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Development of programmable photonic devices for future flexible optical networks is ongoing. To this end, an innovative, multi-format QAM transmitter design is presented. It comprises a segmented-electrode InP IQ-MZM to be fabricated in InP, which can be directly driven by low-power CMOS logic. Arbitrary optical QAM format generation is made possible using only binary electrical signals, without the need for high-performance DACs and high-swing linear drivers. The concept enables a host of Tx-side DSP functionality, including the spectral shaping needed for Nyquist-WDM system concepts. In addition, we report on the development of a optical channel MUX/DEMUX, based on arrays of microresonator filters with reconfigurable bandwidths and center wavelengths. The device is intended for operation with multi-format flexible transceivers, enabling Dense (D)WDM superchannel aggregation and arbitrary spectral slicing in the context of a flexible grid environment. Keywords: coherent optical systems, flexible optical networks, flexible transceiver, MUX/DEMUX INTRODUCTIONThe coherent revolution that has shaped modern telecom networks began roughly 10 years ago, when it became apparent that state-of-the-art CMOS technology could deliver cost-and energy-efficient real-time digital signal processing (DSP) for demodulation and impairment mitigation at the Gbaud-rates required by telecom optical systems. After more than a decade of hibernation, coherent intradyne detection suddenly re-emerged as a prominent topic of research in the field of telecoms, promising a significant boost in both capacity and reach over legacy systems based on simple modulation formats and direct detection. It was only a matter of time before optical transport network (OTN) 100G technology became standardized, with subsequent commercial adoption arriving in 2010. Today's core optical networks are starting to be dominated by 100G optical channels, based on Dual-Polarization (DP) Quadrature Phase Shift Keying (QPSK) at 28/32 Gbaud, definitively proving the commercial viability of the technology.Scaling next-generation optical networks to higher capacities will necessitate further innovations: The insatiable demand for bandwidth is stretching physical layer capacity and dictating the migration towards flexible optical network architectures. Moreover the changing nature of data traffic, which is becoming more volatile and unpredictable, has prompted system designers to think about introducing flexibility in both modulation format and elasticity in spectrum utilization, by abandoning the fixed grid and allowing dynamic adjustment of throughput and wavelength allocation. The foundations for this fundamental paradigm shift were laid by the ITU-T as early as 2012: Recommendation G.694.1 [1] defines the Flexible Dense Wavelength Division Multiplexing (DWDM) grid, designed to accommodate optical lightpaths with mixed-bitrates and modulation formats, in slots that can be adjusted to any spectral width with 12.5 GHz granularity. Several elastic optical networ...

Abstract-Segmented Mach-Zehnder modulators are a promising solution to generate complex modulation schemes in the migration towards optical links with a higher-spectral efficiency. We present an optical transmitter comprising a segmentedelectrode InP IQ-MZM, capable of multi-level optical signal generation (5-bit per I/Q arm) by employing direct digital drive from integrated, low-power (1 W) CMOS binary drivers. We discuss the advantages and design trade-offs of the segmented driver structure and the implementation in a 40 nm CMOS technology. Multi-level operation with combined phase and amplitude modulation is demonstrated experimentally on a single MZM of the device for 2-ASK-2PSK and 4-ASK-2-PSK, showing potential for respectively 16-QAM and 64-QAM modulation in future assemblies.

A segmented modulator which shapes the optical spectrum of the modulated signal is presented. 1.5-fold bandwidth enhancement of driving electronics is shown. 40 Gb/s eye and error-free transmission over 9 km SSFM are measured. Advantage over standard modulators is demonstrated

Optical terabit transmitter and receiver based on passive polymer and InP technology for high-speed optical connectivity between datacenters,"