Perspectives of Radio over Fiber Technologies
A.M.J,Koonen,M,García Larrodé,A,Ng’oma*,K,Wang,H,Yang,Y,Zheng,E,Tangdiongga
COBRA Institute,Dept,of Electrical Engineering,Eindhoven University of Technology,
Den Dolech 2,P,O,Box 513,NL 5600 MB Eindhoven,The Netherlands,e-mail,a.m.j.koonen@tue.nl
(* A.Ng’oma is now with Corning Inc.,NY,USA)
Abstract,Radio-over-Fiber technologies enable efficient provisioning of broadband wireless
services both in access and in in-building networks,in particular when combined with flexible
optical routing and dispersion-robust RoF transport techniques,such as optical frequency
multiplying,
2008 Optical Society of America
OCIS codes,(060.2330) Fiber optics communications; (060.5625) Radio frequency photonics
1,Introduction
Wireless services are taking a steadily increasing share of the telecommunications market,The end users not only
benefit from its main virtue,mobility,but are also demanding ever larger bandwidth,Larger wireless capacity per
user requires the reduction of the wireless cell size,i.e,establishing pico-cells,which is enabled by increasing the
radio microwave frequency,The wireless LAN IEEE 802.11g WiFi standard offers up to 54 Mbit/s in the 2.5 GHz
range; the IEEE 802.16 WiMAX standard offers up to 100 Mbit/s in the range of 10 to 66 GHz; IEEE 802.15.3
UWB operates at frequencies up to 60 GHz,offering short-range capacity up to 480 Mbit/s,Smaller radio cells
imply that ever more antennas are needed to cover a certain area,Such an area may encompass the rooms in a
residential home,but may also be a hospital,an office building,an airport lounge,a conference site,etc,When
needing so many antenna sites,it becomes economically attractive to locate the microwave signal generation and
modulation not at every antenna,but centrally in a cabinet from where optical fibers with their inherent low losses
and wide bandwidth can nicely bring the signal to the antennas,The antennas then only have to do the simple
optical-to-electrical conversion,and to emit and receive the wireless signal,Centralizing the sophisticated signal
handling eases maintenance and upgrading,The signal handling may include techniques for multiple-input-
multiple-output antenna schemes,smart beam forming antennas,mobility and connection handovers,feeding
multiple radio standards to an antenna,reconfiguration of services to antennas,etc,Hence radio-over-fiber (RoF)
technologies can bring many advantages in operating,maintaining and upgrading wireless networks,
This paper addresses two major application areas of RoF,outdoor fixed wireless access via standard single-
mode fiber,where the last link to the end user’s premises is established wirelessly,and indoor wireless access via
preferably multimode fiber (already widely installed in buildings),where flexible local networks need to be
realized,
2,Radio over Fiber technologies
A lot of techniques have been reported to transport radio signals over fiber to the antenna site,
Basically,one may directly modulate the light intensity of the optical source by the radio signal,At the antenna
station,the received optical signal just needs a photodetector and bandpass amplifier,and the regained radio signal
is then to be radiated by the antenna,However,the bandwidth and linearity requirements on the laser transmitter
and the receiver are high,Also careful fiber dispersion compensation techniques may be needed at higher RF
frequencies and longer fiber lengths,Thus the application of this intensity-modulation (IM) scheme is restricted to
the low/medium RF range,
Alternatively,one may use various optical frequency conversion methods to generate the microwave signal at
the antenna site,As a first method,two narrow-linewidth laser diodes may be deployed,of which one is intensity-
modulated with the data signal,When the optical frequency spacing between these two lasers is carefully kept equal
to the desired microwave frequency,after traveling through the fiber link,the heterodyning of the two optical
signals in the photodiode generates the modulated microwave carrier,However,the linewidth of the microwave
signal is equal to the sum of the linewidths of the two laser diodes,and may exceed the requirements for adequate
detection of the usually multilevel signal modulation format (such as multi-level QAM),Hence the linewidth of the
laser diodes needs to be very small,which is e.g,achievable by injection locking,
A second optical frequency conversion method uses just a single laser followed by a Mach Zehnder
Interferometer (MZI) modulator which is biased at its inflexion point (V
π
) and is driven by a sinusoidal signal at
half the desired microwave frequency [1],At the MZI’s output,a two-tone optical signal emerges with a tone
spacing equal to the microwave frequency,and with suppressed optical carrier,When modulating the laser with the
a828_1.pdf
OThP3.pdf
OFC/NFOEC 2008
data signal,heterodyning in the photodiode at the receiver generates the modulated microwave signal at f
RF
,This
method suppresses the phase noise of the laser diode,and hence creates a clean microwave,
A third method deploys the generation of many harmonics by the so-called Optical Frequency Multiplying
(OFM) technique,Its principle is shown in Fig,1,The optical frequency of a wavelength-tunable laser diode in the
headend station is periodically swept over an optical frequency range β?ω
m
with a harmonic sweep signal having a
frequency ω
m
,After passing the fixed MZI,by FM-to-IM conversion many harmonics of the sweep frequency are
generated,The strengths of the harmonics can be set by adjusting the frequency modulation index β,At the antenna
site,when neglecting the fiber’s attenuation and dispersion,the output current signal i
out
(t) of the photodiode
contains all these harmonics n·ω
m
with n-th order Bessel function weight J
n
(2β ·sin(ω
m
τ /2) ),according to [2]
( ) ( )[ ]{}τ?τωτωτωβ &+++?=
02
1
2
1
0
21 )(cossincos)( tIti
swswout
in which I
0
is the DC current proportional to the received optical power,τ is the delay difference in the MZI arms,
ω
0
is the central frequency of the laser diode,and
dttd /)( =&
is its phase noise,
fibre
LD
BPF
n·ω
m
PD
λ sweep
signal ω
m
ampl.
i
out
(t)
τ
MZI
+?
-?
+ data
-data
RF
n·ω
m
Fig,1 Optical Frequency Multiplying
Freq,offset from 38.4 GHz carrier [Hz]
38.4GHz
< 100Hz
RF powe
r [dBm]
-30
-60
-90
-500 0 +500
RF powe
r [dBm]
Fig,2 38.4 GHz microwave carrier
generated by OFM
The data signal is present on all the harmonics,After photodetection,a bandpass filter extracts the desired harmonic
(or several harmonics),which is amplified and emitted as a microwave carrier bearing the data signal,The laser
phase noise has negligible impact if
2/πτ? <<&
,i.e,when the laser linewidth is much smaller than a quarter of the
Free Spectral Range?ω
FSR
= 2π / τ of the MZI,This condition is easily met,as the MZI’s FSR is typically around
10 GHz,and thus the OFM process effectively suppresses the laser phase noise,Hence very pure microwave signals
can be generated,Linewidths below the measurement resolution (< 100 Hz) have been obtained when generating a
38.4 GHz carrier as the 6
th
harmonic of a 6.4 GHz sweep signal,whereas the linewidth of the laser diode was more
than 1 MHz; see Fig,2,Moreover,by using a high order harmonic,OFM permits to use only a relatively low-
frequency sweep generator in the headend,which can be of high quality while still at low cost,
3,Radio over single-mode fiber in access networks
Direct RF intensity modulation of a laser diode yields a double-sideband (IM-DSB) spectrum,Fiber dispersion
causes phase shifts between the two sidebands,which leads to severe fading of the microwave at certain fiber
lengths,as shown in Fig,3 [3],On the other hand,the OFM technique is very robust against chromatic dispersion in
single-mode fiber,as shown also in Fig,3 over 72km of SMF,This dispersion-robustness is very useful when
operating in link-switched networks,where the fiber connecting the headend to an antenna may vary in length,
0 20 40 60 80
-80
-60
-40
-20
0
20
Fibre Length,[km]
S
i
g
nal
S
t
r
engt
h,
[
d
B
]
IM-DSB
OFM
Fig,3 Measured impact of SMF dispersion on relative
strength of 30 GHz carrier,using IM-DSB or
OFM (excluding fiber losses)
τ
MZI
LD
λ
1
sweep
freq,f
1
data 1
MZI
mod.
LD
λ
2
sweep
freq,f
2
data 2
MZI
mod.
LD
λ
N
sweep
freq,f
N
data N
MZI
mod.
WD
M mux
λ-multicasting
tun,OADM
f
mm,x
BPF
PD
λ-multicasting
tun,OADM
λ
x
f
mm,y
,f
mm,z
BPF
PD
λ
y,
λ
z
BPF
PDλ
x
λ
-m
ult
i
cast
ing
tun
.
O
A
DM
f
mm,y
λ
y
OADM
control
WD
M mux
λ
-m
ult
i
cast
ing
tun
.
O
A
DM
Fig,4 Flexible routing of radio capacity in Fixed Wireless Access
Fig,4 shows such a network where at the headend station different microwave signals are generated by OFM in
different wavelength channels,Using routing by means of tunable wavelength add-drop modules,one or more of
these wavelength channels can be dropped to an antenna site,and thus the radio capacity can be flexibly assigned
among these antennas depending on the local traffic demands,Moreover,the frequency chirping of the source
a828_1.pdf
OThP3.pdf
OFC/NFOEC 2008
which is inherent to the OFM principle yields an increase of the Stimulated Brillouin Scattering (SBS) threshold,
and thus it enables to transport significantly higher optical power levels and generate stronger microwave signals
from the antenna,Experimentally it was observed that the OFM system on a 25 km SMF link exhibited a much
higher SBS threshold than the IM-DD system (i.c,7 dB higher,from 10 to 50 mW),
4,Radio over multimode fiber in in-building networks
Multimode (silica or plastic) optical fiber is widely used in in-building networks,due to its ease of installation,Its
modal dispersion,however,is hampering radio signal transport,The OFM technique has shown to be robust against
modal dispersion; it has been derived mathematically that its generated harmonics scale with the fiber’s frequency
characteristics,Thanks to the very pure microwave carrier generated with the OFM technique,transmission of
16-QAM and 64-QAM signals up to 120 Mbit/s in the 24-30 GHz band has successfully been demonstrated over
4.4 km of silica 50μm core graded index fiber [4],Using five subcarriers,over the same link simultaneous
transmission of five 64-QAM signals with a total bitrate of 210 Mbit/s has been demonstrated [5],Also a 100
Mbit/s 16-QAM bidirectional system at 17.2 GHz over 100m of 50μm core graded-index POF has been shown,
where for upstream transmission the microwave signal received at the antenna site is downconverted with the 17.2
GHz microwave carrier generated at the headend; see Fig,5 [6],When creating pico-cells for broadband wireless
communication at high microwave frequencies,the required line-of-sight prevents communication between rooms,
However,transparent transport of the microwave signals by means of radio-over-fiber techniques can establish
communication between two or more rooms,Fig,6 shows how with a transparent optical switch in the HCC (Home
Communication Controller) rooms can flexibly be interconnected,and thus their pico-cells can be merged into a
reconfigurable,wireless virtual private network”,without interference with other wireless VPN-s,The remote
antenna concept will add latency with respect to the conventional case where the wireless protocols are terminated
in the base station at the antenna site,This will reduce the network’s throughput,For centrally scheduled MAC
protocols,such as WiMAX,it has been shown that this reduction will be only small (<1%) when fiber link lengths
are less than 500 metres,
Fig,5 16-QAM 100 Mbit/s 17.2 GHz bi-directional
radio-over-POF link
HCC
access
network
fibres
(POF)
Fig,6 Flexible inter-room wireless communication using switched
RoF links
5,Conclusions
Radio-over-Fiber technologies can provide transport of broadband microwave signals for SMF and MMF based
networks,Flexible optical routing and dispersion-robust transport techniques,such as Optical Frequency
Multiplying,enable to improve the network’s throughput and operational efficiency,
6,References
[1] R.A,Griffin,P.M,Lane,J.J,O’Reilly,“Radio-over-fibre distribution using an optical millimeter-wave/DWDM overlay”,Proc,OFC’99,San
Diego,Feb,22-25,1999,paper WD6
[2] A.M.J,Koonen and A,Ngoma,“Integrated broadband optical fibre/ wireless LAN access networks,” in Broadband Optical Access Networks
and Fiber-to-the-Home,System Technologies and Development Strategies,New York,Wiley,2006
[3] A,Ng’oma,G.-J,Rijckenberg,A.M.J,Koonen,“Building extended-recah radio-over-fiber links by exploiting Optical Frequency
Multiplication’s dispersion tolerance”,Proc,IEEE Int,Microwave Symp.,Honolulu,June 3-8,2007
[4] M,Garcia Larrode,A.M.J,Koonen,J.J,Vegas Olmos,“Transmission of microwave signals beyond the modal bandwidth of multimode fiber
links”,Proc,of Int,Top,Meeting on Microwave Phot.,Grenoble,Oct,3-6,2006
[5] H,Yang,M,Garcia Larrode,G.-J,Rijckenberg,A,Ng’oma,E,Tangdiongga,A.M.J,Koonen,“Radio-over-fibre transmission of multi-carrier
64-QAM radio signal at 18 GHz”,Proc,of BroadBand Europe,Antwerp,Dec,3-6,2007
[6] A,Ng’oma,J,Zeng,H.P.A,van den Boom,Y,Watanabe,A.M.J,Koonen,“Bi-Directional Polymer Optical Fiber-based System for
Distributing 100 Mbps WiMAX Signals Exceeding 17 GHz”,Proc,of AP-MWP2007,Jeju Island,South Korea,April 25-27,2007
a828_1.pdf
OThP3.pdf
OFC/NFOEC 2008
A.M.J,Koonen,M,García Larrodé,A,Ng’oma*,K,Wang,H,Yang,Y,Zheng,E,Tangdiongga
COBRA Institute,Dept,of Electrical Engineering,Eindhoven University of Technology,
Den Dolech 2,P,O,Box 513,NL 5600 MB Eindhoven,The Netherlands,e-mail,a.m.j.koonen@tue.nl
(* A.Ng’oma is now with Corning Inc.,NY,USA)
Abstract,Radio-over-Fiber technologies enable efficient provisioning of broadband wireless
services both in access and in in-building networks,in particular when combined with flexible
optical routing and dispersion-robust RoF transport techniques,such as optical frequency
multiplying,
2008 Optical Society of America
OCIS codes,(060.2330) Fiber optics communications; (060.5625) Radio frequency photonics
1,Introduction
Wireless services are taking a steadily increasing share of the telecommunications market,The end users not only
benefit from its main virtue,mobility,but are also demanding ever larger bandwidth,Larger wireless capacity per
user requires the reduction of the wireless cell size,i.e,establishing pico-cells,which is enabled by increasing the
radio microwave frequency,The wireless LAN IEEE 802.11g WiFi standard offers up to 54 Mbit/s in the 2.5 GHz
range; the IEEE 802.16 WiMAX standard offers up to 100 Mbit/s in the range of 10 to 66 GHz; IEEE 802.15.3
UWB operates at frequencies up to 60 GHz,offering short-range capacity up to 480 Mbit/s,Smaller radio cells
imply that ever more antennas are needed to cover a certain area,Such an area may encompass the rooms in a
residential home,but may also be a hospital,an office building,an airport lounge,a conference site,etc,When
needing so many antenna sites,it becomes economically attractive to locate the microwave signal generation and
modulation not at every antenna,but centrally in a cabinet from where optical fibers with their inherent low losses
and wide bandwidth can nicely bring the signal to the antennas,The antennas then only have to do the simple
optical-to-electrical conversion,and to emit and receive the wireless signal,Centralizing the sophisticated signal
handling eases maintenance and upgrading,The signal handling may include techniques for multiple-input-
multiple-output antenna schemes,smart beam forming antennas,mobility and connection handovers,feeding
multiple radio standards to an antenna,reconfiguration of services to antennas,etc,Hence radio-over-fiber (RoF)
technologies can bring many advantages in operating,maintaining and upgrading wireless networks,
This paper addresses two major application areas of RoF,outdoor fixed wireless access via standard single-
mode fiber,where the last link to the end user’s premises is established wirelessly,and indoor wireless access via
preferably multimode fiber (already widely installed in buildings),where flexible local networks need to be
realized,
2,Radio over Fiber technologies
A lot of techniques have been reported to transport radio signals over fiber to the antenna site,
Basically,one may directly modulate the light intensity of the optical source by the radio signal,At the antenna
station,the received optical signal just needs a photodetector and bandpass amplifier,and the regained radio signal
is then to be radiated by the antenna,However,the bandwidth and linearity requirements on the laser transmitter
and the receiver are high,Also careful fiber dispersion compensation techniques may be needed at higher RF
frequencies and longer fiber lengths,Thus the application of this intensity-modulation (IM) scheme is restricted to
the low/medium RF range,
Alternatively,one may use various optical frequency conversion methods to generate the microwave signal at
the antenna site,As a first method,two narrow-linewidth laser diodes may be deployed,of which one is intensity-
modulated with the data signal,When the optical frequency spacing between these two lasers is carefully kept equal
to the desired microwave frequency,after traveling through the fiber link,the heterodyning of the two optical
signals in the photodiode generates the modulated microwave carrier,However,the linewidth of the microwave
signal is equal to the sum of the linewidths of the two laser diodes,and may exceed the requirements for adequate
detection of the usually multilevel signal modulation format (such as multi-level QAM),Hence the linewidth of the
laser diodes needs to be very small,which is e.g,achievable by injection locking,
A second optical frequency conversion method uses just a single laser followed by a Mach Zehnder
Interferometer (MZI) modulator which is biased at its inflexion point (V
π
) and is driven by a sinusoidal signal at
half the desired microwave frequency [1],At the MZI’s output,a two-tone optical signal emerges with a tone
spacing equal to the microwave frequency,and with suppressed optical carrier,When modulating the laser with the
a828_1.pdf
OThP3.pdf
OFC/NFOEC 2008
data signal,heterodyning in the photodiode at the receiver generates the modulated microwave signal at f
RF
,This
method suppresses the phase noise of the laser diode,and hence creates a clean microwave,
A third method deploys the generation of many harmonics by the so-called Optical Frequency Multiplying
(OFM) technique,Its principle is shown in Fig,1,The optical frequency of a wavelength-tunable laser diode in the
headend station is periodically swept over an optical frequency range β?ω
m
with a harmonic sweep signal having a
frequency ω
m
,After passing the fixed MZI,by FM-to-IM conversion many harmonics of the sweep frequency are
generated,The strengths of the harmonics can be set by adjusting the frequency modulation index β,At the antenna
site,when neglecting the fiber’s attenuation and dispersion,the output current signal i
out
(t) of the photodiode
contains all these harmonics n·ω
m
with n-th order Bessel function weight J
n
(2β ·sin(ω
m
τ /2) ),according to [2]
( ) ( )[ ]{}τ?τωτωτωβ &+++?=
02
1
2
1
0
21 )(cossincos)( tIti
swswout
in which I
0
is the DC current proportional to the received optical power,τ is the delay difference in the MZI arms,
ω
0
is the central frequency of the laser diode,and
dttd /)( =&
is its phase noise,
fibre
LD
BPF
n·ω
m
PD
λ sweep
signal ω
m
ampl.
i
out
(t)
τ
MZI
+?
-?
+ data
-data
RF
n·ω
m
Fig,1 Optical Frequency Multiplying
Freq,offset from 38.4 GHz carrier [Hz]
38.4GHz
< 100Hz
RF powe
r [dBm]
-30
-60
-90
-500 0 +500
RF powe
r [dBm]
Fig,2 38.4 GHz microwave carrier
generated by OFM
The data signal is present on all the harmonics,After photodetection,a bandpass filter extracts the desired harmonic
(or several harmonics),which is amplified and emitted as a microwave carrier bearing the data signal,The laser
phase noise has negligible impact if
2/πτ? <<&
,i.e,when the laser linewidth is much smaller than a quarter of the
Free Spectral Range?ω
FSR
= 2π / τ of the MZI,This condition is easily met,as the MZI’s FSR is typically around
10 GHz,and thus the OFM process effectively suppresses the laser phase noise,Hence very pure microwave signals
can be generated,Linewidths below the measurement resolution (< 100 Hz) have been obtained when generating a
38.4 GHz carrier as the 6
th
harmonic of a 6.4 GHz sweep signal,whereas the linewidth of the laser diode was more
than 1 MHz; see Fig,2,Moreover,by using a high order harmonic,OFM permits to use only a relatively low-
frequency sweep generator in the headend,which can be of high quality while still at low cost,
3,Radio over single-mode fiber in access networks
Direct RF intensity modulation of a laser diode yields a double-sideband (IM-DSB) spectrum,Fiber dispersion
causes phase shifts between the two sidebands,which leads to severe fading of the microwave at certain fiber
lengths,as shown in Fig,3 [3],On the other hand,the OFM technique is very robust against chromatic dispersion in
single-mode fiber,as shown also in Fig,3 over 72km of SMF,This dispersion-robustness is very useful when
operating in link-switched networks,where the fiber connecting the headend to an antenna may vary in length,
0 20 40 60 80
-80
-60
-40
-20
0
20
Fibre Length,[km]
S
i
g
nal
S
t
r
engt
h,
[
d
B
]
IM-DSB
OFM
Fig,3 Measured impact of SMF dispersion on relative
strength of 30 GHz carrier,using IM-DSB or
OFM (excluding fiber losses)
τ
MZI
LD
λ
1
sweep
freq,f
1
data 1
MZI
mod.
LD
λ
2
sweep
freq,f
2
data 2
MZI
mod.
LD
λ
N
sweep
freq,f
N
data N
MZI
mod.
WD
M mux
λ-multicasting
tun,OADM
f
mm,x
BPF
PD
λ-multicasting
tun,OADM
λ
x
f
mm,y
,f
mm,z
BPF
PD
λ
y,
λ
z
BPF
PDλ
x
λ
-m
ult
i
cast
ing
tun
.
O
A
DM
f
mm,y
λ
y
OADM
control
WD
M mux
λ
-m
ult
i
cast
ing
tun
.
O
A
DM
Fig,4 Flexible routing of radio capacity in Fixed Wireless Access
Fig,4 shows such a network where at the headend station different microwave signals are generated by OFM in
different wavelength channels,Using routing by means of tunable wavelength add-drop modules,one or more of
these wavelength channels can be dropped to an antenna site,and thus the radio capacity can be flexibly assigned
among these antennas depending on the local traffic demands,Moreover,the frequency chirping of the source
a828_1.pdf
OThP3.pdf
OFC/NFOEC 2008
which is inherent to the OFM principle yields an increase of the Stimulated Brillouin Scattering (SBS) threshold,
and thus it enables to transport significantly higher optical power levels and generate stronger microwave signals
from the antenna,Experimentally it was observed that the OFM system on a 25 km SMF link exhibited a much
higher SBS threshold than the IM-DD system (i.c,7 dB higher,from 10 to 50 mW),
4,Radio over multimode fiber in in-building networks
Multimode (silica or plastic) optical fiber is widely used in in-building networks,due to its ease of installation,Its
modal dispersion,however,is hampering radio signal transport,The OFM technique has shown to be robust against
modal dispersion; it has been derived mathematically that its generated harmonics scale with the fiber’s frequency
characteristics,Thanks to the very pure microwave carrier generated with the OFM technique,transmission of
16-QAM and 64-QAM signals up to 120 Mbit/s in the 24-30 GHz band has successfully been demonstrated over
4.4 km of silica 50μm core graded index fiber [4],Using five subcarriers,over the same link simultaneous
transmission of five 64-QAM signals with a total bitrate of 210 Mbit/s has been demonstrated [5],Also a 100
Mbit/s 16-QAM bidirectional system at 17.2 GHz over 100m of 50μm core graded-index POF has been shown,
where for upstream transmission the microwave signal received at the antenna site is downconverted with the 17.2
GHz microwave carrier generated at the headend; see Fig,5 [6],When creating pico-cells for broadband wireless
communication at high microwave frequencies,the required line-of-sight prevents communication between rooms,
However,transparent transport of the microwave signals by means of radio-over-fiber techniques can establish
communication between two or more rooms,Fig,6 shows how with a transparent optical switch in the HCC (Home
Communication Controller) rooms can flexibly be interconnected,and thus their pico-cells can be merged into a
reconfigurable,wireless virtual private network”,without interference with other wireless VPN-s,The remote
antenna concept will add latency with respect to the conventional case where the wireless protocols are terminated
in the base station at the antenna site,This will reduce the network’s throughput,For centrally scheduled MAC
protocols,such as WiMAX,it has been shown that this reduction will be only small (<1%) when fiber link lengths
are less than 500 metres,
Fig,5 16-QAM 100 Mbit/s 17.2 GHz bi-directional
radio-over-POF link
HCC
access
network
fibres
(POF)
Fig,6 Flexible inter-room wireless communication using switched
RoF links
5,Conclusions
Radio-over-Fiber technologies can provide transport of broadband microwave signals for SMF and MMF based
networks,Flexible optical routing and dispersion-robust transport techniques,such as Optical Frequency
Multiplying,enable to improve the network’s throughput and operational efficiency,
6,References
[1] R.A,Griffin,P.M,Lane,J.J,O’Reilly,“Radio-over-fibre distribution using an optical millimeter-wave/DWDM overlay”,Proc,OFC’99,San
Diego,Feb,22-25,1999,paper WD6
[2] A.M.J,Koonen and A,Ngoma,“Integrated broadband optical fibre/ wireless LAN access networks,” in Broadband Optical Access Networks
and Fiber-to-the-Home,System Technologies and Development Strategies,New York,Wiley,2006
[3] A,Ng’oma,G.-J,Rijckenberg,A.M.J,Koonen,“Building extended-recah radio-over-fiber links by exploiting Optical Frequency
Multiplication’s dispersion tolerance”,Proc,IEEE Int,Microwave Symp.,Honolulu,June 3-8,2007
[4] M,Garcia Larrode,A.M.J,Koonen,J.J,Vegas Olmos,“Transmission of microwave signals beyond the modal bandwidth of multimode fiber
links”,Proc,of Int,Top,Meeting on Microwave Phot.,Grenoble,Oct,3-6,2006
[5] H,Yang,M,Garcia Larrode,G.-J,Rijckenberg,A,Ng’oma,E,Tangdiongga,A.M.J,Koonen,“Radio-over-fibre transmission of multi-carrier
64-QAM radio signal at 18 GHz”,Proc,of BroadBand Europe,Antwerp,Dec,3-6,2007
[6] A,Ng’oma,J,Zeng,H.P.A,van den Boom,Y,Watanabe,A.M.J,Koonen,“Bi-Directional Polymer Optical Fiber-based System for
Distributing 100 Mbps WiMAX Signals Exceeding 17 GHz”,Proc,of AP-MWP2007,Jeju Island,South Korea,April 25-27,2007
a828_1.pdf
OThP3.pdf
OFC/NFOEC 2008
