• Current Optics and Photonics
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• v.6 no.6
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• pp.634-641
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• 2022

A frequency stable and tunable optoelectronic oscillator (OEO) incorporating an optical phase shifter and a phase-shifted fiber Bragg grating (PS-FBG) is designed and analyzed. The frequency tunability of the OEO can be realized by using a tunable microwave photonic bandpass filter consisting of a PS-FBG, a phase modulator. The optical phase compensation loop is used to compensate for the phase variations of the RF signal from the OEO by adjusting an optical phase shifter. Simulation results demonstrate that the output RF signals of the OEO can be tuned in a frequency range of 118 MHz to 24.092 GHz. When the ambient temperature fluctuates within ±3.9 ℃, the frequency drifts of the output RF signals are less than 68 Hz, the side-mode suppression ratios are more than 69.39 dB, and the phase noise is less than -92.49 dBc/Hz at a 10 kHz offset frequency.

• Current Optics and Photonics
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• v.6 no.1
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• pp.15-22
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• 2022

This paper describes the construction of a phase shifter with low loss and small volume. To construct it, we use the two graphene layers that are separated by a hexagonal boron nitride (hBN) and embedded in a silicon waveguide. The refractive index of the waveguide is adjusted by applying a bias voltage to the graphene sheet to create an optical phase shift. This waveguide is a compact device that only has a radius of 5 ㎛. It has a phase shift of 6π. In addition, the extinction ratio (ER) is 11.6 dB and the insertion loss (IL) is 0.031 dB. Due to its unique characteristics, this device has great potential in silicon on-chip optical interconnection and all-optical multiple-input multiple-output processing.

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.246-247
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• 2005

• Korean Journal of Optics and Photonics
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• v.15 no.3
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• pp.274-277
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• 2004

An integrated photonic radio frequency (RF) phase shifter has been proposed and fabricated using a nested dual Mach-Zehnder modulator configuration in a new electro-optic polymer. The fabricated device shows a continuous voltage control of the RF signal phase. A near-linear phase shift exceeding 108$^{\circ}$was obtained for a 16-GHz microwave signal by tuning the do control voltage over a 7.8- $V_{pp}$ range.e.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.3-4
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• 2006

• ETRI Journal
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• v.21 no.3
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• pp.1-5
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• 1999

A clock and data recovery circuit with a phase-locked loop for 10 Gb/s optical transmission system was realized in a hybrid IC form. The quadri-correlation architecture is used for frequency-and phase-locked loop. A NRZ-to-PRZ converter and a 360 degree analogue phase shifter are included in the circuit. The jitter characteristics satisfy the recommendations of ITU-T. The capture range of 150 MHz and input voltage sensitivity of 100 mVp-p were showed. The temperature compensation characteristics were tested for the operating temperature from -10 to $60^{\circ}C$ and showed no increase of error. This circuit was adopted for the 10 Gb/s transmission system through a normal single-mode fiber with the length of 400 km and operated successfully.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.36-43
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• 2001

We evaluate the optical characteristics of planar distributed feedback (DFB) waveguides with quarter-wavelength phase-shifter. To analyze explicitly its band-pass and resonance properties, we present and newly develop a modal transmission-line theory (MTLT) based on Floquet's theorem and Babinet's principle. The numerical results reveal that this approach offers a simple and analytic algorithm to analyze either the filtering or the oscillating characteristic of DFB gratings with quarter-wavelength phase-shifter, and has a novel physical insight that may not be achieved in other approximating approaches

• Korean Journal of Optics and Photonics
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• v.15 no.2
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• pp.142-148
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• 2004

We investigated a Ti:LiNbO$_3$ based integrated-optic polarization controller with a Ti-indiffused waveguide along the z-axis utilizing the electro-optic effect. The device consists of a first quarter-wave (λ/4) phase-shifter followed by a half-wave(λ/2) and a second quarter-wave(λ/4) wave-plate, which is rotated synchronously with the first quarter-wave phase-shifter. We analyzed the operation principles of the device utilizing cascaded transfer matrices based on Jones matrix and Poincare sphere, simulated driving voltages for various input states of polarization (SOP), and theoretically confirmed transformations from any arbitrary input SOP into any general output SOP.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.390-390
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• 2006

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.397-402
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• 1993

This paper presents a new computational algorithm of phase-shifting interferometry which can effectively eliminate the uncertainty errors of the reference phases encountered in obtaining multiple interferograms. The algorithm treats the reference phases as additional unknowns and determines their exact values by analyzing interferograms using numerical least square technique. A series of simulations prove that this algorithm can improve measuring accuracy being unaffected by the nonlinear and random errors of phase-shifters.