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. 2015 Sep 1;5:13649. doi: 10.1038/srep13649

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Copyright © 2015, Macmillan Publishers Limited

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(RF: radio frequency; PS: phase shifter; DAC: digital-analog-convertor, working at 25-GHz clock; EA: electrical amplifier; ECL: external cavity laser; MZM: Mach–Zehnder modulator; I/Q Mod.: In-phase and quadrature modulator; PM-TOF: polarization-maintaining tunable optical filter; PM-OC: polarization-maintaining optical coupler; T1, T4: tunable optical delay-line consists of fixed fiber jumper and manually tunable optical time delay; ATT: tunable attenuator; PBC: polarization beam combiner; SSFM: stand single-mode fiber; S: switch; WSS: wavelength selective switch; EDFA: erbium doped fiber amplifier; LO: local oscillator).