On Optical Communication,Reflections and Perspectives
Herwig Kogelnik
Bell Labs,Lucent Technologies,Crawford Hill Lab,Holmdel,NJ 07733,USA,herwig@lucent.com
Abstract Optical communication has advanced into the tera-era deploying 1/2 terameter of fiber and carrying
several Tb/s per fiber,Remaining challenges include extending the success of point-to-point long-haul to
metropolitan networks and broadband access applications,
Introduction
Reflecting on the past 15 years of optical
communication,one can only marvel at the amazing
advances in this technology and in its applications,
Technical progress seems to continue in spite of the
recent burst of the telecom bubble,At the end of
1994,a little less than ten years ago,somewhat more
than 50 million km of optical fiber had been deployed
worldwide for all applications.
1
Today more than 500
million km,i.e,one half of a terameter,are deployed,
More than 10 percent of this deployment is
attributable to recent installations in China,It is good
to remind ourselves that a fiber of 0.5 Tm length can
be wound more than 10 000 times around the earth,
In 1988 our technical community celebrated a major
milestone in optical fiber communication,This was the
deployment of the transatlantic fiber system TAT8
linking Europe and North America using about 6000
km of optical fiber cable,By 1991 fiber carried more
information traffic over international digital links than
communication satellites,Today a map of the global
undersea fiber network looks like a spider web
covering the globe with more than 600 000 km of fiber
cable.
2
And there is news of new construction of
undersea systems,particularly in the Indian Ocean
region,including the Falcon,SEA-ME-WE 4,and
Polarnet systems,
WDM and Optical Amplifiers
The early 1990’s witnessed a vigorous worldwide
effort to ready the network elements and components
for wavelength division multiplexing (WDM),These
included WDM laser sources,erbium-doped fiber
amplifiers,WDM routers and others,WDM provided
the parallelism needed to maintain increases in the
transmission capacity per fiber at the rate of 100
every 10 years,It also provided a new degree of
freedom and flexibility for the design of networks by
adding the wavelength dimension to the traditional
network dimensions of space and time,The economic
benefits of WDM were enabled by the optically
transparent amplifiers that can be shared between
many WDM channels,
The extensive deployment of WDM technology in the
AT&T long-haul network in 1995/1996 marks another
milestone in optical communications and the
beginning of the WDM revolution,This large-scale
installation of WDM systems involved thousands of
optical fiber amplifiers and hundreds of WDM SONET
terminals.
1,3
Terabits Capacity per Fiber
In addition to the new WDM components,researchers
conceived of new WDM system techniques
counteracting fiber impairments such as dispersion
and nonlinearities and allowing transmission at higher
capacities over longer distances,This includes the
discipline of dispersion management,where
detrimental nonlinear effects are balanced by a clever
choice of local fiber dispersion,In 1996 three
laboratories
4,5,6
simultaneously demonstrated system
research experiments achieving transmission at the
milestone capacity of 1 Terabit/second per fiber,In
2001,right on schedule with the traditional trend of
increasing capacity by a factor of ten every five years,
two laboratories
7,8
accomplished transmission
capacities of 10 Tb/s,The next milestone would be
100 Tb/s in 2006,However,there are not many who
expect that this can be accomplished,in particular as
attention is shifting to lower cost systems and ultra-
long-haul (ULH) transmission,
Today,modern commercial transmission systems
offer capacities of several Tb/s per fiber as illustrated
in one vendor’s table
9,10
shown below,The table also
shows the trend of system transmission capabilities
expressing progress better than words,Note the ULH
capability of 4000 km spans,the 5 petabit/s.km
capacity distance product,and the 40 Gb/s bit-rate
per WDM channel,Other recent advances include the
use of Raman fiber amplifiers,of advanced forward
error correction (FEC),and of WDM laser sources
tunable over 100 WDM channels,Further systems
advances are expected from new modulation formats
such as RZ-DPSK
11
offering more tolerance to system
impairments and/or better bandwidth efficiency,
Optical Networking
As the cost of optics is driven down,the applications
of fiber communication are expanding from long-haul
point-to-point systems to multipoint metropolitan
networks and to broadband access.
9
The new ULH
capabilities promise to enable all-optical networks,
Worldwide R&D efforts are exploring the networking
flexibility provided by the new WDM dimension,An
example is the 5-year,DARPA-led MONET program
conducted by AT&T,Bellcore,Bell Atlantic,Bell
South,Lucent,PacTel,and other RBOCs,Their goal
was to explore the realization of a seamless,fully
configurable,all-optical regional and national network
infrastructure.
12
Many new R&D programs have
sprouted from MONET and its counterparts,an
example being the new IRIS program,This explores
the design of scalable optical routers with throughput
of more than 100 Tb/s
using photonic integrated
circuits with a high level of integration and new
architectural ideas such as load balancing.
13
Conclusions and Outlook
The R&D community in optical fiber communication
has achieved much in the past and advanced the
technological capabilities by orders of magnitude,It
can be truly proud of these accomplishments,Many
challenges remain,including the extension of
broadband capabilities from the core network to the
end user,In this connection we will observe with great
interest the evolution of new network architectures,
the growth of 10-Gb Ethernet,and the fiber-to-the-
home projects in Korea and Japan.
14
References
1 C,Fan and L,Clark,Opt,& Photon,News,
vol.6,pp 26-32,(1995),
2 N,S,Bergano,Optical Fiber Telecom IVB,p,154
I,P,Kaminow and T,Li eds.,Academic (2002),
3 H,Kogelnik,Proc,ECOC 1996,paper MoA.2.2
4 H,Onaka,et al,Proc,OFC 1996,paper PD19
5 A,H,Gnauck,et al,Proc,OFC 1996,paper PD20
6 T,Morioka,et al,Proc,OFC 1996,paper PD21
7 K,Fukuchi,et al,Proc,OFC 2001,paper PD24
8 S,Bigo,et al,Proc,OFC 2001,paper PD25
9 R.C,Alferness,et al,in The Optics Encyclopedia,
pp 2119-2135,Wiley,(2004),
10 H,Kogelnik,IEEE J,Select,Topics in Quantum
Electronics,vol,6,pp 1279-1286 (2000),
11 A,H,Gnauck,et al,Proc,OFC 2002,paper
FC-2,
12 A,A,M,Saleh,Proc,OFC 1996,paper ThI3,
13 M,Zirngibl,Stanford Workshop on Load Balancing
May,2004,
14 H,Shinohara,Proc,OFC 2004,paper ThW2,
Table1,Commercial Transmission Systems
System Year
Wave-
length
WDM
chan-
nels
Bit rate/
channel
Bit rate/
Fiber
Voice
channels
per fiber
Regen
spans
FT3 1980 0.82 μm 1 45 Mb/s 45 Mb/s 672 7 km
FT3C 1983 0.82 μm 1 90 Mb/s 90 Mb/s 1,344 7 km
FTG-417 1985 1.3 μm 1 417 Mb/s 417 Mb/s 6,048 50 km
FTG-1.7 1987 1.3 μm 1 1.7 Gb/s 1.7 Gb/s 24,192 50 km
FTG-1.7 WDM 1989
1.3/1.55
μm
2 1.7 Gb/s 3.4 Gb/s 48,384 50 km
FT-2000 1992 1.3 μm 1 2.5 Gb/s 2.5 Gb/s 32,256 50 km
FT-2000 WDM 1992
1.3/1.55
μm
2 2.5 Gb/s 5 Gb/s 64,120 50 km
NGLN 1995 1.55 μm 8 2.5 Gb/s 20 Gb/s 258,000 360 km
NGLN II 1997 1.55 μm 16 2.5 Gb/s 40 Gb/s 516,000 360 km
WaveStar
TM
400G
1999 1.55 μm
80
40
2.5 Gb/s
10 Gb/s
200 Gb/s
400 Gb/s
2,580,000
5,160,000
640 km
640 km
WaveStar
TM
800G
2000 1.55 μm 80 10 Gb/s 800 Gb/s 10,320,000 640 km
WaveStar
TM
1.6T
2001 1.55 μm 160 10 Gb/s 1.6 Tb/s 20,640,000 640 km
LambdaXtreme 2003 1.55 μm
128
64
10 Gb/s
40 Gb/s
1.28 Tb/s
2.56 Tb/s
16,512,000
33,024,000
4000 km
1000 km
Herwig Kogelnik
Bell Labs,Lucent Technologies,Crawford Hill Lab,Holmdel,NJ 07733,USA,herwig@lucent.com
Abstract Optical communication has advanced into the tera-era deploying 1/2 terameter of fiber and carrying
several Tb/s per fiber,Remaining challenges include extending the success of point-to-point long-haul to
metropolitan networks and broadband access applications,
Introduction
Reflecting on the past 15 years of optical
communication,one can only marvel at the amazing
advances in this technology and in its applications,
Technical progress seems to continue in spite of the
recent burst of the telecom bubble,At the end of
1994,a little less than ten years ago,somewhat more
than 50 million km of optical fiber had been deployed
worldwide for all applications.
1
Today more than 500
million km,i.e,one half of a terameter,are deployed,
More than 10 percent of this deployment is
attributable to recent installations in China,It is good
to remind ourselves that a fiber of 0.5 Tm length can
be wound more than 10 000 times around the earth,
In 1988 our technical community celebrated a major
milestone in optical fiber communication,This was the
deployment of the transatlantic fiber system TAT8
linking Europe and North America using about 6000
km of optical fiber cable,By 1991 fiber carried more
information traffic over international digital links than
communication satellites,Today a map of the global
undersea fiber network looks like a spider web
covering the globe with more than 600 000 km of fiber
cable.
2
And there is news of new construction of
undersea systems,particularly in the Indian Ocean
region,including the Falcon,SEA-ME-WE 4,and
Polarnet systems,
WDM and Optical Amplifiers
The early 1990’s witnessed a vigorous worldwide
effort to ready the network elements and components
for wavelength division multiplexing (WDM),These
included WDM laser sources,erbium-doped fiber
amplifiers,WDM routers and others,WDM provided
the parallelism needed to maintain increases in the
transmission capacity per fiber at the rate of 100
every 10 years,It also provided a new degree of
freedom and flexibility for the design of networks by
adding the wavelength dimension to the traditional
network dimensions of space and time,The economic
benefits of WDM were enabled by the optically
transparent amplifiers that can be shared between
many WDM channels,
The extensive deployment of WDM technology in the
AT&T long-haul network in 1995/1996 marks another
milestone in optical communications and the
beginning of the WDM revolution,This large-scale
installation of WDM systems involved thousands of
optical fiber amplifiers and hundreds of WDM SONET
terminals.
1,3
Terabits Capacity per Fiber
In addition to the new WDM components,researchers
conceived of new WDM system techniques
counteracting fiber impairments such as dispersion
and nonlinearities and allowing transmission at higher
capacities over longer distances,This includes the
discipline of dispersion management,where
detrimental nonlinear effects are balanced by a clever
choice of local fiber dispersion,In 1996 three
laboratories
4,5,6
simultaneously demonstrated system
research experiments achieving transmission at the
milestone capacity of 1 Terabit/second per fiber,In
2001,right on schedule with the traditional trend of
increasing capacity by a factor of ten every five years,
two laboratories
7,8
accomplished transmission
capacities of 10 Tb/s,The next milestone would be
100 Tb/s in 2006,However,there are not many who
expect that this can be accomplished,in particular as
attention is shifting to lower cost systems and ultra-
long-haul (ULH) transmission,
Today,modern commercial transmission systems
offer capacities of several Tb/s per fiber as illustrated
in one vendor’s table
9,10
shown below,The table also
shows the trend of system transmission capabilities
expressing progress better than words,Note the ULH
capability of 4000 km spans,the 5 petabit/s.km
capacity distance product,and the 40 Gb/s bit-rate
per WDM channel,Other recent advances include the
use of Raman fiber amplifiers,of advanced forward
error correction (FEC),and of WDM laser sources
tunable over 100 WDM channels,Further systems
advances are expected from new modulation formats
such as RZ-DPSK
11
offering more tolerance to system
impairments and/or better bandwidth efficiency,
Optical Networking
As the cost of optics is driven down,the applications
of fiber communication are expanding from long-haul
point-to-point systems to multipoint metropolitan
networks and to broadband access.
9
The new ULH
capabilities promise to enable all-optical networks,
Worldwide R&D efforts are exploring the networking
flexibility provided by the new WDM dimension,An
example is the 5-year,DARPA-led MONET program
conducted by AT&T,Bellcore,Bell Atlantic,Bell
South,Lucent,PacTel,and other RBOCs,Their goal
was to explore the realization of a seamless,fully
configurable,all-optical regional and national network
infrastructure.
12
Many new R&D programs have
sprouted from MONET and its counterparts,an
example being the new IRIS program,This explores
the design of scalable optical routers with throughput
of more than 100 Tb/s
using photonic integrated
circuits with a high level of integration and new
architectural ideas such as load balancing.
13
Conclusions and Outlook
The R&D community in optical fiber communication
has achieved much in the past and advanced the
technological capabilities by orders of magnitude,It
can be truly proud of these accomplishments,Many
challenges remain,including the extension of
broadband capabilities from the core network to the
end user,In this connection we will observe with great
interest the evolution of new network architectures,
the growth of 10-Gb Ethernet,and the fiber-to-the-
home projects in Korea and Japan.
14
References
1 C,Fan and L,Clark,Opt,& Photon,News,
vol.6,pp 26-32,(1995),
2 N,S,Bergano,Optical Fiber Telecom IVB,p,154
I,P,Kaminow and T,Li eds.,Academic (2002),
3 H,Kogelnik,Proc,ECOC 1996,paper MoA.2.2
4 H,Onaka,et al,Proc,OFC 1996,paper PD19
5 A,H,Gnauck,et al,Proc,OFC 1996,paper PD20
6 T,Morioka,et al,Proc,OFC 1996,paper PD21
7 K,Fukuchi,et al,Proc,OFC 2001,paper PD24
8 S,Bigo,et al,Proc,OFC 2001,paper PD25
9 R.C,Alferness,et al,in The Optics Encyclopedia,
pp 2119-2135,Wiley,(2004),
10 H,Kogelnik,IEEE J,Select,Topics in Quantum
Electronics,vol,6,pp 1279-1286 (2000),
11 A,H,Gnauck,et al,Proc,OFC 2002,paper
FC-2,
12 A,A,M,Saleh,Proc,OFC 1996,paper ThI3,
13 M,Zirngibl,Stanford Workshop on Load Balancing
May,2004,
14 H,Shinohara,Proc,OFC 2004,paper ThW2,
Table1,Commercial Transmission Systems
System Year
Wave-
length
WDM
chan-
nels
Bit rate/
channel
Bit rate/
Fiber
Voice
channels
per fiber
Regen
spans
FT3 1980 0.82 μm 1 45 Mb/s 45 Mb/s 672 7 km
FT3C 1983 0.82 μm 1 90 Mb/s 90 Mb/s 1,344 7 km
FTG-417 1985 1.3 μm 1 417 Mb/s 417 Mb/s 6,048 50 km
FTG-1.7 1987 1.3 μm 1 1.7 Gb/s 1.7 Gb/s 24,192 50 km
FTG-1.7 WDM 1989
1.3/1.55
μm
2 1.7 Gb/s 3.4 Gb/s 48,384 50 km
FT-2000 1992 1.3 μm 1 2.5 Gb/s 2.5 Gb/s 32,256 50 km
FT-2000 WDM 1992
1.3/1.55
μm
2 2.5 Gb/s 5 Gb/s 64,120 50 km
NGLN 1995 1.55 μm 8 2.5 Gb/s 20 Gb/s 258,000 360 km
NGLN II 1997 1.55 μm 16 2.5 Gb/s 40 Gb/s 516,000 360 km
WaveStar
TM
400G
1999 1.55 μm
80
40
2.5 Gb/s
10 Gb/s
200 Gb/s
400 Gb/s
2,580,000
5,160,000
640 km
640 km
WaveStar
TM
800G
2000 1.55 μm 80 10 Gb/s 800 Gb/s 10,320,000 640 km
WaveStar
TM
1.6T
2001 1.55 μm 160 10 Gb/s 1.6 Tb/s 20,640,000 640 km
LambdaXtreme 2003 1.55 μm
128
64
10 Gb/s
40 Gb/s
1.28 Tb/s
2.56 Tb/s
16,512,000
33,024,000
4000 km
1000 km
