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.
A novel approach for optical DPSK/PolSK orthogonal encoding based on four-wave mixing effect in a semiconductor
optical amplifier is proposed and tested using VPI simulation platform. The combined DPSK/PolSK signal is
successfully generated and demodulated with clear and open eyes.
Simultaneous noninverted and inverted dual-wavelength conversion is proposed and demonstrated by using a cross-polarization modulation effect in a semiconductor optical amplifier (SOA). Experiments show that noninverted and inverted conversions lead to power penalties of 1.3 dB and 0.8 dB, respectively, at a bit rate of 10 Gb/s. Based on this scheme, we have demonstrated, for the first time to our knowledge, an all-optical modulation format conversion from amplitude-shift keying (ASK) to frequency-shift keying (FSK). A frequency-shift keying signal with flexible tone spacing and high bit rate can be successfully generated by using this method.
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.
We propose an all-optical wavelength conversion method that can preserve the polarization information of an original signal based on four-wave mixing in a semiconductor optical amplifier. Using this method, we experimentally demonstrate wavelength conversion for a 10-Gb/s polarization shift keying signal with 1.6-dB power penalty at a 10−9 bit error rate. To our knowledge, it is the first experiment reported on all-optical wavelength conversion for a polarization shift keying format. The converted polarization shift keying signal is successfully transmitted over a 75-km standard single mode fiber with 1.8-dB transmission penalty.
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.
An injection locked semiconductor lasers is a promising low cost alternative to implement an all-optical wavelength conversion. We demonstrate high speed wavelength conversion in this paper by injecting dual wavelength laser into a laser diode. The 10Gb/s inverting and non-inverting conversions are obtained in experiments. 30nm conversion range is also achieved.
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