Optical Parametric Gain of Tellutire/Phosphate Highly Nonlinear
Optical Fiber
Edmund Samuel, Tong Hoang Tuan, Koji Asano,Takenobu Suzuki and Yasutake Ohishi
Research Center for Advanced Photon Technology, Toyota Technological Institute,
2-12-1 Hisakata Tempaku, Nagoya 468-8511, Japan
Keywords: Optical Parametric Amplifier, Microstructured Optical Fiber, Chromatic Dispersion.
Abstract: We optimized the optical pump power to realize better phase-matching, higher parametric amplification
gain and broader bandwidth for highly nonlinear optical fibers with tailored chromatic dispersions. The
core-clad materials have large refractive index difference of 0.49. The gain bandwidth calculated are 108
and 104 nm for the step index and hybrid micorstructured optical fibers with two zero dispersion
wavelengths respectively. The broadest bandwidth in our calculation is 108 nm for step index fiber at pump
wavelength 1238 nm.
1 INTRODUCTION
The need of modern and future communication
system of multi-terabit transmission in optical
communication is to be ultrafast capability with
wider bandwidth. The demand of highly nonlinear
optical fibers is increasing in optical signal
processing for applications such as wavelength
division multiplexing and optical time division
multiplexing systems. These highly nonlinear optical
fibers appear to be promising solutions and superior
as they are passive, low cost and robust optical
processors. In addition to these features the fiber
optical parametric amplifiers (FOPAs) are spectrally
flexible and operational with low noise (Djordjevic,
2011); (Nugent et al., 2009).
The optical parametric amplifier (OPA) through
four wave mixing (FWM) can deliver amplified
signal gain at arbitrary wavelengths to compensate
the fiber loss (Droques et al., 2011); (Djordjevic,
2011); (Lavoute et al., 2010); (Mussot et al., 2006);
(Vedadi et al., 2006); (Parolari et al., 2005). In
optical communication system with wavelength
division multiplexers needs to equalize optical
power levels of the various channels which can be
achieved by such OPA with highly nonlinear optical
fibers. Moreover, fiber OPA has great potential
applications such as signal generation, broadband
wavelength conversion, optical sampling and optical
switching.
Recently much attention has been given to non-
silica high index and high nonlinear materials such
as tellurite, fluoride and chalcogenide (Zhang et al.,
2012); (Stepien et al., 2010); (Gao et al., 2013);
(Souza et al., 2006). Moreover, these materials have
excellent optical transparency in comparison to
silica which has the transmission window limited to
less than 3 µm. The tellurite glasses have generated
broad interest due to excellent properties such as
corrosion resistance, lowest phonon energy among
oxides, high linear and nonlinear refractive indices,
single mode guidance, dispersion control and good
glass stability.
Figure 1: The schematic design of highly nonlinear
tellurite/phosphate (a) Step Index fiber and (b)
microstructured optical fiber.
Tong et al., has successfully demonstrated the
tellurite-glass core and phosphate cladding fiber
(Tuan et al., 2012). This core-clad combination
provides much better flexibility to tailor chromatic
407
Samuel E., Hoang Tuan T., Asano K., Suzuki T. and Ohishi Y..
Optical Parametric Gain of Tellutire/Phosphate Highly Nonlinear Optical Fiber.
DOI: 10.5220/0004610704070411
In Proceedings of the 4th International Conference on Data Communication Networking, 10th International Conference on e-Business and 4th
International Conference on Optical Communication Systems (OPTICS-2013), pages 407-411
ISBN: 978-989-8565-72-3
Copyright
c
2013 SCITEPRESS (Science and Technology Publications, Lda.)
dispersion, because the core and clad materials have
large refractive index difference of 0.49. It was
observed that by changing tellurite core diameter of
fiber from 0.8 to 6.0 µm, the zero dispersion
wavelength changes from 1150 to 1850 nm.
However, the nonlinear properties especially FOPA
performance of the tellurite/phosphate optical fiber
has not yet been clarified. Hence, the
tellurite/phosphate hybrid microstructured optical
fiber (HMOF) as shown in Fig. 1 was used for our
simulation work in this paper.
2 PARAMETRIC GAIN THEORY
The refractive indices (n) as a function of
wavelength for tellurite and phosphate glasses are
given by the Sellmeier dispersion equation (Ghosh
and Yajima, 1998).
3
1
22
2
2
1)(
ii
i
L
A
n
(1)
where λ is the wavelength in µm and the Sellmeier
fitting coefficients A
i
and L
i
(Tuan et al., 2012).
They are tabulated in Table 1.
Table 1: Sellmeier fitting coefficients for tellurite and
phosphate.
Material Tellurite Phosphate
A
i
L
i
A
i
L
i
i=1 1.6719 0.0216 1.24285 0.100699
i=2 1.3482 0.2391 0.23711 6.99996
i=3 0.62186 6.8356 9.96689 999.9990
Optical parametric amplifiers have attracted
immense interest due to their ability of providing
uniform gain bandwidth with low noise figure. In
addition to this smaller length fiber and low peak
power required for FWM process to be occurred.
Moreover, the single pump OPA has broad
parametric gain bandwidths. The net parametric gain
(G) in fiber optical parametric amplification is given
by Eq. (2) (Agrawal, 2000a); (Chaudhari et al.,
2012).
2
sinh
2
1
2
2
gL
g
P
G
(2)
where, g is the gain coefficient given by Eq. (3), is
nonlinear coefficient, L is the fiber length and P is
pump power.
2/1
22
2
4
1
PPg
(3)
The gain coefficient includes phase-match Δβ which
is given by Eq. (4). Phase-matching is a key factor
for parametric amplification and it has been
calculated analytically to realize the efficient
parametric gain (Agrawal, 2000a); (Yaman et al.,
2005).
1
2
2
)!2(
2
m
m
ps
m
m
(4)
where,
m2
are dispersion parameter coefficients, ω
p
and ω
s
are pump and signal frequency, respectively.
When
2
becomes very small, higher order
dispersion parameters must be considered at
wavelengths close to ZDW. Therefore, phase-
matching condition (Agrawal, 2000b) is expressed
as follows
02
12
1
4
4
2
2
P
(5)
where
2
and
4
are the second and fourth order
derivative of the propagation,
=
s
-
p
is the shift
in frequency between signal and pump frequency.
3 RESULTS AND DISCUSSION
Figure 2(a) shows the calculated parametric gain for
a step index fiber with core diameter of 0.944 m
and a chromatic dispersion with two ZDW at 1223
and 1252 nm. The parametric gain was obtained for
the different pump-wavelength p. It has been
observed from Fig. 2(b) that there is symmetrical
decrease in bandwidth on both side of the pump
wavelength (p=1238 nm). This is due to the
dependence of parametric gain on chromatic
dispersion and dispersion parameters which are also
symmetrical in nature. Here, the parametric gains at
each ZDW are similar and much flatter in
comparison to parametric gain observed for different
pump wavelengths. When p=1238 nm, the gain
bandwidth of step index fiber is 108 nm.
Figure 2(b) shows the view of parametric gain
which was calculated using the chromatic dispersion
as shown in Fig. 2(a). The broader and brighter
shade between 1223 and1252 nm clearly reveals the
presence of peak parametric gain and broad
bandwidth between two ZDWs and the peak value
of the parametric gain is 33 dB. However, the
bandwidth changes with pump wavelengths as
OPTICS2013-InternationalConferenceonOpticalCommunicationSystems
408
shown in Fig. 2(b). This is because
2
moves from
the normal to anomalous regime and returns to
normal regime again.
Figure 2: (a) Parametric gain for two ZDW step index
fiber with P=100mW and L=1m, (b) Parametric gain
spectra view for wide range of pump and signal
wavelength.
Figure 3(a) and (b) show the parametric gain
variation with signal and pump wavelengths for
HMOF whose chromatic dispersion is shown in Fig.
3(a). It was assumed that the peak power P=100 mW,
fiber length L=1 m, core diameter of HMOF D=0.9
μm, air hole diameter d=1μm and pitch p=1.4 μm.
When p=1255 nm, the gain bandwidth of HMOF is
104 nm and the maximum peak gain of 29 dB can
be obtained. However, we can see that the
parametric gain spectrum and bandwidth
mainly
depends on pump wavelength. The parametric gain
reduces to 20 dB with a narrow bandwidth (64 and
63 nm) at each ZDW (1241 and 1269 nm), but
significantly has flatter bandwidth at each ZDW.
Figure 3: (a) Parametric gain for two ZDW MOF with
P=100mW and L=1m, (b) Parametric gain spectra view
for wide range of pump and signal wavelength.
The phase-matching diagrams for the step index
fiber and HMOF with P changed from 10000 to
40000 m
-1
were calculated. The phase-matching
conditions were calculated using Eq. (5). The phase-
matching is very significant obligation in order to
achieve efficient parametric amplification. Figure
4(a) shows the phase-matching curves for the two
ZDW step index fiber. This shows that signal
wavelengths are much closer to pump wavelengths
between the first and second ZDW (1223 and 1252
1100 1150 1200 1250 1300 1350 1400
0
5
10
15
20
25
30
35
Signal wavelength (nm)
Param etric G ain (dB )
p
=1223 nm
p
=1238 nm
p
=1252 nm
Dispersion (ps/km-nm)
1100 1150 1200 1250 1300 1350 1400
-30
-25
-20
-15
-10
-5
0
5
Dis
p
ersion
(p
s/km-nm
)
0
=1223 & 1252 nm
SI (D=0.944
m)
ZDW1
ZDW2
1150 1200 1250 1300 1350
1150
1200
1250
1300
1350
Pump wavelength (nm)
Signal wavelength (nm )
5
10
15
20
25
30
0
=1223 & 1252 nm
SI (D=0.9 44
m)
1150 1200 1250 1300 1350 1400
1150
1200
1250
1300
1350
1400
Pump wavelength (nm)
Signal wavelength (nm)
5
10
15
20
25
MOF (D=0.9
m)
0
=1241 & 1269 nm
a
a
b
b
OpticalParametricGainofTellutire/PhosphateHighlyNonlinearOpticalFiber
409
nm). Their variation in this region reveals the effect
of nonlinear coefficient and peak power significantly.
When P increases from 10000 to 40000 m
-1
the
signal and idler wavelengths shift away from each
other. The phase-matching curves observed for
HMOF with two ZDW is as shown in Fig. 4(b). In
Fig. 4(b) the similar phase-matching curves were
observed between the first and second ZDW (1241
and 1269 nm) for different P values.
Figure 4: Phase-matching curves for (a) Step Index fiber
and (b) Hybrid microstructured optical fiber.
4 CONCLUSIONS
The HMOF has the bandwidth of 104 nm and it has
been shown that for the given set of nonlinearity
coefficient and peak power a parametric gain 33 dB
for step index fiber and 29 dB for HMOF can be
obtained. While, the phase-matching curves for the
step index and HMOF with two ZDW were
observed to be between their respective ZDWs. It is
concluded that for broad bandwidth it is very much
necessary to have very small values of
2
and
4
simultaneously.
ACKNOWLEDGEMENTS
This research was by the Ministry of Education, Culture,
Sports, Science and Technology under the support
Program for Forming Strategic Research Infrastructure
(2011-2015).
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