Engineering ultra-flattened-dispersion photonic crystal
fibers with uniform holes by rotations of inner rings
Jin Hou,
1,
* Jiajia Zhao,
1
Chunyong Yang,
1
Zhiyou Zhong,
1
Yihua Gao,
2
and Shaoping Chen
1
1
Hubei Key Laboratory of Intelligent Wireless Communications, College of Electronics and Information Engineering,
South-central University for Nationalities, Wuhan, Hubei 430074, China
2
Wuhan National Laboratory for Optoelectronics (WNLO), School of Physics, Huazhong University of Science and
Technology, Wuhan, Hubei 430074, China
*Corresponding author: houjin@mail.scuec.edu.cn
Received November 1, 2013; revised February 21, 2014; accepted March 10, 2014;
posted March 10, 2014 (Doc. ID 200434); published March 28, 2014
We present a novel method for engineering ultra-flattened-dispersion photonic crystal fibers with uniform air holes
by rotations of inner air-hole rings around the fiber core. By choosing suitable rotation angles of each inner ring,
theoretical results show that normal, anomalous, and nearly zero ultra-flattened-dispersion fibers in wide spectra
ranges of interest can be obtained alternatively. Moreover, in our dispersion sensitive analysis, these types of fibers
are robust to variations from optimal design parameters. The method is suitable for the accurate adjustment of fiber
dispersion within a small range, which would be valuable for the fabrication of ultra-flattened-dispersion fibers and
also have potential applications in wide-band high-speed optical communication systems. © 2014 Chinese Laser
Press
OCIS codes: (060.5295) Photonic crystal fibers; (060.2400) Fiber properties; (060.2280) Fiber design and
fabrication.
http://dx.doi.org/10.1364/PRJ.2.000059
1. INTRODUCTION
In high-speed optical communication systems, fiber
dispersion is a crucial factor that has great influence on the
bandwidth of information transmission. Conventionally, in or-
der to decrease the dispersion effect, dispersion-shifted fiber
and zero-dispersion single-mode fiber are designed for com-
munication wavelengths. In recent years, photonic crystal
fiber (PCF) [
1], has became a preeminent method for trans-
mitting information because of its unique optical properties
and flexible designs. The variety of possible geometries in
PCF offers great possibility to control its dispersion proper-
ties, particularly useful in designing dispersion flattened fibers
over a wide range of wavelengths.
Over the last decade, various PCFs have been proposed and
studied to obtain ultra-flattened-dispersion property. Initially,
characterized by the lattice constant and hole diameter, rela-
tive flattened dispersion can be achieved [
2,3]. After that, in
order to improve dispersion flatness over a wider bandwidth,
more complicated design methods have been exploited, such
as doping additional materials such as GeO
2
in the central part
of the silica core [
4,5], changing the diameter of the air holes
belonging to the first two or three inner rings [
6,7], modifying
the circular air holes into other shapes [
8–10], selectively
filling the PCF with liquids [
11], designing a hybrid core region
with three-fold symmetry for the fiber [
12], assembling addi-
tional defected air holes in the central core region [
13], or
combining two or more of these methods, for instance, intro-
ducing both GeO
2
-or F-doped silica and also modifying the
circular holes into hollow rings in the PCFs [
14]. While won-
derful dispersion flatness performance could be obtained, the
modifications either broke the uniformity of the holes’ size or
introduced additional materials, which will raise complexity
during the design of fibers. In addition, minor variations of
these design parameters that would be introduced in the fab-
rication process are likely to cause a large change of the
dispersion characteristic. Therefore, the realization of ultra-
flattened-dispersion PCFs with low sensitivity by a relatively
simple method is still a challenge.
In this paper, we propose a novel design approach for
achieving ultra-flattened-dispersion PCFs over wide wave-
length regions with low sensitivity just by rotations of two
inner air-hole rings around the fiber core. The approach can
obtain ultra-flattened-dispersion PCFs while maintaining the
uniformity of the PCFs’ air-hole size. Numerical results show
that our proposed method for control of dispersion in PCFs
works well. The paper is organized as follows. In Section
2,
the topology and design principle of proposed PCFs are pre-
sented. Then, in Section
3, dispersion engineering for nearly
zero-dispersion PCFs, normal dispersion PCFs, and abnormal
dispersion PCFs is investigated in detail. In Section
4, a sen-
sitive analysis is performed to determine the variations of the
dispersion characteristic arising from inevitable imprecision
angles of the inner rings. Finally, conclusions are given in
Section
5.
2. SCHEMATIC TOPOLOGY AND DESIGN
PRINCIPLE
The schematic cross section of the proposed PCF topology
structure is depicted in Fig.
1. The host material is pure silica,
and the number of air-hole rings is assumed to be 11. It is
composed of circular air holes arranged in a triangular array
of lattice constant Λ with the central air hole missing, and all
Hou et al. Vol. 2, No. 2 / April 2014 / Photon. Res. 59
2327-9125/14/020059-05 © 2014 Chinese Laser Press