock loop combined systems

Optical injection locking and optical phase-lock loops have been used for laser synchronization. The use of a combined optical injection locking and phase-lock loop system is proposed here. We have taken into account the modification of the slave laser phase response induced by the injection locking to calculated the phase-error signal spectrum and the phase-error variance for an optical injection locking and phase-lock system. They show that this system presents both a wide locking range, given by the optical injection locking action, and a low phase error for low frequencies, given by the optical phase-lock loop action. These results can improve the system tracking capability and decrease the final phase-error variance compared with those in isolated systems.

Generation of microwave signals by active mode locking in a gain bandwidth restricted laser structure

A simple method of generating microwave signals by using an active DFB InP-InGaAsP laser structure integrated with a passive extended cavity is presented. High spectral purity (<-94 dBc/Hz, 10 kHz offset) is achieved by locking the laser mode spacing to harmonics of an electrical drive signal applied to the laser bias current.

Carrier reuse with gain compression and feed-forward semiconductor optical amplifiers

The results of two techniques for optical carrier regeneration and wavelength reuse using semiconductor optical amplifiers (SOAs) are presented in this paper. The main objective is to recover an optical carrier by erasing its amplitude modulation. The first technique employs gain compression of deeply saturated SOAs. The second technique uses a feed-forward approach, where a delayed current signal is injected into the SOA with the same shape of the incoming optical pulse. The second technique could be capable to recover the optical carrier with less than 3-dB noise. However, it was observed that the SOA gain recovery time limits the maximum usable bit rate. Theoretical simulation showed good agreement with experimental results.

Global WSS-based equalization strategies for SDN metropolitan mesh optical networks

We experimentally demonstrate the benefits of global (end-to-end) WSS-based spectrum equalization for multiple ROADMs in cascade. We introduce three equalization strategies to enable OSNR enhancement in a SDN metropolitan mesh optical network test-bed with 80 × 128 Gb/s.

Simple feed-forward wide-range frequency offset estimator for optical coherent receivers

We propose and experimentally demonstrate a simple, feed-forward, wide-range frequency offset estimator. This frequency offset estimator is robust to spectrum asymmetry caused by electrical and optical filtering of the signal.

Global ROADM-Based Spectrum Equalizer in SDN Architecture for QoT Optimization at DWDM Networks

We introduce a global (end-to-end) ROADM-based spectrum equalizer algorithm running over DWDM networks on SDN architecture. Significant OSNR improvements are experimentally demonstrated for a DWDM coherent 80×112Gb/s system compared with local equalization schemes.

An EDFA theoretical analysis considering different configurations and pumping wavelengths

The propagation behavior of an erbium-doped fiber amplifier parameters is theoretically analyzed in this work for different amplifier configurations and pumping wavelengths. These configurations were devised from the basic amplifier arrangement and developed to improve specific amplifier operational characteristics. By using the amplifier basic theory for pumping at 980 nm and 1480 nm, the configurations were modeled and simulated for given input boundary conditions. As a result, the longitudinal characteristics of signal, pumping, spontaneous emission, and noise figure were observed for all configurations and compared to those of the conventional amplifier. All simulations were carried out using parameters from a commercial erbium-doped fiber.

Optical injection locking to optical frequency combs for superchannel coherent detection.

Optical injection locking characteristics of a distributed feedback laser are experimentally investigated for multiple-wavelength injection. Using a three-wavelength source generated by intensity modulation as the injected signal, it was found that the presence of adjacent lines could cause disturbance to the locking if a minimum guard band between the respective locking limits of two adjacent lines was not observed. With a 21-line comb with 20 GHz line spacing as the injected signal, the injection locking range was observed to become asymmetrical in relation to the laser free-running frequency under high-power injection conditions and was found to be dependent on whether the laser was locked to lines located at centre and or edges of the comb. Finally, the use of the injection locked laser as a seed laser for generating a local oscillator (LO) comb for superchannel coherent detection was investigated and the phase error between the input and LO combs analysed.