Hae Geun Kim

Pulse-amplitude equalization of rational harmonic mode-locked fiber laser using a semiconductor optical amplifier loop mirror

Abstract The authors demonstrate, for the first time to our knowledge, the amplitude equalization of high-repetition-rate pulses generated from a rational harmonic mode-locked fiber laser using a semiconductor optical amplifier loop mirror. Here, the loop mirror acts as an all-optical pulse-amplitude equalizer. Optimized parameters of the loop mirror for pulse-amplitude equalization were determined by a simulation. The pulse-amplitude equalization was successfully demonstrated up to the thirteenth rational harmonic mode-locked pulse train (∼14 GHz).

A simple packet-level clock extraction scheme using a terahertz optical asymmetric demultiplexer

The authors experimentally demonstrate simple packet-level clock extraction using a modified terahertz optical asymmetric demultiplexer without wavelength-division-multiplexed couplers in the loop mirror. For a 10-Gb/s optical packet composed of identical pulses, we have obtained more than 10-dB contrast ratio between the packet-level clock pulse and the other pulses.

Wavelength dependent performance of a wavelength converter based on cross-gain modulation and birefringence of a semiconductor optical amplifier

By exploiting pump-induced birefringence in addition to cross-gain modulation, we have obtained improved extinction ratio and reduced optical power penalties for a wavelength converter using a semiconductor optical amplifier. In the probe beam wavelength range of 1528-1566 nm, while extinction ratios and power penalties of a conventional wavelength converter are found to be 4.5-9.2 dB and -0.5-2.1 dB, those of the proposed converter are 6.6-10 dB and -0.7-1.0 dB, respectively. The proposed converter shows better performance for all wavelengths in the range examined for both extinction ratio and power penalty. Especially, more improvements have been obtained in the longer wavelength.

Polarization-independent all-optical clock division using a semiconductor optical amplifier/grating filter switch

We propose and experimentally demonstrate, for the first time to our knowledge, polarization-independent all-optical clock division (CD) of an optical pulse train at 2.88 GHz. This is achieved using a semiconductor-optical amplifier (SOA)/grating-filter switch, where the SOA acts as a spectral shifter by a self-phase modulation (SPM) and the grating filter acts as a spectral shutter. The proposed scheme is very insensitive to the polarization of input pulses and requires very low switching energy (/spl sim/102 fJ). After the all-optical CD operation, we have obtained the output pulse train at 1.44 GHz, which is half the input repetition rate, with high extinction ratio (>20 dB).

Efficient 3N-optical pulse generator based on multistage fiber loop mirror

Abstract We propose a novel power efficient multistage fiber loop mirror pulse generator (FLMPG) scheme which transforms a single optical pulse into 3N optical pulses. While a conventional parallel scheme loses 2/3 of total power to convert an optical pulse into three optical pulses, our scheme loses only 2/5 of total power, improving the efficiency 1.8 times. The 3N optical pulse generator combined with the well-known ladder scheme 2N optical pulse generator can provide more flexibility for generating an arbitrary number of optical pulses. Two-stage and three-stage fiber loop mirror pulse generators are analyzed theoretically by the Jones matrix method. In addition, we have successfully realized two-stage and three-stage FLMPGs which generate three and nine pulses out of one pulse, respectively.