Polarization-maintaining few mode fiber
composed of a central circular-hole
and an elliptical-ring core
JIAJIA ZHAO,
1
MING TANG,
1,
*KYUNGHWAN OH,
2
ZHENHUA FENG,
1
CAN ZHAO,
1
RUOLIN LIAO,
1
SONGNIAN FU,
1
PERRY PING SHUM,
3
AND DEMING LIU
1
1
Next Generation Internet Access National Engineering Laboratory (NGIA), School of Optical and Electronic Information,
Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, China
2
Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, South Korea
3
School of EEE, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
*Corresponding author: tangming@mail.hust.edu.cn
Received 9 March 2017; revised 20 April 2017; accepted 20 April 2017; posted 26 April 2017 (Doc. ID 290365); published 30 May 2017
We propose a novel waveguide design of polarization-maintai ning few mode fiber (PM-FMF) supporting ≥10
non-degenerate modes, utilizing a central circular air hole and a circumjacent elliptical-ring core. The structure
endows a new degree of freedom to adjust the birefringence of all the guided modes, including the fundamental
polarization mode. Numerical simulations demonstrate that, by optimizing the air hole and elliptical-ring core,
a PM-FMF supporting 10 distinctive polarization modes has been achieved, and the effective index difference
Δn
eff
between the adjacent guided modes could be kept larger than 1.32 × 10
−4
over the whole C L band. The
proposed fiber structure can flexibly tailored to support an even larger number of modes in PM-FMF (14-mode
PM-FMF has been demonstrated as an example), which can be readily applicable to a scalable mode division
multiplexing system.
© 2017 Chinese Laser Press
OCIS codes: (060.2420) Fibers, polarization-maintaining; (060.2400) Fiber properties; (060.2280) Fiber design and fabrication;
(060.2330) Fiber optics communications.
https://doi.org/10.1364/PRJ.5.000261
1. INTRODUCTION
In the emerging era of big data and its applications, data
amounts have been exploding, and the workload for optical
networks and data centers (DCs) is approaching its physical
limits [1]. It is reported that the current transmission system
based on traditional single-mode fibers (SMFs) is rapidly reach-
ing its ultimate capacity following the nonlinear Shannon limit
[2]. In order to solve these imminent traffic bottlenecks, space-
division multiplexing (SDM) transmissions have been recently
intensively investigated as a viable measure [3]. The multicore
fiber (MCF) [4–6], as one of the spatial multiplexing tech-
niques, is the most straightforward solution in SDM. However,
there are a great deal of technical challenges in the design and
manufacture of high-core-count, low-loss, and low-crosstalk
MCF. It is increasingly challenging to couple signals in and out
of each core because the cores have to be closely packed in a
scalable MCF [7]. The few mode fiber (FMF) [8–10] acts as
another practical avenue in SDM, due to its mass-fabricated
capability and low loss connectivity with conventional SMFs.
The crosstalk among propagation modes is being regarded as
the most crucial issue in FMF data links. To solve this issue,
two different methods have been proposed. One is using the
multiple input multiple output (MIMO) digital signal process-
ing (DSP) at the receiver to electronically recover the signals
carried over guided modes [11]. The drawback of this tech-
nique is that the complexity of MIMO scales up nonlinearly
with the number of modes, easily depleting the DSP capacity
and its electric power consumption. The other method is using
specially designed FMF with large difference in the effective
indices Δn
eff
between the adjacent propagation modes to fun-
damentally suppress the mode coupling [12]. Previous experi-
ments have proved that the crosstalk can be efficiently suppressed
when the effective index difference is larger than ∼10
−4
[13].
The latter method would have a clear advantage in energy ef-
ficiency; therefore, it would be especially suitable for the short-
reach transmission in the DCs. This is the motivation of our
research to design FMF flexibly scalable with a high Δn
eff
for
guided modes.
Elliptical core fibers (ECFs) [14–16] have been widely used
as a polarization maintaining fiber (PMF), provided an efficient
form-birefringence in the guided modes. In ECF, the effective
index difference Δn
eff
between the adjacent LP modes can be
Research Article
Vol. 5, No. 3 / June 2017 / Photonics Research 261
2327-9125/17/030261-06 Journal © 2017 Chinese Laser Press
资源评论
