Phase-sensitive frequency conversion of quadrature modulated signals

Optics Express (Impact Factor: 3.49). 05/2013; 21(10):12713-27. DOI: 10.1364/OE.21.012713
Source: PubMed


Two mechanisms that can make frequency conversion based on nonlinear mixing dependent on the phase of the input signal are identified. A novel phase-to-polarization converter that converts the orthogonal phase components of an input signal to two orthogonally polarized outputs is proposed. The operation of this scheme and a previously reported scheme at an increased symbol rate are simulated with semiconductor optical amplifiers (SOAs) as the nonlinear devices. Experimental results demonstrate the effectiveness of SOAs for nonlinear mixing over a wide range of wavelengths and difference frequencies and confirm the accuracy of the numerical model.

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    • "It must be added that intra-channel FWM will be present though is not very significant in this situation because the XGM gain fluctuations acting on the pump cause a much stronger interfering effect with larger spectral extent. We base our simulations on an SOA model that can mimic the effects of nonlinear-style SOAs [17] that are typically used for optical signal processing. "
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    ABSTRACT: In this work, the performance of all-optical wavelength conversion (WC) of Nyquist-WDM superchannels is investigated for future implementation in optical networks. We consider advanced modulation formats of DQPSK and 16-QAM for the subchannel modulation format achieving raw bit rates of 448 and 896 Gbit/s respectively. We demonstrate through simulations the WC of Nyquist-WDM superchannel using degenerate and nondegenerate four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). We consider the effects of raised cosine (RC) and root raised cosine (RRC) signal pulse shaping within the wavelength conversion process. We find that the performance of the converted superchannel is severely impaired by crosstalk due to cross-gain modulation (XGM) of the pump by the superchannel. Optimum performance of the converted superchannel is achieved by setting the detuning between the continuous-wave pump and the central wavelength of the superchannel to be around 200 GHz and using pumps of double the gain saturation power of the SOA with 23 dB pump to signal power ratio.
    Journal of Lightwave Technology 10/2015; Vol.33(Issue. 19). DOI:10.1109/JLT.2015.2461021 · 2.97 Impact Factor
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    • "In spite of the operation of the scheme having been numerically predicted at a symbol rate as high as 40 Gbaud, and positive conversion efficiencies having been reported with pump spacings of 600 GHz [8], pattern effects need to be addressed when processing high bit rate signals in SOAs, due to a relatively slow carrier recovery time. To fully exploit the benefits of all-optical signal processing, bit rate transparent operation is a desirable condition. "
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    IEEE Photonics Technology Letters 06/2014; 26(12):1207-1210. DOI:10.1109/LPT.2014.2318992 · 2.11 Impact Factor
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    ABSTRACT: We describe the first experimental demonstration of a novel all-optical phase discrimination technique, which can separate the two orthogonal phase components of a signal onto different frequencies. This method exploits nonlinear mixing in a semiconductor optical amplifier (SOA) to separate a 10.65 Gbaud QPSK signal into two 10.65 Gb/s BPSK signals which are then demodulated using a delay interferometer (DI). Eye diagrams and spectral measurements verify correct operation and a conversion efficiency greater than 9 dB is observed on both output BPSK channels when compared with the input QPSK signal.
    Optics Express 11/2013; 21(22):25664-9. DOI:10.1364/OE.21.025664 · 3.49 Impact Factor
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