A wavelength filter is a key component for numerous photonic integrated circuit applications in optical communication. Researchers put forward several methods to design wavelength filters for which the Echelle grating de-multiplexers (EG-DMUXs) are popular and have been extensively studied. In comparison with the traditional EG-DMUXs based on the Rowland mounting, EG-DMUXs based on the two stigmatic points (TSP) method were reported rather late. This paper will present the basic design theory and a high-performance device fabricated on a 250 nm silicon-on-insulator (SOT) platform for validation. The simulation and measurement results of this 1 x7 EG-DMUX with 800 GHz channel spacing will be presented and compared. Although the fabricated device has the merits of compact on-chip footprint, low insertion loss and low crosstalk, its narrow 1-dB bandwidth may limit its application in practice. We present our solution to widen the transmission spectrum based on the TSP EG-DMUXs and multimode interferometers.

Multimode interferometers (MMIs) are key components for high-performance transceivers in upgrading the data transmission of future detector systems. According to their power splitting ratio, they are used in Mach-Zehnder modulators and for working point control, respectively. To meet with special requirements, we investigate MMIs with engineered refractive index where sub-wavelength gratings and shallow etching techniques were adopted. By engineering the refractive index of the relevant parts of MMIs, the on-chip footprint and the phase errors can be decreased dramatically, making them suitable for advanced silicon photonic integrated transceivers. These MMIs are compared to two MMIs designed using conventional methods and fabricated on a 250 nm silicon-on-insulator (SOI) platform.

We present standard and radiation-hardened pn depletion-type Mach-Zehnder modulators (MZM) to be used in high-bandwidth, fully-integrated wavelength division multiplexing (WDM) transmitter designs, aiming to upgrade the optical data transmission of future detector systems. A detailed characterization of the modulators with respect to modulation efficiency and RF response was carried out. Based on this work, a first optical link with a data rate of 11.3 Gb/s was set up.

One promising solution for the ever increasing transmission capacity demand from fundamental research and data centers is the silicon-photonic integrated WDM transmitter. We designed an easily scalable, high-bandwidth transmitter unit composed of radiation-hardened Mach-Zehnder modulators (MZMs) and Echelle grating (de-)multiplexers (EG-DMUXs). Our 3 mm MZMs have customized slabs with a reduced etch depth to improve their radiation hardness. Our current MZMs feature a V-pi.L of 4.6 V.cm and an insertion loss of 4.84 dB. Additionally, an error-free transmission was achieved successfully at a speed of 11.3 Gb/s while driving the modulators with a PRBS-7 signal and an amplitude of less than 2 V-pp. The Echelle grating (de-)multiplexers were designed and simulated numerically. The presented 1x7 device is compact and low-loss: the on-chip footprint is 680 mu m x 380 mu m, the channel spacing is 800 GHz, and the measured average insertion loss and crosstalk are 2.5 dB and -22 dB, respectively. With optimized components, higher bandwidth systems with more channels are achievable.

Multimode interferometers (MMIs) are key components for high-bandwidth transceivers in upgrading the data transmission of future detector systems. We present two conventional highperformance MMIs fabricated on a 250 nm SOI platform with different power splitting ratios which operate as 50%:50% power splitter for Mach-Zehnder modulators and as 86%:14% power splitter for loop control in future transceiver designs, respectively. Besides, we present the novel MMIs based on sub-wavelength gratings. By engineering the refractive index of relevant parts, more compact 50%:50% MMIs and multi-port, low phase error MMIs become feasible.

The data throughput of future detector readout systems is ever increasing. We propose a high-performance optical link, based on silicon photonics and wavelength-division multiplexing (WDM) technology, to cope with ultra-broad bandwidth requirements. The key components of the proposed optical link are monolithically integrated transmitter units, each one integrating multichannel on-chip Echelle grating (de-)multiplexers and Mach-Zehnder modulators (MZMs). In our current design, each transmitter unit consists of four MZMs, which corresponds to four transmission channels with distinct optical carrier wavelengths, a common optical demultiplexer and a common optical multiplexer. In this paper, we present the design and experimental results of all these building blocks as well as a first transmission experiment. Additionally, experimental results of a thermal modulator to be used in a future design for working point control are presented.

The data throughput of future detector readout systems is ever increasing. To satisfy the requirements of ultra-broad bandwidth, we propose a high-performance optical link utilizing silicon photonics and wavelength division multiplexing. The key components are monolithically integrated transmitter units, each comprising Echelle grating (de-)multiplexers and Mach- Zehnder modulators. In this paper, we present the design and measurements of the building blocks as well as the first data transmission experiment.

Driven by the increasing demands of ultra-broad bandwidth transmission in telecommunications as well as in large-scale scientific experiments, interests in developing on-chip DWDM networks based on silicon photonics is increasing rapidly. With compact structures, low loss and robust fabrication, Echelle grating (EG) (de-)multiplexers become one of the key components. Two competitive design methods are the Rowland circle (RC) and the two stigmatic points (TSP) method, with the latter one offering remarkable advantages on optical aberrations and degrees of freedom. We demonstrate a self-developed design kit for both methods involving MATLAB calculation, COMSOL Multiphysics simulation and GDSII layout. In our kit, several parameters are reserved to optimize the geometry in terms of device footprint, reflector configurations etc.. By making rigorous simulation on an HPC cluster, we obtained well-performing, robust and compact EG (de-)multiplexers based on the two stigmatic points method. For the 7-channel, 9th diffraction order and 800 GHz channel spacing device, we get a simulated average optical loss of 2.3 dB and a crosstalk of less than -20 dB with an on-chip footprint of 400×690 μm2. Our silicon-photonic devices were fabricated on a 250 nm silicon-on-insulator (SOI) platform using e-beam lithography and dry etching. The comparison between measurement results of fabricated devices and simulation results was carried out, as well as a comparison between designs based on both design methods. Additionally, the experimental result of a 25- channel (de-)multiplexer with 200 GHz channel spacing in the C-band is presented to study the performance of the TSP method for a narrow channel spacing and large footprint design.

We present an efficient and easy-to-use process for a permanent fiber-to-chip coupling arrangement with angle-polished single-mode optical fibers (SMF) to maintain a planar profile while surface-coupling to grating couplers of a silicon photonic integrated circuit (PIC). The SMF are polished with a standard polishing machine to match the appropriate coupling angle. Due to the simplicity of the process, it is suitable for both packaging of photonic devices ready for commercialization and the rapid coupling of components at an early stage of development. The coupling arrangement does not impose additional insertion loss compared to a continuously controlled fiber alignment and remains stable even under strong variation of ambient temperature and humidity.

We report on our recent progress in developing an optical transmission system based on wavelength division multiplexing (WDM) to enhance the read-out data rate of future particle detectors. The design and experimental results of the prototype of a monolithically integrated multi-wavelength transmitter are presented as well as temperature studies of electro-optic modulators. Furthermore, we show the successful permanent coupling of optical fibers to photonic chips, which is an essential step towards packaging of the opto-electronic components.

We propose a new silicon photonics-based optical transmission system utilizing wavelength division multiplexing (WDM). This technology has the possibility of reading out all raw data from a detector even without massive local data reduction. The transmitter in the detector volume consists of multiple integrated Mach-Zehnder modulators monolithically integrated with wavelength (de-)multiplexers. The first demonstrator currently under development aims for a data rate of 160 Gbit/s per fiber, scalable to 5 Tbit/s and beyond. We report on our recently developed Echelle grating WDM multiplexers with up to 45 channels on an area of 0.5mm(2) and electro-optic modulators providing a bandwidth of 18 GHz.

An open converged metro-access network approach allows for sharing optical layer resources like fibers and optical spectrum among different services and operators. We demonstrated experimentally the feasibility of such a concept by the simultaneous operation of multiple services showing different modulation formats and multiplexing techniques. Flexible access nodes are implemented including semiconductor optical amplifiers to create a transparent and reconfigurable optical ring network. The impact of cascaded optical amplifiers on the signal quality is studied along the ring. In addition, the influence of high power rival signals in the same waveband and in the same fiber is analyzed.

In this paper the authors describe a novel system on chip (SoC) that is especially developed for digital signal processing of high-speed orthogonal frequency division multiplexing (OFDM) signals with data rates up to gigabits per second. Besides offering a new degree of freedom for the tradeoff between flexibility and performance during runtime, the modular concept of the SoC also allows a tradeoff between performance and costs during design time. The flexibility to adapt the OFDM system parameters by software enables even system designers without a good knowledge of hardware design to implement high-speed OFDM systems. An example configuration of the architecture was implemented on a Virtex-6 FPGA in order to set up a software-defined OFDM transmitter, achieving data rates of several gigabits per second. The paper closes with implementation and performance results of experiments using the developed transmitter and an optical transmission of the generated OFDM signals.

We demonstrate 448 Gbit/s (224 Gbit/s) dual channel DP-16QAM (QPSK) transmission over four cascaded, linear SOAs using advanced modulation formats. As an application we envision dedicated high-capacity business paths in future converged metro-access networks.

We demonstrate a remotely seeded flexible passive optical network (PON) with multiple low-speed subscribers but only a single optical line terminal transceiver operating at a data rate of 31.25 Gbits/s. The scheme is based on a colorless frequency division multiplexing (FDM)-PON with centralized wavelength control. Multiplexing and demultiplexing in the optical network unit (ONU) is performed in the electronic domain and relies either on FDM with Nyquist sinc-pulse shaping or on orthogonal frequency division multiplexing (OFDM). This way the ONU can perform processing at low speed in the baseband. Further, the ONU is colorless by means of a remote seed for upstream transmission and a remote local oscillator for heterodyne reception, all of which helps in keeping maintenance and costs for an ONU potentially low and will simplify wavelength allocation in a future software defined network architecture. To extend the reach, semiconductor optical amplifiers are used for optical amplification in the downstream and upstream.

We investigate the performance of a fiber-based OFDM transmission system for wireless backhauling with a target data rate of 2.5...10 Gbit/s using directly modulated lasers. Newly developed semiconductor DFB lasers in index and complex coupled curved stripe technology as well as lasers with ridge waveguide resonators were experimentally characterized and found to be suitable for direct modulation at the required data rates. Based on measured data, we implemented a numerical laser model and studied by simulation the limits and the optimum operating conditions of an optical OFDM network for wireless backhauling.