Introduction to CML Technology

CML™ is a technology that I plan to discuss in many more postings.

CML stands for Chirp Managed Laser. CML technology was originally developed by a company called Azna which Finisar acquired in 2007. The original team remains largely intact and we are continuing to develop this technology in our Wilmington, MA facility.

One of the key advantages of CML technology is that it has extremely good dispersion properties over fiber. For example, Finisar has developed an XFP that is dispersion tolerant to over 200km of SMF at 10Gb/s. At OFC this year, we also published a post-deadline paper showing the results of some testing where we were able to make an SFP+ at 10Gb/s run without dispersion compensation over 360km of fiber. Of course, this 360km SFP+ is not a real product, only a lab experiment, but it puts into light some of the awesome capabilities of this technology.

We are developing several flavors of CML transmitters (including TOSA and butterfly packages) in our Wilmington, MA facility, and all of these will be manufactured in our Shanghai facility. Many of those will end-up in Finisar modules.

If you have any questions or thoughts about Finisar’s CML technology, feel free to comment here.

OFC ‘09, ROADM technology and the future network

This week’s entry comes from Ian Clarke. Ian is one of our key technical guys in our Sydney facility, where Finisar develops and manufactures our WSS (Wavelength Selective Switch) modules.

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OFC 2009 felt like a giant planning meeting for 100 Gb/s systems. Everywhere could be heard debate and proposals for components, protocols and modulation methods. The most difficult component is clearly the transponder. In particular, the ASICs for the receivers look very challenging to build. How do you build an analog–to-digital converter that runs at 60+ Gb/s; and when you do, how do you process the data fast enough?

However, my real interest was the requirements for wavelength selective switches (WSS), which also received plenty of attention. The most interesting requirement for an engineering manager like me is to know when we need to deliver these parts.

On Sunday, Glenn Wellbrock from Verizon described a series of trials of 100 Gb/s Ethernet signals. On Monday Jim King from AT&T described their initial build out of their 40 Gb/s system between “NFL cities” (the 25 biggest cities in the US). He stated that he could use 100 Gb/s channels now if he could get them, but in reality he didn’t think he would be deploying them seriously until 2011. Similarly, a Nokia–Siemens paper suggested that 2012 would be the critical year for 100 Gb/s systems. However, Glen Wellbrock’s message was that they wanted to be building 100 Gb/s ready systems that ran 40 Gb/s until the transponders were ready. This suggests that we are likely to see requirements for ROADMs, amplifiers and other components to be “100 Gb/s ready” quite soon.

This raises the question: what sort of WSS should we be building for 100 Gb/s systems? The required bandwidth depends on the modulation format that finally dominates. Last year, Chandresekhar’s paper from ALU Bell Labs used PM-RZ DQPSK (polarization multiplexed return-to-zero differential quadrature phase shift keying) needing a huge 44.5 GHz bandwidth (try to fit that in a 50 GHz window!). Renaudier’s paper (also from ALU, this time from France and also published last year, but mentioned in this year’s workshop) needed only 35 GHz to achieve zero penalty on a PM-RZ-QPSK with coherent detection. 16-QAM (quadrature-amplitude modulation) systems are more efficient, but are so complex to build that I feel would be unlikely to be the first system used. Other contenders are 8-PSK (phase shift keyed) and OFDM (orthogonal frequency division multiplexing), but these have their own issues. Coherent detection systems have advantages in CD chromatic dispersion) and PMD (polarization mode dispersion) tolerance. If we assume that the initial 100 Gb/s systems will use a coherent PM-RZ-QPSK modulation format, which is a reasonable guess at the moment, then targeting a ±17.5 GHz real, concatenated bandwidth for 2010 would be reasonable.

Ian Clarke is an Engineering Manager for Finisar Australia (Ian.Clarke@finisar.com).

40Gb/s DWDM DQPSK with EDFA and WSS ROADM architecture….say what?

The fiber optic communications industry can often sound like an alphabet soup. For example, when we talk about common transceiver/transponder form factors, you often hear terms like SFF, SFP, SFP+, XFP, XPAK and X2. In the ROADM world, a WSS stands for Wavelength Selective Switch and ROADM means Reconfigurable Optical Add/Drop Multiplexer. These short acronyms may save a few important minutes in your day by facilitating more efficient communication not to mention a few vital breaths. Needless to say, there is an endless list of commonly used acronyms in our industry.

That all said, I have often found it helpful to refer to the Finisar Optics Acronyms Reference Guide and Optical Modules Reference Guide created by our very own marketing team. The acronym reference guide provides a short list of commonly used acronyms in the optics industry while the Optical Modules guide defines the major transceiver/transponder form factors available in the industry, not to mention colorful examples of typical datacom and telecom networks.

So if the first things that comes to mind when you see the letters “RFoG” is a small green amphibian (not Radio Frequency over Glass), then go ahead and look it up on our blog. I hope you’ll find both reference guides as useful as I do. Feel free to pass these on and send me your favorite optics acronyms so I can add them to the list.  

OFC Wrap-Up and the Difference Between CFP and CXP

OFC is over. This concludes one of the most grueling weeks for a marketing guy in this industry!

To steal the words of one of our engineers from Sydney, OFC 2009 could be seen “as a great planning meeting for 100G.” Examples of this are as follows:

1. The introduction of the CFP form factor for 100Gb/s and 40Gb/s applications.

2. A very nice debut for CXP. Note that CXP is a very different form factor to the CFP mentioned above – don’t let the fact that the names look similar fool you. I have added more details on the differences between these form factors below. There were multiple companies (including Finisar) at OFC that appear to be backing CXP for clustering and high-speed computing applications, and I believe this bodes well for CXP’s adoption.

3. And most certainly, lots and lots of discussion about 100G line-side and all the different technical solutions, system architectures, and development options to get products to market.

Both CXP and CFP are pluggable form factors incorporating transmitter and receiver capabilities, and can be used at data rates up to 100G+. However, that is the extent of their similarities.

These form factors are very different in size. The CXP cage footprint on a host board is roughly 45mm (length) x 27mm (width). By contrast, the footprint of the CFP rail assembly is about 120mm (length) x 86mm (width).

CXP is a form factor targeted at extremely dense high-speed parallel interconnections for 12xQDR InfiniBand (120Gb/s) applications, multimode 100GE applications, and proprietary protocols for inter-chassis links. It includes up to 12 transmit and receive channels in a very small package. With each channel running at 10Gb/s, this form factor can enable a front panel density 9x greater than that of an SFP+ running at 10Gb/s. It is designed to be used with parallel multi-mode fiber ribbons and would typically be used for applications up to 100 meters. CXP is currently being standardized by the Infiniband Trade Association (IBTA).

By contrast, CFP is a highly flexible form factor for 40Gb/s and 100Gb/s applications. The flexibility will come from the fact that many different types of data rates, protocols and link lengths can be supported by this single form factor. This will make it easy for our customers to design systems that can ultimately incorporate things like 40GbE, 100GbE, OC-768/STM-256, and OTU3 over different media types including both multimode and single mode fiber and over varying link distances. The CFP is a multi-source agreement with Finisar, Opnext and Sumitomo being the 3 founding members .

For more coverage of OFC 2009, check out these videos from Lightwave Channel and Lightreading TV.

OFC Wrap-Up and the Difference Between CFP and CXP

OFC is over. This concludes one of the most grueling weeks for a marketing guy in this industry!

To steal the words of one of our engineers from Sydney, OFC 2009 could be seen “as a great planning meeting for 100G”. Examples of this are as follows:
1. The introduction of the CFP form factor for 100Gb/s and 40Gb/s applications.
2. A very nice debut for CXP. Note that CXP is a very different form factor to the CFP mentioned above – don’t let the fact that the names look similar fool you. I have added more details on the differences between these form factors below. There were multiple companies (including Finisar) at OFC that appear to be backing CXP for clustering and high-speed computing applications, and I believe this bodes well for CXP’s adoption.
3. And most certainly, lots and lots of discussion about 100G line-side and all the different technical solutions, system architectures, and development options to get products to market.