• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.93-100
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• 2008

Laser interferometry is widely used as a measuring system in many fields because of its high resolution and ability to measure a broad area in real-time all at once. In conventional LASER interferometry, for example Out-of-plane ESPI(Electronic Speckle Pattern Interferometry), In plane ESPI, Shearography and Holography, it uses PZT or other components as a phase shift instrumentation to extract 3D deformation data, vibration mode and others. However, in most cases PZT has some disadvantages, which include nonlinear errors and limited time of use. In the present study, a new type of LASER interferometry using a laser diode is proposed. Using LASER Diode Sinusoidal Phase Modulating (LD-SPM) interferometry, the phase modulation can be directly modulated by controlling the LASER Diode injection current thereby eliminating the need for PZT and its components. This makes the interferometry more compact. This paper reports on a new approach to the LD Modulating interferometry that involves four-buckets phase shift method. This study proposes a four-bucket phase mapping algorithm, which was developed to have a guaranteed application, to stabilize the system in the field and to be a user-friendly GUI. In this paper, the theory for LD wavelength modulation and sinusoidal phase modulation of LD modulating interferometry is shown. Four-bucket phase mapping algorithm is then introduced.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.158-161
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• 1995

A new laser diode range-finding speedometer is proposed, which is modulated by a pair of positive and negative triangular pulse current superimposed on a dc current. Since a target velocity is directly obtained form a pure Doppler beat frequency measured during the non-modulation period, the new sensor is free from the difficulties due to the critical velocity encountered in the previous sensor. Furthermore, the different amplitude of the two triangular pluses are so adjusted that the measurable range using only one laser head is greatly expanded to 10cm through 150cm, which is about two times that of the previous sensor. The measurement accuracy for velocity of .+-.6mm/s through .+-.20mm/s and for range is about 1%, and 2%, respectively. Because the new sensor can be operated automatically using a microcomputer, it will be useful for application of a 3-D range image measurement of a slowly moving object.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.309-312
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• 2008

We study signal characteristics of the injection-locked Fabry-Perot laser diodes(FP-LDs) for the development of a costeffective WDM-PON solution. The output power and system performance of WDM-PON using injection locked FP-LD are depend on optical characteristics of injection source. The effect of optical power and polarization state of the injection source experimentally investigated. We also measured BER characteristics of the directly modulated FPLD and its power penalty at the BER of $10^{-9}$.

• Journal of information and communication convergence engineering
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• v.4 no.3
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• pp.101-104
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• 2006

We have investigated the spectral characteristics of the semiconductor lasers locked to the sidebands of the master laser in this paper, which were expressed by a series of the Bessel function. The numerical model for the semiconductor lasers based on the typical Lang's equation has been extended in order to take into account the simultaneous injection of the multiple sidebands of the directly modulated ML. We analyses characteristics of direct intensity modulation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.926-929
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• 2005

Recently, laser interferometer is widely used as a measuring system in many fields because of its high resolution and its ability to measure a board area in real-time ail at once. In conventional laser interferometer, for examples Out of plane ESPI, In plane ESPI, Shearography and Holography, it uses PZT or other components as a phase shift instrumentation to extract 3-D deformation data, vibration mode and others. However, in most cases PZT has some disadvantages, which include noli-linear errors and limited time of use. In present study, a new type of laser interferometer using a laser diode(LD) is proposed. Using Laser Diode Sinusoidal Phase Modulating(LD-SPM) interferometer, the phase modulation can be directly modulated by controlling the LD injection current thereby eliminating the need for PZT components.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.143-148
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• 2006

A new method of measuring the Brillouin gain spectrum of optical fiber is proposed and demonstrated. Unlike existing methods, both the pump light and the counter-propagating probe light are generated from a single laser diode whose optical frequency is directly modulated by injection current modulation. The frequency difference between the pump and the probe is scanned continuously through optical frequency chirp occurring when the injection current is modulated with a square wave. The measured Brillouin gain spectrum of telecom single-mode fiber agrees well with that shown in other literature.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.11
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• pp.28-34
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• 2015

By incorporating a 966nm near infrared laser, we demonstrated bidirectional current triggering of between 0 and 10mA in a two-terminal planar device based on a highly resistive vanadium dioxide ($VO_2$) thin film grown by a pulsed laser deposition method. A two-terminal planar device, which had an electrode separation of $100{\mu}m$ and a $50{\mu}m-wide$ $VO_2$ conducting layer, was fabricated through ion beam-assisted milling and photolithographic techniques. A bias voltage range for stable bidirectional current triggering was determined by investigating the current-voltage curves of the $VO_2-based$ device in a current-controlled mode. Bidirectional current triggering of up to 10mA was realized by directly illuminating the $VO_2$ film with a focused infrared laser beam, and the transient responses of triggered currents were analyzed when the laser was modulated at various pulse widths and repetition rates. A switching contrast between off- and on-state currents was evaluated as ~3571, and the rising and falling times were measured as ~40 and ~20ms, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.7
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• pp.65-72
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• 2009

Laser interferometry is widely used as a measuring system in many fields because of its high resolution and its ability to measure a broad area in real-time all at once. In conventional laser interferometry, for example out-of-plane ESPI (Electronic Speckle Pattern Interferometry), in plane ESPI, shearography and holography, it uses PZT or other components as a phase shift instrumentation to extract 3-D deformation data, vibration mode and others. However, in most cases PZT has some disadvantages, which include nonlinear errors and limited time of use. In the present study, a new type of laser interferometry using a laser diode is proposed. Using Laser Diode Sinusoidal Phase Modulating (LD-SPM) interferometry, the phase modulation can be directly modulated by controlling the laser diode injection current thereby eliminating the need for PZT and its components. This makes the interferometry more compact. This paper reports on a new approach to the LD (Laser Diode) Modulating interferometry that involves four-frame phase shift method. This study proposes a four-frame phase mapping algorithm, which was developed to have a guaranteed application, to stabilize the system in the field and to be a user-friendly GUI. In this paper, the theory for LD wavelength modulation and sinusoidal phase modulation of LD modulating interferometry is shown. Using modulating laser and research of measurement algorithm does comparison with existent ESPI measurement algorithm. Algorithm measures using GPIB communication through most LabVIEW 8.2. GPIB communication does alteration through PC. Transformation of measurement object measures through modulating laser algorithm that develops. Comparison of algorithm of modulating laser developed newly with existent PZT algorithm compares transformation price through 3-D. Comparison of 4-frame phase mapping, unwrapping, 3-D is then introduced.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.2029-2036
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• 2014

The performance analysis of optoelectronic oscillator(OEO) based on a directly modulated semiconductor laser was theoretically achieved. First, the analysis was performed on the open response of the key components that constitute the OEO loop. Using the results, we simulated the open-loop characteristics of the OEO loop. By combining oscillation conditions of loop oscillator in addition to the open-loop magnitude and phase responses, theoretical performance analysis such as OEO's oscillation frequency, spurious tones and phase noise was successfully completed.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.313-317
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• 2012

We have evaluated a 1.3 ${\mu}m$ vertical-cavity surface-emitting laser (VCSEL), whose bottom mirror and central active layer were grown by metal organic chemical vapor deposition (MOCVD) and whose top mirror was covered with a dielectric coating, for 10 Gb/s data transmission over single-mode fibers (SMFs). Successful demonstration of error-free transmission of the directly modulated VCSEL signals at data rate of 10 Gb/s over a 10 km-long SMF was achieved for operating temperatures from $20^{\circ}C$ to $60^{\circ}C$ up to bit-error-rate (BER) of $10^{-12}$. The DC bias current and modulation currents are only 7 mA and 6 mA, respectively. The results indicate that the VCSEL is a good low-power consuming optical signal source for 10 GBASE Ethernet applications under controlled environments.