• Current Optics and Photonics
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• 제2권1호
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• pp.27-33
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• 2018

We report the physical implementation of a tunable photonic microwave delay line filter based on injection locking of a single Fabry-Perot laser diode (FP-LD) to a reflective semiconductor optical amplifier (RSOA). The laser generates equally spaced multiple wavelengths and a single tapped-delay line can be obtained with a dispersive single mode fiber. The filter frequency response depends on the wavelength spacing and can be tuned by the temperature of the FP-LD varying lasing wavelength. For amplitude control of the wavelengths, we use gain saturation of the RSOA and the offset between the peak wavelengths of the FP-LD and the RSOA to decrease the amplitude difference in the wavelengths. From the temperature change of total $15^{\circ}C$, the filter, consisting of four flat wavelengths and two wavelengths with slightly lower amplitudes on both sides, has shown tunability of about 390 MHz.

• 디지털산업정보학회논문지
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• 제11권1호
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• pp.171-182
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• 2015

The general wavelet transform has profitable property in non-stationary signal analysis specially. The tunable Q-factor wavelet transform is a fully-discrete wavelet transform for which the Q-factor Q and the asymptotic redundancy r, of the transform are easily and independently specified. In particular, the specified parameters Q and r can be real-valued. Therefore, by tuning Q, the oscillatory behavior of the wavelet can be chosen to match the oscillatory behavior of the signal of interest, so as to enhance the sparsity of a sparse signal representation. The TQWT is well suited to fast algorithms for sparsity-based inverse problems because it is a Parseval frame, easily invertible, and can be efficiently implemented. The transform is based on a real valued scaling factor and is implemented using a perfect reconstruction over-sampled filter bank with real-valued sampling factors. The transform is parameterized by its Q-factor and its over-sampling rate, with modest over-sampling rates being sufficient for the analysis/synthesis functions to be well localized. This paper describes filter design of 2D discrete-time wavelet transform for which the Q-factor is easily specified. With the advantage of this transform, perfect reconstruction filter design and implementation for performance improvement are focused in this paper. Hence, the 2D transform can be tuned according to the oscillatory behavior of the image signal to which it is applied. Therefore, application for performance improvement in multimedia communication field was evaluated.

• Journal of information and communication convergence engineering
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• 제8권3호
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• pp.263-266
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• 2010

In this paper, a novel defected ground structure (DGS) pattern with enhanced effective capacitance (varactor diode) and a hole in PCB center is presented. The increase in effective capacitance enables the new DGS pattern to achieve a lower resonance than the DGS pattern for the same etched square dimension. The hole in the center also can make resonator frequency lower with better characteristic. According to the tunable characteristic of varactor diode, the resonant frequencies can be tunable. Simulation results show that a lower resonance is achieved with active device, compared to a common DGS pattern.

• Current Optics and Photonics
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• 제6권6호
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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.

• 한국광학회:학술대회논문집
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• 한국광학회 1998년도 제15회 광학 및 양자전자 학술발표회 논문집
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• pp.168-169
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• 1998

• 한국광학회:학술대회논문집
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• 한국광학회 1998년도 제15회 광학 및 양자전자 학술발표회 논문집
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• pp.166-167
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• 1998

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2001년도 종합학술발표회 논문집 Vol.11 No.1
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• pp.344-344
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• 2001

• 한국광학회:학술대회논문집
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• 한국광학회 1999년도 제16회 광학 및 양자전자 학술발표회Proceedings of 16th Optics and Quantum Electronics Conference, 1999
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• pp.90-91
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• 1999

• 한국광학회지
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• 제17권1호
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• pp.99-103
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• 2006

본 논문에서는 UV 나노임프린트 기술을 이용하여 파장가변 필터를 제안하고 구현하였다. 제안된 소자는 폴리머 도파로 기반의 브래그 격자와 열 광학효과를 위한 히팅용 전극으로 구성되어 있다. 도파로 패턴과 브래그 격자 패턴이 결합된 임프린트용 스탬프를 이용하여 브래그 격자를 구현하였다. 전극에 전력을 인가하여 폴리머의 열 광학효과를 통하여 필터의 중심파장을 효과적으로 이동시킬 수 있었다. 제작된 소자는 브래그 파장대역인 1560 nm 에서 대역저지 소멸비가 15 dB이며, 대역폭이 0.8 nm였다. 또한 소비전력이 7 mW일 때 중심파장은 1560 nm에서 1558 nm로 이동되었다. 이 때 열 광학효과 파장가변 특성이 약 0.28 nm/mW 였다.

• 한국광학회지
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• 제19권1호
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• pp.36-42
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• 2008

PZT형 파장가변 필터를 이용하여 파장스윕(wavelength-swept) 광원을 구성할 때 발진파장의 변화율을 일정하게 하려면 필터의 이력(hysteresis)특성을 알아야 한다. 이력특성을 무시하고 필터를 구동할 경우 파장스윕 광원을 사용하는 optical frequency domain reflectometry(OFDR) 시스템의 분해능이 떨어진다. 광스펙트럼 분석기(OSA)를 이용하여 필터의 이력특성을 측정할 수도 있지만 측정시간이 너무 길고 실제 구동조건에서의 이력특성은 측정할 수 없다는 문제가 있어 실제 구동조건에서 필터의 이력특성을 고속으로 측정할 수 있는 OFDR의 원리에 기초한 이력 측정법을 제시하였다. 파장스윕 광원과 간섭계, 신호처리 장치, 그리고 PC 프로그램으로 구성된 고속 이력측정장치를 구현하고, 이를 사용하여 필터 구동조건에서의 이력특성을 측정하였다. 마지막으로 측정된 이력특성을 파장스윕광원의 구동에 적용하여 선형적 파장변화를 얻음으로써 새로운 이력측정법의 유효성을 검증하였다.