• Journal of the Optical Society of Korea
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• v.12 no.4
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• pp.281-287
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• 2008

An acousto-optic tunable filter based 3-D micro surface profile measurement using an equally spaced 5 spectral phase shifting is described. The 5-bucket spectral phase shifting method is compared with a Fourier-transform method in the spectral domain. It can provide a fast measurement capability while maintaining high accuracy since it needs only 5 pieces of spectrally phase shifted imaging data and a simple calculation in comparison with the Fourier transform method that requires full wavelength scanning data and relatively complicated computation. The 3-D profile data of micro objects can be obtained in a few seconds with an accuracy of ${\sim}10nm$. The 3-D profile method also has an inherent benefit in terms of being speckle-free in measuring diffuse micro objects by employing an incoherent light source. Those simplicity and practical applicability is expected to have diverse applications in 3-D micro profilometry such as semiconductors and micro-biology.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.105-106
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• 2008

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.457-463
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• 1993

We investigated that the CARS signals generated from resonant or nonresonant contributions can be selectively suppressed by phase-controlled nonlinear interferometry. To control the phase of the CARS signal over a broad spectral range, a home-made phase shifting unit was used, whose thickness was automatically controlled as the wavelength of Stokes beam scaned. Using this technique, we recovered the Q-branch resonance lines of carbon monoxide and HC1 which had been distorted and buried by the nonresonant and resonant signal of propane respectively. All the spectrum measured have been normalized by reference signal which had no resonance lines over the spectral range of interest.

• Journal of electromagnetic engineering and science
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• v.4 no.4
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• pp.162-167
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• 2004

In this paper, optimal position of optical phase conjugator(OPC) for best compensating distorted WDM channels due to both chromatic dispersion and self phase modulation(SPM) is numerically investigated, and the compensation characteristics of overall WDM channels at this position is investigated, comparing with that in case of OPC placed at mid-way of total transmission length. It is confirmed that the compensation extents in WDM system with OPC is more improved by the shifting OPC position from the mid-way of total transmission length. And, we confirmed that the optimal position of OPC must be selected to the position decreasing not only eye opening penalty(EOP) of overall WDM channels but also EOP deviation between WDM channels, and this OPC position should be altered as various system parameters such as modulation format, and fiber dispersion, etc. Using proposed configuration, it is possible to remove all in-line dispersion compensator, reducing span losses and system costs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1123-1131
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• 2005

In this paper, optimal position of optical phase conjugator (OPC) for best compensating distorted WDM channels due to both chromatic dispersion and self phase modulation (SPM) in $8{\times}40$ Gbps WDM systems is numerically investigated, and the eye opening penalty (EOP) and bit error rate (BER) characteristics of overall WDM channels at this position is investigated, comparing with that in case of OPC placed at mid-way of total transmission length. It is confirmed that the compensation extents in WDM system with OPC is more improved by the shifting OPC position from the mid-way of total transmission length, depending on the modulation format and fiber dispersion coefficient. Ant it is confirmed that, from a viewpoint of the reception performance, EOP of each channel is more or less different with one another, but the BER characteristics of overall channels are almost equal.