Hybrid optical wavelength demultiplexer
and power combiner for TWDM PON
CHUNSHENG LI,
1
XINYOU QIU,
1
AND XUN LI
2,
*
1
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
2
Department of Electrical and Computer Engineering, McMaster University, Hamilton, ON L8S 4K2, Canada
*Corresponding author: lixun@mcmaster.ca
Received 9 December 2016; revised 12 January 2017; accepted 19 January 2017; posted 24 January 2017 (Doc. ID 282534);
published 28 February 2017
In this paper, we have proposed a hybrid optical wavelength demultiplexer and power combiner for a hybrid time-
and wavelength-division multiplexing (TWDM) passive optical network (PON), i.e., a single passive optical de-
vice that functions as a 1 × N wavelength demultiplexer for distributing the downstream signal in multiple wave-
lengths from the optical line terminal (OLT) to the N optical network units (ONUs), and simultaneously as an
N × 1 power combiner for collecting the upstream signal in the same wavelength from the N ONUs to the OLT.
Through a design examp le of a 32 channel hybrid optical wavelength demultiplexer and power combiner on the
silicon-on-insulator platform, our numerical simulation result shows that the insertion loss and adjacent channel
crosstalk of the downstream wavelength demultiplexer are as low as 4.6 and −16.3 dB, respectively, while the
insertion loss and channel non-uniformity of the upstream power combiner can reach 3.5 and 2.1 dB, respectively.
The proposed structure can readily be extended to other material platforms such as the silica-based planar light-
wave circuit. Its fabrication process is fully compatible with standard clean-room technologies such as photo-
lithography and etching, without any complicated and/or costly approach involved.
© 2017 Chinese Laser Press
OCIS codes: (130.3120) Integrated optics devices; (130.7408) Wavelength filtering devices; (230.1360) Beam splitters.
https://doi.org/10.1364/PRJ.5.000097
1. INTRODUCTION
With the growing bandwidth demand for Internet and other
bandwidth-hungr y applications [1], there has been fast devel-
opment for optical access technologies, such as fiber-to-the-
home/curb (FTTH/FTTC) [2,3] networks, to overcome the
bandwidth bottleneck. In the conventional time-division mul-
tiplexing (TDM) passive optical network (PON) [4], the band-
width and optical power available to each optical network unit
(ONU) are limited due to the splitting loss. Although the wave-
length-division multiplexing (WDM) PON can overcome the
limitation, in which each ONU is assigned to a specific wave-
length, thus enjoying dedicated bandwidth, the high cost has
limited its real-world deployment [5,6]. To achieve a proper
balance between the performance and cost of PONs, a hybrid
TDM/WDM (TWDM) PON [7–10] has been proposed as a
promising solution for access networks in which WDM and
TDM technologies are separately used for downstream and
upstream transmissions, respectively. The asymmetric hybrid
TWDM PON in which the download bandwidth is often
much greater than the upload bandwidth, is suitable for much
more intensive network service, such as high definition televi-
sion and massive online games. In addition, for upstream trans-
mission, identical low-cost transmitters with their wavelength
set at 1310 nm can be adopted by all ONUs for cost minimiz-
ing [11].
As key components in the hybrid TWDM PON, the wave-
length demultiplexer [12–14] for downstream transmission and
the power combiner [15–17] for upstream transmission have
been widely studied. However, the optical module based on
multiple discrete components in separated downstream and up-
stream path design was bulky and not readily scalable with a large
number of ONUs [11]. In this work, we have proposed a single
passive optical device that can function as a 1 × N wavelength
demultiplexer for downstream signal transmission and simulta-
neously as an N × 1 optical power combiner for upstream signal
transmission. The silicon-on-insulator (SOI) waveguide has been
chosen as the platform to show the device design idea. The pro-
posed structure can be readily implemented on other material
platforms, such as the silica-based planar lightwave circuit
(PLC), depending on specific application requirements weighed
by multiple factors, including bending and scattering losses, size
and uniformity, processing ease, fabrication cost, and production
yield. The working principle of the device is described briefly in
Section 2. The device design is detailed in Section 3.Wethen
show the numerical simulation results in Section 4, and have our
work summarized in Section 5.
Research Article
Vol. 5, No. 2 / April 2017 / Photonics Research 97
2327-9125/17/020097-06 Journal © 2017 Chinese Laser Press