Swook Hann

TDOA-based optical wireless indoor localization using LED ceiling lamps

We propose an optical wireless indoor localization using light emitting diodes (LEDs) and demonstrate it via simulation. Unique frequency addresses are assigned to each LED lamp, and transmitted through the light radiated by the LED. Using the phase difference, time difference of arrival (TDOA) localization algorithm is employed. Because the proposed localization method used pre-installed LED ceiling lamps, no additional infrastructure for localization is required to install and therefore, inexpensive system can be realized. The performance of the proposed localization method is evaluated by computer simulation, and the indoor location accuracy is less than 1 cm in the space of 5m x 5 m x 3 m.

White LED ceiling lights positioning systems for optical wireless indoor applications

An indoor positioning system based on white LED communications is proposed and demonstrated. This positioning system shows that mean of distance errors is 0.651 cm in the space of 30 cm × 30 cm × 50 cm.

Tunable OTDR Based on Direct Modulation of Self-Injection-Locked RSOA for In-Service Monitoring of WDM-PON

We propose a tunable optical time-domain reflectometer (OTDR) for in-service monitoring of wavelength- division- multiplexing passive optical networks (WDM-PONs). The proposed method uses a reflective semiconductor optical amplifier, which is self-injection-locked by a tunable fiber Bragg grating. The proposed tunable OTDR has a tuning range of 30 nm and a resolution of 50 m. The performance of the proposed scheme is experimentally evaluated to demonstrate the in-service monitoring of WDM-PON.

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

An all-fibre robust and tunable Raman fibre laser with reconfigurable asymmetric cavities

A robust Raman fibre laser (RFL) for tunable and multiple outputs has been proposed using an all-fibre asymmetric cavity which is composed of a wideband chirped fibre Bragg grating (CFBG) and narrowband tunable fibre Bragg gratings (TFBGs). The wideband CFBG has high reflectivity across the spectral range from 1404 to 1465 nm as an input reflector. Output couplers (OCs) consist of three TFBGs with center wavelengths of 1410, 1425 and 1440 nm, respectively, which can each be tuned over 10 nm. The output power and wavelength can be flexibly controlled by tuning of TFBGs in the 14xx nm band.

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.

A Surveillance Technique based on spectral analysis of SL-RSOA for PS-PON

We propose and experimentally demonstrate a surveillance technique based on spectral analysis of self-injection locked reflective semiconductor optical amplifier (SL-RSOA) for in-service monitoring of power splitter - passive optical networks (PS-PON). The proposed technique analyzes the cavity mode frequency of upstream transmitter at the optical network unit (ONU) to distinguish each branch fiber from other fiber branches of PS-PON without utilizing any additional surveillance source at the central office (CO).

Fabrication of the reliable (14-18)×1 fiber laser power combiner by the novel double bundling method

Recently, the high power fiber laser has attracted much attention and the laser power combiner is one of the key components for power scaling in the high power laser system. Up to now, several methods have been exploited to develop the combiner and among them the tapered fusion bundling method becomes one of the most popular and reliable technology. In the conventional tapered fusion bundling method, the input fibers were bundled with the honeycomb configuration then fused tapered and spliced to the output fiber. In the method, however, the fiber ports configuration was constrained to certain values such as 3×1, 7×1, 19×1, and 35×1 to satisfy the compactness and reliability in the bundling procedure. In this study, we suggest a novel double bundling method to make combiners with the large flexibility in the fiber port configuration. In making the (14-18)×1 combiners, seven input fibers in the honeycomb stacking configuration was fused bundled and a single layer of secondary 7-11 fibers were stacked outside of the bundle and subsequently tapered and spliced to a output fiber. As a result, (14-18)×1 laser power combiners were made using 105/125 μm input fibers (0.15 NA) and a 200/220 μm output fiber (0.46 NA). In the bundling procedures a LPG torch was used and process parameters such as the gas flow and the tapering length/speed/frequency were optimized. The power transmission efficiency of the combiner was larger than 93% in all ports at the handling power of 100 W.

Tunable OTDR (TOTDR) based on direct modulation of self-injection locked RSOA for line monitoring of WDM-PON

We demonstrate a TOTDR based on direct modulation of self-injection locked RSOA for line monitoring of WDM-PON. The proposed TOTDR has 30 nm tuning range and 50 m resolution.

Tunable OTDR using self-locked RSOA for line monitoring of WDM-PON

Tunable OTDR based on self-locked RSOA for in-line monitoring of WDM-PON is proposed and demonstrated. The characteristics of self-locked RSOA were experimentally studied. The tunable OTDR was successfully demonstrated for a range of 25 nm, having a dynamic range of about 15 dB. Under in-service state of 2.5-Gb/s data, the power penalty induced by the line monitoring channel was about 0.1 dB at BER of 10-9. The proposed tunable OTDR is cost-effective and useful to monitor the status of WDM-PON.