Ze Li

Zhejiang University, Hang-hsien, Zhejiang Sheng, China

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Publications (17)24.88 Total impact

  • IEEE Photonics Technology Letters 11/2012; 24(22):2001-2004. · 2.04 Impact Factor
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    ABSTRACT: A photonic approach to implementing a microwave channelized receiver based on dense wavelength division multiplexing using an optical comb is proposed. In the approach, a flat optical comb with 11 comb lines is generated using two cascaded Mach-Zehnder modulators. Frequency analysis of a microwave signal with multiple-frequency components is realized by using the optical comb together with an optical etalon with a periodic transfer function, a wavelength division multiplexer (WDM) and a photodetector array. The system is investigated numerically. Frequency measurement of a multi-frequency signal with a measurement range from 0.5-11.5 with an accuracy of ± 0.5 GHz is achieved. The reconfigurability of the system realized by tuning the comb-line spacing and the peak positions of the etalon is also evaluated. The improvement of the dynamic range of the system using an optimized periodic filter is also discussed.
    Optics Communications 05/2012; 285(9):2311–2315. · 1.44 Impact Factor
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    ABSTRACT: A photonic approach to realizing instantaneous measurement of microwave frequency using a pair of fiber Bragg grating (FBG)-based optical differentiators is proposed and experimentally demonstrated. In this approach, a first-order and a second-order FBG-based optical differentiators are used to achieve a linear power ratio function with a uniform measurement resolution and improved system dynamic range. A proof-of-concept experiment is performed. A frequency measurement range of 6.5-15 GHz with a measurement resolution of ±0.3 GHz at different input microwave power levels is realized. The dynamic range of the system is analyzed and an improvement of about 10 dB is obtained.
    Microwave Photonics (MWP), 2012 International Topical Meeting on; 01/2012
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    ABSTRACT: A continuously tunable microwave fractional Hilbert transformer (FHT) implemented based on a nonuniformly spaced photonic microwave delay-line filter is proposed and demonstrated. An FHT has a frequency response with a unity magnitude response and a phase response having a phase shift between 0 and $\pi$ at the center frequency. A seven-tap photonic microwave delay-line filter with nonuniformly spaced taps is designed to provide such a frequency response. The advantage of using nonuniform spacing is that an equivalent negative coefficient can be achieved by introducing an additional time delay leading to a $\pi$ phase shift, corresponding to a negative coefficient. An FHT operating at a center frequency around 8.165 GHz with a tunable order between 0.24 and 1 is implemented. A classical HT operating at a center frequency of 7.573 GHz with a bandwidth greater than 4.5 GHz is also implemented. The use of the classical HT to perform temporal Hilbert transform of a Gaussian-like electrical pulse is demonstrated.
    Journal of Lightwave Technology 01/2012; 30(12):1948-1953. · 2.56 Impact Factor
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    ABSTRACT: A continuously tunable microwave fractional Hilbert transformer (FHT) implemented based on a photonic microwave delay-line filter is proposed and demonstrated. The photonic microwave delay-line filter with negative coefficients is realized based on polarization-modulation using a polarization modulator (PolM) and polarization-modulation to intensity-modulation conversion in an optical polarizer. The tunability of the fractional order is achieved by tuning the coefficient of the zeroth tap. An FHT with a tunable order from 0.3 to 1 is demonstrated. The accuracy of the FHT is evaluated; a phase deviation less than 5<sup>°</sup> within the passband is achieved.
    IEEE Photonics Technology Letters 12/2011; · 2.04 Impact Factor
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    ABSTRACT: A microwave bandpass differentiator implemented based on a finite impulse response (FIR) photonic microwave delay-line filter with nonuniformly-spaced taps is proposed and experimentally demonstrated. To implement a microwave bandpass differentiator, the coefficients of the photonic microwave delay-line filter should have both positive and negative coefficients. In the proposed approach, the negative coefficients are equivalently achieved by introducing an additional time delay to each of the taps, leading to a π phase shift to the tap. Compared with a uniformly-spaced photonic microwave delay-line filter with true negative coefficients, the proposed differentiator features a greatly simplified implementation. A microwave bandpass differentiator based on a six-tap nonuniformly-spaced photonic microwave delay-line filter is designed, simulated, and experimentally demonstrated. The reconfigurability of the microwave bandpass differentiator is experimentally investigated. The employment of the differentiator to perform differentiation of a bandpass microwave signal is also experimentally demonstrated.
    Journal of Lightwave Technology 11/2011; 29(22):3470-3475. · 2.56 Impact Factor
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    ABSTRACT: A photonic approach to realizing phase-coded microwave signal generation with large frequency tunability is proposed and demonstrated. Two coherent optical wavelengths are generated based on external modulation by biasing a Mach-Zehnder modulator (MZM) at the minimum transmission point to generate ±1 -order sidebands while suppressing the optical carrier. The two ±1-order sidebands are then sent to a fiber Sagnac interferometer (SI) incorporating an optical phase modulator (PM) and a broadband flat-top fiber Bragg grating (FBG), with one of the sidebands being phase modulated at the PM. A frequency tunable phase-coded microwave signal is generated by beating the two sidebands at a photodetector (PD). The proposed technique is experimentally investigated. The generation of a frequency tunable phase-coded microwave signal at 22 and 27 GHz is demonstrated.
    IEEE Photonics Technology Letters 07/2011; · 2.04 Impact Factor
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    ABSTRACT: An all-optical approach to realizing optical single-sideband (OSSB) modulation based on optical Hilbert transform implemented using a fiber Bragg grating (FBG) is proposed and demonstrated. In the proposed approach, an optical double-sideband (ODSB) signal is divided equally into two channels with the output at one channel being the in-phase (I) component and that at the other being the quadrature phase (Q) component. An FBG-based optical Hilbert transformer (HT) is incorporated in the Q channel, making the two sidebands out of phase at the output of the HT. The combination of the two optical signals from the two channels leads to the cancellation of one sideband, thus an OSSB signal is generated. An experiment is performed. An OSSB signal with a frequency from 6 to 15 GHz and a sideband suppression ratio (SSR) as large as 20 dB is generated. The transmission of the OSSB signal over a single-mode fiber of 45.6 km is also studied.
    IEEE Photonics Technology Letters 06/2011; · 2.04 Impact Factor
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    ABSTRACT: A photonic-assisted fractional Hilbert transformer with tunable fractional order implemented based on temporal pulse shaping (TPS) is proposed and experimentally demonstrated. The proposed fractional Hilbert transformer consists of a phase modulator and two dispersive elements with complementary dispersion. The fractional Hilbert transform (FHT) is realized if a step function is applied to the phase modulator to introduce a phase jump. The proposed technique is investigated numerically and experimentally. The results show that a real-time FHT is achieved with a tunable fractional order by tuning the step function applied to the phase modulator.
    IEEE Photonics Technology Letters 06/2011; · 2.04 Impact Factor
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    ABSTRACT: A photonic approach to realizing instantaneous microwave frequency measurement based on frequency to optical power ratio mapping using a special fiber Bragg grating (FBG) is proposed and demonstrated. The special FBG is designed to have a spectral response with two slopes that are inversely proportional to optical frequency, which enables the realization of a linear power ratio function, leading to an increased measurement range and improved measurement accuracy. The FBG is fabricated and the incorporation of the FBG in a system for frequency measurement is experimented. Instantaneous microwave frequency measurement with a measurement range of 1-10 GHz and a measurement accuracy of ±0.2 GHz under different input microwave power levels is realized.
    IEEE Microwave and Wireless Components Letters 01/2011; 21(1):52-54. · 1.78 Impact Factor
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    ABSTRACT: A photonic approach to generating a phase-coded millimeter-wave (mm-wave) signal with large frequency tunability is proposed and demonstrated. Two ${\pm}$ second-order optical sidebands are generated by using a Mach-Zehnder modulator that is biased at the maximum transmission point and an optical notch filter. A polarization-maintaining fiber Bragg grating is then utilized to make the two sidebands orthogonally polarized. By sending the two orthogonally polarized sidebands to a polarization modulator, to which a phase-coding signal is applied, a frequency-quadrupled phase-coded mm-wave signal is generated. The generation of a phase-coded mm-wave signal with tunable frequencies at 40, 42, and 50 GHz is experimentally demonstrated. A pulse compression ratio of about 128 is achieved.
    IEEE Microwave and Wireless Components Letters 01/2011; 21(12):694-696. · 1.78 Impact Factor
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    ABSTRACT: A photonic approach to implementing microwave channelized receiver based on an optical comb is proposed. In this approach, a flat optical comb with 11 comb lines is generated using two cascaded Mach-Zehnder modulators (MZMs). Frequency analysis of an intercepted microwave signal with multiple microwave frequencies is realized by using the optical comb together with a Fabry-Perot (F-P) etalon, a wavelength division multiplexer (WDM) and a photodetector array. A simulation is performed. A tunable operating bandwidth of 11 or 16.5 GHz with a tunable accuracy of ±0.5 or ±0.75 GHz is obtained.
    01/2011;
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    ABSTRACT: A novel photonic approach to generating binary phase-coded microwave is proposed and demonstrated. The generation of a binary phase-coded microwave signal with a tunable carrier frequency from 18 GHz to 22 GHz is experimentally demonstrated.
    01/2011;
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    ABSTRACT: An analysis on pulse distortions due to the third-order dispersion (TOD) and dispersion mismatches in a phase-modulator- (PM) based temporal pulse shaping (TPS) system for the generation of a repetition-rate-multiplied pulse burst is performed. We demonstrate that the profile of a repetition-rate-multiplied pulse burst and the shape of the individual pulses in the pulse burst are distorted due to the TOD and the dispersion mismatches of the dispersive elements. The tolerance of the system to the TOD and the dispersion mismatches when employing an input optical pulse with different pulsewidth is studied. A technique to use predistortion of the RF modulation signal to tackle the pulse distortions is discussed.
    Journal of Lightwave Technology 11/2010; · 2.56 Impact Factor
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    ABSTRACT: A novel method is proposed and demonstrated to simultaneously realize phase-to-intensity modulation conversion (PM-IM) and efficiency improvement using a fiber Fabry-Perot (FFP) tunable filter. To achieve the conversion of phase modulation to intensity modulation, the phase-modulated light is transmitted from one of the slopes of the FFP tunable filter to break the amplitude balance of the sidebands. Meanwhile, the modulation depth is increased due to the more suppression of the optical carrier than one of the first-order sidebands. The results demonstrate that the PM-IM conversion has been achieved and an about 10-dB gain of electrical signal power could be obtained with suitable optical carrier suppression for both 10-and 20-GHz microwave input. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2090–2095, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25389
    Microwave and Optical Technology Letters 08/2010; 52(9):2090 - 2095. · 0.59 Impact Factor
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    ABSTRACT: A photonic approach to realizing instantaneous measurement of microwave frequency based on optical monitoring using a fiber Bragg grating (FBG) is proposed and demonstrated. In the approach, a frequency-unknown microwave signal is modulated on an optical carrier in a Mach–Zehnder modulator biased at the minimum transmission point. After detecting the transmission and reflection optical powers at the output of the FBG, the microwave frequency can be determined according to the value of transmission-to-reflection power ratio, due to the fixed relationship between the microwave frequency and the power ratio. A proof-of-concept experiment has been performed, which demonstrates that a measurement resolution of ±0.08GHz over a 10GHz measurement bandwidth is achieved. The measurement performance in terms of resolution is better than previously reported results.
    Optics Communications 01/2010; 283(3):396-399. · 1.44 Impact Factor
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    ABSTRACT: We propose a novel photonic approach to implementing instantaneous microwave frequency measurement with improved measurement range and resolution. A polarization modulator (PolM) is employed, which functions with a polarizer as an intensity modulator (IM) in one channel, and with a length of polarization-maintaining fiber as a two-tap photonic microwave bandpass filter (PMBF) in another channel. A linear amplitude comparison function (ACF) that relates the microwave frequency and the microwave powers at the outputs of the two channels is obtained, which ensures an improved frequency measurement range and resolution. An experiment is performed. A measurement range of 0.5-40 GHz with a resolution of ±0.5 GHz under different input microwave power levels is realized.
    01/2010;