Reconfigurable non-blocking four-port optical router
based on microring resonators
Lin Yang,* Hao Jia, Yunchou Zhao, and Qiaoshan Chen
State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors,
Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
*Corresponding author: oip@semi.ac.cn
Received January 5, 2015; revised February 6, 2015; accepted February 6, 2015;
posted February 9, 2015 (Doc. ID 231925); published March 13, 2015
A reconfigurable non-blocking four-port optical router with the least optical switches is demonstrated. The device is
based on microring resonators tuned through thermo-optic effect. The optical signal-to-noise ratio of the device at its
nine routing states is about 15 dB. A 25 Gbps data transmission has been performed on its whole 12 optical links, and
8-channel wavelength division multiplexing data transmission has been implemented to expand its communication
capacity. The energy efficiency of the device is 23 fJ/bit, and the response time of the device is about 25 μs. © 2015
Optical Society of America
OCIS codes: (200.4650) Optical interconnects; (130.3120) Integrated optics devices; (130.4815) Optical switching
devices; (250.5300) Photonic integrated circuits; (230.5750) Resonators.
http://dx.doi.org/10.1364/OL.40.001129
Networks-on-chip (NoCs) for high-performance multi-
core processors have attracted substantial interest in
recent years [
1,2]. However, traditional metallic-
interconnect-based NoC gradually becomes a bottleneck
for improving the performance of a multi-core processor
because of its high power consumption, limited
bandwidth, and long latency [
3]. Photonic NoC is one
alternative interconnection technology that promises
high-speed data transmission, low latency, and power
consumption [
4]. An optical router is an essential compo-
nent for photonic NoC, which is responsible for switch-
ing the data from one optical link to another [
5–8].
Several strict non-blocking four-port optical routers
based on microring resonators (MRs) have been demon-
strated [
9–12]. A universal method for constructing a
strict non-blocking N-port optical router based on MRs
or Mach–Zehnder (MZ) interferometers has also been
reported [
13,14]. These optical routers have the same
characteristic that for a specific input–output optical link
in all routing states, the routing path is certain and
unique. This characteristic makes their routing algo-
rithms quite simple, while they occupy N × N − 2
switch elements to establish all possible optical links,
where N is the number of port. For example, all reported
strict non-blocking four-port optical routers have eight
switching elements [
9–12]. Reconfigurable non-blocking
routing offers the optical router with a prominent char-
acteristic that, for a specific input–output optical link in
all routing states, possibly different routing paths can be
selected to establish it. An absolutely reconfigurable non-
blocking optical router makes full use of the optical links
of a 2 × 2 optical switch and combination of routing paths
and, thus, is a hopeful way to compact the structure of
optical router. Fewer switch elements mean more effi-
ciency in footprint, power consumption, and latency.
A partly reconfigurable non-blocking four-port optical
router composed of six switch elements has been re-
ported [
15]. In this Letter, a reconfigurable non-blocking
four-port optical router with the least MR optical
switches is fabricated and characterized. 8 × 25
Gbps wavelength division multiplexing (WDM) data
transmission has been implemented through each optical
link of the optical router.
The schematic of the four-port optical router is shown
in Fig.
1, where four MRs are used as 2 × 2 optical
switches and four waveguide crossings are included.
We denote the optical link from input port i to output
port j as I
i
→ O
j
. A four-port optical router has 12 optical
links, among which four optical lin ks including I
1
→ O
2
,
I
2
→ O
1
,I
3
→ O
4
, and I
4
→ O
3
can be established
passively since the four MR optical switches are off-
resonance at the working wavelengths. If the four MR op-
tical switches are removed, the four optical links still can
be established. In other words, the four optical links are
established with four optical waveguides directly. Thus,
there are eight optical links le ft to be manipulated with
on-resonance MR optical switches. Each MR optical
switch can, at most, manipulate two optical links simul-
taneously, so at least four MR optical switches are
needed to construct the remaining eight optica l links.
This is the fewest MR optical switches for a reconfigur-
able non-blocking four-port optical router.
Table
1 shows the routing table of the four-port optical
router. “ON” or “OFF” in the routing table indicate that
the corresponding MR optical switch is on- or off-
resonance at the working wavelengths. Blocking only
occurs when one MR optical switch is on-resonance at
the working wavelengths in one optical link while being
off-resonance at the working wavelengths in another
optical link, while the two optical links should be
established simultaneously in a specific routing state.
Fig. 1. Schematic of the reconfigurable non-blocking four-port
optical router.
March 15, 2015 / Vol. 40, No. 6 / OPTICS LETTERS 1129
0146-9592/15/061129-04$15.00/0 © 2015 Optical Society of America