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Parity-time–symmetric optoelectronic oscillator

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Science Advances  08 Jun 2018:
Vol. 4, no. 6, eaar6782
DOI: 10.1126/sciadv.aar6782
  • Fig. 1 Block diagram of the PT-symmetric OEO.

    LD, laser diode; PC, polarization controller; MZM, Mach-Zehnder modulator, SMF, single-mode fiber; PBS, polarization beam splitter; Σ, microwave combiner; EA, electrical amplifier; ESA, electrical spectrum analyzer.

  • Fig. 2 Gain difference enhancement with PT symmetry.

    The gain difference between the oscillating mode and the secondary mode within a regular single-loop OEO (blue) and a PT-symmetric OEO (red) is illustrated for comparison.

  • Fig. 3 S21 magnitude response of the OEO with only one loop closed.

    It is measured by a vector network analyzer (VNA) connected between the MZM and the EA with the measurement direction indicated in Fig. 1.

  • Fig. 4 The electrical spectra of the microwave signals generated by the PT-symmetric OEO.

    The spectra are measured at a central frequency at 9.867 GHz. (A) Multimode oscillation measured with a resolution bandwidth (RBW) of 3 MHz. (B) Single-mode oscillation measured with an RBW of 3 MHz. (C) Single-mode oscillation measured with an RBW of 9.1 kHz. (D) Single-mode oscillation measured with an RBW of 9 Hz.

  • Fig. 5 The phase noise measurements of the generated microwave signal.

    The PT-symmetric OEO is operating with three different loop lengths of 20.31 m, 433.1 m, and 9.166 km. The corresponding phase noise at an offset frequency of 10 kHz is −92.94, −103.4, and −142.5 dBc/Hz. For comparison, the phase noise of a microwave signal generated by a commercial microwave source is also presented, indicating a 26.6-dB phase noise improvement at an offset frequency of 10 kHz for the 9.166-km-long OEO.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/6/eaar6782/DC1

    section S1. Balanced photodetection

    section S2. PT symmetry

    section S3. Loop length–dependent phase noise

    fig. S1. Block diagram of the BPD used in the experiment.

    fig. S2. Optical to electrical conversion at the BPD.

    fig. S3. Open-loop response of the OEO.

    fig. S4. Phase noise enhancement with a long OEO loop.

    movie S1. Phase noise of a 5.26 GHz signal from a PT-symmetric OEO.

    movie S2. Electrical spectrum of the 5.26 GHz signal.

    movie S3. A 10-GHz microwave signal generated by the OEO with PT symmetry.

    movie S4. Output of the OEO without PT symmetry.

  • Supplementary Materials

    This PDF file includes:

    • section S1. Balanced photodetection
    • section S2. PT symmetry
    • section S3. Loop length–dependent phase noise
    • fig. S1. Block diagram of the BPD used in the experiment.
    • fig. S2. Optical to electrical conversion at the BPD.
    • fig. S3. Open-loop response of the OEO.
    • fig. S4. Phase noise enhancement with a long OEO loop.

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    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.mp4 format). Phase noise of a 5.26 GHz signal from a PT-symmetric OEO.
    • movie S2 (.mp4 format). Electrical spectrum of the 5.26 GHz signal.
    • movie S3 (.mp4 format). A 10-GHz microwave signal generated by the OEO with PT symmetry.
    • movie S4 (.mp4 format). Output of the OEO without PT symmetry.

    Files in this Data Supplement:

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