Matthias Steeg

Compact triple transit region photodiode module with WR-12 rectangular waveguide output

Here, we present a compact photonic transmitter module featuring an integrated InP-based 1.55 μm triple transit region photodiode (TTR-PD) chip and a WR-12 rectangular waveguide output for E-band (60-90 GHz) radio-over-fiber applications. In order to enable work capability in broadband wireless E-band communications over long- and medium-range distances, the fabricated TTR-PD module provides excellent frequency flatness exhibiting a maximum deviation of ±1 dB within the complete 71-86 GHz band and high-power levels in excess of -5 dBm (without external amplification) at a photocurrent of 10 mA. In addition, we report for the first time on non-isothermal analyses of TTR-PDs using the drift-diffusion model with integrated Joule heat generation.

Integrated 110 GHz coherent photonic mixer for CRoF mobile backhaul links

An integrated 110 GHz coherent photonic mixer (CPX) is designed and fabricated for coherent RoF (CRoF) mobile backhaul links. The CPX simultaneously performs optical WDM channel selection and direct optical-to-RF conversion. Due to its broadband performance, the CPX simultaneously supports future wireless systems operating in the 57-64 GHz, 71-76 GHz, 81-86 GHz bands and even research-type W-band systems. The RF frequency response of the CPX in the 60 GHz and 70/80 GHz bands is about 4 dB higher as compared to a commercial 110 GHz photodiode. A CRoF experiment is carried out to also prove the advantageous performance of the new 110 GHz CPX against a commercially available 110 GHz photodiode in a CRoF system experiment with a 25 km standard single-mode fiber (SMF) and a 40 m long 71-76 GHz wireless link. This experiment reveals a significant improvement in optical receiver sensitivity of the radio access unit (RAU) with a required optical signal power as low as -32 dBm at a BER=2×10-3 for a 1 Gbit/s NRZ-OOK data signal.

Compact E-Band (71–86 GHz) bias-tee module for external biasing of millimeter wave photodiodes

This paper focuses on the development and characterization of a novel E-band planar bias-tee (BT) circuit featuring a high-speed millimeter wave photodiode (mm-wave PD) module to be integrated in next generation access and mobile networks (5G). The designed bias-tee circuit together with the integrated mm-wave PD chip, i.e., triple transit region photodiode (TTR-PD) allows the development of high-power Radio-over-Fiber (RoF) E-band (70/80 GHz) photonic transmitters (PTs) to be used in wireless extension and mobile backhaul links. The introduced BT circuit provides the protection to the hybrid integrated RF amplifier from being damaged by the PD bias voltage and prevents the leakage of the RF signal through the DC path. The vector network analyzer (VNA) measurements of the BT circuit show that in the frequency range from 70 to 75 GHz, the return loss (RL) is higher than 11 dB, the RF signal suppression level (IS) in the DC path is higher than 30 dB, while the insertion loss (IL) is lower than 2 dB. For optical RF signal generation, two laser sources are used to generate an optical heterodyne signal. Lower dark current levels and a 3-dB bandwidth in the frequency range from 71 to 86 GHz have been demonstrated at the BT output.

10 GHz channel spacing ultra-dense WDM networks transparently extended by mm-wave coherent RoF links

The extension of ultra-dense WDM passive optical networks (PONs) by millimetre-wave coherent radio-over-fiber (RoF) links is investigated. For a seamless and transparent integration of the RoF links coherent heterodyne detection is used for the generation of the wireless RF signals out of the optical baseband data signals. Simulations of the optical SIR in the PON are carried out in dependence on the WDM channel spacing. The projected impact on the transmission quality is derived and WDM CRoF experiments are performed. In the experiments three data modulated optical channels are transmitted over 10 km SMF to simulate the PON, before arriving at the E-band radio access unit (RAU). The RAU utilizes heterodyne detection with an optical LO for converting the 1 Gb/s optical baseband signal to a 75 GHz RF signal. After 40 m wireless transmission the signal is received by an antenna and downconverted to baseband using a low-cost SBD based receiver for envelope detection. The filtering of WDM channels with an optical channel spacing of down to 10 GHz showed very little penalty versus single channel transmission, relying only on the filter characteristic of the used LNAs and antennas and using no optical filters. Still the receivers sensitivity is only -57 dBm for a bit error rate (BER) of 2·10-3, thus it is shown that an ultra-dense WDM PON can be extended wirelessly using coherent RoF techniques without the need for optical filtering.

Spectral efficient 64-QAM-OFDM terahertz communication link

We report on a record spectral efficient terahertz communication system using a coherent radio-over-fiber (CRoF) approach. High spectral efficient back-to-back and wireless THz transmission around 325 GHz is experimentally demonstrated using a 64-QAM-OFDM modulation format and a 10 GHz wide wireless channel resulting in a data rate of 59 Gbit/s.

E-Band 76-GHz Coherent RoF Backhaul Link Using an Integrated Photonic Mixer

An E-band 76-GHz coherent radio-over-fiber (CRoF) system has been developed employing an integrated coherent photonic mixer (CPX) in the radio access unit (RAU) and a Schottky envelope detector in the wireless receiver. The CPX basically consists of a 2 × 2 multi-mode interferometer (MMI) coupled to a balanced photodiode (PD). It enables direct conversion of the optical baseband signal to the wireless RF signal with a carrier frequency at 76 GHz using a local oscillator located in the RAU. The developed CPX module features a V-type connector. The 3-dB cut-off frequency and 1-dB saturation output power of the CPX module are estimated as ~70 GHz and -2.43 dBm, respectively. It is shown that due to the integration of the MMI and the balanced PD, the developed CPX outperforms a commercial 110-GHz PD in terms of conversion efficiency up to 92 GHz. Experimentally, long-distance wireless transmission is shown using the constructed CRoF system and highly directive antennas with a gain of 43 dBi each. A wireless transmission of 1 Gb/s non-return-to-zero data signal at 76 GHz carrier frequency is demonstrated up to 230 m. The receiver sensitivity of the constructed wireless receiver for a pre-FEC bit error rate of 10-3 has been measured to be -34.8 dBm. This has enabled wireless data transmission over 92 m and 230 m at transmit power levels as low as -11.17 dBm and -3.36 dBm, respectively. It is shown that the experimental transmit power levels agree well with the expected figures calculated using an analytic Friis model describing the wireless channel. It is also estimated that the system could support maximum wireless distances up to 2000 m.

High data rate 6 Gbit/s steerable multibeam 60 GHz antennas for 5G hot-spot use cases

We present a steerable 60 GHz band multibeam antenna for high-capacity 5G hot-spot-scenarios. The developed SIW-LWA-antenna provides about 40° beam steering and a 14 dBi H-plane directivity. Wireless transmission to multiple users and maximum user data rates up to 6 Gbit/s are demonstrated.