Physical layer data encryption using two-level constellation
masking in 3D-CAP-PON
Shuaidong Chen (陈帅东)
1
, Bo Liu (刘 博)
1*
, Yaya Mao (毛雅亚)
1
, Jianxin Ren (任建新)
2
, Xiumin Song (宋秀敏)
2
,
Rahat Ullah
1
, Delin Zhao (赵德林)
1
, Lei Jiang (姜 蕾)
1
, Shun Han (韩 顺)
1
, Jianye Zhao (赵建业)
1
, Jiajia Shen (沈佳佳)
1
, and
Xueyang Liu (刘雪阳)
3
1
Nanjing University of Information Science and Technology, Nanjing 210044, China
2
Beijing University of Posts and Telecommunications, Beijing 100876, China
3
University of Wollongong, NSW 2522, Australia
*Corresponding author: bo@nuist.edu.cn
Received July 20, 2020 | Accepted September 4, 2020 | Posted Online November 24, 2020
A novel physical layer data encryption scheme using two-level constellation masking in three-dimensional (3D) carrier-less
amplitude and phase modulation (CAP) passive optical network (PON) is proposed in this Letter. The chaotic sequence
generated by Chua’s circuit model realizes two-level encryption of displacement masking and constellation rotation for
3D constellations. We successfully conduct an experiment demonstrating 8.7 Gb/s 3D-CAP-8 data transmission over
25 km standard single-mode fiber. With two-level constellation masking, a key space size of 2.1 × 10
85
is achieved to bring
about high security and good encryption performance, suggesting broad application prospects in future short-range secure
communications.
Keywords: physical layer data encryption; constellation masking; carrier-less amplitude and phase modulation; passive
optical network.
DOI: 10.3788/COL202119.010601
1. Introduction
Recently, due to th e rapid development of information technol-
ogies such as 4K video, cloud computing, and virtual reality
(VR) and due to the merging of optical and wireless communi-
cations, bandwidth demand by the end users is continuously
increasing
[1]
. As far as the current access network is concerned,
the passive optical network (PON) has proved to be a future-
oriented network architecture due to its provision of high band-
width, with low cost and high-speed data transmission rate
across the long haul networks
[2,3]
. Further, various researches
are proposed for introducing new and advanced modulation
formats that are deployed in the PON system. A time division
multiplexing (TDM) and wavelength division multiplexing
(WDM)/TDM long reach 10 Gb/s PON architecture of
100 km reach with no infield amplification or dispersion com-
pensation was achieved
[4]
. A colorless scheme supporting
40 Gb/s downlink and uplink transmissions-based differential
phase shift keying (DPSK) and on–off keying (OOK), resp ec-
tively, was produced
[5]
. Similarly, a symmetrical 50 Gb/s
TDM-PON system for the O-band based on 25G optics was
investigated
[6]
. A 100 Gb/s space-division multiplexing PON
(SDM-PON) system using commercial 10G class directly
modulated laser (DML) that is modulated with 25/28 Gb/s data
signals was presented
[7]
. In addition, a traffic estimation based
on a long short-term memory neural network for PON was pro-
posed to improve the performance of the system
[8]
. Although
the PON expands the scope of access, it usually sends downlink
data in the form of a broadcast. All optical netwo rk units
(ONUs) connected to the optical line terminal (OLT) can receive
downlink data frames. Therefore, an illegal ONU can be dis-
guised as a legal ONU to hijack the downlink data signal sent
by the OLT, so it is extremely important to encrypt the informa-
tion before its transmission via downlink of the PON sys-
tem
[9,10]
. Among various current physical layer encryption
schemes, chaotic-based secure communication technology has
broad prospects in the field of secure commun ication due to
its high initial sensitivit y, large bandwidth, and noise-like char-
acteristics. Encrypted communication schemes with chaotic sys-
tems have been widely studied and proved to have superior
confidentiality and anti-deciphering capabilities. Therefore,
applying chaotic systems to encrypt the communication at
the physical layer is considered a promising encryption
scheme
[11–14]
.
However, these chaotic encryption methods for the PON at
the physical layer are based on the quadrature amplitude
Vol. 19, No. 1 | January 2021
© 2021 Chinese Optics Letters 010601-1 Chinese Optics Letters 19(1), 010601 (2021)