• Proceedings of the Optical Society of Korea Conference
• /
• 2001.02a
• /
• pp.166-167
• /
• 2001

과장 변환기는 WDM (wavelength division multiplexing) 시스템에서 wavelength relocation을 가능하게 하여 시스템의 유연성과 효율성을 향상시킨다는 측면에서 매우 중요한 기능을 갖는다. WDM 시스템의 채널의 수가 점차 증가함에 따라 채널의 간격이 100 GHz에 이르고 있으며 향후 더욱 조밀해 질것이다. 이러한 DWDM (Dense WDM)시스템에서 사용될 수 있는 파장변환기는 100 GHz단위의 파장변환 기능과 광대역 가변 변위가 필수적이다. (중략)

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.3
• /
• pp.31-38
• /
• 2004

The wavelength variation of a scanned fiber laser is analyzed using quadrature sampling technique. By time delayed sampling of a phase modulated Mach-Zender interferometer, the wavelength information can be precisely determined regardless of the nonlinearity in the Fabry-Perot wavelength filter which scanned the fiber laser. A wavelength readout resolution of ～20 pm was obtained at 2 KHz M-Z modulation frequency, and it was shown that the resolution could be improved in case of using an electro-optic phase modulator.

• Proceedings of the Optical Society of Korea Conference
• /
• 2004.02a
• /
• pp.86-87
• /
• 2004

• Journal of the Optical Society of Korea
• /
• v.19 no.4
• /
• pp.346-350
• /
• 2015

We report a measurement of the effective refractive index of a nematic liquid crystal (NLC) inside a Fabry-Perot (FP) etalon according to the applied electric fields. The effective refractive index of the NLC depends on the intensity of the applied electric field. A wavelength-swept laser with a polygon-scanner-based wavelength filter is used as a wide-band optical source to measure the effective refractive index of the NLC. The bandwidth of the optical source is greater than 90 nm around 1300 nm. The fabricated NLC FP etalon consists of glass substrates, gold layers as the electrodes with highly reflective surfaces, polyimide layers as the planar alignment layers, and an LC layer. Furthermore, we measured the Freedericksz transition voltages for three types of NLC FP etalons having thicknesses of $30.6{\mu}m$, $55.4{\mu}m$, and $108.8{\mu}m$. The Freedericksz transition voltages in the three cases are nearly equal. The measured effective refractive indices in the three cases decreased from 1.67 to 1.51 as the applied electric field intensity was increased. Beyond the threshold electric field, the effective refractive indices quickly decreased and eventually saturated at a value of 1.51 for all cases.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.3 no.4
• /
• pp.16-24
• /
• 1966

The LASER Amplifier is treated in the manner of a Fabry-Perot Resonator with an active media, five layers are considered: air, reflector, active medium(ruby), reflector and air. One dimensional scalar wave equations are derived using the method of boundary value probrems in which it is assumed that incident coherent radiation falls normally on the surface wall. All equations are treated from the transient analysis point of view using the Laplace transform nethods, and are arranged steady state region as an amplifier and transient region as a self excited oscillator. Also some remarks are given on the design problem of LASER amplifier in connection with the transient terms involved.

• Current Optics and Photonics
• /
• v.2 no.5
• /
• pp.395-399
• /
• 2018

This article investigates the mechanism of electronic signal phase noise degradation induced by laser phase noise in optical links comprising optical resonators. Through theoretical derivation, we find that the phase noise of the output electronic signal has the same spectral shape of optical intensity noise as the output of the optical resonator. We propose that the optical resonator transfers laser phase noise to light intensity fluctuation and then the intensity fluctuation is converted to electric phase noise through AM-PM conversion mechanism in the photodiode. An optical link comprising a Fabry-Perot resonator was constructed to verify the proposed mechanism. The experimental results agree with our theoretical prediction verifying that the supposition is correct.

• Journal of the Optical Society of Korea
• /
• v.17 no.4
• /
• pp.323-327
• /
• 2013

A laser ultrasonic inspection system has the advantage of nondestructive testing. It is a non-contact mode using a laser interferometer to measure the vertical displacement of the surface of a material caused by the propagation of ultrasonic signals with the remote ultrasonic generated by laser. After raising the ultrasonic signal with a broadband frequency range using a pulsed laser beam, the laser beam is focused to a small point to measure the ultrasonic signal because it provides an excellent measurement resolution. In this paper, foreign materials are measured by a non-destructive and non-contact method using the laser ultrasonic inspection system. Mixed foreign material on the corroded part is assumed and the laser ultrasonic experiment is conducted. An ultrasonic wave is generated by pulse laser from the back of the specimen and an ultrasonic signal is acquired from the same location of the front side using continuous wave laser and Confocal Fabry-Perot Interferometer (CFPI). The characteristic of the ultrasonic signal of existing foreign material is analyzed and the location and size of foreign material is measured.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.46 no.1
• /
• pp.43-48
• /
• 2009

We constructed a simple wavelength readout system for a tunable fiber laser which was used for a fiber Bragg grating sensor array system. A quadrature sampling method was used to demodulate wavelength variations of the tunable laser which consisted of a SOA(semi-conductor optical amplifier) and a fiber-optic Fabry-Perot filter. Internal triggers, which have a 90 degree phase period, have been generated by using a double-pass Mach-Zehnder interferometer. From Lissajous plots with quadrature sampled data, a mean phase error of ${\sim}2.51$ mrad was obtained. From the wavelength readout experiments, an accurate and fast linear wavelength demodulation has been confirmed.

• Journal of the Korean Vacuum Society
• /
• v.15 no.1
• /
• pp.24-30
• /
• 2006

Integrated cavity output spectroscopy(ICOS) is a simple, non-intrusive absorption measurement technique that can detect and quantify trace-level gas species. The spectral absorbance of a gas is quantified from the integrated optical output of the modulated high-finesse cavity containing the sample which is irradiated by a wavelength-swept laser source. We constructed an experimental setup by using a tunable single mode external cavity diode laser operating at the wavelength near 765 nm and a Fabry-Perot cavity with length modulation achieved by a piezoelectric transducer where one of the cavity mirrors sat on. In the experiment performed on minute oxygen gas at the wave-length near 764.5nm, we demonstrated the minimum detectable absorption of $8.45\times10^{-8}cm^{-1}$.

• Korean Journal of Optics and Photonics
• /
• v.21 no.2
• /
• pp.74-81
• /
• 2010

A modeling methodology for the analysis of injection-locked Fabry-Perot laser diodes (FP-LDs), promising for cost-effective WDM-PON sources, is proposed. The time-domain large-signal model that is used is found to provide quite similar results to some experimental ones. With our methodology, we model characteristics of FP-LDs, such as influence of reflectivity at a facet and detuning on injection-locking. The eye diagram characteristics are also investigated. It is observed that the facet reflectivity at the injection side should be lower than 1% to provide stable operation in terms of good side-mode suppression ratio and independence from detuning between narrow-band injection noise and LD modes. It is also observed that good eye opening can be obtained for 155 Mbps modulation while the parameters such as the active region thickness should be properly optimized to obtain reasonable eye opening at 1.25 Gbps.