Sebastian Babiel

60GHz radio-over-fibre wireless system for bridging 10Gb/s ethernet links

We present a 60 GHz radio-over-fibre system for broadband wireless transmission up to 12.5 Gb/s sufficient for bridging 10 Gb/s Ethernet links. The potential for km-range wireless transmission is further discussed.

Optoelectronic

We propose and demonstrate a K -band optoelectronic oscillator with ultralow phase noise performance and a frequency tuning range exceeding 1 GHz. The operation principle is based upon using two parallel optoelectronic loops with similar but not equal length and an electrical phase shifter for frequency tuning. We experimentally demonstrate tunable microwave signal generation within 20.7-21.8 GHz with a coarse frequency resolution of ~100 MHz. Fine tuning of the generated signal within a range of ±5 MHz is also achieved. The linewidth and phase noise of the generated microwave signal are <;3 Hz and -105 dBc/Hz at 10-kHz offset, respectively. Within the full gigahertz tuning range, the phase noise and output power of the generated microwave signal varies by only ±1.5 and <;1 dB, respectively.

K

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.

-Band Oscillator With Gigahertz Tuning Range and Low Phase Noise

A new coherent optical heterodyne radio-over-fiber (CRoF) scheme is proposed for seamless integration of next generation millimeter-wave wireless systems into a (ultra-dense) next generation passive optical network (NG-PON2). For seamless integration with the (ultra-dense) WDM infrastructure of high-capacity and longer-reach NG-PON2 networks, we propose novel radio access units (RAU) using coherent optical heterodyne detection for the generation of the millimeter-wave radio signals. The proposed CRoF concept supports the provision of multiple services over a single optical distribution network including next generation optical and wireless access services and high-capacity fixed wireless links for mobile backhaul. A proof-of-concept experiment is demonstrated in the context of backhauling. An E-band RAU utilizing CRoF is used for converting 2.5 Gb/s optical baseband data after 20 km fiber transmission to a 76 GHz wireless signal. After subsequent wireless transmission over 40 m (limited by the lab environment), the wireless E-band signal is directly reconverted to 2.5 Gb/s baseband data using a low-cost 76 GHz wireless receiver with RF envelope detection. The receivers sensitivity is only -47 dBm for a bit error rate (BER) of 2.10-3. Within international regulations, the transmit RF power can be further increased by about 68 dB, i.e. wireless distances way beyond 2 km can be expected even in the case of rain.

Integrated 110 GHz coherent photonic mixer for CRoF mobile backhaul links

We report on the generation of low phase noise millimeter-wave signal at 100 GHz with a dual-frequency laser and a high-speed photodiode. The laser beatnote is phase-locked on the tenth harmonic of a 10 GHz synthesizer through a new photonic down-converter based on a phase modulator. The spectral purity of the millimeter-wave signal has been fully characterized: it is spurious free over a large bandwidth and its phase noise is limited by the synthesizer itself (-90 dBc/Hz at 10 kHz).

Coherent radio-over-fiber (CRoF) approach for heterogeneous wireless-optical networks

We report on the generation of a low phase noise millimeter-wave signal at 100 GHz with a dual-frequency laser and a high-speed photodiode. The laser beatnote is phase-locked on the 10th harmonics of a 10 GHz synthesizer through an original photonic down-conversion scheme. The spectral purity of the millimeter wave signal has been fully characterized: it is spurious free over a large bandwidth and its phase noise is limited by the synthesizer itself (-90 dBc/Hz at 10 kHz).

Dual-Frequency Laser Phase Locked at 100 GHz

We propose and demonstrate a 50 GHz opto-electronic dual-loop oscillator with low phase noise of −95 dBc/Hz at 10 kHz offset from a 50 GHz carrier and a frequency tunability of more than 100 MHz.

100 GHz phase-locked dual-frequency laser

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.

Opto-electronic dual-loop 50 GHz oscillator with wide tunability and low phase noise

In this paper, we present a photonic wireless system operating in the W-Band (75-110 GHz) featuring ultra-high bandwidth as well as simple NRZ-OOK modulation format. By using a cascaded optical RF and data modulation approach on the transmitter side, flexible adjustment of the wireless RF carrier in the W-Band is achieved, while direct electrical to optical conversion with advanced photonic components on the receiver side enables true photonic wireless bridging. In first experiments, data rates up to 10 Gb/s have been experimentally demonstrated.

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

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.