Multicore Photonic Crystal
Fiber Based 1x16 Intensity
Splitters/Couplers
Dror Malka and Zeev Zalevsky
Faculty of Engineering, Bar-Ilan University, Israel.
dror.malka@biu.ac.il
1
Spoiler
We demonstrated a new design of a
multicore PCF that can divide a single
optical power equally into sixteen ports.
2
Photonic Crystal Fiber (PCF)
PCF is a new type of optical fiber which obtains
its waveguide properties from a periodic
arrangement of tiny and closely spaced
variations of the refraction index which go
along the whole length of fiber
3
Guiding mechanisms
1. Index guiding mechanism (similar to the one in
classical optical fibers):
If the defect of the structure is realized by
removing the central capillary then guiding of
electromagnetic wave in a PCF can be regarded as
a modified total internal reflection mechanism.
2. Photonic bandgap mechanism:
If the central defect is realized by inserting a
central air capillary, which has a diameter different
than other capillaries (usually bigger), then we can
obtain a photonic bandgap.
4
Splitting technique
The optical splitter can be obtain by changing the
value of the refractive index in z axis
Refractive index profile of the
intensity splitter 1x8 .XZ
cross section (y=0)
5
Splitting technique
We use a new technique based on air holes with
different sizes.
This technique describes the relationship
between the distances between neighboring
cores and air hole size.
By optimization of selecting air hole diameter
which corresponds to the distance between the
cores we can neglect the other coupling
coefficients.
6
PCF Design
Silica
• d is the hole diameter
of large air-holes
•  pitch- distance
between two air holes
• d', d'' are the hole
diameter of small airholes.
• The coupling
coefficients are:
1 ,  2 , 3 ,  4 , 5 , 6 , 7
•
, L2 are distances
between cores.
L1
d'
d
d ''
 0.23,  0.441,  0.303



  2.64 m, L1  12.1 m, L 2  20.957  m
7
(a)
(b)
(c)
Refractive index profile of the intensity splitter 1x16:
(a) the xy plane. (b) the xz plane. (c) the yz plane
8
Coupled-mode equations
Since the structure is symmetrical and cores are
identical the amplitudes fulfill:
a1  a 2 ,a 3  a 4 ,a 5  a 6  a 7  a 8
a 9  a10  a11  a12 ,a13  a14 ,a15  a16
The coupling characteristics can be describe:
da 0
da1
 ja 0   j2a11  2a 3 2  ,
 ja1   ja 0 1  2a 5  4  a15 7 
dz
dz
da 3
da 5
 ja 3   ja 0 2  2a 5 3  a13 6  ,
 ja 5   ja14  a 3 3  a 9 5 
dz
dz
da 9
da15
da13
 ja 9   ja 5 5 ,
 ja15   ja17 ,
 ja13   ja 3 6
dz
dz
dz
9
Physical conditions
In order to obtain a complete transfer of the
energy from core 0 to the other cores the
following condition should take place:
1   2
3   4
5   6   7
This conditions depends on the geometrical
values ​of the PCF structure.
we perform optimizations of the geometric
values ​in order to obtain the required conditions.
10
Simulation Results
We solve the PCF structure using RSoft Photonics
CAD Suite software which is based on BPM.
first step, we launch an optical signal at wavelength
of 1.55m into the central core.
second step, we calculated the output power of the
16 channels along different axial positions (different
values ​of z).
Finally we found the appropriate value for z that
satisfies the physical conditions.
11
Simulation
Contour Map of Transverse Field
Contour Map of Transverse Field
30
1.0
1.0
20
20
10
10
Y (m)
Y (m)
30
0
0
-10
-10
-20
-20
-30
-30
-20
-10
0
X (m)
(a)
10
20
30
0.0
-30
-30
-20
-10
0
10
20
30
0.0
X (m)
(b)
The intensity splitting 1x16 of the optical signal
simulation of 2D xy cross sections: (a) z=0. (b)
z=3.582mm
  1.55m
12
Simulation
Core 0
Core 1
Core 3
Core 5
Core 9
Core 13
Core 15
The propagation distance z as a function of the
normalized power propagation
13
Conclusions
• The energy of the optical signal at 1550nm
wavelength can be divided into sixteen cores in a PCF
structure with dimensions of 60m x 60m x
3.582mm, where the ratio of the total power in each
port is about 6.25% of the overall injected power.
• The fabrication of this PCF structure is feasible and it
is significantly easier to fabricate in comparison to
previously published approaches for PCF based
couplers/splitters.
• The concept can be extended for designing PCF
splitter/couplers with higher splitting ratio such as:
1x32 and 1x64.
14