IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 28, NO. 9, MAY 1, 2016 947
Five-Port Optical Router Based on Silicon Microring
Optical Switches for Photonic Networks-on-Chip
Hao Jia, Yunchou Zhao, Lei Zhang, Qiaoshan Chen, Jianfeng Ding, Xin Fu, and Lin Yang
Abstract—We demonstrate a five-port optical router composed
of eight silicon microring optical switches tuned by thermo-
optic effect. The optical signal-to-noise ratio of the device on the
tested routing states is over 11 dB at the working wavelength.
32-Gb/s data transmission has been performed on its 20 optical
links, and eight-channel wavelength division multiplexing data
transmission in the wavelength range from 1525 to 1565 nm has
been implemented to expand its communication capacity. The
average energy efficiency of the optical router is 68.2 fJ/bit, and
its response time is ∼20 µs.
Index Terms—Multiprocessor interconnection, optical
resonators, optical switches, wavelength division multiplexing.
I. INTRODUCTION
T
HE performances of multi-core processor are determined
not only by the performances of processor cores but
also by the communication efficiency among them. With
more processor cores integrated on a chip, interconnect of
multi-core processor shifted from traditional bus interconnect
to more sophisticated networks-on-chip (NoC) [1], [2].
Electrical interconnect is becoming the bottleneck for
improving performances of multi-core processor due to its
large power consumption, limited bandwidth and long latency.
Optical interconnect is considered as a potential solution [3].
Several architectures for photonic NoC have been widely
studied, such as Mesh, Fat-Tree, Clos and Crossbar [4]–[7].
Recent studies are gradually focused on Mesh photonic NoC
due to its symmetric architecture, good scalability and simple
routing algorithm. As a building block of Mesh photonic NoC,
5-port optical router has attracted much attention [7]–[9].
Microring resonator has many advantages such as small
footprint, low power consumption and wavelength selective
property. So it has been widely used to realize optical circuit
switching [7]–[16] and optical wavelength routing [17]–[19].
Several 5-port optical routers based on microring optical
switches have been proposed and demonstrated [7]–[9]. These
optical routers distribute a unique routing path to establish
Manuscript received November 12, 2015; revised December 31, 2015;
accepted January 10, 2016. Date of publication January 18, 2016; date of cur-
rent version March 17, 2016. This work was supported in part by the 863 Pro-
gram of China under Grant 2015AA010103 and Grant 2015AA017001, in part
by the Beijing Science and Technology Plan under Grant Z151100003615005,
and in part by the National Natural Science Foundation of China under
Grant 61235001, Grant 61535002, and Grant 61575187.
The authors are with the State Key Laboratory on Integrated
Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences,
Beijing 100083, China (e-mail: jiah@semi.ac.cn; zhaoyc@semi.ac.cn;
zhanglei@semi.ac.cn; chenqs@semi.ac.cn; jjding@semi.ac.cn; fuxin@semi.
ac.cn; oip@semi.ac.cn).
Color versions of one or more of the figures in this letter are available
online at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/LPT.2016.2518869
Fig. 1. Schematics of (a) the optical router and (b) the microring optical
switch.
each input-output optical link in different routing states so that
their routing algorithms are simple. However, these optical
routers use redundant switching elements to avoid possible
conflict among different optical links and therefore are not
compact in footprint and not efficient in power consumption.
By reasonably arranging several different routing paths for the
unique and specific optical links in different routing states,
some redundant switching elements can be removed and the
optical router can be more compact in footprint and more
efficient in power consumption. In this letter, we demonstrate
a 5-port optical router composed of 8 silicon microring optical
switches tuned by thermo-optic effect. 8×32 Gbps wavelength
division multiplexing (WDM) data transmission has been
implemented through its optical link in the wavelength range
from 1525 nm to 1565 nm.
II. T
OPOLOGY AND PRINCIPLE
Fig. 1 (a) shows the architecture of the 5-port optical router,
which consists of 8 microring optical switches denoted as
S
i
(i = 1, 2,...,8). As shown in Fig. 1 (b), the microring
optical switch is designed to be off-resonance at its working
wavelength in the “cross” state and on-resonance at its working
wavelength in the “bar” state. We denote the optical link from
input port i to output port j as I
i
→ O
j
and the off-resonance
and on-resonance microring optical switches as S
of f
i
and S
on
i
respectively.
This optical router is designed for Mesh photonic NoC.
Input port I
i
and output port O
j
with the same subscript
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