Kaoru Higuma

25.6-Tb/s WDM Transmission of Polarization-Multiplexed RZ-DQPSK Signals

We demonstrate record 25.6-Tb/s transmission over 240 km using 160 WDM channels on a 50-GHz grid in the C+L bands. Each channel contains two polarization-multiplexed 85.4-Gb/s RZ-DQPSK signals, yielding a spectral efficiency of 3.2b/s/Hz in each band.

100-Gb/s DQPSK Transmission: From Laboratory Experiments to Field Trials

We discuss the generation, detection, and long-haul transmission of single-polarization differential quadrature phase shift keying (DQPSK) signals at a line rate of 53.5 Gbaud to support a net information bit rate of 100 Gb/s. In the laboratory, we demonstrate 10-channel wavelength-division multiplexed (WDM) point-to-point transmission over 2000 km on a 150-GHz WDM grid, and 1200-km optically routed networking including 6 reconfigurable optical add/drop multiplexers (ROADMs) on a 100-GHz grid. We then report transmission over the commercial, 50-GHz spaced long-haul optical transport platform LambdaXtremereg. In a straight-line laboratory testbed, we demonstrate single-channel 700-km transmission, including an intermediate ROADM. On a field-deployed, live traffic bearing Verizon installation between Tampa and Miami, Florida, we achieve 500-km transmission, with no changes to the commercial system hardware or software and with 6 dB system margin. On the same operational system, we finally demonstrate 100-Gb/s DQPSK encoding on a field-programmable gate array (FPGA) and the transmission of real-time video traffic.

High-speed optical DQPSK and FSK modulation using integrated Mach-Zehnder interferometers

We investigated an integrated optical modulator consisting of two Mach-Zehnder interferometers. The modulator can generate optical signals in various types of modulation formats, which have advantages for long-haul transmission, optical labeling, etc. By using a fabricated versatile optical modulator having traveling-wave electrodes designed for high-speed signals, we demonstrated generation of optical 40Gb/s frequency-shift-keying signals, which can be demodulated by an optical filter. 80Gb/s optical differential quadrature-shift-keying modulation was also demonstrated, where 40Gb/s in-phase and quadrature data were, simultaneously, fed to the modulator.

Transmission of 107-Gb/s DQPSK over Verizon 504-km Commercial LambdaXtreme® Transport System

A 107-Gb/s field trial was conducted on a traffic carrying long-haul LambdaXtreme® transport platform over an active 504-km Verizon route in Florida thus proving upgradeability to 100 G of the Alcatel-Lucent 50-GHz spaced ULH DWDM system.

70 dB extinction-ratio LiNbO/sub 3/ optical intensity modulator for two-tone lightwave generation

We demonstrated high extinction ratio intensity modulation for two-tone lightwave generation, by using an integrated Mach-Zehnder modulator with active trimmers which can compensate imbalance in the modulator due to fabrication errors. The extinction ratio was larger than 70 dB

Electrically tunable delay line using an optical single-side-band modulator

The authors propose a tunable delay line using an optical single-side-band modulator, a fiber Bragg grating and an optical fiber loop. The number of times light circulates in the loop can be controlled by the electric signal fed to the modulator. Packets of any lengths can go through the proposed delay line without any collisions, even if the length of the packet is larger than that of the delay loop.

Tunable lithium niobate waveguide loop

A novel, compact, and tunable lithium niobate (LN) planar waveguide loop structure composed of two Y junction reflectors is proposed for optical and radio frequency signal processing applications. The preliminary device shows a high quality factor of 6.5/spl times/10/sup 4/, due to the low propagation loss of the titanium-diffused LN waveguide. The tunability of the loop by electric field is estimated.

120-Gb/s NRZ-DQPSK signal generation by a thin-lithium-niobate-substrate modulator

A high-speed DQPSK optical modulator is fabricated with a thin lithium niobate substrate. Decrease in the propagation loss of electrodes and a low half-wave voltage, which can be realized by fabrication of a ridge-type optical waveguide structure, can help achieve 120-Gb/s (60-Gbaud) NRZ-DQPSK modulation with full electrical-time-division-multiplexing technique.

107-Gb/s Transmission over 700 km and One Intermediate ROADM using LambdaXtreme® Transport System

We demonstrate 107-Gb/s single-channel transmission over the commercial all-Raman LambdaXtreme® transport system. Both RZ-DQPSK and NRZ-DQPSK formats were transmitted over 700 km with one reconfigurable optical add drop multiplexer (ROADM) node at 500 km.

Double-stub structure for resonant-type optical modulators using 20-μm-thick electrode

We propose a resonant-type LiNbO/sub 3/ optical modulator with low halfwave voltage. We optimize the phase constant of the electric wave with thick electrodes to reduce the halfwave voltage. The halfwave voltage of the fabricated modulator with 20-/spl mu/m-thick electrodes is 5.8 V at 10.6 GHz.