Seongmin Ju

Development of a highly sensitive compact sized optical fiber current sensor

We have experimentally developed a highly sensitive and a compact size current sensor by using the CdSe quantum dots-doped bend insensitive optical fiber, operating in the visible band of wavelength. The modified sensitivity of this sensor was about 675 microrad/(Turn.A.m) for the loop radius of just 10 mm, which is more than 16 times larger than that of the single mode optical fiber current sensor.

Thermo-optic coefficient measurement of liquids based on simultaneous temperature and refractive index sensing capability of a two-mode fiber interferometric probe

A fiber-optic interferometric probe based on a two-mode fiber (TMF) is proposed and demonstrated for measuring the thermo-optic coefficients (TOCs) of liquid samples. The proposed probe can be simply fabricated by fusion-splicing a short piece of TMF to a lead single mode fiber (SMF) with small lateral offset, which makes interference between LP(01) and LP(02) modes. The sensing responses of the probe to temperature and surrounding refractive index (SRI) have been experimentally investigated to show the capability of simultaneous measurements; the phase change of the reflection spectrum was related to temperature variation and the intensity change was to SRI variation. The data analysis is made not only in the spectral domain but in the Fourier domain also to effectively quantify the measurements. The TOCs of several liquid samples including water, ethanol, and acetone have been obtained with the proposed method.

Single-mode optical fiber design with wide-band ultra low bending-loss for FTTH application

We propose a new design of a single-mode optical fiber (SMF) which exhibits ultra low bend sensitivity over a wide communication band (1.3 microm to 1.65 microm). A five-cladding fiber structure has been proposed to minimize the bending loss, estimated to be as low as 4.4x10(-10) dB/turn for the bend radius of 10 mm.

Enhanced current sensitivity in the optical fiber doped with CdSe quantum dots

A new optical fiber current sensor using a CdSe quantum dots doped optical fiber has been demonstrated with high Faraday rotation for remote sensing of current from 0 to 40 Amperes. It showed enhancement in the current sensitivity by about 2 times than that of the single mode optical fiber current sensor at 632 nm.

Design of a trenched bend insensitive single mode optical fiber using spot size definitions.

We have designed a bend insensitive single mode optical fiber with a low-index trench using spot-size definitions and their optimization technique. The bending loss at a 5 mm of bending radius was negligible, while single mode properties were intact.

Fabrication and optical characteristics of a novel optical fiber doped with the Au nanoparticles.

Optical fibers containing gold metal nanoparticles were developed by modified chemical vapor deposition, in which Au(OH)3 and tetraethyl-orthosilicate (TEOS) was used via sol-gel process to incorporate gold metals by providing the reduction atmosphere. The absorption peak appeared near 490 nm was found to be due to the surface plasmon resonance of the gold nanoparticles incorporated in the fiber core.

Design and development of a trenched optical fiber with ultra-low bending loss

We have designed and experimentally demonstrated a single mode optical fiber with a very low bending loss of about 0.014 dB/loop at 1550 nm for a bending radius of 5 mm.

800-nm upconversion emission in Yb-sensitized Tm-doped optical fiber

We report, for the first time, the upconversion emission at 800 nm in Yb-sensitized Tm-doped alumino-germano-silicate glass optical fiber when pumped with the 980-nm laser diode. Maximum gain of 6 dB was measured at 808 nm and the upconversion is contributed to the energy transfer from Yb3+ ions to Tm3+ ions

Analysis of 1064-nm Pumped Tm-doped Silica Glass Fiber Amplifier Operating at 1470 nm

An approximate model, along with the experimental verification for thulium (Tm)-doped silica glass fiber amplifier at 1470 nm upon 1064-nm pumping, has been proposed to estimate the optimum parameters and to analyze its performance in terms of gain, bandwidth, and noise performance. The Tm-doped silica glass fiber amplifier was found to be suitable for wavelength division multiplexing application, although a high pump power of more than 1000 mW was needed to achieve a significant gain

A Nd-YAG laser-pumped Tm-doped silica glass optical fiber amplifier at 840 nm

We report a simulation model as well as experimental realization of a novel single-mode Tm-doped silica glass optical fiber amplifier optimized for first-window optical communication wavelength band. A peak gain of about 11 dB at 840 nm was obtained upon pumping with a 1064-nm Nd-YAG laser source