Ultra-compact four-lane hybrid-integrated ROSA based
on three-dimensional microwave circuit design
Zeping Zhao (赵泽平)
1,2
, Jiaojiao Wang (王姣姣)
1,2
, Xueyan Han (韩雪妍)
1,2
,
Zhike Zhang (张志珂)
1,2
, and Jianguo Liu (刘建国)
1,2,
*
1
State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors,
Chinese Academy of Sciences, Beijing 100083, China
2
College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences,
Beijing 100049, China
*Corresponding author: jgliu@semi.ac.cn
Received October 8, 2018; accepted December 27, 2018; posted online March 5, 2019
An ultra-compact hybrid-integration receiver optical subassembly (ROSA) with four channels is demonstrated
in our laboratory with the size of 23.3 mm × 6.0 mm × 6.5 mm. The ROSA is comprised of a planar lightwave
circuit (PLC) arrayed waveguide grating (AWG) chip, a top-illuminated positive-intrinsic-negative
photodetector array chip, and a three-dimensional microwave circuit that is specially designed for compact pack-
aging. For each transmission lane, the −3 dB bandwidth of the ROSA is up to 20 GHz, and the maximum
responsivity is up to 0.53 A/W. The proposed package structure can be used for smaller package sizes and would
be an easy assembling solution for 100 GbE optical communication devices.
OCIS codes: 040.1240, 060.4230, 230.5160, 250.0040.
doi: 10.3788/COL201917.030401.
With the rapid growth of data traffic for hyper-scale
internet data centers, the demand for high speed optical
transceiver modules to interconnect among the intra
and inter data centers beyond 100 Gbit/s becomes strong.
To meet the demand, 100 Gigabit Ethernet (GbE) was
standardized in 2010, and 400 GbE is now being standard-
ized by an Institute of Electrical and Electronics Engineers
(IEEE) task force
[1]
. The 100 GbE standard defines four
transmission channels using wavelength division multi-
plexing (WDM) technology to achieve high capacity
transmission. Coarse wavelength division multiplexer
(CWDM) and local area network (LAN) WDM are two
commonly used wavelength allocations that comply with
the International Telecommunication Union (ITU)
standards. For CWDM, the center wavelengths of the four
channels are 1270 nm (Lane 0), 1290 nm (Lane 1), 1310 nm
(Lane 2), and 1330 nm (Lane 3), and the center wavelengths
of the four channels for LAN-WDM are 1295.56 nm (lane 0),
1300.05 nm (lane 1), 1304.58 nm (lane 2), and 1309.14 nm
(lane 3), respectively
[2]
. Due to the wide wavelength spacing
of the CWDM system, it reduces the requirements for lasers.
For example, the emission wavelength accuracy of the laser
can be relaxed to 3 nm. Moreover, within the operating
temperature range of −5–70°C, the wavelength drift caused
by temperature changes is still within the allowable range.
Therefore, the lasers in the CWDM system do not require
chillers to keep the temperature constant, resulting in reduc-
ing power consumption of the system. In addition, the larger
wavelength interval means that the structure of the optical
multiplexer (MUX)/demultiplexer (DEMUX) is greatly
simplified, which leads to an increase in yield and a cost
reduction.
Due to the limited space of the high port density line
card data network center, the optica l transceivers modules
with small form factor and low power consumption are re-
quired to increase port density of line cards in communi-
cation systems. One of the key issues for miniaturization is
hybrid integration technology to assemble various discrete
components in an ultra-compact tube, such as integration
of laser chips, microwave circuit, optical MUX, and focus-
ing lenses into a transmitter optical subassembly (TOSA)
module
[3,4]
or integration of a photodetector (PD) array
chip and optical DEMUX into a receiver optical subassem-
bly (ROSA) module
[5,6]
. In order to achieve a compact
package and enhance the performances of the packaged
module at the same time, researchers have done a moun-
tain of studies. For example, in 2011, Nippon Telegraph
and Telephone (NTT) Phot onics Labor atories reported
a compact TOSA with the size of 12 mm × 20 mm ×
8.1 mm. To decrease the electrical crosstalk and realize
smaller volume, a novel bridge-type radio frequency
(RF) circuit board was proposed
[7]
. Then, in 2013, their
group developed the first ultra-compact 100 GbE TOSA,
a very small volume of 8.0 mm × 35 mm × 6.5 mm, in
which a three-dimensional (3D) RF circuit board sup-
ported by a spacer was designed
[8,9]
. In Ref. [10], a 3D
RF impedance matching circuit was demonstrated for
the packaging of an electroabsorp tion modulation laser
(EML) array. However, most of these studies are about
TOSA modules. In the packaging process of ROSA mod-
ules, the microwave circuit usually contains two parts of
an RF circuit and a bias network on which many capac-
itors and resistors are mounted. If they are all installed in
the one circuit board, it will easily cause crosstalk and
COL 17(3), 030401(2019) CHINESE OPTICS LETTERS March 10, 2019
1671-7694/2019/030401(6) 030401-1 © 2019 Chinese Optics Letters