SOI Technology for Tunable Optical Add-Drop Multiplexers

Pirelli has leveraged SOI and related wafer-level substrate engineering in a new generation of optical telecom components.

Faced with a growing number of bandwidth-hungry applications like IPTV and VoIP, and increasing stress on metro and access networks, optical networking equipment makers need cost-competitive, flexible solutions.

Pirelli Broadband Solutions, the broadband access and photonics company within the Pirelli Group, is leveraging SOI technology and related wafer-level engineering technology, in a suite of tunable components to meet those needs. Tunability helps “future-proof” networking equipment, and makes it much less expensive to operate: updates can be done in software, rather than arduous, disruptive manual manipulations.

The latest addition to our tunable product line (which already includes a laser, modules and subsystems) is a Tunable, filter-based Optical Add-Drop Multiplexer (TOADM), featuring 100GHz bandwidth and data transmission capability of up to 10Gb/s.


The role of the TOADM is to manage (add or drop) a fixed number of wavelengths (for example, four), but they can be chosen within a certain optical bandwidth (C-band). The result of this flexibility is that the optical component is able to drop or add any lambda from any one of four channel-ports. The “secret” of this large flexibility is in the silicon itself – and even more so in SOI, wherein you can also manage the degree of isolation of the optical mode in this waveguide regime.

SOI technology for integrated optical functionality is driving a new generation of optical components for telecom. Compared to expensive III-V solutions, silicon’s large optical-thermal coefficient opens the possibility of using silicon waveguides as widely tunable building blocks for next-generation optical components. Thanks to the high-index contrast and excellent propagated light confinement, we are able to create structures with dimensions in the submicron scale with tight tolerances.

Pirelli’s 100Ghz Tunable, filter-based Optical Add-Drop Multiplexer (TOADM), with data transmission capability of up to 10Gb/s, is built on SOI with ultrathick BOX. (Courtesy: Pirelli Labs, Milan, Italy)

We can offer highly-integrated solutions by leveraging miniaturization and integration of optical components at the wafer level. Key enablers are Smart Cut™ and technology from Tracit that allows us to obtain a low loss optical functionality by using SOI wafers with ultra-thick BOX.

In addition to reducing size and potentially power consumption, the combination of all of these nanotechnology techniques should lead to a decrease of at least one order of magnitude in the cost of photonic devices, making them suitable for high-volume applications. We see it first as a key to the dissemination of optical transmission in the networks of small- and medium- enterprises (fiber-to-the-building (FTTB), fiber-to-the-cabinet (FTTC)), and before too long, fiber-to-the-home (FTTH).

Leave a Reply

Your email address will not be published. Required fields are marked *