A method called coherent hybrid is proposed to monitor the deficiency of differential phase shifted keying (DPSK) either
generated by the bias offset drift of Mach-Zehnder modulator or an unmatched drive voltage applied to a phase
modulator (PM) is proposed and demonstrated. The hybrid power ratio of the maximum to the minimum after mixing the
unmodulated local oscillation lightwave with the modulated signal from the same light source is employed to measure
the degree of deficiency, simultaneously eliminate the dependence on light source power. Our experimental results
reveal that a±5% bias offset of MZI can produce 0.3dB power variation, larger than that of 0.02dB in the traditional
method by measuring the signal average power, and a drive voltage with a more than 10 percent deviation from the halfwave
voltage can be detected when it is applied to a PM. A feedback and control circuit based on this scheme is
developed and applied in our system. The impairments given by the unparallel orientation between the polarizations of
signal and local oscillation lightwave and the transient time of modulation signal pulse is discussed. By properly setting
the control parameters in the feedback control process, the impairments can be minimized.
We present a novel method to generate ultra-wideband (UWB) monocycle pulses using polarization state rotation filtering of optical negative pulses. Monocycle-like optical pulses with reversed polarities can be generated with appropriate polarization adjustment.
We propose a method to generate high-speed frequency-shifted keying (FSK) signal by demodulating two phase-shifted
keying (PSK) signals with proper wavelength detuning. The generated FSK is easy for detection and has a small crosstalk
to optical label signal. In an 85km SMF transmission demonstration, we achieve 1.5dB power penalty in 10Gbit/s
FSK payload and 1dB power penalty in 155Mbit/s amplitude-shifted keying (ASK) label. Compared with the phase
continuous FSK, this kind of FSK occupies wider bandwidth due to its phase discontinuity but is simpler in its
All-optical NOR and OR gates using the same setup, based on cross-polarization modulation in a single semiconductor optical amplifier, have been demonstrated experimentally at 10 Gbit/s with two and three input signals. The results show good dynamic extinction ratios of 13.2 and 11.0 dB for NOR and OR outputs, respectively. The logic output performance of this logic configuration versus input signal and probe power have been investigated experimentally.
In this paper, a novel scheme of all optical logic gates by using an injection-locked semiconductor laser is proposed. We use a model to describe the dynamics of the injection-locked laser. The simulation results show that NOR and XOR gates can be achieved with properly designed parameters.
We have studied an all-optical wavelength converter utilizing cross-polarization modulation in a semiconductor optical amplifier, and presented a feedback scheme for polarization based on the monitoring the light intensity of converted signal and adjusting the voltages of the polarization controller, which realized an error-free conversion of 10Gbit/s NRZ signal for more than 2 hours.
A novel wavelength converter based on cross-polarization modulation is optimized for all-optical network application. Stable error-free application result is achieved for 10 Gbit/s NRZ signal after transmission through 80 km single-mode fibers between network nodes without dispersion compensation.
Wavelength converter is key equipment in dynamic optical networks and the injection locking technology in semiconductor lasers is a promising low cost candidate. High speed injection-locked wavelength conversion (10 Gbit/s, NRZ, PRBS) has been achieved in our simulations and experiments, both logically inverting and non-inverting. In this paper, injection-locked model in FP lasers is analyzed and the results are consistent with those in both static and
dynamic experiments. The situation when input and output lights are at different facets is also theoretically compared with that at the same facet and it's derived that the latter may have better performance.