ECE (PCRL) at SPIE Conference 2017

SPIE Conference 2017 took place on January/February in San Francisco, California, United States. PCRL researchers Giannis Giannoulis and Konstantinos Tokas, PhD candidates of ECE, presented the following papers:

  • Giannis Poulopoulos et al., “Integrated polymer polarization rotator based on tilted laser ablation”, Proc. SPIE 10106, Integrated Optics: Devices, Materials, and Technologies XXI, 101060C (February 16, 2017); doi:10.1117/12.2250873.

Abstract: The ubiquitous need for compact, low-cost and mass production photonic devices, for next generation photonic enabled applications, necessitates the development of integrated components exhibiting functionalities that are, to date, carried out by free space elements or standard fiber equipment. The polarization rotator is a typical example of such tendency, as it is a crucial part of the PBS operation of future transceiver modules that leverage polarization multiplexing schemes for increasing the optical network capacity. Up to now, a variety of integrated polarization rotating concepts has been proposed and reported, relying, mainly, on special waveguide crossection configurations for achieving the rotation. Nevertheless, most of those concepts employ SiPh or III-V integration platforms, significantly increasing the fabrication complexity required for customizing the waveguide crossection, which in turn leads to either prohibitively increased cost or compromised quality and performance. In this manuscript we demonstrate the extensive design of a low-cost integrated polymer polarization rotator employing a right-trapezoidal waveguide interfaced to standard square polymer waveguides. First the crossection of the waveguide is defined by calculating and analyzing the components of the hybrid modes excited in the waveguide structure, using a Finite Difference mode solver. Mode overlaps between the fundamental polymer mode and each hybrid mode reveal the optimum lateral offset between the square polymer and the trapezoidal waveguide that ensures both minimum interface loss and maximized polarization rotation performance. The required trapezoidal waveguide length is obtained through EigenMode Expansion (EME) propagation simulations, while more than 95% maximum theoretical conversion efficiency is reported over the entire C-band, resulting to more than 13dB polarization extinction ratio. The polarization rotator design relies on the development of angled polymer waveguide sidewalls, employing the tilted laser ablation technology, currently available at CMST. Therefore, the aforementioned simulation steps adhere fully to the respective design rules, taking into account the anticipated fabrication variations.

  • Giannis Giannoulis et al., “Fieldtrial demonstration of an extended-reach GPON-supporting 60-GHz indoor wireless access”, Proc. SPIE 10103, Terahertz, RF, Millimeter, and SubmillimeterWave Technology and Applications X, 101030M (February 24, 2017); doi:10.1117/12.2252538.

Abstract: The 5G era is nearly upon us, and poses several challenges for system designers; one important question is how the (soon to be standardized) mmWave bands of wireless mobile access can coexist harmoniously with optical links in fixed telecom networks. To this end, we present a Radio-over-Fiber (RoF) backhauling concept, interfaced to a 60-GHz indoor femto-cell via a field-installed optical fiber link. We successfully demonstrate generation of a RoF signal up to 1 Gb/s and transmit it optically over 43 km of deployed Single Mode Fiber (SMF), as well as investigate the performance of the 60-GHz access link as a function of distance. The optical link introduces negligible degradation, contrasting the effect of multipath fading in the 60-GHz wireless channel; the latter requires adaptive equalization using offline DSP. The proposed scheme is further validated by demonstration of a 60-GHz Remote Antenna Unit (RAU) concept, handling real traffic from commercial Gigabit Passive Optical Network (GPON) equipment. Proper RAU operation at 1.25 Gb/s is achieved, accommodating true data packets from a Media Converter emitting at 1310 nm through an in-building fiber link. System performance is confirmed through Bit Error Rate (BER) and Error Vector Magnitude (EVM) measurements. EVMs of ~11 and 19% are achieved with BPSK signals, for distances of 1 and 2 m respectively. As standardization of mmWave technologies moves from 5G testbeds to field-trial prototypes, successful demonstration of such 60-GHz wireless access scenarios over a telecom operator’s commercial fiber infrastructure is even more relevant.

Figure 1: Drawing and photos of the experimental setup of the field-trial demonstration of the extended-reach GPON-supporting 60-GHz indoor wireless access

Contact Persons

  • Giannis Poulopoulos: jpoul[at]mail.ntua.gr
  • Giannis Giannoulis: jgiannou[at]mail.ntua.gr
  • Konstantinos Tokas: ktok[at]mail.ntua.gr
  • Hercules Avramopoulos: hav[at]mail.ntua.gr