Silicon Mach-Zehnder modulator of extinction ratio beyond 10 dB at 100-125 Gbps

Abstract

Silicon Mach-Zehnder modulators with reduced series resistance in lateral PN junction rib-waveguide phase shifters for enhanced high-speed response are fabricated and characterized. Extinction ratio higher than 10 dB is obtained at 10.3-11.7 Gbps with mask margins of 27% (10.3-Gbps 10GBE), 16% (10.7-Gbps STM-64/OC-192) and 10% (11.3-Gbps STM-64/OC-192) in eye-diagram measurements incorporating mask tests using a RF cut-off filter. In unfiltered eye-diagram measurements without mask tests, extinction ratio higher than 13 dB is obtained at 10.0-12.5 Gbps. The silicon modulators reveal high-speed performance comparable with that of lithium-niobate modulators in high-speed optical fiber telecommunications.

Fundamental characteristics and high-speed applications of carrier-depletion silicon Mach-Zehnder modulators

“…Vertical boundary of PN junction is positioned in the middle of the rib. The dimensions were determined with respect to high modulation speed and low optical loss [16].…”

“…Extensive study has been devoted to traveling-wave lateral PN-junction carrier-depletion Si MZ modulators in major modulation formats in OOK and PSK [6,7,12,13,16,23,24,25,26,27]. Some of the results reported for high-speed performances in NRZ OOK are listed in Table I.…”

Silicon Mach-Zehnder modulator using low-loss phase shifter with bottom PN junction formed by restricted-depth doping

“…For comparison, we also fabricated a waveguide using the whole-area-PN structure [8,14]. As mentioned in section 2.1, the whole-area-PN structure has a doped region from the top of the rib to the bottom and the same dimensions as the proposed structure.…”

“…For long-distance optical communications, signal qualities such as extinction ratio (ER) and chirp characteristics are important. The silicon MZM with a reduced series resistance is able to provide a high ER over 10 dB at 10-12.5 Gbps [8] and achieved long-distance transmission up to 80 km [9]. For a modulator to see commercial use, it must have low insertion loss in addition to the high-quality signal.…”

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

“…We have confirmed extinction ratio higher than 13 dB in 10-Gb/s OOK and Q-factor as high as 20 dB in 20-Gb/s differential PSK (DPSK) with total optical loss as low as ~11 dB using a Si MZ modulator with reduced series resistance. 4,5 The Si MZ modulator is comparable with LN MZ modulators in the high-speed performance in OOK and DPSK. Further reduction in total optical loss of the Si MZ modulator is desired to achieve modulator performances fully comparable with those of LN MZ modulators.…”