Panos Groumas

Serial 100 Gb/s connectivity based on polymer photonics and InP-DHBT electronics.

We demonstrate the first integrated transmitter for serial 100 Gb/s NRZ-OOK modulation in datacom and telecom applications. The transmitter relies on the use of an electro-optic polymer modulator and the hybrid integration of an InP laser diode and InP-DHBT electronics with the polymer board. Evaluation is made at 80 and 100 Gb/s through eye-diagrams and BER measurements using a receiver module that integrates a pin-photodiode and an electrical 1:2 demultiplexer. Error-free performance is confirmed both at 80 and 100 Gb/s revealing the viability of the approach and the potential of the technology.

All-Optical RZ-to-NRZ Conversion of Advanced Modulated Signals

A generic scheme for return-to-zero (RZ) to nonreturn-to-zero (NRZ) format conversion of optical signals is analyzed. It relies on a simple delay interferometer with frequency periodicity twice as high as the input symbol rate and a subsequent optical band-pass filter. Simulation results at 40 Gbaud indicate the compatibility of the technique with a variety of advanced modulation formats. RZ-to-NRZ conversion of 40 Gb/s differential phase shift keying signals is experimentally demonstrated with 1.5 dB power penalty compared to the back-to-back measurement.

Complex monolithic and InP hybrid integration on high bandwidth electro-optic polymer platform.

We report on the monolithic integration of multimode interference couplers, Bragg gratings, and delay-line interferometers on an electro-optic polymer platform capable of modulation directly at 100 Gb/s. We also report on the hybrid integration of InP active components with the polymer structure using the butt-coupling technique. Combining the passive and the active components, we demonstrate a polymer-based, external cavity laser with 17 nm tuning range and the optical assembly of an integrated 100 Gb/s transmitter, and we reveal the potential of the electro-optic polymer technology to provide the next generation integration platform for complex, ultra-high-speed optical transceivers.

Multi-100 GbE and 400 GbE Interfaces for Intra-Data Center Networks Based on Arrayed Transceivers With Serial 100 Gb/s Operation

We demonstrate a 2 × 100 Gb/s transmitter and a 4 × 100 Gb/s receiver as the key components for multi-100-GbE and 400-GbE optical interfaces in future intradata center networks. Compared to other approaches, the two devices can provide significant advantages in terms of number of components, simplicity, footprint, and cost, as they are capable of serial operation with nonreturn-to-zero on-off keying format directly at 100 Gb/s. The transmitter is based on the monolithic integration of a multimode interference coupler with two Mach-Zehnder modulators on an electro-optic polymer chip, and the hybrid integration of this chip with an InP laser diode and two multiplexing and driving circuits. The receiver on the other hand is based on the hybrid integration of a quad array of InP photodiodes with two demultiplexing circuits. Combining the two devices, we evaluate their transmission performance over standard single-mode fibers without dispersion compensation and achieve a BER of 10-10 after 1000 m and a BER below 10-8 after 1625 m at 2 × 80 Gb/s, as well as a BER below 10-7 after 1000 m at 2 × 100 Gb/s. Future plans including the development of tunable 100 GbE interfaces for optical circuit-switched domains inside data center networks are also discussed.

\(2 \times 100\) -Gb/s NRZ-OOK Integrated Transmitter for Intradata Center Connectivity

We demonstrate an integrated transmitter that can generate two 100-Gb/s optical channels with simple nonreturn-to-zero-ON-OFF keying format. The transmitter is based on the combination of an ultrafast electro-optic polymer platform for the photonic integration and the optical modulation with ultrafast InP-double heterojunction bipolar transistor electronics for the multiplexing and the amplification of the 100-Gb/s driving signals. Through error-free transmission of 2 × 80-Gb/s signals over 1 km of SMF and transmission of 2 × 100-Gb/s signals over 500 m of single-mode fiber with error performance way below the forward error correction limit, we reveal the potential of the approach for parallel 100-GbE optical interfaces in small footprint transceivers for intradata center networks.

Tunable 100 Gbaud Transmitter Based on Hybrid Polymer-to-Polymer Integration for Flexible Optical Interconnects

We introduce a hybrid integration platform based on the combination of passive and electro-optic polymers. We analyze the optical and physical compatibility of these materials and describe the advantages that our hybrid platform is expected to have for the development of transmitters in terms of operation flexibility and speed. We combine our platform with InP electronics and develop a transmitter with 22-nm tunability in the C-band and potential for serial non-return-to-zero on-off-keying operation directly at 100 Gb/s. We investigate its transmission performance at 80 and 100 Gb/s using dispersion uncompensated standard single-mode fiber and demonstrate bit-error rate (BER) lower than 10-10 at 80 Gb/s after 1625 m, lower than 10-10 at 100 Gb/s after 500 m, lower than 10-9 at 100 Gb/s after 1000 m, and BER 10-7 at the same rate after 1625 m. We also employ the transmitter inside an experimental setup, which aims to emulate an optical circuit switched (OCS) domain of an intradata center network, and demonstrate at 100 Gb/s the way, in which its wavelength tunability can resolve contentions and improve the flexibility and the efficiency of the network. Finally, we outline our next plans, including the development of flexible and ultra-fast transmitters for coherent systems using the same polymer-to-polymer integration platform.

Multi-Flow Transmitter Based on Polarization and Optical Carrier Management on Optical Polymers

We propose a novel multi-flow transmitter concept capable of controlling the number, type, wavelength, and destination of the generated optical flows depending on the client traffic. The concept is based on the selection of the number of optical carriers per flow and the selection between single- and dual-polarization flows. We demonstrate the proof-of-concept combining two commercial In-Phase/Quadrature (IQ) modulators with two prototype polymer circuits, which integrate three tunable lasers for flexible wavelength allocation, four thermo-optic switches for flexible optical routing on-chip, and elements for polarization handling on-chip. We incorporate this transmitter inside an optical node, and we investigate one-flow scenarios with dual-carrier or dual-polarization quadrature phase shift keying (QPSK) modulation, and two-flow scenarios based on two independent QPSK signals. The transmitter and node configuration are controlled by a software-defined optics platform. We demonstrate dynamic operation at 28 GBd and error-free coherent transmission over 100 km of the standard single-mode fiber.

New set of design rules for resonant refractive index sensors enabled by FFT based processing of the measurement data.

It is still a common belief that ultra-high quality-factors (Q-factors) are a prerequisite in optical resonant cavities for high refractive index resolution and low detection limit in biosensing applications. In combination with the ultra-short steps that are necessary when the measurement of the resonance shift relies on the wavelength scanning of a laser source and conventional methods for data processing, the high Q-factor requirement makes these biosensors extremely impractical. In this work we analyze an alternative processing method based on the fast-Fourier transform, and show through Monte-Carlo simulations that improvement by 2-3 orders of magnitude can be achieved in the resolution and the detection limit of the system in the presence of amplitude and spectral noise. More significantly, this improvement is maximum for low Q-factors around 104 and is present also for high intra-cavity losses and large scanning steps making the designs compatible with the low-cost aspect of lab-on-a-chip technology. Using a micro-ring resonator as model cavity and a system design with low Q-factor (104), low amplitude transmission (0.85) and relatively large scanning step (0.25 pm), we show that resolution close to 0.01 pm and detection limit close to 10-7 RIU can be achieved improving the sensing performance by more than 2 orders of magnitude compared to the performance of systems relying on a simple peak search processing method. The improvement in the limit of detection is present even when the simple method is combined with ultra-high Q-factors and ultra-short scanning steps due to the trade-off between the system resolution and sensitivity. Early experimental results are in agreement with the trends of the numerical studies.

Passive and electro-optic polymer photonics and InP electronics integration

Hybrid photonic integration allows individual components to be developed at their best-suited material platforms without sacrificing the overall performance. In the past few years a polymer-enabled hybrid integration platform has been established, comprising 1) EO polymers for constructing low-complexity and low-cost Mach-Zehnder modulators (MZMs) with extremely high modulation bandwidth; 2) InP components for light sources, detectors, and high-speed electronics including MUX drivers and DEMUX circuits; 3) Ceramic (AIN) RF board that links the electronic signals within the package. On this platform, advanced optoelectronic modules have been demonstrated, including serial 100 Gb/s [1] and 2x100 Gb/s [2] optical transmitters, but also 400 Gb/s optoelectronic interfaces for intra-data center networks [3]. To expand the device functionalities to an unprecedented level and at the same time improve the integration compatibility with diversified active / passive photonic components, we have added a passive polymer-based photonic board (polyboard) as the 4th material system. This passive polyboard allows for low-cost fabrication of single-mode waveguide networks, enables fast and convenient integration of various thin-film elements (TFEs) to control the light polarization, and provides efficient thermo-optic elements (TOEs) for wavelength tuning, light amplitude regulation and light-path switching.

High performance refractive index sensor based on low Q-factor ring resonators and FFT processing of wavelength scanning data

We extend our previous simulation study and we present experimental results regarding our Fast Fourier Transform method for the calculation of the resonance shifts in biosensors based on micro-ring resonators (MRRs). For the simulation study, we use a system model with a tunable laser at 850 nm, an MRR with 1.5∙104 quality factor, and a detection system with 50 dB maximum signal-to-noise ratio, and investigate the impact on the system performance of factors like the number of the resonance peaks inside the scanning window, the wavelength dependence of the laser power, and the asymmetry of the transfer functions of the MRRs. We find that the performance is improved by a factor of 2 when we go from single- to four-peak transfer functions, and that the impact of the wavelength dependence of the laser power is very low. We also find that the presence of asymmetries can lead to strong discontinuities of the transfer functions at the edges of the scanning window and can significantly increase the measurement errors, making necessary the use of techniques for their elimination. Using these conclusions, we build a system with sensing MRRs on TriPleX platform, and we experimentally validate our method using sucrose solutions with different concentrations. Involving techniques in order to exclude the noise originating from the microfluidic system, we achieve a wavelength resolution close to 0.08 pm, when the system operates with 0.5 pm scanning step. In combination with the sensitivity of the MRRs, which is measured to be equal to 93.7 nm/RIU, this wavelength resolution indicates the possibility for a limit of detection close to 8.5·10-7 RIU, which represents to the best of our knowledge a record performance for this type of optical sensors and this level of scanning steps.