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

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 www.optcom-polito.it

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 www.optcom-polito.it

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 www.optcom-polito.it

The ancient WWW: telegraph network 1866: first transatlantic cable 1901: telegraph network www.optcom-polito.it

1895-1901: Guglielmo Marconi went wireless 1929: UK wireless network www.optcom-polito.it

From the analog to the digital age 1880-1980: 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 www.optcom-polito.it

The optical fiber A tiny pipe (125 mm diameter) for light, made of glass www.optcom-polito.it

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 loss @ 1550 nm 1982: MCI installs SMF from New York to Washington carrying a single wavelength @ 400 Mbit/s 1987: (University of Southampton) EDFA operating @ 1550 nm 1996: First unrepeated trans-Atlantic link (TAT 12/13) single wavelength per fiber, 5 Gbit/s www.optcom-polito.it

Optical Communications history (II) 1996 - 2000: 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 10000 km 2000: several trans-Atlantic and trans-Pacific systems are being built at 160 Gbit/s (16 x 10 Gbit/s) per fiber 2000-2005: 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 www.optcom-polito.it

2015: undersea optical cables www.optcom-polito.it

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 www.optcom-polito.it

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 !!!!! www.optcom-polito.it

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 www.optcom-polito.it

What next? In modern fibers the low-loss available spectral window is roughly 30-40 THz We are currently exploiting only the C-band because of amplifier bandwidth A realistic mid-term forecast is for Bopt=15 THz www.optcom-polito.it

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 www.optcom-polito.it

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! www.optcom-polito.it

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 www.optcom-polito.it

How many internet users? www.optcom-polito.it

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 www.optcom-polito.it

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 www.optcom-polito.it

Wireless vs. wired Global IP traffic Traffic from wireless and mobile devices will exceed traffic from wired devices by 2016. 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 www.optcom-polito.it

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 www.optcom-polito.it

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 www.optcom-polito.it

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 www.optcom-polito.it

Some results… ECOC 2015 OFC 2016 www.optcom-polito.it

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 www.optcom-polito.it

Thank you for your attention www.optcom-polito.it