Trends in ROADM Line Card Development

Finisar is not only the leading manufacturer of LCoS-based Wavelength Selective Switches (WSS) but has also been a supplier of ROADM linecards, based on our range of WSS, for over 5 years. During this time, we have established the capability to supply both the components and sub-assemblies comprising line cards (including WSS, Optical Channel Monitors and Optical Amplifiers, both EDFA and Raman) as well as the line cards themselves1.

The evolution of ROADM line cards exemplifies the impact of the network operators’ needs for reductions in both Opex and Capex costs, size and power consumption whilst also providing greater flexibility and capability to support future network architectures.

These requirements are forcing a rethink of how line cards are designed and manufactured. Gone are the days of simply buying a bunch of optical subsystems from different manufacturers and assembling them on a circuit board with some additional control hardware. Instead, many designs require a complex disaggregation of optical modules to allow them to fit in the increasingly constrained space available2. Together with the need to optimize the relative performance of the different subsystems, this is driving changes in the way line cards are designed and manufactured.

To visualize what is happening, consider how an EDFA, which is a key subsystem on most line cards, can be transformed from an integrated module to a distributed system. In the latter, the pumps can be placed in the optimum location for thermal management, the Erbium fiber and fiber components can be arranged to fit around any other optical hardware, whilst the control electronics can be located wherever there’s room on the main line card circuit board.

Building on this idea of a distributed EDFA, the control electronics can also be designed to share common components (e.g. processors) amongst multiple subsystems which saves cost, circuit board real-estate and, critically, power the disaggregation and sharing of components allows the designer to optimize the packing density of optical functionality on the line card but that, in turn raises the problem that higher component density generally leads to greater thermal load (per unit area). Great care must therefore be taken to correctly model the thermal dissipation and ensure (as far as is possible) an effective layout of electronics and optics to optimize the thermal loading across the line card.

In addition to being able to pack more functionality into a given space by disaggregating the components, the fact that Finisar manufactures all the optical subsystems on a line card allows us to optimize the trade-offs between the different optical functions. We can therefore provide not only a smaller, lower power design, but also one that has improved functionality and hence provides more ‘bang for the buck’ for our customers.

To reduce costs, manufacturing practices must also change. For example, the ‘birds-nest’ of individual fibers, spliced together and placed in a fiber organizer is being replaced by ribbonized fibers where ever possible to simplify the assembly process and reduce costs. Ribbonized connectors like MTP assist in the process, as do subsystems such as multi-port Optical Channel Monitors. However, there is still some way to go before all the optical subsystems in a line card can be connected by fiber ribbon assemblies.

Looking ahead, the increased demand for denser packing is driving a requirement for ‘single-slot’ line cards. Whilst these can provide up to 2x the functional density of traditional double-height line cards, they introduce further pressure on component packing density and hence good thermal management engineering becomes even more important. For example, advanced cooling technologies such as heat-pipes3 may be required to prevent localized ‘hot-spots’ exceeding design temperatures.

The author would like to thank Ian Clarke and Ken Falta for useful discussions and inputs to this post.

2Clarke, I., “Building the next generation of linecards: the pleasure and pain of integration” Asia Communications and Photonics Conference (ACP), Beijing, November 2013
3See e.g.

Finisar Australia Founders Hono(u)red

Finisar Australia’s founders, Dr. Simon Poole and Dr. Steven Frisken, were honored last month as recipients of the prestigious 2013 Australian Academy of Technological Sciences and Engineering Clunies Ross Award for innovation in science and engineering. The citation for the award reads:

“To Dr Simon Poole and Dr Steven Frisken: Australia’s most successful commercialisers of new technologies which have shaped the internet worldwide, some of which are key components of the NBN in Australia. Their products, including undersea communication systems, have been sold to all the major telecommunications equipment manufacturers in Europe, the United States, Japan and China, and have generated exports worth hundreds of millions of dollars for Australia.”

2013 Australian Academy of Technological Sciences and Engineering Clunies Ross  Award

Dr. Poole and Dr. Frisken were presented with certificates and medals by Dr. Megan Clark, CEO of CSIRO Australia.

In accepting the award, Simon Poole and Steve Frisken emphasized that although they were the individuals receiving the award, it was a team effort to build and grow a company and that it was only through the hard work and dedication of everyone involved that technologies could be successfully commercialized.

Congratulations to Simon and Steve!

Finisar WSS WHITE PAPER: Balancing Performance, Flexibility, and Scalability in Optical Networks

The availability of Wavelength Selective Switches (WSS) supporting 100 Gb/s and 400 Gb/s data rates enables network operators to significantly increase bandwidth capacity in DWDM optical networks with substantial CAPEX and OPEX savings. Moving to such higher data rates, however, requires a shift from the continuing trend of implementing narrower optical channel spacing given that data rates beyond 100 Gb/s cannot fit within a 50 GHz channel….

Download Finisar’s latest WSS white paper from our website (see blue downloads box): Balancing Performance, Flexibility, and Scalability in Optical Networks

Finisar’s Flexgrid™ on display in Sydney’s Powerhouse Museum

Finisar’s DWP range of Wavelength Selective Switches, with their unique Flexgrid™ dynamic channel bandwidth technology, form the centrepiece of a new exhibition at Sydney’s Powerhouse Museum. The exhibition, which highlights Australia’s leading engineering success stories, was opened by Brendyn Williams, Engineers Australia Sydney Division President and Matthew Connell, Principal Curator, Physical Sciences & IT, Powerhouse Museum on the February 1, 2012. The opening was attended by engineers from the Finisar Australia team that developed the Flexgrid technology, together with 150 guests. Located in the entrance area of the museum, the exhibition will run until the end of 2012. More information can be found here.
Photos: Marinco Kojdanovski
Reproduced courtesy of the Powerhouse Museum, Sydney.

Finisar’s Flexgrid™ wins National Engineering Award

Finisar Australia’s Flexgrid™ technology has won another award – a National Engineering Excellence Award from the Institute of Engineers Australia. Fresh from winning the coveted Bradfield Award for best engineering project from the Sydney division of the IEAust, Flexgrid™ was one of only 6 national awards presented this year. The award was received by Steve Winnall, Director of Product Engineering, at a black-tie awards dinner in front of 600 guests at Parliament House in Canberra last month.

To quote the judges: “With the exponential growth of data capacity on the internet, the demand for more flexible and efficient optical network services from telecoms carriers is ever increasing. Finisar has met this demand with its new Flexgrid technology. Flexgrid is a unique software enhancement which allows telecommunications carriers to deploy bandwidth, flexibly and dynamically in their networks. Well ahead of their global competitors, Finisar have overcome several engineering challenges and have now successfully launched Flexgrid to the market.”

A video of Steve’s acceptance speech can be found at

Finisar was also represented at the ceremony by Andrew Bartos, Steve Frisken and Simon Poole, who, along with Steve Winnall and the MC for the evening, Sally Dominguez from the New Inventors TV Show, are shown in the photo below.

Congratulations to all involved in the Flexgrid™ program – and thank you for your hard work and dedication which have made the project so successful.