Crosstalk-aware RCSA for spatial division multiplexing
enabled elastic optical networks with multi-core fibers
Ruijie Zhu (朱睿杰)
1,2
, Yongli Zhao (赵永利)
1
, Hui Yang (杨 辉)
1
, Haoran Chen (陈浩然)
1
,
Jie Zhang (张 杰)
1,
*, and Jason P. Jue
2
1
State Key Laboratory of Information Photonics and Optical Communication,
Beijing University of Posts and Telecommunications, Beijing 100876, China
2
University of Texas at Dallas, Texas 75080, USA
*Corresponding author: lgr24@bupt.edu.cn
Received June 8, 2016; accepted August 26, 2016; posted online September 30, 2016
In this Letter, we propose two crosstalk-aware routing, core, and spectrum assignment (CA-RCSA) algorithms
for spatial division multiplexing enabled elastic optical networks (SDM-EONs) with multi-core fibers. First, the
RCSA problem is modeled, and then a metric, i.e., CA spectrum compactness (CASC), is designed to measure
the spectrum status in SDM-EONs. Based on CASC, we propose two CA-RCSA algorithms, the first-fit (FF)
CASC algorithm and the random-fit (RF) CASC algorithm. Simulation results show that our proposed
algorithms can achieve better performance than the baseline algorithm in terms of blocking probability and
spectrum utilization, with FF-CASC providing the best performance.
OCIS codes: 060.1155, 060.4250, 060.4251.
doi: 10.3788/COL201614.100604.
Currently, the emergence of heterogeneous and band-
width-intensive applications, such as cloud computing
and high definition video streaming, is placing a high
flexibility requirement on optical networks. Enabled by
orthogonal frequency division modulation (OFDM) tech-
nology and a sliceable bandwidth-variable transponder,
elastic optical networks (EONs) can be a promising tech-
nique for these diverse applications
[1]
. In EONs, the optical
spectrum is sliced into finer granularity, such as 6.25 or
12.5 GHz.
However, network traffic is expected to increase expo-
nentially, and the transmission capacity of EONs based
on a single-core fiber (SCF) is approaching its physical
limitations
[2]
. To further increase network flexibility and
capacity, the concept of EONs can be extended into the
spatial domain, in which “spatial resources” can be flex-
ibly assigned to different traffic demands. One approach
for utilizing spatial resources is to deploy spatial-division
multiplexing EONs (SDM-EONs)
[2,3]
. Experiments illus-
trated that a multi-core fiber (MCF) can be a promising
candidate for SDM-EONs
[4]
. In SDM-EONs, the tremen-
dous increment in transmission capacity must be com-
bined with effective software defined networking (SDN)
functionalities
[5]
, guaranteeing flexible connection provi-
sioning, efficient re-optimization solutions
[6]
, and failure
recovery techniques.
With the introduction of the spatial domain, the rout-
ing and spectrum assignment (RSA) problem
[7–10]
for
EONs has to be extended to the routing, core, and spec-
trum assignment (RCSA) problem for SDM-EONs
[11,12]
.
The RSA problem has been well studied in EONs; how-
ever, the RCSA problem is more challenging, and there are
several new features in SDM-EONs, such as the mitigation
of spectrum continuity constraint, which means that the
signal can be exchanged from core to core freely while
maintaining the same spectrum slice
[13]
. Furthermore,
there is an additional physical constraint introduced by
inter-core crosstalk. When the same spectrum slices over-
lap on the adjacent cores, crosstalk will occur. Because the
crosstalk of different spectrum slices or non-adjacent cores
is quite small, then it can be eliminated. However, the
crosstalk between adjacent cores can severely impact the
signal during the propagation process, so it is extremely
important to consider crosstalk during the RCSA process.
Note that crosstalk checking is a complex process. When a
newly requested lightpath is provisioned, the physical
layer impairment of both the new lightpath and other
already provisioned lightpaths should satisfy a predefined
threshold because the additional crosstalk caused by the
new path may make the signal quality of the provisioned
paths worse. Thus, it is extremely important to consider
the crosstalk during the RCSA process, which is not con-
sidered in the standard RSA problem.
Several previous works have studied the RCSA prob-
lem. In Ref. [
11], the RCSA problem was formulated
using the integer linear programming (ILP) formulation.
Tode et. al., introduced the prioritized area concept, and
two kinds of crosstalk-aware (CA) RCSA algorithms: the
strict constraint and best-effort approaches
[12]
. However,
these works just utilized a simple crosstalk check method
to check the crosstalk of the new provisioned lightpath,
and the crosstalk of the provisioned lightpaths were not
maintained.
In this Letter, we propose two CA-RCSA algorithms for
SDM-EONs with an MCF, i.e., the first-fit (FF) algorithm
and the random-fit (RF) algorithm. We first introduce a
model to solve the RCSA problem and analyze the inter-
core crosstalk. Then a metric named the CA spectrum
COL 14(10), 100604(2016) CHINESE OPTICS LETTERS October 10, 2016
1671-7694/2016/100604(5) 100604-1 © 2016 Chinese Optics Letters