For those of you that have been in the industry for what seems to be 100 years, but is really about 25 years, you know that the one “connector” that hasn’t changed much is the RJ45. While there have been improvements by adding compensation for the error that was made way back when AT&T developed the wiring pattern (splitting the pair causing major crosstalk issues), the connector itself has remained intact. Contrastingly, optical connectors for datacom applications have changed several times – ST to SC to MT-RJ to LC. They have finally seemed to settle on the LC and perhaps on a transceiver form factor – the SFP+. The SFP was originally introduced at 1G, was used for 2G and 4G and with slight improvements has become the SFP+ and the dominant form factor now used for 10G. Well, it is in the process of getting some slight improvements again and promises to make it all the way to 32G. That’s six generations of data rates – pretty impressive. But how?
The INCITS T11.2 Committee's Fibre Channel Physical Layer – 5 (FC-PI-5) standard was ratified in September. It specifies 16G Fibre Channel. Meanwhile, the top transceiver manufacturers have been demonstrating pre-standard 16G SFP+ SW devices. But, wait a minute – short-wavelength VCSELs were supposed to be very unstable when trying to modulate them at data rates above 10G right? Well, it seems that at least Avago and Finisar have figured this out. New microcontrollers and adding at least one clock and data recovery (CDR) device in the module to help clean up the signals have proven to be keys. Both vendors believe it is possible to do this and not add too much cost to the modules. In fact, both also think that possibly by adding electronic dispersion compensation (EDC) they can push the SFP+ to 32G as well - which is the next step for Fibre Channel - hoping to stop at 20G and 25G to cover developments in Ethernet and InfiniBand.
And what about long wavelength devices? It has always been a challenge fitting the components needed to drive long distances into such a small package mainly because the lasers need to be cooled. But not anymore – Opnext has figured it out. In fact, it was showing its 10km 16G FC SFP+ devices long before any of the SW ones were out (March 2010). Of course, this isn't surprising considering Opnext has already figured out 100G long haul as well.
These developments are important to datacom optical networking for a few of reasons:
- They show that Fibre Channel is not dead.
- The optical connector and form factor "wars" have seemed to subsided so transceiver manufacturers and optical components vendors can focus on cooperation instead of positioning.
- They will impact the path other networking technologies are taking – Ethernet and InfiniBand are using parallel optics for speeds above 10G – will they switch back to serial?
Stay tuned for more on these points later.
In our rush to want to discuss all the new technologies, it seems to me that analysts have forgotten that part of our job is to also point out ongoing trends in existing products. So while talking about Gigabit transceivers might not be as appealing as talking about Terabit Ethernet, it’s also a necessity – especially since, without these devices and the continuing revenue they produce, we wouldn’t have 40/100G or even 10G Ethernet. So what are the important points to make about Gigabit transceivers?
- The market for Gigabit Ethernet transceivers (copper and optical) is expected to be about $2.5-billion in 2010 according to CIR, but it is also supposed to start declining in 2011 when more 10GigE will take its place.
- Pricing for a 1000BASE-SX SFP module is now at about $20 for OEMs. End users still pay Cisco or Brocade or their agents about 8x that much (more about this later).
- Low pricing makes it difficult on profit margins so transceiver vendors hope to make it up in volume.
- While SFP is certainly the preferred form factor, there is still a decent amount of GBIC modules being sold.
- SFP direct-attach copper cable assemblies have become an option for top-of-rack switches to servers instead of using UTP Category patch or fiber cabling, although the majority of implementations today are still UTP patch cords, mainly because the connections within the rack are still 100M with the uplink being Gigabit Ethernet of the 1000BASE-SX variety.
- While 10/100/1000 ports are the norm for desktop and laptop computers, most of these devices are still connected back through standard Category 5e or 6 cabling to 100M switch ports in the telecom room.
- Gigabit Fibre Channel business is pretty much non-existent now. It was quickly replaced by 2G and has progressed through 4G and 8G is expected to become the volume application this year. Look for more on Fibre Channel in future posts.
- Avago Technologies and Finisar top the list of vendors for 1000BASE-SR devices. JDSU has all but disappeared from the scene, mainly because they have de-emphasized this business in favor of their telecom products. In fact, rumor has it that JDSU is shopping its datacom transceiver business and has been for some time.
A note on JDSU: It appears that the optical components giant has taken the technology that was developed at IBM, E2O and Picolight and thrown it away. Picolight was once a leader in parallel optics and, along with E2O, long-wavelength VCSELs. IBM pioneered v-groove technology and the oxide layer that enabled the next leap in speed and improved reliability for 850nm VCSELs. All of these technologies look like they are destined to die a slow, painful death after being acquired by JDSU. The company’s attention is clearly focused on its tunable technology and telecom applications, which is where, of course, it started. JDSU has never had a good reputation for assimilating acquisitions, so none of this should be a surprise. I was optimistic when JDSU bought these companies thinking that now these emerging technologies would be supported by a larger pocketbook. What is the reasoning for JDSU deemphasizing the technologies it acquired? Is it trying to get rid of short-reach competition in hopes that all optical networking would move towards long-wavelength devices? This would have been naïve; the likes of Finisar, Avago, MergeOptics and others would still be supporting 850nm optics and there remains a healthy market for them in enterprise networks and data centers—albeit a very competitive one as stated above.
Yesterday, I sat through a workshop hosted by the Optical Interconnecting Forum (OIF) on its “Common Electrical Interface (CEI) project for 28G Very Short Reach (VSR).” What quickly became clear to me was that I was in a room of VERY optimistic engineers.
I sat through presentations that were characterized as “Needs of the Industry,” which consisted of content from the leaders of IEEE 802.3ba (40/100G Ethernet), T11.2 (Fibre Channel) and InfiniBand standards groups. Yet all of these representatives made sure they carefully stated that what they were presenting was their own opinions and not that of their standards groups, which I found odd since most of what they showed was directly from the standards. Legalities I guess. I also noticed that they never really sited any kind of independent market research or analysis of what the “needs of the industry” were. For instance, one speaker said that InfiniBand has a need for 26AWG, 3-meter copper cable assemblies for 4x25G operation in order to keep the cost down within a cabinet. Yet, he did not present any data or even mention what customers are asking for this. Maybe this exists, but to me unless it is presented, the case for it is weak. I do have evidence directly from some clustering folks that they are moving away from copper in favor of fiber for many reasons – lower power consumption, weight of cabling, higher density, and room in cabinets, pathways and spaces.
Today, data center managers are really still just starting to realize the benefits of deploying 10G, which has yet to reach its market potential. I understand that standards groups must work on future data rates ahead of broad market demands, but this seems extremely premature. None of the current implementations for 40/100G that use 10G electrical signaling have even been deployed yet (except for maybe a few InfiniBand ones). And, from what I understand from at least one chip manufacturer who sells a lot of 10G repeaters to OEMs for their backplanes, it is difficult enough to push 10G across a backplane or PCB. Why wouldn’t the backplane and PCB experts solve this issue that is here today before they move onto trying to solve a “problem” that doesn’t even exist yet?
Maybe they need to revisit optical backplanes for 25G? It seems to me that 25G really won't be needed any time soon and that their time would be better spent on developing something that would appear to have relevancy beyond 25G. To me, designing some exotic DSP chip that would allow 25G signals to be transmitted over four-to-12 inches of PCB and maybe 3m of copper cable for one generation of equipment may not be very productive. Maybe this is simpler than I anticipate, but then again, there was a similar but a little more complicated problem with 10GBASE-T and look how that turned out...
