Danny Morlion

MT-compatible laser-ablated interconnections for optical printed circuit boards

Integration of optical interconnections on a printed circuit board (PCB) is very challenging, since compatibility should be maintained with standard PCB manufacturing technology. This paper describes the use of laser ablation, a technique already used in PCB manufacturing for drilling microvias, as a suitable technique for the fabrication of multimode polymer waveguides, micromirrors, alignment features, and microlenses. A frequency-tripled Nd-YAG laser and a KrF excimer laser are used, both mounted on the same stage, resulting in very high alignment accuracies. This paper demonstrates a parallel optical link over approximately 5-cm-long PCB integrated waveguides, fully connected using a standard MT-based connector. This proves that laser ablation can be a key technology in optical board manufacturing to reach the stringent coupling tolerances.

Parallel optical interconnections for future broad band systems, based on the "fibre in board technology"

A novel interconnection technology based on the integration of glass optical fibres in a standard printed circuit board is presented to overcome the interconnection bottleneck in the nest generation of broad band switching fabrics. Within these systems, the parallel electro-optical modules will be: integrated on the switching board itself which has a switching capacity of 20 Gbit/s. A robust and automated technology is used for the realisation of optical interconnections between these electro-optical (E/O) modules and the off-board connectors at the edge of the board. Dedicated surface optical contacts have been developed, capable of handling 16 parallel channels. These surface optical contacts can be integrated everywhere on the board and can be used for mounting an electro-optical module or a multifibre connector compatible with this technology. Electro-optical modules (8 channel transmitters and 4 channel receivers) and multifibre optical back panel connectors have been integrated on an engineering prototype for the evaluation of the technology. Off-board links, over 200 m MM (graded index) fibre, and on-board links are operational at 622 Mbit/s. The boards have been subjected to reliability tests and preliminary results reveal no degradation of the board after thermal cycling. Precision moulding techniques are presented to make the proposed technology more cost-effective and suitable for volume production.

An improved triaxial cell for transfer impedance measurements on multipins backplane connectors

An improved triaxial cell for measuring the transfer impedance of the shields of multipins backplane connectors has been developed. Much attention has been paid to the design of the outer and inner transmission line of the test cell. In particular the excitation of the connector and the connection of the connector shield to the inner conductor of the test cell have been optimised which allows determination of the transfer impedance up to 3 GHz. Various connector configurations have been compared, showing a large influence of the signal pin location in the connector and of the connector shields.