Polarization division multiplexed 4 × 10 Gbps
simultaneous transmissions in 1.0-µm waveband
and C-waveband over a 14.4-km-long holey fiber
using an ultra-broadband photonic transport
system
Yu Omigawa,1,2 Naokatsu Yamamoto,1,* Atsushi Kanno,1 Tetsuya Kawanishi,1 Yasuaki
Kurata,2 and Hideyuki Sotobayashi2
1
National Institute of Information and Communications Technology (NICT), 4-2-1 Nukui-kitamachi, Koganei-shi,
Tokyo 184-8795, Japan
2
Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara-shi, Kanagawa 252-5258, Japan
*
naokatsu@nict.go.jp
Abstract: Polarization division multiplexing (PDM) and wavelength
division multiplexing (WDM) are essential techniques for enhancing the
capacity of photonic networks and facilitating the efficient use of optical
frequency resources. 2 PDM × 2 WDM × 10 Gbps error-free simultaneous
transmissions in the 1.0-µm waveband and C-waveband are successfully
demonstrated for the first time using an ultra-broadband photonic transport
system over a 14.4-km-long holey fiber transmission line.
©2012 Optical Society of America
OCIS codes: (060.2330) Fiber optics communications; (060.4510) Optical communications;
(060.4005) Microstructured fibers.
References and links
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data transmission in 1-mum, C-, and L-wavebands over a single holey fiber using an ultra-broadband photonic
transport system,” Opt. Express 18(5), 4695–4700 (2010).
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Received 13 Feb 2012; revised 7 May 2012; accepted 18 May 2012; published 19 Jun 2012
2 July 2012 / Vol. 20, No. 14 / OPTICS EXPRESS 14864
13. N. Yamamoto, Y. Omigawa, Y. Kinoshita, A. Kanno, K. Akahane, T. Kawanishi, and H. Sotobayashi,
“Development of broadband optical frequency resource over 8.4-THz in 1.0-µm waveband for photonic
transport systems,” Proc. SPIE 7958, 79580F, 79580F-9 (2011).
14. R. Noé, S. Hinz, D. Sandel, and F. Wüst, “Crosstalk Detection Schemes for Polarization Division Multiplex
Transmission,” J. Lightwave Technol. 19(10), 1469–1475 (2001).
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Electron. Lett. 37(23), 1399–1401 (2001).
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Using Large-Aeff Holey Fibers Enabling Transmission over 600nm Bandwidth,” in Optical Fiber
Communication Conference, OSA Technical Digest Series (Optical Society of America, 2008), paper OThR.
1. Introduction
The ever-increasing demand for high data transmission capacities has necessitated the use of
alternative wavebands and the development of methods for enhancing the transmission
capacities of existing photonic networks. Photonic transport systems in the C-waveband
(1530–1565nm) and the L-waveband (1565–1625nm) have been used extensively in
conventional photonic networks [1]. Recently, we have focused on the development of a
novel alternative 1.0-µm photonic waveband (1000–1260nm), which is shorter than the Owaveband (1260–1360nm) [2]. This short waveband is referred to as the thousand-waveband
(T-waveband). The T-waveband is considered an attractive alternative waveband for future
photonic transport systems on the basis of the assumption that optical frequency resources
greater than approximately 50~60 THz may be employed in this waveband [2–4]. Moreover,
the currently available ytterbium-doped fiber amplifier (YDFA) can be used as a 1R repeater
in the 1.0-µm waveband [5]. In addition, high-performance, ultra-broadband and
environmentally friendly photonic devices such as high-power lasers, broad-band optical gain
devices using a novel nano-structured material such as a quantum dot, and group-IVsemiconductor-based high-speed photonic receivers are compatible with this waveband [6–
10].
The capacity of existing photonic networks can be significantly enhanced by using a
photonic transport system that employs wavelength division multiplexing (WDM) technique
in novel and conventional wavebands [11–13]. Moreover, a polarization division multiplexing
(PDM) technique has also been investigated intensively by R. Noe et al., and K. Suzuki et al.
to enhance the photonic network capacity [14, 15]. We therefore proposed an ultra-broadband
PDM and WDM photonic transport system that is compatible with the 1.0-µm waveband and
the C-waveband to create a high capacity photonic network system. In the proposed system, a
14.4-km-long holey fiber (HF) is used as a novel photonic transmission line. In this study, we
successfully demonstrated for the first time 2 PDM × 2 WDM × 10 Gbps error-free
simultaneous transmissions in the 1.0-µm waveband and the C-waveband using the proposed
ultra-broadband photonic transport system.
2. Ultra-broadband photonic transport system with PDM and WDM in the T- and Cwavebands
PDM and WDM are essential techniques for enhancing the capacity of photonic networks and
facilitating the efficient use of optical frequency resources. We constructed and demonstrated
the operation of an ultra-broadband PDM and WDM photonic transport system in the T- and
C-wavebands. Figure 1 shows the experimental setup used for the demonstration. A
wavelength-tunable GaAs-based semiconductor laser diode was used as the narrow-line width
light source (approximately 200 kHz) for the T-waveband. The carrier wavelength was tuned
to 1063.7nm. The optical output of the T-waveband light source was amplified to
approximately 10 dBm using an InGaAs/GaAs-based semiconductor optical amplifier (SOA).
A distributed feedback (DFB) semiconductor laser diode with a wavelength of 1550.0nm was
used as the light source for the C-waveband. Two LiNbO3 (LN) intensity modulators were
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Received 13 Feb 2012; revised 7 May 2012; accepted 18 May 2012; published 19 Jun 2012
2 July 2012 / Vol. 20, No. 14 / OPTICS EXPRESS 14865
used to generate data streams in the T- and C-wavebands. In this experiment, a 9.953 Gbps
(OC-192, STM-64) pseudo-random binary sequence (PRBS), which was 27-1 digits in length
was used to generate non-return zero (NRZ) on-off keying (OOK) data signals in each
channel. A polarization beam splitter (PBS) and a polarization beam combiner (PBC)
connected to polarization-maintaining (PM) optical fibers were used to multiplex orthogonal
linear polarized signals in the T- and C-wavebands. Two polarization rotators placed before
the PBSs were used to control the polarization axis. Two orthogonal linear polarizations
directed toward the X- and Y-axis were used as shown in Fig. 1. Two PM optical fiber delay
lines were used at the two input ports for inducing Y-axis polarization (In-Py) and for
generating two different data streams with orthogonal polarizations in the T- and Cwavebands. The optical signals in the T- and C-wavebands were amplified using a YDFA and
an erbium-doped fiber amplifier (EDFA), respectively. WDM coupler and splitter were used
at both ends of the transmission line for combining and separating the optical signals in the Tand C-wavebands.
PPG
9.953 Gbps
T-waveband
1063.7 nm
wavelengthtunable laser
In-Px
Pol. X
YDFA
PC
Delay
LiNbO3
Intensity
Modulator
SOA
PBS
C-waveband
1550.0 nm DFB laser
PBC
In-Py
Pol. Y
In-Px
Pol. X
EDFA
WDM
coupler
Single-mode and
ultra-broadband
transmission line
Delay
PBS
Receiver
BERT
PD
Communications
analyzer
CDR
ATT
PBC
In-Py
Pol. Y
Out-Px
Filter YDFA
Holey fiber
(cross section)
distance: 14.4 km
PBS
Out-Py
Out-Px
Filter EDFA
WDM
splitter
PBS
Out-Py
Fig. 1. Ultra-broadband PDM and WDM photonic transport system using a 14.4-km-long
holey fiber transmission line for simultaneous transmissions in the T- and C-wavebands. PBS:
polarization beam splitter, PBC: polarization beam combiner, and PC: polarization controller.
YDFA: ytterbium-doped fiber amplifier for T-band, EDFA: erbium-doped fiber amplifier for
C-band, and SOA: semiconductor optical amplifier. ATT: optical attenuator, PD: broadband
photo-detector for T- and C-wavebands, and CDR: electrical clock-data recovery circuit.
An optical fiber as a long-distance transmission line is crucial to an ultra-broadband
photonic transport system. Therefore, we used a HF, which is a photonic crystal fiber, as the
transmission line for the ultra-broadband photonic transport system. HFs are considered
suitable for ultra-broadband transmission owing to their endlessly single-mode (ESM)
characteristic [16]. Furthermore, the dispersion characteristics and the mode field diameter of
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Received 13 Feb 2012; revised 7 May 2012; accepted 18 May 2012; published 19 Jun 2012
2 July 2012 / Vol. 20, No. 14 / OPTICS EXPRESS 14866
@ 1050nm
@ 1550nm
Fig. 2. Simulated optical mode field in the holey fiber at wavelengths of 1050nm and 1550nm
used for the estimation of the endlessly single-mode characteristics.
(a) Before transmission
0
Power (dBm)
Power (dBm)
(b) After transmission
T-waveband
0
C-waveband
-20
-40
-60
T-waveband
-20
C-waveband
-40
-60
1000
1200
1400
Wavelength (nm)
1600
(c) Polarization cross-talk
in the T-waveband
-10
1000
1200
1400
Wavelength (nm)
(d) Polarization cross-talk
in the C-waveband
-10
Out-Py
Connected:
In-Py
-17.1 dB
-30
-40
Connected:
In-Px
-50
1062
1063
1064
Wavelength (nm)
Power (dBm)
-40
Out Twaveband
-30
-22.5 dB
Connected:
In-Px
-40
1550
1551
Wavelength (nm)
1552
(f) Wavelength cross-talk
in the C-waveband
-20.8 dB
Out Cwaveband
-60
1062
-20
-50
1549
1065
(e) Wavelength cross-talk
in the T-waveband
-20
Power (dBm)
Connected:
In-Py
1063
1064
Wavelength (nm)
1065
Power (dBm)
Power (dBm)
Out-Py
-20
1600
-20
-40.6 dB
Out C-waveband
-40
Out T-waveband
-60
1549
1550
1551
Wavelength (nm)
1552
Fig. 3. Optical spectra (a) before and (b) after transmission. Estimation of polarization crosstalk using optical spectra in the (c) T- and (d) C-wavebands. Estimation of wavelength crosstalk using optical spectra in the (e) T- and (f) C-wavebands.
a HF can be optimized by varying the hole size and the distances of the holes from the fiber
core [17]. Figure 2 shows the simulated optical modes of the fabricated HF in both of the T-
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and C-wavebands. This result demonstrates that single mode operations in the ultrabroadband photonic transport system can be achieved using HFs. The zero-dispersion
wavelength was estimated to be approximately 1200nm, and the dispersion values were found
to be −20.1 ps/nm/km at 1.0 µm and 32.5 ps/nm/km at 1.55 µm. In this transmission
experiment, the input powers to the HF transmission line were fixed at 6.6 dBm for the Twaveband and −2.5 dBm for the C-waveband. The length of the HF was 14.4 km. The
transmission losses of the HF were estimated to be approximately 0.89 dB/km at 1.0 µm and
0.43 dB/km at 1.55 µm. After simultaneous transmissions, the optical signals in the T- and Cwavebands were separated by the WDM splitter. Then, the optical signals in the T- and Cwavebands were amplified by the YDFA and EDFA, respectively. Optical band pass filters
placed after the YDFA and EDFA were used to eliminate the amplified spontaneous emission
(ASE) noise generated by the fiber amplifiers. The polarization axes were controlled by using
the two polarization rotators placed before the PBS. The PBS, which was connected to the
PM optical fibers, was used to de multiplex the orthogonal linear polarized signals in the Tand C-wavebands. The optical signals of each wavelength were detected by a photonic
receiver, which consisted of a broadband photodetector and an electrical clock and data
recovery (CDR) circuit.
Eye-diagrams and the bit error rate (BER) of the electrical output signal from the photonic
receiver were measured using a communications analyzer and a BER tester, respectively. In
addition, optical spectra before and after the simultaneous transmission were examined using
an optical spectrum analyzer (OSA). We also estimated the polarization cross-talk and
wavelength cross-talk in the proposed PDM and WDM photonic transport system in the Tand C-wavebands, respectively, using an OSA.
3. Simultaneous transmission characteristics of the ultra-broadband PDM and WDM
photonic transport system for the T- and C-wavebands
Figure 3(a) and 3(b) shows the optical spectra measured before and after the simultaneous
transmission, respectively, over a wide wavelength range. A clear peak was observed at a
wavelength of 1063.7nm and 1550.0nm in the spectra measured before and after the
simultaneous transmission, respectively. The observation of these two peaks indicates that
simultaneous transmissions in the T- and C-wavebands can be achieved using the 14.4-kmlong HF transmission line. Figure 3(c) and 3(d) shows the optical spectra, which was
measured at the output port with Y-axis polarization (Out-Py) in the T- and C-wavebands,
respectively, by selecting each of the input ports, In-Px and In-Py, separately. Polarization
cross-talk of less than −17 dB in the T-waveband and −22 dB in the C-waveband was
measured. Figure 3(e) and 3(f) shows the optical spectra measured at the back of the WDM
splitter after transmission. Wavelength cross-talk of less than −20.8 dB in the T-waveband
and −40.6 dB in the C-waveband was measured. The polarization and wavelength cross-talk
values are summarized in Table 1. From this table, it is found that the cross-talks in the Twaveband are slightly higher than that in the C-waveband. As a one of the reasons, it is
considered that we used optical-components (such as PBC and PBS) optimized at 1045nm
and 1550nm for constructing the ultra-broadband photonic transport system.
Table 1. Polarization and Wavelength Cross-talk Values in the T- and C-Wavebands
T-band
C-band
Polarization crosstalk
−17.1 dB
−22.5 dB
Wavelength crosstalk
−20.8 dB
−40.6dB
Figure 4 shows eye diagrams for the 10 Gbps data-stream transmission observed at the
Out-Px and Out-Py in the T-waveband. Eye openings were clearly observed, when the each
input ports and then both In-Px and In-Py were selectively connected for the transmission of
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data with orthogonal polarization. Moreover, we also confirmed a large BER (>10−1) at the
output port for the unused polarization axis. It is also confirmed that eye openings were
clearly observed at the Out-Px and Out-Py in the C-waveband. Figure 5 shows the BER
dependencies on the received optical power at the Out-Px, Out-Py and back-to-back (BtoB) in
both (a) the T- and the (b) C-wavebands, respectively. BERs of <10−9 were observed when
the 10 Gbps optical data signals with orthogonal linear polarization were transmitted over the
HF in the T- and C-wavebands. Power penalties between the 14.4-km-long transmission and
the BtoB were found to be 2.03 dB and 0.95 dB in the T- and C-wavebands, respectively. A
high amplification rate of YDFA was needed after a data-transmission, because the
transmission loss in the T-waveband is higher than that in C-waveband. That is, it is
considered that a performance of the data transmission in T-waveband over the long-distance
HF is slightly worsened by the transmission loss and ASE-noise of the YDFA in comparison
with a performance of C-waveband. In case of BtoB, we consider that a performance of Twaveband might be improved compared with that of C-waveband, because a high-intensity
laser amplified with the SOA was used for an optical data formation. From BER estimations,
these results indicate that 2 PDM × 2 WDM × 10 Gbps error-free simultaneous photonic
transmissions were realized over a 14.4-km-long HF in the novel T-waveband and the
conventional C-waveband.
After transmission in the T-waveband
Connected: In-Px
Disconnected: In-Py
Disconnected: In-Px
Connected: In-Py
Connected:
In-Px and In-Py
Connected:
In-Px and In-Py
without CDR
BER > 10-1
OutPx
BER > 10-1
OutPy
20 ps/div.
Fig. 4. Eye diagrams after transmission at each output port Out-Px and Out-Py of the ultrabroadband PDM and WDM photonic transport system for the T-waveband.
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Received 13 Feb 2012; revised 7 May 2012; accepted 18 May 2012; published 19 Jun 2012
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(a) T-waveband
-4
Log10BER
HF: 14.4 km
Out-Px
-6
HF: 14.4 km
Out-Py
-7
-9
-10
Log10BER
Connected:
In-Px and In-Py
-5
-8
(b) C-waveband
-4
-5
Connected:
In-Px and In-Py
-6
HF: 14.4 km
Out-Py
-8
BtoB
Out-Py
HF: 14.4 km
Out-Px
-7
BtoB
Out-Py
-9
-22 -20 -18 -16 -14 -12
Received power (dBm)
-10
-22 -20 -18 -16 -14 -12
Received power (dBm)
Fig. 5. Dependence of the BER on the received power in the ultra-broadband PDM and WDM
photonic transport system for the (a) T- and (b) C-wavebands.
4. Conclusion
We propose an ultra-broadband photonic transport system that employs PDM and WDM for
transmission over a 14.4-km-long HF. This new system with improved transmission capacity
can be used in future photonic networks. This study will open up new avenues for photonic
data transmission and will facilitate the effective use of optical frequency resources. 2 PDM ×
2 WDM × 10 Gbps simultaneous photonic transmissions in the T- and C-wavebands were
successfully demonstrated over a 14.4-km-long HF transmission line. Clear eye openings
were observed and error-free simultaneous transmissions were successfully achieved in the Tand C-wavebands. In addition, low cross-talk (−17 dB) was measured at the output ports with
X- and Y-axis polarizations. Further, low wavelength cross-talk (−20 dB) was observed
between the T- and C-wavebands. These results indicate that the proposed ultra-broadband
photonic transport system for the T- and C-wavebands using a 14.4-km-long HF transmission
line with PDM and WDM is a breakthrough in the field of ultra-broadband optical frequency
resources, and will therefore facilitate the effective use of these optical frequency resources in
an access photonic network and/or a data-center as next-generation photonic network
systems.
Acknowledgment
The authors would like to thank Dr. K. Mukasa, Dr. K. Imamura, Dr. R. Miyabe, Dr. R.
Sugizaki, Dr. T. Yagi, and Dr. S. Ozawa of Furukawa Electric Co. for providing the novel
optical fibers. The authors are extremely grateful to Dr. K. Akahane and Dr. I. Hosako of the
National Institute of Information and Communications Technology (NICT) for their
encouragement. The authors also thank the staff of the Photonic Device Laboratory (PDL) at
NICT.
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Received 13 Feb 2012; revised 7 May 2012; accepted 18 May 2012; published 19 Jun 2012
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