Kuniaki Motoshima

NRZ-OOK-to-RZ-BPSK modulation-format conversion using SOA-MZI wavelength converter

A novel all-optical modulation-format conversion from nonreturn-to-zero on-off keying (NRZ-OOK) to return-to-zero binary phase-shift keying (RZ-BPSK) is proposed. A Mach-Zehnder interferometric (MZI) wavelength converter consisting of integrated semiconductor optical amplifiers (SOAs) is utilized to implement the proposed format conversion. Error-free operation at a bit rate of 10.7 Gb/s is experimentally demonstrated in order to show the feasibility of the proposed scheme. The received sensitivity of the converted signal is improved by 2.9 dB compared with a back-to-back NRZ-OOK signal at BER=10 -9. In addition, a reasonable dispersion tolerance of the converted signal up to plusmn500 ps/nm is observed. The numerical simulation based upon the carrier-rate equation verifies the experimental results

Polarization-Insensitive Monolithic 40-Gbps SOA–MZI Wavelength Converter With Narrow Active Waveguides

A polarization-insensitive monolithic 40-Gbps semiconductor optical amplifier (SOA)-Mach-Zehnder interferometer wavelength converter has been developed. Based on the photon-electron rate equation, we optimized the dimensions of the waveguide structure to maximize the field confinement in the active layer. An InGaAsP active layer with narrow SOA waveguide effectively enables polarization-insensitive high-speed wavelength conversion. High-precision wafer processing technique enabled the fabrication of submicrometer-wide active waveguides with low current leakage. Input waveguide arrays were fabricated at intervals of 25 mum and mounted in a module with two-lens aspherical lens optics. The 40-Gbps nonreturn-to-zero wavelength conversion experiment demonstrates a clear eye opening over full C-band operation

A Burst-Mode Bit-Synchronization IC With Large Tolerance for Pulse-Width Distortion for Gigabit Ethernet PON

A burst-mode bit-synchronization IC applied to the upstream transmission in a gigabit Ethernet passive optical network (PON) was experimentally verified to have a large tolerance for pulse-width distortion within plusmn0.66 UI. The extra tolerance of 0.22 UI over the IEEE 802.3ah specification can be assigned to additional distortion generated at an optical receiver incorporated into an optical line terminal. Such a large tolerance was attained by precisely generated eight-phase clocks based on theoretical analyses of distortion tolerance considering real circuit parameters and by an enhanced data selector incorporating a pulse-width detector to monitor the pulse-widths of isolated bits. The IC developed includes a burst into series transformer to permit connection to commercially available PON LSI developed for serial data transmission in Ethernet systems. The theoretical study into the numbers of allowable bit errors and consecutive pattern matches in byte synchronization established following two conditions: 1) allowable error more than one bit in synchronization pattern with 10-bit length was required to hold the synchronization loss rate to less than a few times per year and 2) consecutive pattern matching more than twice was required to hold the synchronization error rate to less than a few times per year

Polarization-Insensitive SOA-MZI Monolithic All-Optical Wavelength Converter for Full C-band 40Gbps-NRZ Operation

Bulk InGaAsP SOA-MZI monolithic wavelength converter has been optimized for fast gain recovery and clear eye openings at 40Gbps-NRZ format. Full C-band operation and polarization-insensitive operation were achieved at 40Gbps-NRZ.

Label-based path switching and error-free forwarding in a prototype optical burst switching node using a fast 4/spl times/4 optical switch and shared wavelength conversion

We demonstrate for the first time optical burst switching using fast and scalable EO switch and a shared wavelength converter for contention resolution. 3.5 /spl mu/m label routing of variable-length bursts and error-free operation was achieved at 10 Gbps payload.

Optical Burst Switching Router With 40-,10-Gb/s Bit-Rate Transparent Contention Resolution

We report a bit-rate transparent optical burst switching (OBS) router prototype using a fast 5 times 5 PLZT [(Pb,La)(Zr,Ti)O3 ] optical matrix switch. Dynamic switching in a two-wavelength, 2 times 2 OBS switch is demonstrated. Contention resolution using a tunable Mach-Zehnder interferometer wavelength converter for both 40- and 10-Gb/s bursts is demonstrated for the first time. Error-free operation was achieved for both bit rates under the same settings, as required in autonomous networks

All-optical format conversion from NRZ-OOK to RZ-BPSK using SOA-MZI wavelength converter

We propose a novel all-optical NRZ-OOK/RZ-BPSK format conversion scheme, using cross-phase modulation effects in a MZI-SOA. We experimentally demonstrate error free conversion at 10.7 Gb/s with a negative power penalty of 2.9 dB

Efficient Pump Depolarizer Analysis for Distributed Raman Amplifier With Low Polarization Dependence of Gain

This paper discusses a method of reducing the polarization dependence of gain (PDG) of a distributed Raman amplifier. Reducing its PDG is important for a Raman amplifier because it is higher than that of an erbium-doped fiber amplifier and can degrade transmission performance. Raman PDG is determined primarily by two factors, namely 1) polarization-mode dispersion (PMD) of the transmission fiber and 2) degree of polarization (DOP) of the pump source. The authors propose a simple analytical model to show the required pump light DOP for a given transmission fibers PMD and the allowable PDG. For instance, a low pump DOP of 5% produces a low PDG of 0.2 dB under typical fiber PMD conditions, in which the analytical model agrees well with experiment. Subsequently, to achieve the required DOP, the pump source configuration is investigated in detail. The authors used one length of polarization-maintaining fiber (PMF) as an efficient pump depolarizer and evaluated its performance for various pump light spectra. It has been shown that the DOP following the depolarizer is determined simply by Fourier transformation of the pump light spectrum. The analysis in this paper has led to the important result that a Fabry-Perot laser diode pump with a short piece of PMF is effective in achieving a low pump DOP due to its multimode spectrum when the length of the PMF is properly adjusted for the longitudinal-mode spacing frequency. It has been verified that a Raman amplifiers PDG can be reduced by the proposed efficient depolarizer sufficiently for a PDG-reduced Raman amplifier repeater to be applicable to long-haul transmission systems

Hybrid integration of waveguide photodiode and preamplifier IC using Au stud bump

The authors developed an InP photodiode (PD) module integrated with an InP HBT preamplifier IC by using an Au stud bump. Theoretical analysis shows that the deviation of the group delay linearly increases in the inductance between the PD and IC. The flip-chip bonding based on the Au stud bump effectively reduces the inductance without sacrificing the individual device performance and reliability. Experimental results show that this technique is suitable for the receiver modules designed for applications with a bandwidth greater than 40 Gb/s

Enhanced queue status reporting scheme on PON

Feature Issue on Passive Optical Network Architectures and TechnologiesIn the passive optical network (PON) system, the optical line terminal (OLT) assigns bandwidth to each optical network unit (ONU) in accordance with the traffic condition at an ONU. The OLT needs to predict the remote ONUs required bandwidth. We give consideration about the error margin in the bandwidth prediction, and point out a problem in the future high-bit-rate PON and propose an enhanced queue status reporting method.