1. Optical Communications: from the Smoke Signals to Gigabit Internet
Vittorio Curri
OptCom
DET, Politecnico di Torino, Torino, Italy.

2. The origin Communications is a fundamental need for human beings
With the growth of social structures also telecommunications became fundamental
Eyes are the longest-reach human senses
So wireless optical communications was the first option

3. Wireless optical communications
For thousands of years optical wireless numerical telecommunications has been the only choice
1793: Chappe’s optical telegraph…
…and its encoding table

4. Telecommunications based on EM signals
1837: telegraph
Across 18th-19th century theory of electricity was developed
The telegraph was the first application of electricity in telecommunications, still numerical transmission
Then the telephone was invented and the analog age started
1856: telephone

5. The ancient WWW: telegraph network
1866: first transatlantic cable
1901: telegraph network

6. 1895-1901: Guglielmo Marconi went wireless
1929: UK wireless network

7. From the analog to the digital age
: The analog century
Telephone
Radio broadcasting
TV broadcasting
1980’s: The digital age starts
Personal Computers
Cellular phone
Optical fiber communications
A connected world exchanging information on the global network  INTERNET

8. The optical fiber A tiny pipe (125 mm diameter)
for light, made of glass

9. Optical Communications history (I)
1977: (Bell Labs) one-million hours lifetime for diode lasers
1978: (NTT Lab) single-mode fiber (SMF) with 0.2 dB/km 1550 nm
1982: MCI installs SMF from New York to Washington carrying a single 400 Mbit/s
1987: (University of Southampton) EDFA 1550 nm
1996: First unrepeated trans-Atlantic link (TAT 12/13) single wavelength per fiber, 5 Gbit/s

10. Optical Communications history (II)
: thanks to WDM performances of optical systems doubles steadily every nine months
2000: long-distance links with 100 channels at 10 Gbit/s per channel (1 Tbit/s) are demonstrated over km
2000: several trans-Atlantic and trans-Pacific systems are being built at 160 Gbit/s (16 x 10 Gbit/s) per fiber
: No major advances due to the internet bubble
2009: Multilevel modulation formats with coherent receiver at 100 Gbit/s per channel
2014: 10 Tbit/s per fiber commercially available reaching thousands of kilometres

11. 2015: undersea optical cables

12. Optical communications: state-of-the art……
Pseudo Nyquist WDM transmission
Bopt = 5 THz
Rs=32 Gbaud (25 net + 28% FEC+protocol overhead)
Channel spacing: Df= 50 GHz  Nch = 100 ch/fiber
Modulation format: up to 8 bit per symbol (BpS)
Net bit rate per channel: Rb up to 8x25= 400 Gbps/ch
Overall aggregated rate: 40 Tbps/fiber

13. Optical communications: state-of-the art
Several fibers/cable
Let’s assume Nf=100
It means Nfp=50 bidirectional fiber pairs
Overall fiber cable bidirectional capacity:
2 million Gbitps !!!!!

14. How many internet conections?
1 Gbps corresponds to 100 internet connections at 10 Mbitps
So, at the state of the art, a fully spectrally populated fiber link including 100 fibers/cable may carry up to
Quite impressive, isn’t it?
And we are far from saturation….
200 million internet connections at 10 Mbitps

15. What next?
In modern fibers the low-loss available spectral window is roughly THz
We are currently exploiting only the C-band because of amplifier bandwidth
A realistic mid-term forecast is for Bopt=15 THz

16. 1 billion internet connections at 10 Mbitps
What next?
So, we can envision a more than 3-times bandwidth extension
We can also envision a reduction of channel spacing down to the symbol rate  pure NyWDM
Let’s redo some math…
Bopt=16 THz
Nch= 16000/32=500 channel per fiber
1 billion internet connections at 10 Mbitps

17. The highway metaphor
We have - or we’ll have soon - the availability of huge highways for IP traffic
Outside the highways we have an increasing dimension web of local roads
The challenge for the future is to be able to fill the highways!

18. The internet galaxy
Internet is the union of back-bone and access networks
Back bone networks are made of high capacity optical links
Access technologies are a mix of wireless and wired solutions

19. How many internet users?

20. Overall IP traffic Global IP traffic
Global IP traffic has increased fivefold over the past five years, and will increase threefold over the next five years. Overall, IP traffic will grow at a compound annual growth rate (CAGR) of 23 percent from 2014 to 2019.
Busy-hour Internet traffic is growing more rapidly than average Internet traffic.
Global IP traffic

21. Which applications? Global IP traffic
The sum of all forms of IP video, which includes Internet video, IP VoD, video files exchanged through file sharing, video-streamed gaming, and videoconferencing, will continue to be in the range of 80 to 90 percent of total IP traffic. Globally, IP video traffic will account for 80 percent of traffic by 2019 
Global IP traffic

22. Wireless vs. wired Global IP traffic
Traffic from wireless and mobile devices will exceed traffic from wired devices by By 2016, wired devices will account for 47 percent of IP traffic, and Wi-Fi and mobile devices will account for 53 percent of IP traffic. In 2014, wired devices accounted for the majority of IP traffic, at 54 percent.
Global IP traffic

23. Evolution of optical networks (I)
Regarding the optical back-bone networks, solutions are incremental starting from state of the art…
Firm constraints of carriers regard maximal exploitation of installed equipment
They aim at maximizing economical returns without replacing installed transmission equipment
Regarding the use of the spectrum
Keeping fixed grid
Migrating to flex-grid

24. Evolution of optical networks (II)
Keeping fixed WDM grid
Introduction of transparent wavelength routing in nodes
Use of elastic transponder
Improvement of amplifiers’ quality using hybrid Raman/EDFA fiber amplifiers
Use of spatial division multiplexing among the available fibers
Extension of bandwidth per fiber
Migrating to flex-grid
Many different options depending on the transponder technology
OFC 2014
JLT invited paper, Jan 2016

25. A novel approach to the network analysis
In modern networks based on NyWDM and multilevel channels, lightpath QoT depends on
where
thanks to the GN-model developed by the OptCom group
JLT best paper award 2015

26. Some results…
ECOC 2015
OFC 2016

27. How to move forward?
Joint NUST-POLITO laboratory on Broadband Networks
Research areas
Transmission techniques
Node/transponder structure
Energy efficiency
Flexible optical networks
Traffic modeling, including Wireless generated traffic
Student exchange
Faculty collaboration
Joint research project
Industrial partnership

28. Thank you for your attention