Kyoungmin Kim

In-service monitoring of 16 port x 32 wavelength bi-directional WDM-PON systems with a tunable, coded optical time domain reflectometry.

We propose a multi-port, multi-wavelength supervisory system for the in-service transmission line monitoring of a bidirectional WDM-PON system. Identifying unique requirements for the performance monitoring of a real field WDM-PON system, we define the architecture for the supervisory system and utilize the most up-to-date technologies (Simplex coding, tunable source, and optical switches) to demonstrate a successful interrogation of a transmission line up to 16 ports x 32 nodes (512 user) capacity. Monitoring of individual branch traces up to 60 km was achieved with the application of a 127-bit simplex code corresponding to a 7.5dB SNR coding gain. In-service transmission experiments showed negligible penalty from the monitoring system to the transmission signal quality, at a 2.5Gbps / 125Mbps (down / up stream) data rate.

Coded optical time domain reflectometry: principle and applications

In this paper, we will briefly outline our contributions for the physical realization of coded OTDR, along with its principles and also highlight recent key results related with its applications. For the communication network application, we report a multi-port / multi-wavelength, high-speed supervisory system for the in-service monitoring of a bidirectional WDM-PON system transmission line up to 16 ports x 32 nodes (512 users) capacity. Monitoring of individual branch traces up to 60 km was achieved with the application of a 127-bit simplex code, corresponding to a 7.5dB SNR coding gain effectively reducing the measurement time about 30 times when compared to conventional average mode OTDR. Transmission experiments showed negligible penalty from the monitoring system to the transmission signal quality, at a 2.5Gbps / 125Mbps (down / up stream) data rate. As an application to sensor network, a Raman scattering based coded-OTDR distributed temperature sensor system will be presented. Utilizing a 255-bit Simplex coded OTDR together with optimized sensing link (composed of cascaded fibers with different Raman coefficients), significant enhancement in the interrogation distance (19.5km from coding gain, and 9.6km from link-combination optimization) was achieved to result a total sensing range of 37km (at 17m/3K spatial/temperature resolution), employing a conventional off-shelf low power (80mW) laser diode.

Optimization of the material parameters for Silicon nanocluster sensitized Er-doped waveguide amplifier

Recent progress in the effort of realizing nanocluster silicon sensitized, Er-doped silica waveguide amplet is introduced. Approaches for the optimization of key device / material parameters, in terms of numerical assessment and experimental means will be detailed.

Differential Monitoring of AWG-Filtered Reflection Signal for Accurate Transmitter Power Control of Injection-Locked WDM PON Systems

We propose a simple and robust, automatic power control architecture for the injection-locked, wavelength-division-multiplexed passive optical network system. Monitoring the differential of reflected signal power from the mid-stage fiber mirror placed after the arrayed waveguide grating in the central office, the problem of transmitted signal power fluctuation experienced in conventional, back-facet photodiode monitoring schemes is eliminated. Results show the excellent control of the transmitted power within a peak-to-peak fluctuation of 0.1 dB over a wide operating range of temperature and injection power level.

Multi-port, multi-wavelength supervisory system for in-service monitoring of bi-directional WDM-PON systems

We define and demonstrate a supervisory system for WDM-PON applications. Utilizing most up-to-date technologies (Simplex coding, tunable source, and optical switches), successful interrogation of the whole network (16 port times 32 node = 512 user) was achieved without any transmission penalty.

Enhancement of Crystallinity with Fluorinated Amorphous Silicon (a-Si:H;F) Film by XeCl Excimer Laser Annealing

The Effects of fluorine atoms on laser-induced crystallization have been studied. The defect states of hydrogenated amorphous silicon (a-Si:H) film, which are related to weak hydrogen bonds, were reduced by involving fluorine atoms, before laser annealing. In laser annealing, the crystallinity was also enhanced to 63 %, while that of a-Si:H was 45 % at the energy density of 300 mJ/cm 2 . It may be considered that the fluorine atoms reduce the hydrogen atoms cause to the degradation of film in laser annealing, and increase the heat capacity which results in promotion of crystallinity in melt-solid phase transition.