Segmented optical transmitter comprising a CMOS driver array and an InP IQ-MZM for advanced modulation formats

Segmented Mach-Zehnder modulators are promising solutions to generate complex modulation schemes in the migration towards optical links with a higher-spectral efficiency. We present an optical transmitter comprising a segmented-electrode InP IQ-MZM, capable of multilevel optical signal generation (5-bit per I/Q arm) by employing direct digital drive from integrated, low-power (1W) CMOS binary drivers. We discuss the advantages and design tradeoffs of the segmented driver structure and the implementation in a 40 nm CMOS technology. Multilevel 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

Analog I/Q FIR filter in 55-nm SiGe BiCMOS for 16-QAM optical communications at 112 Gb/s

We propose a novel implementation of a complex analog equalization filter for the compensation of frequency-dependent variations in coherent optical links. The analog compensation filter can be used in coherent-lite optical communication links where digital signal processing (DSP) is removed to limit the complexity and power consumption. In these links, the filter can compensate for electrical bandwidth limitations and distortion introduced by chromatic dispersion in the fiber. The complex filter is implemented by combining four distributed analog finite-impulse response (FIR) filters to obtain the necessary response. The filter delays are implemented using active delay cell structures to create a compact solution. The analog filter is implemented in a 55-nm BiCMOS technology and consumes 185-mW core power for five complex filter taps. Performance is evaluated using the S-parameter measurements, noise and linearity measurements, and real-time system experiments using 112-Gb/s 16-QAM-modulated signals

A programmable, multi-format photonic transceiver platform enabling flexible optical networks

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 an 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

A DC-coupled 50 Gb/s 0.064 pJ/bit thin-oxide level shifter in 28 nm FDSOI CMOS

High-speed optical interconnects require compact, low-power driver electronics for optical modulators. Inverter based CMOS driver circuits show very low power consumption. However, the output swing is typically limited to the supply voltage which is typically insufficient for optical modulators, requiring a cascoded output driver and level shifter. In this work, we present a new DC-coupled thin-oxide level shifter topology in a 28 nm FDSOI CMOS technology enabling data rates up to 50 Gb/s with a power efficiency of 0.064 pJ/bit

Multi-level optical signal generation using a segmented-electrode InP IQ-MZM with integrated CMOS binary drivers

We present a segmented-electrode 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 (1W) CMOS binary drivers. Programmable, multi-level operation is demonstrated experimentally on one MZM of the device

4:1 silicon photonic serializer for data center interconnects demonstrating 104 Gbaud OOK and PAM4 transmission

With next-generation optical interconnects for data centers aiming for 0.8 Tb/s or 1.6 Tb/s, 100 Gbaud capable transmitters from a single-laser source will become indispensable. However, these lane rates would require bandwidths of 70 GHz or more, doubling the bandwidth requirements of the electrical and optical components with respect to the fastest current generation of optical interconnects running at 53 Gbaud pulse-amplitude modulation (PAM-4). In this paper, we propose an integrated 4: 1 optical serializer topology to achieve 104 Gbaud On-Off Keying (OOK) and PAM-4 transmission using only quarter rate components at the transmitter. We show 104 (208) Gbit/s OOK (PAM4) transmission using four GeSi electro-absorption modulators (EAMs) over 1 km of single-mode fiber (SMF). For 104 Gbaud OOK, clearly open eyes are obtained, while for PAM-4 the performance is limited by the nonlinear E/O-transfer function of the EAM. However, adding pre-emphasis in the electrical driver or replacing the single EAM with our previously demonstrated optical DAC topology-consisting of two EAMs in parallel with a 90 degrees phase difference between each-could substantially improve these results. Additionally, we discuss the possibility of a four channel transmitter (4 x 208 Gb/s) from a single mode locked laser, amounting to a 832 Gb/s rate based on the current demonstrator

70 Gb/s low-power DC-coupled NRZ differential electro-absorption modulator driver in 55 nm SiGe BiCMOS

We present a 70 Gb/s capable optical transmitter consisting of a 50 mu m long GeSi electro-absorption modulator (integrated in silicon photonics) and a fully differential driver designed in a 55 nm SiGe BiCMOS technology. By properly unbalancing the output stage, the driver can be dc-coupled to the modulator thus avoiding the use of on-chip or external bias-Ts. At a wavelength of 1560 nm, open eye diagrams for 70 Gb/s after transmission over 2 km standard single-mode fiber were demonstrated. The total power consumption is 61 mW, corresponding to 0.87 pJ/b at 70 Gb/s. Bit-error rate measurements at 50 Gb/s and 56 Gb/s (performed both back to back and with up to 2 km standard single-mode fiber) demonstrate large (0.4 UI at a BER of 10(-12)) horizontal eye margins. This optical transmitter is ideally suited for datacenter applications that require densely integrated transceivers with a low power consumption