Kalpendu Shastri

Ultra-Low-Power Single-Polarization QAM-16 Generation Without DAC Using a CMOS Photonics Based Segmented Modulator

Long-haul communication systems are requiring more and more spectral efficiency as data rates increase. QAM-16 is a promising candidate for each wavelength in a Wavelength-Division Multiplexed (WDM) system, providing double the spectral efficiency of Quadrature Phase-Shift Keying (QPSK) and four times the spectral efficiency of traditional On-Off Keying (OOK). However, generation of QAM-16 signals can be complex, expensive, and power-hungry when electrical Digital-to-Analog Converters (DACs) are required. We have developed a QAM-16 modulator that precludes the use of an electrical DAC while simultaneously keeping the optical architectural complexity similar to that of a traditional In-phase/Quadrature (IQ) modulator. Using this modulator, we experimentally demonstrate single-polarization, back-to-back transmission, and homodyne detection of QAM-16 signals at rates up to 28.125 Gsymbols/s, resulting in single-polarization system per-wavelength bit rates up to 112.5 Gb/s. This would translate to dual-polarization system per-wavelength bit rates up to 225 Gb/s. This is done using a segmented modulator built on an ultra-low-power CMOS Photonics platform, allowing the modulator and drivers to consume less than 1 W of power.

Silicon Photonic Modulator Based on a MOS-Capacitor and a CMOS Driver

We describe a silicon photonic optical modulator based on a MOS-capacitor and a low power 1V CMOS inverter-based driver IC. In an MZI configuration, this efficient modulator and driver IC combination can produce a 9dB extinction ratio at 28 Gbps, at a wavelength of 1310nm.

Experimental demonstration of ultra-low-power single polarization 56 Gb/s QAM-16 generation without DAC using CMOS photonics

We experimentally demonstrate back-to-back transmission of QAM-16 at 56 Gb/s over a single polarization, representing a dual polarization system link of 112 Gb/s, without using an electrical DAC, on a CMOS Photonics platform.