• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.63-67
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• 2013

We perform an optical vestigial sideband (VSB) filtering using a pair of Fabry-Perot (FP) filters. The transmittance curve of each FP filter is made to have sharp skirts using an offset between input and output coupling fibers. Moreover, the accurate periodicity of FP filters in the optical frequency domain enables the simultaneous VSB filtering of a large number of optical channels. With this VSB filtering technique, we transmit 12.5-GHz spaced $64{\times}12.4-Gb/s$ wavelength-division-multiplexing channels over a single-mode fiber up to 150 km without any dispersion compensations. When the channel spacing is reduced to 10 GHz, we achieve the spectral efficiency of 1 bit/s/Hz in conventional optical intensity modulation systems up to 125 km.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.230-235
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• 1997

Coupling loss variation as the shape of fiber ends and the fiber arrangement in a fiber Fabry-Perot cavity, formed with two optical fibers with dielectric mirror coatings on their ends, is analyzed. For the intended features it is assumed that one of two fibers is processed to have a concave mirror whose curvature is the same as that of the wavefront of the Gaussian beam from the first fiber. In this assumption, it was turned out that the coupling loss at the cavity length of 15 ${\mu}{\textrm}{m}$ is less than 0.5% even with tilt angle of 0.2$^{\circ}$, curvature error of 70 ${\mu}{\textrm}{m}$, cavity length error of 8 ${\mu}{\textrm}{m}$, and lateral alignment error of 0.5 ${\mu}{\textrm}{m}$. Thus, low loss and high-finesse fiber Fabry-Perot filters whose cavity length is greater than several ${\mu}{\textrm}{m}$ can be obtained easily if the receiving fiber end is properly formed.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.235-238
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• 2008

In this paper, we have developed wavelength swept laser system for the swept source optical coherence tomography(SS-OCT). A laser is constructed by using the two SOAs parallel configuration, fiber Fabry-Perot tunable filter(FFP-TF). The wavelength sweeps are repetitively generated with the repetition period of 50Hz. The wavelength tuning range of the laser is more than FWHM of 80nm centered at the wavelength of 1310nm and the line-width of the source is 0.12 nm.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.3
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• pp.31-38
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• 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
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• 2009.02a
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• pp.239-240
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• 2009

• Current Optics and Photonics
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• v.2 no.1
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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.

• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.409-414
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• 2004

A signal processing system of long period grating sensor that works in the optical wavelength domain is proposed. The system is based on a wavelength-swept semiconductor light source that includes an SLD and a F-P tunable filter. The hysteresis effects of PZT in the F-P filter is compensated by using an etalon filter and an athermal Fiber Bragg Grating. The detected signals from the photodiode are transmitted to a computer using an A/D converter and the result of the process is displayed in the monitor.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8A
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• pp.657-662
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• 2003

The OPM(optical performance monitoring module) is needed in order to monitor optical performance. the most importance of OPM is to measure the wavelength of optical signal. In the past time, it was very difficult to get the wavelength value because they used pilot tone. Since then, using AWG(arrayed waveguide grating) and AOTF(acousto optic tuneable filter), the wavelength and the transmission qualify for multi channel signal have been monitored. In this paper, we chose the fiber fabry-perot wavelength variable filter which be evaluated for optical resolution ability to excellent, so that FBG(fiber bragg grating) was used for setting reference wavelength because chose a wavelength variable filter.

• Journal of the Optical Society of Korea
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• v.19 no.4
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• pp.346-350
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• 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 Society for Aeronautical & Space Sciences
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• v.31 no.8
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• pp.44-49
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• 2003

In case of an extrinsic Fabry-Perot interferometric sensor, the phase compensating technique is particularly necessary in applying the interferometer to detecting acoustic emission signals because of signal-fading problems. The technique makes it possible to maintain the phase at the quadrature point. In this paper, we developed the stabilization control sensor system that is composed of a broadband light source, a tunable Fabry-Perot (F-P) filter and a control-circuit board. A tension test of a composite specimen was performed to verify if the developed system could compensate the phase change induced from the tension strain and keep the phase at the quadrature point.