High-capacity transmission over polymer optical fiber

High-capacity transmission over polymer optical fiber
High-capacity transmission over polymer optical fiber
van den Boom, H.P.A.; van Bennekom, P.K.; Tafur Monroy, I.; Khoe, G.D.
Published in:
IEEE Journal of Selected Topics in Quantum Electronics
DOI:
10.1109/2944.962269
Published: 01/01/2001
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Boom, van den, H. P. A., Bennekom, van, P. K., Tafur Monroy, I., & Khoe, G. D. (2001). High-capacity
transmission over polymer optical fiber. IEEE Journal of Selected Topics in Quantum Electronics, 7(3), 461-470.
DOI: 10.1109/2944.962269
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IEEE JOURNAL ON SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 7, NO. 3, MAY/JUNE 2001
461
High-Capacity Transmission Over
Polymer Optical Fiber
H. P. A. van den Boom, W. Li, P. K. van Bennekom, I. Tafur Monroy, and Giok-Djan Khoe, Fellow, IEEE
Abstract—Polymer optical fiber (POF) is a promising transmission medium to provide broad-band telecommunication services
within the customer’s premises. POF offers several attractive features for data transmission such as broad bandwidth and low cost
for in-house, access, and local-area-network (LAN) applications.
This paper presents a review on optical transmission systems using
POF and their enabling technologies. A summary is given of experimental data links with record capacity over record transmission
distances. To conclude, we discuss trends for further development
and research.
Index Terms—Optical communications, optical fiber, polymer
optical fiber.
Fig. 1.
I. INTRODUCTION
N
EW INTERACTIVE services require a broad-band communications network, which should extend into the customer’s premises up to the terminals. At present, twisted pair
and coaxial cables are used as the physical medium to deliver
telecom services within the customer’s premises. These two
media suffer from serious shortcomings when they are considered to serve the increasing demand for broad-band services.
For instance, twisted pair has a limited bandwidth and it is susceptible to electromagnetic interference (EMI). Coaxial cable
offers a large bandwidth, but it poses practical problems due to
its thickness and the effort required to make a reliable connection. Moreover, the coaxial cable is not immune to EMI.
Optical fiber is extensively used for long-distance data transmission and it represents an alternative for transmission at the
customer premises as well. Optical fiber connections offer complete immunity to EMI. Optical silica-glass fibers, however, are
not suitable for use within the customer premises because of
the requirement of precise handling, and thus, the high costs involved. Polymer optical fibers are very attractive for use within
the customer premises with their easy handling and low cost.
This is mainly due to their relatively thick core. In fact, several polymer fiber-based systems are commercially available.
However, these systems are based on the use of the multimode
step index polymer optical fiber (SI-POF), whose bandwidth
distance product is limited to a few MHz km.
The way toward broad-band POF systems is opened by the
use of graded-index polymer optical fiber (GI-POF). The high
bandwidth of the GI-POF (typically 2 GHz km [1]) compared
to SI-POF, is attributable to the graded-index profile in the core.
Manuscript received July 11, 2000; revised June 29, 2001.
The authors are with the COBRA Research Institute, Eindhoven University of
Technology, Telecommunications Technology and Electromagnetics, 5600 MB
Eindhoven, The Netherlands (e-mail: i.tafur@tue.nl).
Publisher Item Identifier S 1077-260X(01)08936-5.
Attenuation of graded index POF.
Additional characteristics of GI-POF are: 1) a large-core diameter (typically 500 m), which allows easy handling, thus the
use of low-cost devices and interconnection devices (similar to
SI-POF) and 2) low attenuation over a wide range of wavelengths, thus enabling the use of wavelength multiplexing for
enhanced capacity.
This paper focuses on the result of transmission experiments
with GI-POF. Single-channel systems with PMMA GI-POF,
perfluorinated-based GI-POF, as well as wavelength-division-multiplexing (WDM) systems will be reported. For a
comparison, experimental transmission systems using thick
silica fiber are reported and discussed. Moreover, enabling
technologies are reviewed, and finally, new trends for development and research are discussed.
II. POF AS TRANSMISSION MEDIUM
This section presents a review of the transmission characteristics of POF.
A. Attenuation
Fig. 1 displays the attenuation of several types of POF for
different wavelengths. Experimental and theoretical curves, as
well as the result for the standard silica fiber, are plotted for
comparison. Polymethyl methacrylate (PMMA) has been generally used as the core material of commercially available stepindex POF. Its attenuation limit is approximately 100 dB/km
in the visible region. Therefore, the high attenuation of POF
compared to the silica-based fiber has limited the POF data
link length, even when the bandwidth characteristics are improved by the GI-POF. Transmission distances can be further
extended by using the perfluorinated (PF) amorphous polymer
base GI-POF, which has a low-loss wavelength region from 500
to 1300 nm (see Fig. 1).
1077–260X/01$10.00 © 2001 IEEE
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IEEE JOURNAL ON SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 7, NO. 3, MAY/JUNE 2001
III. TRANSMISSION EXPERIMENTS
In this section, we present a review of transmission experiments using POF as the transmission medium. Their experimental setup and enabling technologies are described in detail.
Several experiments have been performed to investigate the validity of theoretical models developed to predict the bandwidth
of the fiber. The experiments have also shown the feasibility of
POF links for high-capacity transmission.
A list of world record transmission experiments using POF
can be found in Table I. Fig. 3 indicates the increase in transmission capacity. We denote the experiments carried out in our
group by the TUE (Eindhoven University of Technology) tag.
Fig. 2. Simulated bandwidth as a function of the fiber length: (—-) Without
the effect of DMA, (
)With the effect of DMA.
000
We can observe in Fig. 1 that the experimental total attenuation
of the PF polymer-based GI-POF decreases to 40 dB/km even
in the near infrared region. This means that PF fiber allows for
the use of WDM channels for enhancing capacity.
B. Bandwidth of POF
The advantage in bandwidth of the low material dispersion
of PF polymer-based GI-POF has been theoretically and experimentally clarified in [2]. It has been shown that the low attenuation and low material dispersion of the PF polymer enables
1- and 10-Gb/s transmission at 850- and 1300-nm wavelengths,
respectively, as the PF polymer-based GI-POF has a very low
material dispersion (0.0055 ns/nm km at 850 nm), as compared
with the conventional PMMA-based POF, and compared with
the multimode silica fiber (0.0084 ns/nm km at 850 nm).
Since the PF polymer-based GI-POF has a low attenuation
compared with the conventional PMMA-based POF from the
visible to the near infrared region, not only the 650-nm wavelength region, which is the attenuation window of the PMMA
base GI-POF, but also other wavelengths such as 850 or 1300
nm, etc., can be used for transmission. It was clarified that the
wavelength dependence of the optimum index profiles of the
PF polymer-based GI-POF is very small, although the optimum
index profile of the silica-based multimode fiber (MMF) at 650
nm differs greatly from that at 1300 nm. This result indicates
that the PF polymer-based GI-POF is very tolerant regarding
the index profile for high-speed transmission as compared to
multimode silica fiber. The impulse response function of the
PF polymer-based GI-POF was accurately analyzed with the
Wentzel–Kramer–Brillouin (WKB) numerical computation
method using the measured refractive index profile. On considering all dispersion factors involving the profile dispersion,
the predicted bandwidth characteristic of the PF polymer-based
GI-POF agreed very well with the measurements. Fig. 2
presents the simulated bandwidth as a function of the fiber
length, showing the effect of differential mode attenuation
(DMA), which enhances the bandwidth significantly for the
case of GI-POF. The mathematical formalism of the bandwidth
model is presented in [3].
A. 2.5-Gb/s Transmission Over 200 m of PMMA GIPOF
A 2.5-Gb/s system experiment over 100 m, using a PMMA
GI-POF, a visible light laser at 650-nm wavelength and a silicon PIN photodiode has been reported earlier. In our experiment, the transmission distance is doubled to reach 200 m. Key
elements used in the experiment are a silicon avalanche photodiode (APD) receiver with a record sensitivity of 29 dBm at
2.5 Gb/s and 10 , a bit-error rate (BER) of PMMA GI-POF
with a low attenuation of 0.164 dB/m (Mitsubishi Rayon), and
a laser (NEC) with a modulated spectral width of 0.4 nm at an
average output power of 6.8 dBm. The experiment was carried
out using a nonreturn-to-zero (NRZ) pseudorandom binary se. In Fig. 4, a
quence (PRBS) with a pattern length of
block diagram of the experiment is shown.
One important feature in the APD receiver was the combination of the APD with two limiting amplifiers (HP) in a
low-impedance front-end configuration. In principle, the APD
can be set to a higher gain when combined with just one amplifier, but that will cause degradation caused by excess noise. Another significant improvement is the use of a data and clock recovery IC (Lucent Technologies) instead of using a direct clock
connection and the decision circuit of the BER test equipment.
To avoid electrical reflections, the APD limiting amplifiers and
the clock recovery circuit were mounted as compact as possible.
Another key to the result is a new version of the GI-POF as
compared to those reported earlier. The loss of the GI-POF has
been decreased from 0.2 to 0.164 dB/m by improving the homogeneity along the fiber by minimizing the fiber outer and core diameter variation, asymmetry of the index profile, and its change
along the fiber. This has been achieved by a more precise control
of preform preparation, drawing process, and cabling process.
Contributing to the achievement are measures taken to avoid
reflections and to improve optical coupling efficiency between
laser, fiber, and APD. Laser light is launched by means of a lens
doublet that offers an numerical aperture (NA) of 0.55 at the
laser side and 0.16 at the fiber side. At the receiver side, the
lens doublet used has an NA of 0.25 at the fiber side and 0.55
at the APD side. The diameter of the active area of the APD
was 230 m. Coupling losses for both the laser side and the
APD sides were less than 0.3 dB. The lenses are antireflection
(AR) coated to less than 1% reflection. The fiber end at the
laser side was set at an angle of 4 to avoid reflections into the
laser. The coupling optics was manually adjusted to achieve a
VAN DEN BOOM et al.: HIGH-CAPACITY TRANSMISSION OVER POLYMER OPTICAL FIBER
463
TABLE I
LIST OF EXPERIMENTAL TRANSMISSION RECORDS USING POF
Fig. 5. Eye diagrams of back-to-back transmission and after 200-m GI-POF.
Fig. 3. Capacity increase of transmission systems using POF. Experimental
trials.
Fig. 4. 2.5-Gb/s transmission over 200 m of PMMA GI-POF.
maximum coupling efficiency. The eye diagram of back-to-back
measurement and after 200-m of GI-POF are nearly identical,
indicating a sufficient bandwidth (see Fig. 5).
The BER curve against received average power at the input of
the APD receiver in the back-to-back and after 200 m GI-POF
transmission has been measured (see Fig. 6). The back-to-back
measurement has been carried out with a short piece of GI-POF
of a few meters between transmitter and receiver. The received
power has been changed by altering the distance between laser
and GI-POF. The sensitivity of the receiver was 29 dBm
at 2.5 Gb/s for a BER of 10 . The laser output power was
6.8 dBm, so the available power budget was 35.8 dB.
The attenuation of the 2 100 m GI-POF was 32.8 dB. The
power penalty due to modal dispersion of the fiber was 2 dB
(see Fig. 6). The total coupling losses where 0.6 dB, so a power
budget of 35.4 dB was needed. Moreover, the optical output
spectrum of the modulated laser at an average output power of
6.8 dBm has been measured (see Fig. 7). The width of the spectrum, 3 dB below the maximum value is 0.4 nm, which limits
pulse broadening due to dispersion of the fiber.
It is of interest to analyze why our results outperform those
reported so far. In addition to the receiver sensitivity, we believe
that both the method of excitation, as well as the spectral characteristics of the exciting source play a significant role. Due to the
tilting of the launching beam, back reflections from the fiber’s
input surface into the laser source are avoided. Semiconductor
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IEEE JOURNAL ON SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 7, NO. 3, MAY/JUNE 2001
Fig. 8. Experimental setup for a PF GI-POF data link over 550 m at 840-nm
wavelength, using a VCSEL and a silicon APD.
Fig. 6.
BER measurement results.
of the curves presented in literature. So, the fiber should exhibit
less modal dispersion, because the number of propagated modes
is less than the one that can be excited under full launch condition, and this may lead to a further bandwidth improvement.
The curves suggest that transmission experiments above 5 and
10 Gb/s over 200 m, respectively, may be possible if the fiber is
. Because
graded around the optimum profile region
the intrinsic bandwidth of the used laser was limited to 3 GHz,
these experiments could not be carried out.
B. 2.5- and 5-Gb/sTransmission Experiments With PF GIPOF
Fig. 7. Measured optical spectrum of the modulated laser.
lasers subject to back-reflected waves in optical communication systems may undergo different and complicated states of
behaviors. Unless the reflected light is well monitored, optical
feedback is often detrimental, because it enhances noise and introduces multiple nonlinearity in the emission characteristics,
which degrade the signal-to-noise ratio at the receiver. Obviously, the fact that such an impairment was avoided could have
contributed to the achievement of a good system BER. Another
explanation to the present performance can be found in connection with the spectral characteristics of the exciting source. The
measured spectral width was 0.4 nm as indicated earlier (see
Fig. 7).
This small value certainly balances the effect of the material dispersion of the fiber. The influence of the wavelength has
been checked by referencing to the existing literature. It can be
seen that the bandwidth is significantly enhanced for 0.4 nm
compared to the 2-nm case, as reported in the literature. The
dispersion behavior of the fiber may be even better in the condition of our experiment. Indeed, the exciting beam was nearly
parallel, meaning that the NA was not overfilled as in the case
At 840- and 1310-nm wavelengths, record distances of
550 m for both wavelengths have been achieved at a bit rate
of 2.5 Gb/s. These results are obtained owing to the use of
improved low-loss fiber, with very sensitive large active area
APD receivers laser sources with a small spectral width,
launching the fiber with only a few modes and improved optical
interconnection between the components.
Perfluorinated polymer-based GI-POF has a low-loss
wavelength region from 500 to 1300 nm. Reported losses are
50 dB/km from the visible to the near infrared region [13]. The
550 m of GI-POF we used, has an attenuation of 43.6 dB/km
at 840 nm and 31 dB/km at 1310 nm (Asahi Glass). In our
2.5-Gb/s experiment at 1310 nm, a transmission distance of
550 m has been reached by using a very sensitive large active
area APD receiver and a low-loss interconnection between
the GI-POF and the APD receiver. A 2.5-Gb/s experiment at
840 nm with GI-POF is, as far as we know, reported for the first
time. In this experiment, a vertical-cavity surface-emitting laser
(VCSEL) has been used in combination with a silicon APD
receiver. Fig. 8 shows a block diagram of the 550-m distance
experiment.
Key elements used in the 840-nm experiment are a VCSEL
with a high bandwidth of 2 GHz, a silicon APD with a large
active area of 230 m in diameter, and GI-POF with a low attenuation of 43.6 dB/km at 840 nm, as mentioned before. To
compensate for the insufficient bandwidth of the VCSEL, an
electrical equalizing circuit has been used. Key elements used
in the 1310-nm experiment are a distributed-feedback (DFB)
laser with a high bandwidth of 5 GHz, an InGaAs APD with
an active area of 80 m in diameter, and GI-POF with a low attenuation of 31 dB/km (Asahi Glass) at 1310 nm, as mentioned
before. Both experiments were carried out using a NRZ PRBS
. Contributing to the achievewith a pattern length of
ment are measures taken to avoid reflections and to improve optical coupling efficiency between laser and fiber and fiber and
VAN DEN BOOM et al.: HIGH-CAPACITY TRANSMISSION OVER POLYMER OPTICAL FIBER
Fig. 9. BER 2.5 Gb/s over 550-m PF GI-POF at 840 nm.
Fig. 10.
BER 2.5 Gb/s over 550-m PF GI-POF at 1310 nm.
APD. At the transmitting side in the 840-nm experiment, light is
launched directly from VCSEL component into the GI-POF. Because the VCSEL component was already provided with a lens,
which was not optimized for coupling with the GIPOF, the coupling loss was 1 dB. In the 1310-nm experiment, the light from a
single-mode fiber (SMF) pigtail of the DFB laser was launched
into the large core of the GI-POF by means of a butt coupling
with losses less than 0.1 dB. At the receiver side in both experiments, a lens doublet has been used that has an NA of 0.25 at the
fiber side and 0.55 at the APD side. GI-POF to APD coupling
losses were less than 0.3 dB. The lenses are AR-coated to less
than 1% reflection. The coupling optics was manually adjusted
to achieve a maximum coupling efficiency.
The BER as a function of received average power at the input
of the APD has been measured back-to-back, and after 550-m
GI-POF transmission (see Figs. 9 and 10). The back-to-back
measurements has been carried out with a short piece of GI-POF
of a few meters long between transmitter and receiver. In the
465
Fig. 11. Optical spectrum of modulated 840-nm VCSEL.
case of the 840-nm system, the received power has been changed
by altering the distance between laser and GI-POF. In the case
of the 1310-nm system, a variable attenuator has been used after
the laser diode.
In the 840-nm experiment, the average output power of
the VCSEL was 1.3 dBm, and the sensitivity of the receiver
28.6 dBm at 2.5 Gb/s for a BER of 10 , so the
was
available power budget was 29.9 dB. The attenuation of the
550-m GI-POF was 24.0 dB. The power penalty due to modal
dispersion of the fiber and modal noise was 4.5 dB (see Fig.
9). The total coupling losses were 1.3 dB, so a power budget
of 29.8 dB was needed.
In the 1310-nm experiment, the average output power of the
DFB laser was 0.4 dBm and the sensitivity of the receiver was
28.4 dBm at 2.5 Gb/s for a BER of 10 , so the available
power budget was 28.8 dB. The attenuation of the 550-m
GI-POF was 16.3 dB at 1310 nm. The power penalty, due to
modal dispersion of the fiber and modal noise, was 4.4 dB (see
Fig. 10). The total coupling losses were again 0.4 dB, so a
power budget of 21.1 dB was needed. Because of the difference
between available and needed power of 7.7 dB, a probable
distance of 750 m can be reached. This experiment could not
be carried out because this length of fiber was not available.
The modulated spectral width of the 840-nm laser was
smaller than 1 nm (see Fig. 11) and smaller than 0.1 nm for the
1310-nm laser source. These small values certainly balance the
effect of the material dispersion of the fiber. The dispersion is
further avoided by the launching condition of our experiments.
In case of the 1300-nm experiments, the SMF pigtail of the
laser source was butt jointed to the GI-POF exciting only a few
modes. In case of the 840-nm experiment, only a few modes are
excited because the exciting beam was nearly parallel, meaning
that the NA was not overfilled. So, the fiber should exhibit less
modal dispersion because the number of propagated modes is
less than the one that can be excited under full launch condition,
and this may lead to a further bandwidth improvement.
A PF-GI-POF 2.5-Gb/s transmission system at 645-nm visible light with a distance of 300 m has been carried out. For
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IEEE JOURNAL ON SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 7, NO. 3, MAY/JUNE 2001
Fig. 14.
Principle of operation of the 645-, 840-, 1310-nm demultiplexer.
dBm for a BER of 10 . This sensitivity can be improved by
using a transimpedance amplifier.
C. WDM Experiments
Fig. 12. BER of 2.5 Gb/s over 300-m PF GIPOF at 645 nm.
Fig. 13.
5 Gb/s over 200-m PF GIPOF set up.
this experiment, the transmitter and receiver modules of the
2.5 Gb/s over 200-m PMMA GIPOF have been used. Fig. 12
shows the measured BER against received average power at the
input of the APD with and without 300-m GI-POF. Again, the
back-to-back measurement has been carried out with a short
piece of GI-POF transmitter and receiver. The sensitivity of the
receiver was 29 dBm at 10 BER. The laser output power
was 6.2 dBm, so the available power budget was 35.2 dB. The
attenuation of the 3 100 m GI-POF was 32.6 dB. The power
penalty due to modal dispersion of the fiber and modal noise
was 1 dB (see Fig. 12). The total coupling losses where 0.6 dB,
so a power budget of 34.2 dB was needed.
With the set up of Fig. 13, an error-free transmission experiment at a bit rate of 5 Gb/s has been carried out over 200-m PF
GIPOF at 1300 nm.
Using a metal–semiconductor–metal (MSM) detector, developed by the Electronic Devices Group, Eindhoven University
of Technology, a 2.5 Gb/s over 100-m GIPOF has been carried
out at 840 nm. The MSM detector has a large active area of
100 100 m, and is therefore, easy to couple with a large-core
fiber. The MSM detector was coupled with an amplifier with an
input impedance of 50 ohms. The receiver sensitivity was 6
Perfluorinated polymer-based graded index polymer
optical fiber (GI-POF) has a low-loss wavelength region
from 500 to 1300 nm, so many WDM transmission can be
applied over a broad wavelength range, which can be separated
easily with low-cost devices. As a start of this development, a
demultiplexer for splitting up the wavelengths 645, 840, and
1310 nm has been realized with planar interference filters [17].
In Fig. 14, the principle of operation of the demultiplexer is
shown.
First, the light from the input GI-POF is transformed into a
parallel beam by means of lens 1. Interference filter 1 deflects
the light in the 645-nm wavelength region. The other wavelengths are passed through. Second, to decrease crosstalk, an
extra filter 2 has been used, which is only transparent for the
645-nm wavelength region. Lens 2 focuses the light at the photodiode of the 645-nm receiver. The light in the 840- and 1310-nm
wavelength regions, which passed through filter 1, is split up by
filter 3 Light in the 840-nm wavelength region is deflected by
filter 3, filtered by filter 4, and focused on the detector of the
840-nm receiver by lens 3. The remaining 1310-nm light is focused on the 1310-nm detector by lens 4. The measured insertion losses for all three wavelengths from GI-POF input to photo
detectors are smaller than 1.6 dB. Measured crosstalk levels are
smaller than 30 dB. In Fig. 15, a photograph of the demultiplexer including the three receiver modules is shown. On the
left, the GI-POF can be seen.
The demultiplexer has been used for a three channels operating at 2.5 Gb/s over 200-m GI-POF WDM experiment with a
record bit rate times distance product. A block diagram of the
setup is shown in Fig. 16. For this experiment, the transmitters
and receivers described in Section III A and Section III B have
been used. Moreover, a two-channel at 2.5 Gb/s WDM experiment has been carried out, using the wavelengths 840 and 1310
nm, and a GI-POF fiber with a length of 328 m of one piece.
Because this fiber sample has an attenuation of more than 100
dB/m at 640 nm, this wavelength could not be used. A block
diagram of this setup is shown in Fig. 17.
D. Experiments With Large-Core Silica Graded Index Fibers
Present silica graded index multimode (GIMM) fibers are
mainly produced in two types: 50/125 and 62.5/125 m. These
fibers show a high modal bandwidth, certainly when produced
VAN DEN BOOM et al.: HIGH-CAPACITY TRANSMISSION OVER POLYMER OPTICAL FIBER
Fig. 18.
467
Bandwidth measurement setup with network analyzer.
Fig. 15. Photograph of the realized demultiplexer including the three receiver
modules.
Fig. 16. Block diagram of the 3
GI-POF.
2 2.5-Gb/s WDM experiment over 200-m
Fig. 19. Example of a result of a bandwidth measurement for a silica large-core
graded-index MMF.
Fig. 17. Block diagram of the 2
GI-POF.
2 2.5-Gb/s WDM experiment over 328-m
by for that purpose excellently equipped by the plasma chemical vapor deposition (PCVD) process. The quality of the profile shape is very important in relation to bandwidth. Although
the profile shapes of GI-POF are not perfect, some reports refer
to high bandwidth values. From this point of view, it is interesting to know the bandwidth behavior of large-core silica
GIMM fibers, because that technology is available and present
attenuation values are by far better than those of present PMMA
GI-POFs. A series of investigations have been made using core
sizes of 93, 148, and 185 m. These fibers have been made from
a standard 50- m GIMM PCVD preform, drawn to different
cladding diameters (125, 200, and 250 m, respectively). With
these large-core fibers, it is impossible to excite all transmission
modes at the transmitter side with a laser to obtain an over-filledlaunch (OFL) condition. This condition gives a worstcase bandwidth. The bandwidth can be increased by excitation of a small
number of low-order modes, using a launch from an SMF. This
technique has been used while performing the bandwidth measurements, transmission experiments, and taken into account in
the theoretical analysis.
Using SMF launching, the bandwidth of the three fibers with
a core/cladding diameter of 93/125, 148/200, and 185/250, each
with a length of 2 km, has been measured with a 3-GHz optical
network analyzer at 1300-nm wavelength (see Fig. 18). At the
receiver side, a lens coupling has been used to detect all the
power out of the fiber. The 3-dB bandwidths are 3.0, 2.4, and
2.3 GHz, respectively, and are comparable with the bandwidth
of graded index fiber with standard diameters. An example of
the result of a bandwidth measurement can be seen in Fig. 19.
Moreover, transmission experiments have been carried out at
1300-nm wavelength [18]. Again, a lens coupling has been used
at the receiving end to detect all the power out of the fiber to
avoid modal noise because of masking effects. The attenuation
of the 2-km-long large-core GIMM is less than 1 dB at 1300 nm,
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IEEE JOURNAL ON SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 7, NO. 3, MAY/JUNE 2001
so the fiber introduces hardly any power loss. According to
the bandwidth measurements and calculations, the bandwidth is
sufficient, so for all three fibers at 2.5-Gb/s transmission, a BER
has been measured. Even with two comsmaller than 10
bined 2-km fibers, so in total 4-km transmission distance, the
BER was smaller than 10 . To our knowledge, these 2.5-Gb/s
transmission results over large-core graded index fiber are reported for the first time. A simulation model of the bandwidth
of these fibers including limited fiber launching, mode coupling, chromatic dispersion, and differential mode attenuation
has been developed. The measurement results are accordingly
agreement with the simulation results.
IV. POTENTIALS
Plastic optical fibers offer the potential to serve as the transmission medium for broad-band telecommunications service,
for instance, in in-home networks and for local area network
(LAN) networking environment. There are several alternative
technologies such as copper-based silica SMF, and multimode
glass fiber technologies. However, these technologies suffer
from several drawbacks. Let us examine the advantages and
disadvantages of POF with respect to those technologies.
Compared to copper-based technologies, like coax cables and
twisted pair, POF guarantees electromagnetic compatibility
(EMC) and absence of crosstalk. Polymer optical fiber has
smaller volume, it is less bulky, more flexile, and it has smaller
weight. For data transmission, POF offers higher bandwidth at
longer transmission distances. Compared to multimode glass
optical fiber, POF is easier to handle. POF termination can be
realized faster and cheaper than in the case of multimode glass
fiber. The typical large core of polymer fiber allows for large
tolerance on misalignments that results in the possibility of
making cheaper connectors. For comparison, let us examine the
power loss due to lateral (axial) misalignment of connecting
two graded index (parabolic case) MMF with different core
diameters. Calculations, assuming uniform modal power
distributions for a misalignment of 25 m, yields a loss of
1.76 dB for a 62.5- m core diameter MMF. For the case
of PF GI POF with a core diameter of 200- m, the 25- m
displacement results only in 0.48-dB loss. Another advantage
of large-core PF GI-POF has been observed with respect to the
bandwidth degradation due to modal noise at misalignments
in fiber-to-fiber connections. Namely, PF GI-POF shows very
short time delay at the wide area of the core. This is contrast
to the case of multimode silica fiber with 50- to 62.5- m core,
where small displacements cause severe bandwidth degradation
[24].
With respect to data transmission, POF has the potential
of high bandwidth and less problems of modal dispersion.
Although the attenuation and bandwidth characteristics of POF
are inferior compared to standard SMF, POF offers the already
mentioned advantages of easy of coupling, termination, and
flexibility. In the case of standard SMFs, specialized precision
mechanism has to be used for coupling and handling. We can
see that POF data characteristics, at the current state-of-the
art, do not pair those of standard SMF, however they are
superior to those of copper-based technologies. Furthermore,
the installation and termination of POF are easier and promise
low costs compared to SMF and multimode glass fiber. It is
worth noting that connector devices for POF are not only easier
to assemble compared to those for single-mode glass fiber,
but also easier than those for HF coax cabling. Termination
of coax cabling requires more skilled handling, as improper
termination will cause large loss and considerable increased
ingress noise. This will result in a considerable degradation of
the system performance. On the other hand, POF connectors
can be assembled easily for instance using a low-cost plastic
ferrule [24]. Coupling loss using the above method has been
measured to be in the order of 0.8 dB at 850-nm wavelength
[24]. Large-core glass fiber shows lower attenuation than POF,
however their core size is restricted to 200- m due to the
inherent inflexibility of glass. In this situation, POF offers
again advantages concerning easy handling and termination,
and tolerance to misalignments.
Ethernet is a widely deployed networking technology. Gigabit ethernet standard operating at 1.25 Gb/s supports a range
of transmission lengths: 100 m over copper wire, 550 m over
multimode glass fiber with a 50- or 62.5- m core, and 5 km
over SMF. Recent experiments performed in our group have
successfully demonstrated 1.25-Gb/s ethernet transmission over
PF GI-POF reaching a distance of 990 m with good BER performance. These experiments show that PF GI-POF can be used for
gigabit ethernet applications, in short, to medium link distances.
The transmission results presented in this paper are record experiments. They show the feasibility of POF for high-capacity
transmission. The reported experiments use a receiver with APD
photodetector, which is not a cost competitive option in relation to conventional PIN photodiode receivers. A receiver with
a conventional less costly PIN photodiode may also be used at
expenses of lower receiver sensitivity. Assuming a degradation
of 11 dB in receiver sensitivity (16.9-dBm receiver sensitivity
at 2.5 Gb/s using a PIN detector has been reported in [4]) with
respect to the APD receiver, we estimate the following reachable transmission distances at 2.5 Gb/s. At the 840-nm operating system over PF GI-POF with attenuation of 43.6 dB/km,
a distance of 280 m could be feasible. For a system operating at
1310 nm with a fiber attenuation of 31 dB/km, a transmission
distance of 430 m could be reached. However, for POF technology to be competitive in the customer’s premises, it will have
to operate with low-cost components. These include low-cost
light sources, low-cost receiver modules, and low-cost WDM
devices. We would like to remark that the transmission end
shows less technical problem than the reception end. This also
applies for the case of WDM transmission systems. The WDM
multiplexing can be performed simply by butt joining the pigtailed fibers from the laser sources, for instance, as it has been reported in our experiments. It remains, therefore, of high importance for further development of POF-based transmission systems, the development of low-cost reliable transceiver modules,
connector, and WDM (de)multiplexing devices. Light sources
based on VCSELs are promising solutions. Perhaps the use of
plastic/polymer lens system for fiber to the photodetector coupling could be introduced for the realization of compact and reliable receivers. These, among others, are challenging issues open
for further research and development.
VAN DEN BOOM et al.: HIGH-CAPACITY TRANSMISSION OVER POLYMER OPTICAL FIBER
V. CONCLUSION
The transmission distances of PF GI-POF-based systems are
increasing very fast. At bit rates of 2.5 Gb/s, system spans of 300
m at 645-nm wavelength, and 550 m at 840- and 1310-nm wavelengths have been reached. Using WDM transmission, system
capacities have been further enhanced. For instance, we have
reported a three-channel 2.5-Gb/s GI-POF WDM transmission over 200-m experiment and a two-channel 2.5 Gb/s over
328-m experiment with record bit-rate distance products. These
experiments show the feasibility of high-capacity transmission
over POF. It also has been shown that 2.5-Gb/s transmission
over 4 km of large-core (148 and 185 m) graded index silica
fiber can easily be realized. Maximum transmission distances of
the large-core graded index silica fibers are much larger compared with the graded index polymer fibers. There is a large difference in attenuation between silica and polymer fibers. The
diameter of silica fibers is limited because of the inherent inflexibility of glass materials. Because of the difference in mechanical properties of silica and polymer the handling techniques are
different.
The experimental results resorted in this paper clearly show
the applicability of graded index polymer optical fiber for customer premises and local area networks. We believe that the
record results reported here are important milestones that may
encourage the development of polymer fiber systems and networks.
469
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=
ACKNOWLEDGMENT
The authors would like to acknowledge Y. Koike, Keio University, Yokohama, Japan, for providing the GI-POF samples.
Dr. N. Yoshihara and Dr. M. Naritomi, Asahi Glass, Yokohama,
Japan, are acknowledged for providing us with PF GI-POF samples. Dr. S. Yamazaki, NEC Corporation, Kawasaki, Japan, is
acknowledged for making available 645-nm laser diodes. The
author would like to acknowledge Dr. K. Nakamura and Dr.
Y. Kawaharada, Mitsubishi Rayon, Hiroshima, Japan, for providing PMMA GI-POF samples. G. Kuyt, Plasma Optical Fiber,
Eindhoven, The Netherlands, is acknowledged for providing
samples of large-core silica fiber. Dr. A. Valster, JDS-Uniphase
Netherlands, Eindhoven, The Netherlands, is acknowledged for
making available laser diodes.
REFERENCES
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Boom, W. Li, and G. Yabre, “Status of GIPOF systems and related technologies,” in 25th ECOC’99 Conf., Sept. 26–30, 1999, pp. II/274–II/277.
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2000.
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H. P. A. van den Boom, photograph and biography not available at the time of
publication.
W. Li, photograph and biography not available at the time of publication.
P. K. van Bennekom, photograph and biography not available at the time of
publication.
Idelfonso Tafur Monroy was born in el Castillo (Meta) Colombia, in 1968.
He received the M.Sc. degree in multichannel telecommunications engineering
from the St. Petersburg State University of Telecommunications, (formerly
Bonch-Bruevitch Institute of Telecommunications), St. Petersburg, Russia
and the Technology Licentiate degree in telecommunication theory from
the Royal Institute of Technology, Stockholm, Sweden, at the department of
Signals, Sensor, and System, in 1992 and 1996, respectively. The licentiate
thesis treated the performance analysis of optically preamplified receivers.
He received the Ph.D. degree in electrical engineering from the Eindhoven
University of Technology, The Netherlands, in 1999.
Currently he is a Postdoctoral Researcher in the area optical networking and
communication systems at the Eindhoven University of Technology.
Giok-Djan Khoe (S’71–M’71–SM’85–F’91) was born in Magelang, Indonesia,
on July 22, 1946. He received the Electrical Engineering degree from the Eindhoven University of Technology, Eindhoven, The Netherlands, in 1971.
From 1971 to 1972, he was with the FOM Institute of Plasma Physics,
Rijnhuizen, The Netherlands, where is was involved with laser diagnostics
of plasmas. In 1973, he joined the Philips Research Laboratories. He was
appointed a Part-Time Professor and then Full Professor at the Eindhoven
University of Technology, in 1983 and 1994, respectively,. He is currently
the Chairman of the Department of Telecommunication Technology and
Electromagnetics. His work has been devoted to single-mode fiber (SMF)
systems and components. He has authored and co-authored more than 100
papers, invited papers, and books. He holds more than 40 U.S. patents.
G. Khoe has served in the IEEE/Lasers and Electro-optics Society (LEOS)
Board of Governors, as European representative, vice president, and elected
member. He is also a member of the Executive Committee of the IEEE Benelux
Section. His professional activities include many conferences, where he has
served in technical committees, management committees, and advisory committees as a member or chairman. He has numerous involvements in journal
activities as Associate Editor or as member of the advisory board. In Europe,
he is closely involved in Community Research Programs and Dutch national
research programs, as participant, evaluator, auditor, and program committee
member. He is one of the founders of the Dutch COBRA University Research
Institute. His is one of three recipients of the prestigious “Top Research School
Photonics” Grant that is awarded to COBRA by The Netherlands Ministry of
Education, Culture, and Science, in 1998. He is a recipient of the MOC/GRIN
Award in 1997.
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