Kazuhiro Goi

Silicon Mach-Zehnder modulator of extinction ratio beyond 10 dB at 10.0-12.5 Gbps

Silicon Mach-Zehnder modulators with reduced series resistance in lateral PN junction rib-waveguide phase shifters are characterized in eye-diagram measurements. The modulators reveal extinction ratio beyond 10dB at 10.0–12.5Gbps, approaching lithium-niobate modulators in high-speed performance.

DQPSK/QPSK modulation at 40–60 Gb/s using low-loss nested silicon Mach-Zehnder modulator

44.6-Gb/s DQPSK and 50-to-64 Gb/s QPSK modulation are demonstrated using low-loss nested Silicon MZ modulator with fiber-to-fiber loss of 10dB. Dispersion tolerance of +/-80 ps/nm is observed in the DQPSK transmission.

Low-loss high-speed silicon IQ modulator for QPSK/DQPSK in C and L bands

A low-loss high-speed silicon in-phase (I) quadrature (Q) modulator is designed, fabricated and characterized. The fabricated IQ modulator has a low passive optical loss of 9 dB in C and L bands. Using the modulator, differential quadrature phase-shift keying (DQPSK) transmission at 44.6 Gb/s with differential detection is confirmed with an optical signal-to-noise ratio (OSNR) of 16.3 dB for a bit error rate (BER) of 10(-3) and a dispersion tolerance of -96 to 107 ps/nm. Moreover, in digital coherent detection, quadrature phase-shift keying (QPSK) up to 64 Gb/s are achieved with an OSNR of 11.6-11.8 dB for a BER of 10(-2) at 1530, 1550, and 1610 nm.

128-Gb/s DP-QPSK using low-loss monolithic silicon IQ modulator integrated with partial-rib polarization rotator

128-Gb/s DP-QPSK is realized using silicon IQ modulator monolithically integrated with partial-rib polarization rotator under +/-3.25-Vpp push-pull RF driving condition. Low passive insertion loss 12-13 dB is achieved over C band.

Low-loss high-speed silicon Mach-Zehnder modulator for optical-fiber telecommunications

Low-loss high-speed traveling-wave silicon Mach-Zehnder modulator with reduced series resistance is studied in microwave and optical measurements. Microwave impedance and propagation loss under reverse bias are characterized by S-parameter measurements. Resonant loss due to series inductance-resistance-capacitance coupling limits microwave performances of the traveling-wave modulator. High-speed optical performances are characterized, based on eyediagram measurements in on-off keying at 10-32 Gb/s and constellation and eye-diagram measurements in differential phase-shift keying at 20 Gb/s. Dispersion tolerance in error-free transmission in 10-Gb/s on-off keying and 20-Gb/s differential phase-shift keying is obtained as +/-950 ps/nm and +/-220 ps/nm, respectively by path-penalty measurements. Transmission performance in 10-Gbps on-off keying is comparable with lithium niobate Mach-Zehnder modulator.

20-Gbps BPSK silicon Mach-Zehnder modulator with excellent chirp-free performance

20-Gbps NRZ-BPSK operation using silicon MZM is demonstrated with excellent chirp-free performance. Obtained α-parameter of the modulator is -0.05, and the low chirp modulation under push-pull operation is observed.

High-ON/OFF-contrast 10-Gb/s silicon Mach-zehnder modulator in high-speed low-loss package

10-Gb/s silicon-based Mach-Zehnder modulator is packaged and characterized. The I/O sections of the modulator chip are located at longer-facet sides using bends waveguides for enhancing modulation bandwidth by using short straight configuration of traveling-wave electrodes. Low-insertion loss and high-return-loss optical coupling structure between input/output lenses and the modulator chip is achieved with optical coupling, where both of chip facets and inverted-taper mode-field-convertors are angled with respect to incident light beam. 3-dB electro-optic bandwidth is as high as 12.0-GHz and optical insertion loss is 9-dB or lower. High-contrast eye diagram with an extinction ratio of 13.8-dB is obtained.

128Gb/s DP-QPSK silicon modulator module integrated with driver amplifiers

We report a compact dual-polarization quadrature phase-shift keying (DP-QPSK) modulator module accommodating a silicon DP-QPSK modulator chip and driver amplifiers in a package in a dimension of 15×35×4.5 mm3. 128-Gb/s DP-QPSK transmission in 1000-km single-mode fibre is confirmed with the compact modulator module.

Low-voltage silicon Mach-Zehnder modulator operating at high temperatures without thermo-electric cooling

We demonstrate 10-Gb/s high-on/off-contrast modulation of a carrier-depletion silicon Mach-Zehnder modulator having 3-mm rib-waveguide phase shifter driven with RF 3.6 VPP or lower at temperatures up to 130°C without thermo-electric cooling.

20-Gb/s DPSK transmission with 550-ps/nm dispersion tolerance using silicon Mach-Zehnder modulator

Transmission measurements are performed using a low-loss zero-chirp silicon Mach-Zehnder modulator in 20-Gb/s DPSK with accumulated dispersion of -347 ps/nm to +334 ps/nm. Dispersion tolerance for 2-dB path penalty is as high as 550 ps/nm.