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

• Korean Journal of Optics and Photonics
• /
• v.10 no.3
• /
• pp.248-253
• /
• 1999

In this paper, we have investigated a fiber type active coupler which utilizes the mode coupling between the side polished single mode optical fiber and the active multimode planar waveguide. The proposed device can be used for not only tunable wavelength filter or optical intensity modulator but also a tool for measuring optical properties of guiding material such as refractive index, birefringence, electro-optic coefficient, and thermo-optic coefficient. We gave designed and optimized a coupler structure using the BPM and fabricated the device using thermo-optic polymer as active planar waveguide overlay. The device showed that insertion loss was less then 0.5 dB, extinction ratio was -13 dB at the resonance wavelength, and the wavelength tunablity due to thermo-optic effect was -1.5 nm/$^{\circ}C$. The active coupler using thermo-optic effect can be used as a wavelength tunable filer, an optical intensity modulator and an optical sensor. pulses that are subsequently compressed by a dispersive optical fiber. Experimental results show that $sech^2$ shape pulses with a pulse width of ~14 ps and a time bandwidth product of ~0.34 are successfully generated at 10 GHz repetition rate. In contrast to other methods, such as higher order soliton compression, this approach does not depend on the optical power and thus shows promise for application to low-power lasers.

• Korean Journal of Optics and Photonics
• /
• v.11 no.3
• /
• pp.163-165
• /
• 2000

We propose a new structure of optical cross connect based on a WDM MUX/DEMUX pair and switchable mirrors. In experiment, we demonstrate the operation of the optical cross connect using an optical fiber loop mirror connected to a $2\times2$ optical switch as a switchable mirror.mirror.

• Korean Journal of Optics and Photonics
• /
• v.14 no.1
• /
• pp.17-22
• /
• 2003

We experimentally measured the dependence of FWM efficiency on channel spacing for G.652, G.653, G.655 optical fiber with various dispersion values and compared the results with analytical results. Also, we investigated the dependence of XPM efficiency on channel spacing and dispersion in pump-probe experimental configuration.

• Korean Journal of Optics and Photonics
• /
• v.7 no.1
• /
• pp.60-65
• /
• 1996

Degradation of the optical communication system due to the stimulated Brillouin scattering effect in the optical fiber is measured, and its suppression is demonstrated. In the externally modulated 2.5 Gb/s transmission experiment, bit error rate is increased due to the stimulated Brillouin scattering effect when the signal power (linewidth 3 MHz) incident into the dispersion shifted fiber is larger than 10 dBm. SBS effect is suppressed completely, up to 15 dBm of transmission power, by broadening the source linewidth to 200 MHz.

• Korean Journal of Optics and Photonics
• /
• v.10 no.2
• /
• pp.169-173
• /
• 1999

We have experimentally investigated the eye margin characteristics of intensity modulated 10Gb/s NRZ signals in optically amplified systems depending on optical signal-to-noise ratio and chromatic dispersion. For the practical system application, the minimum optical signal-to-noise ratio was 25 dB. We utilized the negative chirped transmitter and a dispersion compensation fiber to compensate the chromatic dispersion in single mode fiber. We found the optimum eye opening and receiver sensitivity in case of the residual dispersion of 0~+935 ps/nm.

• Korean Journal of Optics and Photonics
• /
• v.14 no.3
• /
• pp.338-342
• /
• 2003

We have studied the properties of stimulated Brillouin scattering (SBS) in an optical fiber using optical pulses and continuous wave light. We find that the thresholds for SBS are the same when the averaged power of pulse light is the same as the power of cw light. From this result, the SBS threshold of pulse light can be deduced from that of continuous wave light, which can be obtained easily and accurately.

• Current Optics and Photonics
• /
• v.7 no.2
• /
• pp.176-182
• /
• 2023

Optical coherence tomography (OCT) is being developed to guide various ophthalmic surgical procedures. However, the high cost of the intraoperative OCT system limits its availability mostly to the largest hospitals and healthcare systems. In this paper, we present a design and evaluation of a low-cost intraoperative common-path free-hand scanning OCT system. The lensed fiber imaging probe is designed and fabricated for intraocular use and the free-hand scanning algorithm that could operate at a low scanning speed was developed. Since the system operates at low frequencies, the cost of the overall system is significantly lower than other commercial intraoperative OCT systems. The assembled system is characterized and shows that it meets the design specifications. The handheld OCT imaging probe is tested on multilayer tape phantom and ex-vivo porcine eyes. The results show that the system could be used as an intraoperative intraocular OCT imaging device.

• Korean Journal of Optics and Photonics
• /
• v.5 no.1
• /
• pp.125-130
• /
• 1994

A new cavity configuration for passive mode locking of fiber laser is proposed and demonstrated. It consists of a dichroic mirror at one end of the cavity, and a nonlinear loop mirror, which is a Sagnac loop, at the other end. The experimental observations are described for both Er-doped fiber laser and Nd-doped fiber laser. laser.

• Korean Journal of Optics and Photonics
• /
• v.29 no.5
• /
• pp.187-203
• /
• 2018

This paper reviews the progress achieved in the field of fiber-optic communications during the last 40 years, and discusses its future directions. In particular, the highlights and milestones in the development of the high-capacity fiber-optic transmission system are presented in historical perspective.