San Fran-Sydney?

Recent travels took me back to Australia, home to the Sydney Opera House, the Outback, the Great Barrier Reef, “The Ashes” (a cricket Test tournament held at least every four years between England and Australia Cricket teams – think the Ryder Cup of Cricket) and of course Finisar Sydney, the home of Finisar’s Wavelength Selective Switch R&D team (whom you may enjoy the pleasure of meeting in the Finisar booth at OFC in San Francisco this March). This is the world’s sixth largest country by land mass, often refered to as the world’s smallest continent or largest island, with national average wealth second only to Switzerland. In spite of a more than 30 hour trek literally to the other side of our globe, coupled with the extreme change in weather from mid-Winter in England to mid-Summer in Australia, all seemed strangely familiar.

Of course this is not too surprising given the English heritage of this still relatively young nation, but the presence of red suited white bearded Santa’s and inflatable snowmen next to ‘snow’ drizzled conifers certainly helped – in particular the 10 giant inflatable santas magically floating on Cockle Bay in Darling Harbour Sydney struck a welcome chord and reminder of the festive season. This trip to Australia included visits to Canberra and a couple of days in Sydney, both firsts for me. As you may expect, Canberra, being the Capital City and centre for the Nation’s Government, is a very well developed, planned and maintained city, the surprise for me being the availability of some of the best and most diverse cuisine I’ve enjoyed for a while. There’s everything here from the familiar pie and chips for us Brits to an explosion of Asian spices in Thai, Malaysian and Indian restaurants. Sydney proved equally impressive on the culinary front, with the addition of a very diverse and edgy nightlife in the downtown area. I had been told by several folks that Sydney ‘is a lot like San Francisco’, but having not inquired much beyond to find out what it is that is similar between the two, I was stunned to find a rolling city built on hills with architecture so akin to that in San Francisco that you could close your eyes (put on a big coat and pretend to be very cold) and imagine yourself in Noe Valley, Russian Hill or The Castro. No words from me could explain just how shockingly similar in look and feel these two cities really are, but I think the term San Fran-Sydney will stay with me for a while…

It’s no secret that the people of Australia are very open and to the point, but what is sometimes lost is that this is also a nation of very social, welcoming and generous people – with England frankly taking the worst possible beating by Australia while I visited (Sidenote – I suspect some of the welcomes were based on the joy of having such an easy target on home soil.). The combination, when applied to the business environment is a very welcome one for me – you are not left guessing if you’ve asked the right question or what the real answer is…you’ll be told directly and politely what you need to know. That same directness is evident in the institutional and national focus on advancement in communications. This is a hot bed of development in optical communications, both the design of the elements required for the next generation of optical networks happening everyday at Finisar’s Sydney office, but also the aggressive initiatives to bring broadband to all homes, offices, schools and institutions in one of the most geographically and meteorologically challenging countries in the world. These efforts in part are driven by a desire to keep Australia on the cutting edge of communications and making sure that all of its citizens have the opportunity for access to our ever shrinking world’s ever growing ‘cloud’ of data, be they in downtown Sydney or Alice Springs.

It’s an exciting time to visit DownUnder in my view and regardless of timing, this is a beautiful, surprising and welcoming destination whether you’re a backpacker or a Smartphone and Tablet junky desperate to remain online – there are many resources here including gold, coal, uranium and no shortage of fibre optic connected data! I look forward to my next visit…

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.

References
1http://investor.finisar.com/releasedetail.cfm?ReleaseID=707170
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. http://www.electronics-cooling.com/1996/09/heat-pipes-for-electronics-cooling-applications/