Yune Hyoun Kim

Measurement method for profiling the residual stress and the strain-optic coefficient of an optical fiber

A method, believed novel, is demonstrated for determining the strain-optic coefficient profile as well as the residual-stress profile of an optical fiber by use of a modified polariscope combined with a fiber-elongation apparatus. Measurement results of the residual-stress and the strain-optic coefficient profiles for Ge-doped and Er-Ge-Al-doped optical fibers are demonstrated with this method.

All-optical switching application based on optical nonlinearity of Yb 3+ doped aluminosilicate glass fiber with a long-period fiber gratings pair

We propose a new fiber-type all-optical switching device based on the optical nonlinearity of Yb(3+) doped fiber and a long-period fiber gratings(LPG) pair. The all-optical ON-OFF switching with the continuous wave laser signal at ~1556nm in the LPG pair including the 25.5cm long Yb(3+) doped fiber was demonstrated up to ~200Hz upon pumping with the modulated square wave pulses at 976nm, where a full optical switching with the ~18dB extinction ratio was obtained at the launched pump power of ~35mW.

Optical DPSK demodulator based on /spl pi/-phase-shifted fiber Bragg grating with an optically tunable phase shifter

We propose and demonstrate a novel optical differential phase-shift keying (DPSK) demodulator with an optically tunable phase shifter. The proposed DPSK demodulator is implemented by using a pi-phase-shifted fiber Bragg grating and an Yb3+-Al3+ codoped optical fiber. A 10-Gb/s DPSK signal was successfully demodulated by the proposed demodulator, showing clearly open eye diagrams as well as bit-error-free performance. Moreover, the phase of delayed optical signal can be tuned by the phase shifter that is controlled by a pumping light at around 980nm

Effect of soaking temperature on concentrations of rare-earth ions in optical fiber core in solution doping process

Effect of soaking temperature on concentration of rare-earth ions in the optical fiber core during solution doping process was investigated. The dopant concentration of Er3+ and Ho3+ in the preforms and the fibers measured by the electron probe microanalysis and the optical spectrum analyzer was found to increase with decreasing the soaking temperature. The increase in the concentration of the Er3+ and the Ho3+ was attributed to the precipitation of the dopants due to the decrease in the solubility by decreasing the temperature.

Optical delay interferometer based on phase shifted fiber Bragg grating with optically controllable phase shifter

We propose a novel optical delay interferometer (ODI) with an optically controllable phase shifter. The proposed interferometer is implemented by using a phase shifted fiber Bragg grating and an Yb(3+)/Al(3+) co-doped optical fiber. The phase of the delayed optical signal is linearly controlled by adjusting the induced pumping power of a laser diode at 976 nm. Polarization dependent loss, polarization dependent center wavelength shift and temperature induced center wavelength shift of the ODI are 0.044 dB, 6 pm, and 9.8 pm/ degrees C, respectively.

Absorption and emission properties of Tm2+ ions in germanosilicate glass fibers.

Absorption and emission properties between 350nm and 1600nm of the Tm2+ ions in optical fibers were investigated using the Tm2+-Tm3+ co-doped germanosilicate glass fibers and its fiber preform. Strong broad absorption band due to Tm2+ ions was found to appear from 350nm to ~900nm together with the absorption bands due to Tm3+ ions. Broad emission from ~600nm to ~1050nm and the other emission from ~1050nm to ~1300nm, which were not shown in the Tm3+ ions, were found upon the Ar ion laser pumping at 515nm. Both absorption and emission results confirm that the Tm2+ ions in the germanosilicate glass have the 4f-5d energy band from 350nm to ~900nm and the 4f-4f energy level at ~1115nm.

Fabrication of Tm/sup 2+//Tm/sup 3+/ co-doped silica fiber and its fluorescence characteristics

For the first time, we have fabricated divalent thulium doped silica optical fiber. The measured fluorescence between 600 nm and 1500 nm upon pumping at 514 nm using Ar ion laser was due to the Tm/sup 2+/ ions in the core of the fiber.

Fiber length dependence of phase change induced by laser-diode pumping in Yb/sup 3+/-Al/sup 3+/ co-doped optical fibers

We investigated the fiber length dependence of the phase change near 1580 nm induced by 980-nm pump beam in Yb/sup 3+/-Al/sup 3+/ co-doped optical glass fibers by use of a long-period fiber grating pair. As the pumping power increased, the phase change linearly increased and then was gradually saturated. Both the saturated phase change and the saturation pump power increased with the increase of the fiber length. The saturated phase change in Yb/sup 3+/-Al/sup 3+/ co-doped fibers of 16.7, 33.2, and 43.5 cm was found to be /spl sim/0.5, /spl sim/0.8, and /spl sim/1.0 rad, respectively. The saturation of the phase change is attributed to the saturation of the absorption from the finite ytterbium ions doped in the fibers.

Measurement of the pump-induced phase change in Yb/sup 3+//Al/sup 3+/ co-doped optical fibers using a long-period fiber grating pair

Summary form only given. We proposed a new measurement method for the nonlinear optical (NLO) property of the Yb/sup 3+//Al/sup 3+/ co-doped optical fibers with low cost, high reliability, and simple measurement setup. A long-period fiber grating (LPG) pair was used as a sensing part of the NLO property measurement together with the target fiber spliced between the pair. The pump-induced phase change of the Yb/sup 3+//Al/sup 3+/ co-doped fibers was measured and the effect of fiber length on the NLO property was investigated. The measured phase change of the Yb/sup 3+//Al/sup 3+/ co-doped fiber around 1580 nm upon pumping with laser diode was found to increase and saturate with increase of the pump power.

Low-cost multimodal analyzer on wavelength and power measurement

Summary form only given: We propose and demonstrate the low-cost multimodal analyzer of wavelength and power. To analyze both wavelength and power with incoming light through free space or fiber, the analyzer has dual detectors with difference window filters. The resolution is achieved up to 0.02nm over 100nm range.