Niels Neumann

Miniaturized Long-Period Fiber Grating Assisted Surface Plasmon Resonance Sensor

This paper presents the design and fabrication of a fiber-optic refractive index (RI) sensor. The novel concept employs a long-period fiber grating (LPG) to achieve surface plasmon resonance (SPR) of a single cladding mode at the gold-coated tip of a single-mode fiber. The sensor combines a high level of sensitivity, a miniaturized sensing area and simple intensity-based interrogation, and is intended for biosensing using portable point-of-care devices or highly integrated lab-on-chip systems.

General Design Rules for the Synthesis of Dispersion and Dispersion Slope Compensation FIR and IIR Filters With Reduced Complexity

Chromatic dispersion is one of the main transmission impairments in optical systems with high bit rates, because the dispersion limit scales with the square of the data rate. Optical delay-line filters can be used to compensate dispersion and dispersion slope. They can be designed as feedforward finite-impulse response filters or as all-pass infinite-impulse response filters. Due to the time-variant property of the dispersion, those filters have to be adaptive, which requires fast and reliable calculation of the filter coefficients. In this paper, a new approach to calculate filter coefficients by applying analytical methods is presented. Design examples are given, and the filter performance is discussed.

Active integrated photonic antenna array

Photonic beam forming networks benefit from the broad bandwidth and low attenuation of optical waveguides. Applying the true time delay (TTD) approach for antenna arrays, the feeding network is independent from the electrical carrier frequency of the signal. Consequently, the performance of this approach is maximized by placing the opto-electrical conversion (photodiode) directly at the feeding point of the antenna. In this work, such a setup that combines the optical TTD technique and photonic feeding is demonstrated with a four element array of Vivaldi antennas working in the broad frequency range from 0.5-2.5 GHz. A photonic feeding network supporting the beamforming of different antenna patterns is designed. Measurements are presented and discussed.

Optical Through-Silicon Vias

An optical Through-Silicon-Via (TSV) is a key element for vertical optical connections in 3D chip stacks. Implementing a manufacturing process based on the well-established electrical TSVs is an important task. Besides the challenging photolithographic, etching, and deposition processes, performance is influenced by geometry (e.g., achievable aspect ratio), tolerances (e.g., sidewall surface roughness), and material system (i.e., refractive indices). The production of TSVs with high aspect ratios of more than ten, low sidewall surface roughness (less than 20 nm), using SU-8 as waveguiding medium is demonstrated. Based on several geometries, a transmission model is developed that may be used to describe waveguiding and non-waveguiding optical TSV structures. System-level measurements complete the results shown in this chapter. It is verified that the TSVs used as transmission medium are much more broadband than the available VCSELs and photodiodes. Due to the low transmission distances, even non-waveguiding schemes show low loss.

Dispersion Estimation via Vestigial Sideband Filtering Using an Optical Delay Line Filter

Vestigial sideband filtering can be used for chromatic dispersion measurements. An optical delay line filter providing upper sideband (USB), lower sideband (LSB), and passband was designed for that application. The straightforward utilization is to measure the time delay between the USB and the LSB. A more practical approach is to estimate the chromatic dispersion (CD) by multiplying the USB and LSB signals in an electronic mixer and filtering out the DC component of the resulting signal. Due to the correlation between the USB and the LSB this signal is a measure for the delay between the sidebands induced by the CD. This approach was successfully demonstrated by experiments at a data rate of 10 Gbit/s. Furthermore, the properties of the optical filter influence (e.g., filter extinction) were assessed by numerical simulations.

Carrier recovery for sub-millimeterwave wireless transmission

The carrier frequencies of wireless systems are expanded to higher and higher frequency bands where huge bandwidths for data-hungry applications can be realized. One of the prospective regions is the sub-millimeterwave band. Wireless transmission needs coherent local oscillators at the transmitter and receiver for efficient operation. At such high frequencies, traditional methods of analog carrier recovery (e.g. narrowband filtering of the residual carrier and re-amplification) fail. At the same time, for high data rates above 10 Gbit/s, digital carrier recovery algorithms used in conjunction with free-running oscillators are too power-hungry and hard to realize. In this paper, a carrier recovery for a 300 GHz system based on the parallel transmission of a reference frequency together with the payload data is proposed. The corresponding electronic circuits for the transmitter and receiver are designed, manufactured and characterized.

Investigation of propagation scenarios for high speed transmission at 300 GHz

A prospective frequency band for short range communication is around 300 GHz where sufficient bandwidth is available for high data rates. Up- and down converters providing around 20 GHz bandwidth at a carrier frequency within 260 GHz to 400 GHz have been used. At such high frequencies, the propagation properties differ significantly from the known behavior at lower frequencies. Hence, different scenarios have been investigated: direct line-of-sight transmission, multiple reflections at dielectric surfaces and reflection on compound materials such as computer boards (PCBs). Data rates up to 42 Gbit/s have been shown. Additionally, an advanced modulation format (PAM-4) has been tested.

Integrated Schottky diode detector for THz spectrometer

The longitudinal beam shape properties, crucial information to operators, can be monitored in modern superconducting linear accelerators measuring the generated THz radiation. Recent semiconductor technology may help to replace the single element THz detectors (e.g. used at the ELBE accelerator in Helmholtz-Zentrum Dresden-Rossendorf (HZDR)) as well as the costly and bulky THz spectrometers. Thats why we develop a simple integrated on-chip spectrometer in a GaAs technology that shall be able to resolve 5 to 20 frequency points in the frequency range between 0.1 THz to 1.5 THz. The core element is an integrated Schottky diode used as a power sensor connected to on-chip antennas and filters. First results show that a multi-narrowband antenna approach is very promising regarding complexity, sensitivity and selectivity. This paper explains the design and presents the first simulation results for an on-chip Schottky diode detector operating at 300 GHz that will be used on the on-chip spectrometer.

Estimation and equalization techniques applied to Radio over Fiber System

In this paper, signal processing techniques applied on the received signal from Radio over Fiber system have been investigated. The structure of the RoF system, starting by the 60 GHz carrier generation using an external modulator, Optical Single Side Band 10 Gb/s QPSK modulation with IQ Dual Parallel Mach Zehnder Modulator, base station, and the electrical coherent receiver is introduced. The performance of the system with attenuation, chromatic dispersion, and frequency offset of the local oscillator at the receiver side is discussed. The frequency domain equalization technique and feedforward carrier recovery algorithm which are used to mitigate the effect of chromatic dispersion on the carrier and the data as well are investigated. Moreover, the proposed solution also covers the frequency offset of the local oscillator at the receiver side. The proposed algorithms are evaluated by simulations run under VPItransmissionMaker environment as well as MATLAB.

Remotely operated active integrated photonic antenna array

Taking advantage of the broad bandwidth and the low attenuation of optical waveguides, photonic antennas can be remotely fed. We present an active integrated photonic antenna array with an photonic feeding network that can be fed over tens of kilometers using single-mode fiber. The influence of dispersive effects in optical domain on the antenna pattern is researched and discussed. Measurement results are presented. Additionally, error-free data transmission over such a system is demonstrated.