Sae-Kyoung Kang

Electrochemical and structural properties of HT-LiCoO2 and LT-LiCoO2 prepared by the citrate sol-gel method

Abstract LT-LiCoO 2 has a slightly modified structure but significantly different electrochemical properties compared to LiCoO 2 prepared at high temperature. In this study, the structure and electrochemical properties of LT-LiCoO 2 have been evaluated using Raman spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), and electrochemical methods. According to the structural analysis, LT-LiCoO 2 has an intermediate structure between a layered and a spinel structure. The first discharge capacity of LT-LiCoO 2 is ∼80 mAh/g (100 μA/cm 2 ).

Weak avalanche discrimination for gated-mode single-photon avalanche photodiodes

The after-pulsing effect is a common problem that needs to be overcome for high-speed single-photon detection based on gated-mode single-photon avalanche photodiodes (SPADs). This paper presents a simple and practical method for suppression of the after-pulsing probability using an auxiliary signal to discriminate quite weak avalanches. The detection efficiency and after-pulse probability of an InGaAs/InP SPAD are investigated with a 10 MHz gating for conventional and proposed methods, and a sharp decrease of after-pulse probability is demonstrated with the application of the proposed method. At a gating frequency of 100 MHz, a detection efficiency of 10.4% is achieved with an after-pulse probability of 5.6% without dead time.

Field Trial of 112 Gb/s Dual-Carrier DQPSK Channel Upgrade in Installed 516 km of Fiber Link and ROADM

A field trial of 100GE signal transmission using dual-carrier differential quadrature phase shift keying (DC-DQPSK) based optical transceiver is demonstrated for 100 Gb/s metro area network. Neither high-end ADC/DSP nor fast optical polarization tracking is required in the DC-DQPSK based optical transceiver, which results in low electrical power consumption of ~ 35 W. The measured OSNR sensitivity of DC-DQPSK optical transceiver at the BER of 10- 3 is 18.3 dB. After the transmission through 516 km of installed fiber and ROADM, an error-free transmission of 100GE signal over 106 hours with OTU4 framer and forward error correction (FEC) decoding proves feasibility of DC-DQPSK optical transceiver for 100G metro network applications.

Analysis of dimensional tolerance for an optical demultiplexer of a highly alignment tolerant 4 × 25 Gb/s ROSA module

We have developed a 4 × 25 Gb/s ROSA (receiver optical sub-assembly) module for 100G Ethernet optical transceiver. This ROSA module has very large alignment tolerance of more than ± 250 µm between the optical DMUX (demultiplexer) and four photodiodes, for the reason it has the advantage of being easily assembled. The large alignment tolerance can be attributed to the dimensional tolerant optical DMUX, which is composed of four thin film filters attached to a parallelogram-shaped optic block. Since it is important to define the fabrication specifications for the dimension of the optic block, we analyze dimensional tolerance for the optic block using three-dimensional simulation. This parallelogram-shaped optical DMUX permits length tolerance of ± 300 µm and angular tolerance of ± 0.1°. The fabricated optical DMUX is estimated to have the angular error of less than 0.09°.

A cost-effective and compact 28-Gb/s ROSA module using a novel TO-CAN package

In this paper, we present the implemented a 28-Gb/s a receiver optical sub-assembly (ROSA) module by employing the proposed TO-CAN package and flexible printed circuit board (FPCB). We have proposed that signal path between the TO-CAN package and the FPCB have straight-line path and the FPCB incorporate signal line with open stub in order to alleviate signal distortion due to impedance mismatch. The 3-dB optical-to-electrical (O-E) bandwidth and receiver sensitivity of the ROSA module were measured as over 17 GHz and below -14 dBm at extinction ratio of 12 dB and bit error rate of 10-12.

Real-time demonstration of QoS guaranteed 25-Gb/s PON prototype with Ethernet-PON MAC/PHY and cost-effective APD receivers for 100-Gb/s access networks.

We demonstrate a real-time 25-Gb/s PON prototype with ethernet-PON MAC/PHY, O-band transmitter, and cost-effective APD receivers. With applying parasitic inductance and capacitance reduction, the frequency response of 25-Gb/s APD ROSA with TO46-pacakge is improved to support high receiver sensitivity around -25 dBm at the BER of 10-3. The 30 dB power budget of 25 Gb/s downstream is achieved at the BER of 10-3. With long-term ethernet packet transmission, 25 Gigabit and 10 Gigabit ethernet traffics are successfully transmitted through the 20-km SMF over 14 hours observation window. Furthermore, QoS and bandwidth re-assignment function of the 25-Gb/s PON prototype are successfully demonstrated with respect to residential, business and mobile backhaul services in ONUs.

A compact 4 × 10-Gb/s CWDM ROSA module for 40G Ethernet optical transceiver

For 40GBASE-LR4 application, we designed and fabricated a 4 × 10-Gb/s CWDM receiver optical sub-assembly (ROSA) module integrated with a collimator, an optical demultiplexer (DMUX), and a TO part. The TO part includes focusing lenses, photodiodes (PDs), transimpedance amplifiers (TIAs), and high-speed TO header. The optical DMUX has insertion loss of −1.2 dB and adjacent crosstalk of less than 30 dB. The focusing lenses in the TO part show aspherical lens shape and provide high alignment tolerance of more than ±300µm for single and array lens types. Especially, electrical crosstalk was less than −40 dB and optical crosstalk was negligible in the TO part. The developed 4 × 10-Gb/s ROSA module shows 3-dB OE bandwidth of about 9.1 GHz GHz and an average receiver sensitivity of −17.7 dBm for four channels at extinction ratio of 6 dB and bit error rate of 10−12.

Silicon AWG as a tunable filter in tunable ONU for TWDM-PON application

We have proposed to use a silicon AWG as a tunable filter for TWDM-PON ONU. Feasibility of the proposed ONU configuration was experimentally demonstrated using the cyclic and the thermally tuned properties of silicon AWG.

Simplified crosstalk floor representation for a design parameter of silicon AWG

The relation between the width variation and the crosstalk floor is derived assuming the fabrication imperfection dominates the phase error. The calculated crosstalk shows linear dependence with the measured crosstalk floor. This reveals the calculated crosstalk floor would be a useful design parameter of AWG to predict the limit of channel isolation.

Highly alignment tolerant and high-sensitivity 100Gb/s (4 × 25Gb/s) APD-ROSA with a thin-film filter-based de-multiplexer

We investigate and demonstrate a 100-Gb/s (4x25-Gb/s) receiver optical sub-assembly (ROSA) based on avalanche photodiodes and a thin-film filter-based de-multiplexer. The overall alignment tolerances of the ROSA are relaxed to have larger than ± 25 μm by improving optical coupling structure. The receiver sensitivity of each lane is also measured to be less than -22.2 dBm, a record minimum to our knowledge, at the bit error ratio of 10-12 for 25.78-Gb/s NRZ signal.