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Bookham mux/demux module based on TFF technology

Posted: 23 Jul 2004 ?? ?Print Version ?Bookmark and Share

Keywords:bookham technology? thin film filter technology? tff technology? multiplexer/demultiplexer module? aed iii?

Bookham Technology is using thin film filter (TFF) technology for a range of high channel count, scalable multiplexer/demultiplexer modules it is sampling for telecom applications.

The England-based company says applying TFF technology to such devices opens a low entry-cost module solution for the market with full expandability of up to 40 channels in DWDM networks operating at 1,550nm.

The same module can be used in both multiplexing/demultiplexing and in reconfigurable optical add/drop (ROADM) applications. Upgrades can be handled in 8 to 10 channel increments in any wavelength order with minimal insertion loss increase.

Optical filtering based on 'banded architecture' arranges separate optical communications channels on a particular wavelength into groups and, instead of processing them one at a time, the filter processes the group, reducing overall footprint and optimizing device efficiency and cost.

Based on Bookham's proprietary AED III (Advanced Energetic Deposition, version III) technology, the banded filters - called '8 skip 0' and '10 skip 0' - are targeted for use in 100GHz channel spacing DWDM systems. The filters enable 8 or 10 channels at a time to be filtered without skipping, or sacrificing, the neighboring channels. The company says this capability is more than double the level of the industry's more commonplace four-channel versions.

Bookham's thin film design team leader, Loren Stokes, explained the significance of the development: "Four years ago, '4 skip 1' - four channel filtering with the loss of one adjacent channel, due to signal degradation/interference at the filter's edge - banded filters were at the forefront of design. By 2002/2003, Bookham and other companies had introduced '4 skip 0' filters to the market, eliminating the need for skipped channels."

Stokes says the devices have achieved both '8 skip 0' and '10 skip 0' filters, and they are ideal for low multiplexers and demultiplexers that can now be built with a simplified, flexible, and lower cost architecture.

8 skip 0 and 10 skip 0 designs require nm-level precision on the thickness of each of 300 different SiO2 and Ta2O5 layers that are part of the design.

- John Walko

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