Optical Alphabet Soup

6:30 PM -- One of the more interesting findings of Heavy Reading's latest report is the fact that a vast majority of service providers have no idea which modulation scheme is best for new 40-Gbit/s and 100-Gbit/s networks. (See The Road to 100G Winds Up Carriers and Optical's Great Leap Forward.)

According to a survey of 105 service providers, which is in the report entitled The Future of Optical Transport Networks: 40G & the Road to 100G, more than 70 percent do not know or are unsure which modulation scheme they should use when deploying higher-capacity networks.


"Based on this research, there's not a tremendous amount of knowledge out there about which modulation scheme is best," says Heavy Reading analyst Sterling Perrin. "Everyone is trying out a different approach, so it will be a challenge for suppliers to convince operators that their solution is the best."

Part of the problem, Perrin says, is that all of the abbreviations for these different modulations schemes look the same -- DQPSK, DPQPSK, DPSK, partial DPSK, etc.

It's what he calls a modulation alphabet soup, which is just serving to confuse the market further.

This becomes problematic as service providers look to deploy 40-Gig technology, because some are doing so with an eye to using the same technology for 100 Gig.

"If you buy into someone's 40-gig equipment you'd probably want to go with them for 100-gig, which is probably the way operators will want to do it," Perrin says.

But how can you bet on a modulation scheme if you aren't sure it's what's best? Or even what the acronym stands for?

— Ryan Lawler, Reporter, Light Reading

paolo.franzoi 12/5/2012 | 2:58:34 PM
re: Optical Alphabet Soup
They were all invented in the 50s and have been around a long time in MODEMs (which depending on which type of MODEM you have has one or more of the modes in it).

At the end of the day, there is really only two questions that need to be asked about a modulation scheme:

1 - How immune to various types of noise sources is it
2 - How much does it cost to implement?

The former will tell you how many bits per symbol you CAN send across a connection. The latter will tell you how many bits per symbol you CAN AFFORD to send across a connection.

The answers to question 1 is well studied for all of these modulation methods, IFF (if and only if) one can describe the noise models. So, if that can be managed then the "best" modulation scheme is a factual piece of information (i.e. it comes from Physics).

The cost of various schemes is much more debatable and involves funny vendor math.

Hope this helps.

cw.774 12/5/2012 | 2:58:33 PM
re: Optical Alphabet Soup although it sounds exactly like the optical duobinary (ODB!!). How many are referrring to the same exact thing is the best question.
rahat.hussain 12/5/2012 | 2:58:29 PM
re: Optical Alphabet Soup For those who do not understand their basics, this press release should clear everything up -


Sterling Perrin 12/5/2012 | 2:58:28 PM
re: Optical Alphabet Soup What do rocket scientists say when referring to easy tasks? Maybe they say, "Well, it's not optical physics." Just a thought.

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