C. van Dam

PHASAR-based WDM-devices: Principles, design and applications

Wavelength multiplexers, demultiplexers and routers based on optical phased arrays play a key role in multiwavelength telecommunication links and networks. In this paper, a detailed description of phased-array operation and design is presented and an overview is given of the most important applications.

Loss reduction for phased-array demultiplexers using a double etch technique

Wavelength Division Multiplexing (WDM) is an effective technique to exploit the huge bandwidth of optical fibres. Key components in such WDM-systems are demultiplexers which spatially separate the different wavelength channels. Phased-array demultiplexers combine ease of fabrication and low insertion losses. Silica-based phased-array demultiplexers are realised with low losses from 2-3 dB [1,2]. InP-based demultiplexers show slightly higher on-chip losses of 4-6 dB [3,4]. In addition they have considerably higher fibre coupling losses (several dB’s), but the advantage of InP-based demultiplexers is that they can be integrated with active components. Earlier we reported a low-loss demultiplexer with reduced fibre coupling loss by applying deeply etched InGaAsP waveguides with a relatively large core and a low index contrast, which had an almost circular mode profile [5]. The component had 4-5 dB on-chip loss and fibre coupling loss of about 1 dB to a tapered fibre. In this article we report a method to further reduce the on-chip losses.

System performance of a 4-channel PHASAR WDM receiver operating at 1.2 Gbit/s

Phased arrays are important key components in wavelength-division multiplexing (WDM) systems. We have realized a 4-channel WDM receiver combining a phased array with photodetectors on InP with a Si bipolar transimpedance amplifier. The channels are spaced at 2.0 nm with a 1.0-nm flat passband. On chip loss was 6-7 dB and detector efficiency was better than 90%. The optical cross talk remains below -20 dB. The electrical bandwidth per channel was 1 GHz. The electrical cross talk at 1 GHz after detection is below -25 dB. We have tested this receiver in a full 4-channel system.