Optics Communications 403 (2017) 222–225
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Optics Communications
journal homepage: www.elsevier.com/locate/optcom
Experimental demonstration of IDMA-OFDM for passive optical network
Bangjiang Lin
a,
*, Xuan Tang
a,
*, Yiwei Li
a
, Min Zhang
a
, Chun Lin
a
, Zabih Ghassemlooy
b
a
Quanzhou Institute of Equipment Manufacturing, Haixi Institutes, Chinese Academy of Sciences, Quanzhou, China
b
Optical Communications Research Group, Faculty of Engineering and Environment, Northumbria University, Newcastle, UK
a r t i c l e i n f o
Keywords:
Passive optical network (PON)
Orthogonal frequency division multiplexing
(OFDM)
Interleave division multiple access (IDMA)
a b s t r a c t
We present interleave division multiple access (IDMA) scheme combined with orthogonal frequency division
multiplexing (OFDM) for passive optical network, which offers improved transmission performance and good
chromatic dispersion tolerance. The interleavers are employed to separate different users and the generated
chips are modulated on OFDM subcarriers. The feasibility of IDMA-OFDM-PON is experimentally verified with
a bitrate of 3.3 Gb/s per user. Compared with OFDMA, IDMA-OFDM offers 8 and 6 dB gains in term of receiver
sensitivity in the cases of 2 and 4 users, respectively.
© 2017 Published by Elsevier B.V.
1. Introduction
Passive optical network (PON) is considered as a very promising
method to implement a fiber-to-the-home (FTTH) system [1–3]. The
exponential growth of global communications nowadays demands next
generation PON with high spectral efficiency and high data rates.
Currently most deployed PONs are gigabit PON (GPON) and Ethernet
PON (EPON), both of which suffer from high transmission impairment
because of chromatic dispersion when the data rate is beyond 10 Gb/s.
Owing to their high spectral efficiency, good chromatic dispersion
tolerance, flexible and dynamic bandwidth allocation as well as the
ability to adapt to frequency dependent channel quality with simple
single-tap equalization [4–6], the orthogonal frequency division multi-
plexing (OFDM) based PONs including orthogonal frequency division
multiple access (OFDMA), wavelength division multiplexing (WDM)-
OFDM-PON, time division multiplexing (TDM)-OFDM-PON and code
division multiple access (CDMA)-OFDM PON [7–11] are investigated as
promising solutions for future optical access. TDM-OFDM-PON suffers
from transmission impairments at higher transmission speeds caused
by burst synchronization and interference between different optical
network units (ONUs). WDM-OFDM PON is impressive for its high
data rate but is relatively expensive and complex due to the use of
high-cost optical components, such as arrayed waveguide gratings. The
management of wavelengths of ONUs is a key technical challenge for
OFDMA-PON [12,13]. CDMA-OFDM-PON has many attractive features,
such as high power budget margins, a secure physical layer and good
chromatic dispersion tolerance.
*
Corresponding authors.
E-mail addresses: linbangjiang@163.com (B. Lin), xtang@fjirsm.ac.cn (X. Tang).
In this paper, we experimentally demonstrate interleave division
multiple access (IDMA) scheme combined with OFDM for PON, in
which the interleavers are employed to separate different ONUs and the
generated chips are modulated on OFDM subcarriers (SCs). IDMA in-
corporates all the attractive features of CDMA and it also provides some
excellent features such as low complexity detection for systems with
large numbers of users and improved transmission performance [14,15].
The concept of IDMA-OFDM has already been widely applied in wireless
communications [16], uplink PON [17], uplink visible light commu-
nication (VLC) systems [18]. The feasibility of IDMA-OFDM-PON is
experimentally verified with a bitrate of 3.3 Gb/s per user. Compared
with OFDMA, IDMA-OFDM offers 8 and 6 dB gains in term of receiver
sensitivity in the cases of 2 and 4 users, respectively.
2. Technique principle
Fig. 1 shows the schematic diagram of downstream IDMA-OFDM-
PON with K users. In the transmitter (Tx), the source data for each
user is fed into a spreader for the purpose of bandwidth expansion. The
bits after spreading are usually called chips. Then a unique interleaver
(𝜋
𝑘
) is allocated to user k (k =1, 2, . . . K), which is used as the only
means to separate different users. Moreover, burst error control can
be achieved by dispersing the sequences of the chips randomly using
the interleavers. After interleaving, chips from all users (𝑥
𝑘
, k =1, 2,
. . . K) are combined and then converted to OFDM symbols with inverse
discrete Fourier transform (IDFT) operation. Cyclic prefix (CP) and
preamble are inserted to combat chromatic dispersion induced inter-
symbol interference (ISI) and for channel estimation, respectively. The
http://dx.doi.org/10.1016/j.optcom.2017.07.050
Received 16 June 2017; Received in revised form 13 July 2017; Accepted 17 July 2017
0030-4018/© 2017 Published by Elsevier B.V.