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Now showing 1 - 10 of 27

Adaptive and secure VCSEL FSO based on simple dual-polarized architecture for short distance transmission
(2020-09-01)
Yeh, Chien-Hung
;
Yang, Yun-Cheng
;
Hsu, Tzu-An
;
Chen, Yu-Wen
;
Chow, Chi-Wai
In this study, using dual-polarized-multiplexing VCSEL based free space optical (FSO) transmission system is demonstrated experimentally. Two orthogonal polarizers (POLs), a beam splitter (BS) and a reflected mirror (M) are applied in the FSO transmitter (Tx) side to combine dual FSO signals into one for data security without code encryption. In the receiver (Rx) side, two blended FSO channels can be decoded adaptively by applying a POL with properly polarization status. Furthermore, when we add two corresponding POLs with orthogonal polarization in the Rx side, the FSO capacity also can double by the presented dual-polarized FSO architecture. Here, the relationships of the detected FSO powers and rotating angle between two POLs are also experimentally discussed.
62nm CW wavelength-selectable erbium-doped fiber compound-ring laser with stable single-mode output
(2019-12-01)
Yeh, Chien-Hung
;
Chang, Yao-Jen
;
Lin, Wen-Piao
;
Xie, Yue-Ru
;
Luo, Chien-Ming
In this demonstration, an erbium-doped fiber (EDF) based laser with stable, wide and wavelength-selectable single-longitudinal-mode (SLM) performances is designed and demonstrated. Here, to achieve SLM oscillation, a compound-ring scheme is constructed in the EDF laser cavity serving as a mode-restriction-filter for densely side-mode suppression. Moreover, the continuous-wave tunability can be scaled from 1520.0 to 1582.0 nm by using the proposed compound-ring scheme and commercial C-band EDF amplifier. In the measurement, the output stability and 3 dB Lorentzian linewidth of each lasing wavelength in the proposed EDF compound-ring laser have also been discussed.
Stable and Tunable Single-Longitudinal-Mode Erbium-Doped Fiber Triple-Ring Laser With Power-Equalized Output
(2016-04-01)
Yeh, Chien-Hung
;
Chen, Jhih-Yu
;
Chen, Hone-Zhang
;
Chen, Jing-Heng
;
Chow, Chi-Wai
In this demonstration, we propose and investigate a stable and tunable single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser structure. Here, in order to achieve the SLM output, the "eye-type" triple-ring scheme is designed in this EDF laser to suppress the densely spaced longitudinal modes. In the measurement, the output power and optical-signal-to-noise ratio (OSNR) are between 8.35 and 8.92 dBm and 33.2 and 35.7 dB, respectively, in the wavelength range of 1530 to 1560 nm. The proposed EDF laser architecture not only has free tuning step but provides stabilized and flattened output power spectrum as well.
Stable Single-Longitudinal-Mode Erbium Fiber Ring Laser Utilizing Self-Injection and Saturable Absorber
(2017-12-01)
Yeh, Chien-Hung
;
Huang, Tzu-Jung
;
Yang, Zi-Qing
;
Chow, Chi-Wai
;
Chen, Jing-Heng
In this work, we demonstrate a wavelength-tunable erbium-doped fiber (EDF) ring laser with stable single-longitudinal-mode (SLM) output. Here using the self-injection method and unpumped EDF-based saturable absorber can suppress other densely side-mode to achieve SLM. Hence, the output power and optical signal-to-noise ratio of proposed EDF ring laser are between -7.1 and 2.1 dBm and 30.1 and 36.5 dB in the tuning range of 1525.0 to 1574.0 nm, respectively. According to the proposed EDF laser structure, the wavelength operation range can extend to shorter L-band from C-band. Moreover, the output stability of the proposed EDF ring laser is also executed experimentally.
Stress measurement of thin film on flexible substrate by using projection moire method and heterodyne interferometry
(2016-06-01)
Chen, Kun-Huang
;
Chen, Jing-Heng
;
Tseng, Hua-Ken
;
Chang, Wei-Yao
;
光電工程學系
We propose a stress measurement system based on a projection moire method and heterodyne interferometry for thin films on a flexible substrate. In the measurement setup, a CMOS camera in which every pixel can receive a series of heterodyne moire signals by using a continuously relative displacement with a constant velocity is used. Furthermore, the phase of the optimized sinusoidal curve and the surface profile of the flexible substrate are determined using a least-squares sine fitting algorithm. The thin-film stress is obtained by representing the cross-sectional curve of the surface profile by using a polynomial fitting method, estimating the resultant curvature radii of the uncoated and coated substrates, and using these two radii in the corrected Stoney formula. The proposed measurement system has the advantages of high accuracy, high resolution, and high capacity for substrates with high flexibility and a large measurement depth. (C) The Authors.
Generating Radially and Azimuthally Polarized Beams by Using a Pair of Lateral Displacement Beamsplitters
(2016-09-01)
Han, Chien-Yuan
;
Wei, Zhi-Hao
;
Hsu, Yung
;
Chen, Kun-Huang
;
Yeh, Chien-Hung
This paper proposes a modified polarization converter for generating radially and azimuthally polarized beams. Based on a Mach-Zehnder-like interferometric structure, the device consists of a pair of lateral displacement beamsplitters (LDBs) and two half-wave plates that manipulate the states of polarization of incident linearly polarized light. Through the coherent superposition of two orthogonal Hermite-Gaussian modes in the far field, radially and azimuthally polarized beams can be obtained simultaneously. A prototype was assembled to demonstrate the feasibility of the design. The proposed design has the advantage of having a simple, symmetric, compact, and robust structure. In addition, the introduction of LDBs substantially reduces the cost of this device. Moreover, the design can be applied to a broadband pulsed laser with considerable potential in high-power applications.
Stable and Wavelength-Tunable Self-Injected Reflective Semiconductor Optical Amplifier-Based Fiber Laser
(2015-08-01)
Wu, Yu-Fu
;
Yeh, Chien-Hung
;
Chow, Chi-Wai
;
Sung, Jiun-Yu
;
Chen, Jing-Heng
In this investigation, we propose and demonstrate a stable and wavelength-tunable self-injected reflective semiconductor optical amplifier (RSOA)-based laser by using the Faraday rotator mirror (FRM) and the fiber mirror (FM) serving as a reflected element, respectively. Here, a 1.2-GHz RSOA can be enhanced to similar to 3 GHz by utilizing a self-injected mechanism. In the measurement, applying the optical orthogonal frequency-division multiplexing quadrature amplitude modulation (OFDM-QAM) with a bit-loading algorithm on the self-injected RSOA directly, the proposed laser can achieve a 3.5-Gb/s data rate in a 20-km single-mode-fiber transmission below a forward error correction (FEC) threshold. Moreover, the related output performance of the proposed RSOA-based laser is also discussed, whereas the FRM and the FM are utilized for comparisons.
Based on Silicon-micro-ring-resonator and Triple-ring Cavity for Stable and Tunable Erbium Fiber Laser
(2018-01-01)
Hsu, Yung
;
Chang, Yuan-Chia
;
Yeh, Chien-Hung
;
Chow, Chi-Wai
;
Chen, Jing-Heng
In this paper, a stable and wavelength-switchable erbium-doped fiber (EDF) laser by utilizing the silicon-micro-ring-resonator (SMRR) and multiple-fiber-ring (MFR) scheme is demonstrated. Here, three optical couplers (CPs) can construct the passive MFR in the proposed and achieve single-longitudinal-mode (SLM) output simultaneously. The SMRR is used inside a fiber cavity as mode restrict element for wavelength-tuning. By properly adjusting the polarization controllers (PCs), the output wavelength can be tuned in a wavelength range of 1544.35 to 1564.10nm with a similar to 2.0 nm tuning step. Hence, the proposed EDF laser can reach the characteristics of SLM output, 35 kHz output linewidth, and optical single-to-noise ratios (OSNRs) of > 54.9 dB. In addition, the output stabilities of the power and wavelength in the proposed EDF laser are also discussed.
Prism-hologram-prism sandwiched recording method for polarization-selective substrate-mode volume holograms with a large diffraction angle
(2018-08-06)
Hsu, Fan-Hsi
;
Han, Chien-Yuan
;
Chen, Kun-Huang
;
Hsu, Ken-Yuh
;
Chen, Jing-Heng
We propose a prism-hologram-prism sandwiched recording method for the fabrication of polarization-selective substrate-mode volume holograms with a large diffraction angle. In fabrication, the C-RT20 photopolymer is sandwiched between two 45 degrees-90 degrees-45 degrees prisms and the interference fringes can be easily recorded in the recording material. The experimental results are in good agreement with the theoretical predictions. The proposed method features of a reflection-type recording setup for a transmission element and belongs to a technique of longer-wavelength construction for shorter-wavelength reconstruction. In addition, the method is much easier than the traditional recording method of two incident beam interference and has application potential in holographic photonics. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Use of proper cavity loss for a stable single-longitudinal-mode erbium fiber laser
(2017-06-01)
Yeh, Chien-Hung
;
Zhuang, Yuan-Hong
;
Tsai, Ning
;
Chow, Chi-Wai
;
Chen, Jing-Heng
A stable and selectable erbium-doped fiber (EDF) ring laser configuration with single-longitudinal-mode (SLM) output is proposed and demonstrated in this paper. In the proposed laser scheme, a proper cavity loss is utilized for significant suppression of the side mode. In the experiment, the different coupling ratios required to produce various cavity losses in the proposed fiber laser are analyzed. Here, to reach the wavelength selection, several fiber Bragg gratings (FBGs) and an optical tunable bandpass filter (OTBF) in the C-band range are employed for demonstration. In addition, the output performance with respect to stability and SLM in the proposed EDF ring laser are also investigated simultaneously.

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