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from Electronics Domain to Fibre Optics,"
Technologies Bell Laboratories.
Technologies Bell Laboratories. He heads all Bell Labs research on optical fibre and
photonics systems.
He was in India recently to address the plenary
session in Photonics ’98 and deliver the keynote address in the ceremony for the
Fibre Optics Person of the Year award.
optics research and usage while giving some interesting insights into the paradigm shifts
in the capability of optical fibres to COLOR="#016077">Shyamanuja Das.
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Today, you have data packets
with intelligence on how they will reach next destinations. With WDM and multiple
channels, you can mark those packets with the final destinations.
do you see the capability of fibre optics 10 years from now? COLOR="#000000">
That is a long period.
Fifty to hundred terabits per second is what one can imagine. But that is also not
practical. Roughly, the capacity increase will be growing by a factor of two every year.
That way, you get 128 terabits per second in seven years. But I don’t think that will
happen. After the initial few years, it should slow down. I think 10 terabits per second
is most likely.
And I am talking of long-distance. Because
the capacity also depends on distance. A big trend today is the metropolitan area
networks, where fibre is being deployed. It started with long-distance. It is coming to
metropolitan networks. It should come to LANs. But there, 10 gigabits is what will get
deployed.
You said a factor of two annually. But electronics, if we
go by Moore’s law, will grow by a factor of two in 18 months. That means there is a
lag. Also, fibre technology is already ahead. Don’t you think there will be a problem
if electronics does not keep pace with the developments in fibre and photonics?
There is already a problem. Even with 10
gigabits per second, if you use TDM, it means your electronics equipment have to switch on
and off at that speed.
But WDM does not require that switching
speeds in electronics. In fact, WDM is actually an answer to that problem. You are not
constrained by the speed of electronics.
But do we need that kind of capacity?
Of course, in the short run, we do. But
after some time, we will have reached a point where we will have excess capacity. Then
there will be a wastage of bandwidth. Today, do you bother about how much hard disk space
lies unused? Does anyone care about efficient management of that resource? When technology
matures, it is available in plenty and people start wasting it. That will happen with
fibre.
Today, there is so much concern, because
bandwidth is scarce. What I am not suggesting is we should not worry about bandwidth.
Today, everyone knows we require bandwidth. But there is a limit. A time will come when it
will be wasted. Say, when every person gets a gigabit of it (laughs)!
But the advances in fibre optics research is only for
higher capacity, higher transmission speeds. Do you think any functionalities of
electronics will come to fibre?
Yes. Routing will come to fibre. Today,
you have data packets with intelligence on how they will reach next destinations. With WDM
and multiple channels, you can mark those packets with the final destinations. And they
will straightaway travel there. All destinations will virtually be point-to-point
connected. The network will become a virtual mesh.
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Is that just a concept ... COLOR="#000000">
No. We are working on it in our labs,
though a field testing is yet to be done. And it is working in the labs. We are trying to
convince the carriers. I think it will happen soon.
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OK. Let’s now come to the most important thing. The
cost. What are you doing to bring the cost down?
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Today, for any researcher that is the
driving factor. In fact, large scale deployment–fibre-to-the-office and
fibre-to-the-home–is possible only when cost comes down drastically. We are working
to reduce the cost of the fibre networks in many ways.
These fibre-based data networks that I
talked about is much cheaper. WDM will make things cheaper as you do not spend on costly
electronics. Greater automation in manufacturing will also help to bring the
costs down. In fact, fibre is already cheap. It is the connectors, filters, the laser
devices which are costly. Fibre is actually cheaper than copper ...
Well, I do not think that is true today. Optical fibre
cables are much costlier than copper cables ...
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Well, I do not understand that. Fibre
should be cheaper than copper. I would like to know why it is not. You should ask these
questions to the people who are selling them. All the companies. As a researcher, I do not
know the dynamics of pricing. But I would definitely like to know why is fibre not cheaper
than copper. I do not see any reason.
Yes, when I say fibre, I am talking of
single-mode fibres which the telcos use. Multimode fibres which are used in corporate
networks are costlier.
I think it has to do with volumes. Fibre volumes are still
much lower compared to copper ...
Probably that is the reason. It is still
tens of thousands, not multi millions.
When do you think developing nations like India will go
for technologies such as WDM?
They should plan now. They can start
small. They do not need to go for 80 wavelengths to start with. They can start at two and
go on adding more boards as and when they need more capacity. But deploying fibre now
makes a lot of business sense, as you will protect investment.
In fact, I think even for India, not
investing now is not sensible. We know the same thing will happen in India what has
happened in the US, when Internet usage grows. When you have time and not much legacy, it
is better to make use of the situation. India can actually avoid the bottlenecks others
are facing. I think India will do that.
Are you hopeful? COLOR="#000000">
Yes. I met Chandrababu Naidu, the chief
minister of Andhra Pradesh. He is planning to deploy a high capacity network in Hyderabad.
He is passionate about his plans.
When do you think the major transition from copper to
fibre will happen globally?
It is beginning now. I think next year,
there will be a lot of activity. And the subsequent year will see that change. I feel the
next two years are very, very important. The diminishing boundaries between voice and
data, between the telco business and enterprise business, will be the catalyst.
To conclude, what are the major challenges before the
fibre optics research community?
I see three major challenges. One, of
course, is more capacity. That means faster electronics for TDM. Efficient use of the
technologies. What I mean is the right combination of TDM and WDM.
Second big challenge is wavelength
agility. Being able to convert from one wavelength to another easily. Today, we are
beginning to do that in labs. It is still not possible commercially.
Third and the biggest challenge is optical
cross connect. Efficiently being able to do that will take us a long way. Today you have
80 channels, and if you use eight fibres, it is 640. Being able to cross connect them is
challenging.
And above all, the
underlying objective, the most important one, as you also said, is cost. Bringing the cost
down. That is the single most important challenge for the whole fibre optic community.