Channel-reuse bidirectional transmission at 10 Gb/s/
λ
in long-reach
DWDM-PON employing self wavelength managed tunable laser
Zhiguo Zhang
n
, Jiahe Wang, Xu Jiang, Xue Chen, Liqian Wang
State Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), Beijing 100876, China
article info
Article history:
Received 28 September 2014
Received in revised form
7 January 2015
Accepted 8 January 2015
Available online 9 January 2015
Keywords:
WDM-PON
Channel-reuse
Tunable laser
Automatic wavelength control
abstract
We experimentally demonstrate a channel-reuse, bidirectional, 10 Gb/s/
λ
, long-reach dense wavelength-
division-multiplexing passive optical network (DWDM-PON) and an optical beat noise-based automatic
wavelength control method for a tunable laser used in a colorless optical network unit (ONU). A 42 km
reach, channel-reuse, full-duplex, 10 Gb/s transmission on a 50 GHz DWDM grid is achieved. Transmis-
sion performance is also measured with different optical-signal-to-Rayleigh-backscattering-noise ratios
(OSRBNRs) and different central wavelength shifts (WSs) between upstream signal and downstream
signal in the channel-reuse system.
& 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND
license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction
The wavelength-division-multiplexing passive optical network
(WDM-PON) has been regarded as a promising solution for next-
generation optical access networks requiring high security, easy
maintenance, great flexibility, and broad bandwidth [1–4]. Driven
by ever-increasing user demands for broad-band services to sup-
port high-quality internet protocol television (IPTV), e-learning,
interactive games, and future looking peer-to-peer multimedia
services, it is expected that the data-rate demand will con-
tinuously grow, and that numerous access nodes will be deployed
over the next few decades. Owing to the continuous growth of
bandwidth-hungry new services, the WDM-PON access networks
will migrate to systems with 100 Gb capacities in the near future
[5–7]. In addition, developments for supporting longer reach and
larger split are also expected [8,9]. As 10 Gb/s per channel will be
one of the typical channel rates of WDM-PONs in the near future
[10–12], the main challenge when increasing the total system ca-
pacity lies in improving the spectral efficiency. Narrow channel
spacing and channel-reuse techniques are promising methods for
increasing the total system capacity of such WDM-PONs.
One important issue for WDM-PONs is achieving low noise, as
well as cost-effective colorless optical sources in the optical net-
work unit (ONU). Various colorless optical sources have been
proposed, including the reflective semiconductor optical amplifier
(RSOA) [13,14], the semiconductor optical amplifier-reflective
electro-absorption modulator (SOA-REAM) [15], and the tunable
laser. The tunable laser (or tunable optical transmitter) is an at-
tractive candidate for a colorless optical source for channel-reuse,
long-reach, and high-speed transmission as the wavelength of the
upstream optical carrier can be set flexibly in the ONU; this can
reduce the Rayleigh backscattering noise existing in loopback
mode-based wavelength-reuse system [16,17]. However, an auto-
matic wavelength control method is required by the tunable laser-
based colorless optical source to realize true colorless operation
with plug-and-play features. Using the Rayleigh backscattering
effect is one means of solving this problem [18]. However, the
control accuracy will degrade as the length of the drop fiber in-
creases. Accordingly, these solutions either cannot effectively
provide the initial wavelength setting, or they increase the system
cost.
In this paper, we propose a dense WDM-PON (DWDM-PON)
scheme. This scheme is tunable laser-based, capable of channel
reuse on 50 GHz DWDM grid, and bidirectional transmission at
10 Gb/s/
λ
. It also exhibits a long reach. Moreover, we propose an
optical beat noise-based automatic w av elength control method using
a downlin k optica l signal to manage the w avelength of the tunable
laser diode (TLD). A channel-reuse, full-duplex, bidirectional, 10 Gb/s
transmission on a 50 GHz DWDM grid is demonstrated using a
Mach–Zehnder (MZ) modulator and a direct detect ion (DD) rec ei ve r
with a 42 km reach. The transmission performance is also measured
with different optical-signal-to-Ra y leigh- backscatt eri ng-noise ratios
Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/optcom
Optics Communications
http://dx.doi.org/10.1016/j.optcom.2015.01.027
0030-4018/& 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
n
Corresponding author.
E-mail address: zhangzhiguo@bupt.edu.cn (Z. Zhang).
Optics Communications 343 (2015) 107–114