Je Soo Ko

Optical clock recovery scheme for a high bit rate nonreturn-to-zero signal using fiber Bragg grating filters

For optical clock recovery of nonreturn-to-zero (NRZ) signals more than 40 Gb/s, we propose and experimentally demonstrate a simple clock recovery scheme using beat processing. Through the proposed scheme, we square the adjustment range of the variable optical attenuator (VOA) and achieved an enhanced clock-to-noise ratio (CNR) of more than 15 dB in the experiment, compared to a system without the proposed scheme.

NRZ-to-PRZ Conversion of a 10 Gb/s NRZ Signal by Tailoring the Optical Spectrum

We experimentally demonstrate a simple NRZ-to-PRZ conversion through tailoring the optical spectrum using a FBG filter. In experiment, frequency components passing through the FBG filter showed the PRZ pattern.

16×42.8 Gb/s unrepeated transmission over 200 km of standard single-mode fiber by using an electroabsorption modulator

We demonstrate an unrepeated transmission of 16×42.8 Gb/s over 200 km of a standard single-mode fiber (SMF) using a commercially available electroabsorption modulator (EAM). In an optical link, a distributed fiber Raman amplifier, a remote pumped optical amplifier, an optical booster amplifier, and an optical preamplifier are used for signal amplification. After transmission of 200 km, Q-values of the 16 channels range from 11.5 to 12.3 dB. The experimental result reveals that the EAM can be used for STM-256 (OC-768)-based long as well as short reach applications.

40GHz clock generation using clock component enhancement modulation and band pass filtering

The applicability of clock and data superposed modulation for clock component enhancement In 40Gb/s NRZ signal was experimentally demonstrated. From this slgoal 40GHz clock was easily extracted by hand-pass filtering. The result showed 0.5dB power penalty Improvement with respect to a conventional clock extraction method of using noo-linear circuits. It is also pointed out that relative amplitude and phase of the two superposed modulation signals are very Important for good BER characteristics.

Optical signal-to-noise ratio monitoring based on tracking of principal states ofpolarization

Feature Issue on Optical Performance Monitoring (OPM). We propose and demonstrate a simple method for monitoring optical signal-to-noise ratio (OSNR) of each channel in wavelength-division multiplexing networks based on tracking of principal states of polarization (PSP) and scrambling at the transmitter part. This technique reduces measurement error caused by the effect of PMD, which limits the performance of a previous polarization extinction method. PSP tracking uses bandpass-filtered power at clock frequency for a non-return-to-zero signal as a feedback signal to separate the two PSPs by aligning them to the axes of a polarization beam splitter (PBS). The scrambling makes it possible to extinguish the polarization of an optical signal from one output of the PBS and to provide maximum and minimum optical powers, thus enabling us to obtain OSNR regardless of the effect of PMD. In a transmission experiment over a 400-km single-mode fiber-dispersion-compensating fiber (SMF+DCF) link, the results showed that the difference between the OSNRs measured by use of the proposed method and by an optical spectrum analyzer (OSA) was less than 1.0 dB.

Investigation of a method to use a single shared delayed interferometer for receiving optical differential phase shift keying wavelength-division multiplexing signals

A receiver configuration using a single shared delay interferometer (DI) for optical differential phase-shift keying (DPSK) wavelength-division multiplexing (WDM) signals is demonstrated and investigated in 40-Gbit/s signal transmission. Experiment comparison between the proposed and conventional configurations is performed for signal performance and a 3-dB bandwidth of the receiver sensitivity penalty. The wavelength mismatch of optical components used and the effects are measured to investigate the wavelength dependency of the proposed configuration. This demonstrates that there is no difference in performance between the two configurations and between WDM channels in the proposed configuration. Thus, it is suggested that the proposed configuration using a single DI can be applied for 20 WDM channels between 1531.116 and 1561.419 nm, with 200-GHz channel spacing in a bandwidth of >30 nm, for receiving DPSK signals.

Transient power suppression in Raman amplifier with multi-wavelength pumping upon channel add-drop

Fast gain control method in Raman amplifier with multi-wavelength pumping scheme is presented. Transient power excursion is controlled within 0.2 dB at 6 dB channel add-drop in C-band Raman amplifier with two wavelength pumps

Novel type of PMD compensator based on separation of PSP and DGD controls

We propose and experimentally demonstrate a novel type of PMD (polarization mode dispersion) compensator (PMDC) that separates PSP (principal states of polarization) control from DGD (differential group delay) control with an automatically adaptive 40 Gb/s PMDC module manufactured on PCBs. The results showed that this method provided a very fast response time of /spl sim/2 /spl mu/s to PSP change and allowed a reduction in compensation time compared with the conventional method of alternately controlling PSP and DGD.

Impact of Electrical Band-Limitation on Transmission Performance of CSRZ and CSRZ-DPSK Modulation Formats for High Spectral Efficiency DWDM Systems

To prevent breakage of flexible conductors of a flat cable soldered to the printed circuit on a printed circuit board, a strain relief member is provided through which the conductors pass, prior to passing through the board to the printed circuit. The relief member has a longitudinal groove extending part way through the member and apertures extending from the bottom of the groove to the bottom surface of the relief member. Bared conductors pass through the apertures and through the board to be soldered to the printed circuit. The end of the insulated portion of the cable is positioned in the groove. The relief member is held in firm contact with the printed circuit board during soldering. Use of the relief member moves the flexing position of the cable away from the end of the wicking of the solder up the conductors during soldering.