Kyung-Rak Sohn

Multiwavelength all-fiber ring laser using side-polished fiber comb filter and mechanically formed long-period fiber gratings

Multiwavelength all-fiber lasers to be operated at room temperature are demonstrated. A side-polished fiber comb filter and mechanically formed long-period fiber gratings (LPFGs) are used to generate colasing operation. By using the band suppression characteristics of the LPFGs to prevent the gain cross-saturation effect, simultaneous lasing of four-wavelength peaks is obtained.

Widely tunable filter based on coupling between a side-polished fiber and a tapered planar waveguide

We demonstrate a tunable filter with a wide tunable wavelength range (>300 nm) based on coupling between a side-polished fiber and a tapered planar waveguide (PWG). The thickness variation, due to sliding of the upper block, of taper PWG on the side-polished fiber region shifted the resonance wavelength of the coupler. Design and fabrication technique are presented.

Wireless CAN communications based on white LED

In this paper, optical wireless communication systems based on a controller area network (CAN) are proposed and demonstrated. The optical transceiver is composed of 25 LEDs array around plus 3 PDs in the center and two CAN transceivers. By means of that, the conventional two-wired CAN bus replaces to the free-space optical channels. To ensure the full-duplex channel isolation, LED driving and PD receiving circuit have their own CAN transceiver, respectively. On-off keying was applied without observable flicker in the target modulation ranges. The performance of data transfer in our prototype shows up to 0.6 m range at the transmission rate of 200kbps.

Gas-Flow Sensor using Optical Fiber Bragg Grating(FBG)

We have proposed and demonstrated an gas-flow sensor using optical fiber bragg grating(FEG). The flow sensor has no electronics and no mechanical parts in its sensing part and the structure is th11s simple and immune to electromagnetic interference(EMI). The FEG sensor was consisted qf the sensing element and a coil heater. The metal coil was used to supply the current to the FEG. While some currents supply to the coil, the refractive index of the FEG under the coil is changed and thus the wavelength shift of fiber optic sensor was induced In this work, the wavelength shift according to flow-rate was experimentally studied and was used to evaluate the gas flow-rate in a gas tube. As a result, it was possible to measure the flow-rate in a linear range from 5 to with a resolution of approximately at the applied currents of 100 mA and 120 mA. The measured sensitivities were for 100 mA and for 120 mA.

Performance of nano-crystalline inductive couplers applied to ship powerline communication

We have proposed a nano-crystalline inductive coupler that can arbitrarily add or move communication facilities in the ship without physical power line contact. Using a nano-crystalline inductive powerline communication system, we have achieved data rates of more than 12 Mbps between two separate cabins in the training-ship and succeeded in transmitting images on the same powerline condition.

Length Effects of Hetero-Core Optical Biosensor based on Evanescent Field Absorption

Sensing performances of evanescent field absorption (EFA) hetero-core fiber sensor has been presented based on EFA by changing the length and the core diameter of the single mode fiber. Experimental results have demonstrated a good feature in their relationship between the length and the core diameter of the single mode fiber. The sensor consists of 2 fiber optics which have the same cladding diameter of However one fiber optic used is single mode and has varying core diameter ranging from 3.3 to . The other fiber is multimode type and has a thicker fixed core diameter of . The 2 fiber optics are thermally spliced together. Experiments conducted to measure the resonance wavelength were carried out over a range of refractive index, to find the optimum sensing length Experiments show that core diameter of the single mode fiber and sensing length offects the linearity and sensitivity.