Requirements for the use case of 5G systems were collected and translated into functionalities and specifications of photonics components. Designs and simulations of HAMLET transceivers were generated and interfaces between the components were defined. DSP algorithms for the optical detection and configuration of the optical beam-forming network (OBFN) were developed. The design of the OBFN was based on the Blass-Matrix architecture to enable multi-beam operation. The heterogeneous / hybrid integration methodologies and the packaging methodologies were consolidated in the final prototype blueprints.
A Pulsed Laser Deposition reactor was set up and a deposition process was developed, enabling high quality PZT material deposition on TriPleX platform. Stress optic phase shifters with 2 µm thick PZT layer on top of the waveguides were designed and fabricated inside Mach-Zehnder interferometers. Static power consumption for pi-phase shift was measured and found in the µW range, while power consumption at 1kHz was found less than 4mW per device. The optical loss was below 0.1 dB/cm, and thus in line with the typical loss of TriPleX waveguides. TriPleX chips with 2x2 and 8x8 Blass matrix Optical Beam Forming Networks (OBFNs) were fabricated for final integration and packaging. The 8x8 OBFN can feed 8 antenna elements on a phased array antenna and can produce and control the direction and shape of 8 microwave beams. A 4x16 Blass matrix network on the TriPleX was designed, put into mask for fabrication.
A method for graphene sheet transfer on PolyBoard platform was developed. GP-EAMs were designed and optimized leading to improved performance and an improved fabrication process (reduced number of required masks). The GP-EAMs were successfully fabricated as an array of 8 modulators installed in two prototypes. 3D integration between the TriPlex and Polyboard platforms was successfully demonstrated. The light transition between the two platforms was realised through vertical directional couplers with coupling loss less than 0.3 dB. The methodology was utilised to fabricate a 3D module that comprised a 1x2 Binary tree based OBFN, a single GP-EAM and two PDs.
A process for PolyBoard-TriPleX integration was defined considering the large number of waveguides and the large number of electrical lines on the chips. Mechanical and thermal simulations were carried out considering the mechanical constants and thermal expansion coefficients of the different materials. Within the project duration, 5 prototypes were assembled and packaged in total. The prototypes demonstrated increased complexity and functionality: (i) "Precursor-1" featured a 2x2 Blass matrix network with two InP-EAMs as the first generation of GP-EAMs did not have the required performance; (ii) "Module-1" was fabricated in two versions featuring a 8x8 Blass matrix network and 17 PD array integrated; (iii) "Precursor-2" has a 8x8 Blass matrix, an 8x array of GP-EAMs, 17x array of PDs and an additional DFB laser-thin film filter-PD assembly on chip that emulates the add-drop functionality for the signals coming from the optical fronthaul. The performance of the prototypes was evaluated using the developed testbeds.
The HAMLET optical beam forming technology was demonstrated live, to representatives from two of the biggest companies in Greece and Balkans, COSMOTE (teleocm operator) and IntraCOM, one (telecom equipment provider), who showed great interest for the demonstrated technology.
