December 2023 / Vol. 184

Mitsubishi Electric

ADVANCEHigh Frequency & Optical Devices• Editorial-Chief
Masahiro Otani• Editorial Advisors
Kenichiro Kurahashi
Hisao Takahashi
Omi Kuriwaki
Asuka Omori
Hiroyuki Teranishi
Satoshi Watanabe
Kenichi Uto
Tsutomu Matsubara
Yasumasa Yamanaga
Takao Ikai
Kunihiko Egawa
Hideya Tadokoro
Kenji Okuma
Yusuke Hirata
Satoru Yamaguchi
Yoshihiro Yamaguchi
Kohei Miki
• Vol. 184 Feature Articles Editor
Yoshihisa Tashiro• Editorial Inquiries
Masahiro Otani
Corporate Productivity Engineering &Logistics Dept.
Fax: +81-3-3218-2465
Mitsubishi Electric Advance is published online quarterly (in March, June, September, andDecember) by Mitsubishi Electric Corporation.
Copyright © 2023 by Mitsubishi Electric
Corporation; all rights reserved.
Printed in Japan.
The company names and product names described herein are thetrademarks or registered trademarks of the respective companies.

CONTENTS
Overview ................................................................................................1
by Kenji Masuda

Technical Reports
10W Class, Wideband GaN Power Amplifier Module for
5G Base – Stations ...............................................................................2
by Shuichi Sakata and Marie Taguchi
Wider – temperature – range CWDM 100Gbps EML Chip for
Data Centers .........................................................................................7
by Yusuke Azuma and Akitsugu Niwa
50Gbps DFB Laser Diode for 5G Base Stations ..............................10
by Go Sakaino and Masaaki Shimada
1.55μm Tunable DFB-LD for 400G Digital Coherent Optical
Transmission System .........................................................................13
by Kazuki Yamaji and Ryosuke Nagao
Thermal Diode Infrared Sensor “MelDIR” and User Support
Tools ....................................................................................................16
by Yasuki Aihara and Satoshi Okuda

PrecisDigital transformation (DX) advances innovation in businessactivities and transformation in lifestyles, so the importance ofcommunications infrastructure and sensor technology is rising. In
this issue, we introduce highly efficient GaN amplifiers and highspeed optical devices for the latest information communications,as well as infrared sensor modules required in applications in theareas of crime prevention and surveillance.

OVERVIEW

Overview

Author: Kenji Masuda*

The Latest Status and Future Outlook of High Frequency & Optical Devices
Due to the progress in digital transformation (DX) that is revolutionizing products, services, and business models
through the utilization of data and digital technology, innovation in business activities and a shift to new lifestyles
are advancing on a global scale. Consequently, information communication infrastructure to support DX is becoming
increasingly important. Accompanying the preparation of communication infrastructure and data centers with larger
capacities, achieving low power consumption as well as high speeds in the high frequency and optical devices essential
to the infrastructure is a significant development issue.
5th generation mobile communication system (5G) features Enhanced Mobile Broadband (eMBB), Ultra Reliable
and Low Latency Communications (URLLC) and Massive Machine Type Communications (mMTC), uses array
antennae with several antenna elements arranged in the base stations, and is able to simultaneously and efficiently
send wideband, modulating signals to each user terminal. For electric power amplifiers for use in 5G base stations,in addition to the establishment of both highly efficient and highly linear operations, there is an increasing demand
for wideband operations. For this use, Mitsubishi Electric is developing and productizing a compact, highly efficient,wideband gallium nitride (GaN) amplifier that generates little heat.
Meanwhile, in optical communication networks which are a core part of the communication infrastructure, we are
increasing the speed and the transmission capacity of all network layers including in data centers. We are developing
optical devices capable of multi-value modulation which doubles the transmission signal capacity per unit time, torealize the low power consumption products of the Distributed FeedBack Laser (DFB-LD) at 50 Gbps and the Electroabsorption Modulated Laser (EML) at 100 Gbps.
Furthermore, we are progressing with the implementation of a high pixel count and the expansion of the detection
temperature range for the high-performance, compact, low-cost infrared sensor module, “MelDIR.” We hope to apply
this in a wide range of fields such as in-vehicle monitoring in addition to uses like crime prevention, indoor monitoring,people counting, and smart buildings.

* Senior General Manager, High Frequency & Optical Device Works
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10W Class, Wideband GaN Power
Amplifier Module for 5G Base – Stations
Authors: Shuichi Sakata* and Marie Taguchi*

1. Introduction
In recent years, implementation of 5th generation
mobile communication system (5G) has spread tomeet the demand for high speed, large capacity
communications. If a single amplifier module is able tosupport a variety of frequencies, then this contributes
to low cost and joint use of the radio units of 5G basestations. In this article, we discuss the 10W class,wideband GaN power amplifier module for 5G basestations which covers almost all the bandwidths of 5G
frequencies in the 3 - 4 GHz band.
2. BackgroundIn recent years, implementation of 5G has spreadto meet the demand for high speed, large capacity
communications. The 5G frequencies allocated in the
3 - 4 GHz band are distributed across a frequency rangeof the order of 700 MHz depending on the country or
region. When using a conventional amplifier module, theoperating bandwidth is at most of the order of 400 MHz,so it was difficult to cover all the 5G frequencies in the
3 - 4 GHz band with a single amplifier. If a single amplifier
module is able to support a variety of frequencies, thenthis contributes to low cost and joint use of the radio unitsof 5G base stations. The Doherty power amplifier, which
has been used until now for the amplifier module’s final
stage, has a narrow band, so extending it to wideband
use was difficult. In addition, the design method(1) which
configures the load modulation circuit in the Doherty
power amplifier using the Tee-Type network in the
Doherty power amplifier’s main amplifier, proposed as amethod to realize compact, highly efficient wideband frombefore, and using the transistor’s parasitic capacitancewithout placing a circuit in the auxiliary amplifier, wasdifficult to employ in this module’s configuration becausea circuit has to be placed in the auxiliary amplifier.
In this article, we will discuss a new design method
which realizes wider band operations even when a circuit
is placed in the auxiliary amplifier, while making use of
the advantages of the conventional design method, by
designing the main amplifier and auxiliary amplifier circuitin an integrated manner. Using this design method, we
created and evaluated a prototype 10W class, GaN
power amplifier module with the result that, in the
700 MHz band from 3.4 - 4.1 GHz, the Adjacent Channel* Information Technology R&D Center

Leakage Ratio (ACLR) after digital pre-distortion was-46 dBc with a 20 MHz modulation bandwidth signal,
while a Power Added Efficiency (PAE) of 42.0 - 44.6%
and a gain of 28.6 - 31.0 dB were achieved.
3. Doherty Power Amplifier’s New Circuit
Design Method
The circuit diagram of the Doherty power amplifier
designed is shown in Fig. 1. The main amplifier andthe auxiliary amplifier are represented ideally with thecurrent source and the shunt parasitic capacitance(Cds,m, Cds,a). We place the Tee-Type network composedof the transmission line between the main amplifier andthe combining point, and set their electrical lengths
and characteristic impedances to θ1, θ2, θ3, Z1, Z2, Z3
respectively. We place the Tee-Type network composedof the lumped component between the auxiliary amplifier
and the combining point, and it is composed of theseries inductor La1, the shunt inductor La2, and the seriescapacitor Ca1 respectively. The series inductor La1 isassumed to be a wire to the transistor. When there isa multi-chip configuration like a module, because it isnecessary to connect the external circuit to the transistor
with a wire, a circuit must be placed in-between theauxiliary amplifier and the combining point.
Next, we will discuss the circuit’s operation principle.
The circuit design method proposed in this article
differs from conventional circuit design methods in thatit transforms the impedance at the combining point.
Specifically, as shown in Fig. 1, the impedance viewed
at the output from the combining point is transformed
into γ·(Ropt,m// Ropt,a) and γ = 1 for conventional circuitdesigns, but in this circuit design method, it is possible toset γ > 1 because the circuit is inserted into the auxiliary
amplifier side. Here, the γ represents the impedance
transformation ratio, and Ropt,m, Ropt,a represent themain amplifier’s and the auxiliary amplifier’s optimal
impedances respectively. To operate as a Doherty
power amplifier, both the main amplifier and the auxiliary
amplifier are required to match the optimal impedances(Ropt,m, Ropt,a) respectively at saturation. In the case ofthis circuit, as shown in Fig. 1(b), it is easy to understandthe operation if the circuit is replaced by an equivalentcircuit that adds the virtual shunt capacitor (Cvir) andthe virtual shunt inductor (Lvir) which cancel each other
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TECHNICAL REPORTS

Auxiliary amplifier

θ1，Z1

θ3，Z3
θ2，Z2

Main amplifier

Impedance transformation circuit

Cds,mCombiningpointγ∙（Ropt,m//Ropt,a）
Outputmatching
circuit

La1
Ca1

La2
Cds,a

Ca,B.O.
(a) Operating principle at power back-off

Auxiliary amplifier

θ1，Z1

θ3，Z3
θ2，Z2

Main amplifier

Impedance transformation circuit (γ∙Ropt,m→Ropt,m)

Cds,m

Cvir

La1
La2

Ca1

Cds,a

Lvir

γ∙
（Ropt,m//Ropt,a）
Outputmatching
circuit

Constants that cancel
each other out

Impedance transformation circuit (γ∙Ropt,a→Ropt,a)(b) Operating principle at saturation

Fig. 1 Circuit schematics of designed Doherty power amplifierout at the combining point. These virtual components
together form an impedance transformation circuit thatprovides the impedance transformation ratio γ for boththe main amplifier and the auxiliary amplifier. Whileat power back-off, to function as a Doherty power
amplifier, the combining circuit must function as a load
modulation circuit for the main amplifier. As shown in
Fig. 1(a), at power back-off, the auxiliary amplifier has
halted operation, so the current source on the auxiliary
amplifier side is open. At this time, the four elements of

the auxiliary amplifier side circuit, Cds,a, La1, La2, and Ca1,
can be represented equivalently as a shunt capacitor(Ca,B.O.). This equivalent shunt capacitor (Ca,B.O.) andthe main amplifier’s Tee-Type network can form the load
modulation circuit in the Doherty power amplifier withthe main amplifier side parasitic capacitance (Cds,m). In
this way, it is possible to function as a Doherty power
amplifier through this circuit, however, it is not east to findcircuit constants to satisfy these operating conditions
at saturation and at power back-off. Therefore, we
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2.0

1.0

0.
－

－1.0

－1.0

2.0
－

5

5

－
5.
0
－
1
－ 0
20

0.

.2
－0

(a) In case of γ = 1(b) In case of γ = 1.8

0

-10
-20
-30
-40

Γmain
Γaux.
Γmain(B.O.)

-50
3.5

3.6 3.7 3.8 3.9Frequency (GHz)(c) In case of γ = 1

4.0

Reflection coefficient (dB)0
Reflection coefficient (dB)

5.0
10
20

0.5

0.5

0.2
－

Reflection coefficient

0.5

2.0

0.5

5.0
10
20

.2
－0

-60
3.4

Γmain(B.O.)

0.2

Reflection coefficient

Γmain
Γaux.

1.0

Γmain(B.O.)

－
5.
0
－
1
－ 0
20

Γmain
Γaux.

Fig. 2(a) and (b), the main amplifier side impedance(Γmain, Γmain(B.O.)) and the auxiliary amplifier side
impedance (Γaux) are shown in a Smith Chart normalized
to their respective optimal impedances. Regarding themain amplifier side impedance, the impedance loci of therespective frequencies are shown in a thin, solid line, andthe frequency dependence of the impedance at powerback-off are shown in a thick, solid line. In Fig. 2(c) and(d), the frequency dependence of the magnitude of thereflection coefficients corresponding to the respective
optimal impedances are shown at saturation (thin,solid line) and at power back-off (thick, solid line) forthe main amplifier, and only at saturation (dotted line)
for the auxiliary amplifier. The parameters used in thissimulation other than γ as follows.
Z1=Z2=Z3=Ropt,m, Cvir=0.9∙Cds,mFrom the diagram, we can see that wider band
matching is obtained when γ = 1.8. In particular, we
can see that a wideband characteristic is obtained for2.0－

established a circuit equation to satisfy the conditions
shown in Fig. 1. In this case, when the values of Z1, Z2,
Z3, La1, γ, Cvir in the circuit are fixed, the other circuit
parameters (θ1, θ2, θ3, La2, Ca1) can be analyticallydetermined uniquely. Therefore, as the parameters of
the Z1, Z2, Z3, and La1 are determined by the module
structure, at the circuit design stage when the module
structure has been decided, it is not possible to choose
them arbitrarily. Therefore, γ, Cvir can be arbitrarily chosen
at the circuit design stage. However, not all combinationsof γ, Cvir have solutions for which the circuit operates asa Doherty power amplifier, and indeed we have found out
from circuit analysis that combinations that have solutions
are limited. Furthermore, we have discovered that,among the combinations for which there are solutions,the solutions in which γ is made large are consistent withwideband. In Fig. 2, we show the results of simulating thefrequency dependence of the Doherty power amplifier’s
load modulation using the current source model. In

-10
-20
-30
-40

Γmain
Γaux.
Γmain(B.O.)

-50
-60
3.4

3.5

3.6 3.7 3.8 3.9Frequency (GHz)4.0(d) In case of γ = 1.8

Fig. 2 Simulation result of frequency dependence of impedance modulationin Doherty Power Amplifier using current source model
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TECHNICAL REPORTS

the main amplifier’s impedance at saturation. Based on
this we see that a wider band Doherty power amplifier
operation is possible than conventionally (γ = 1.0) due tothis circuit design method.

Fig. 3 Designed and fabricated 10W Class,
Wideband GaN Power Amplfier Module for
5G Base-Stations

DE (final), PAE (%), Gain (dB)70
60

Pulse modulation (duty = 10%)Frequency = 3.9 GHz

50
40
30
20

DE (final)
PAE
Gain

10
0
30

35

40
Pout (dBm)

45

50

Fig. 4 Measurement result of fabricated power amplifier
module using pulse modulated signal at 3.9 GHz
Pave
Gain

55

PAE
ACLR

DE (final)
－15

50

－20

45

－25

40

－30

35

－35

30

－40

25

－45

20

－50

15

－55

10
3.4

3.5

3.6

3.7

3.8

3.9

4.0

ACLR (‒dBc)

Pave (dBm), PAE, DE (final) (%), Gain (dB)

4. Results of Creation and Evaluation of
a Prototype 10W Class, Wideband GaN
Power Amplifier Module for 5G Base
Stations
We conducted design and prototype creation of the
10W class, wideband GaN power amplifier module for5G base stations that in the final stage had a Doherty
power amplifier that used the circuit design methodof Chapter 2. Figure 3 shows the module that was
designed and prototyped. The module’s effective area
is 76 mm2. Figure 4 shows the results of the evaluation
when a 3.9 GHz pulse modulated signal was used. The
graph’s vertical axis indicates the final stage Doherty
power amplifier’s drain efficiency (DE (final)), the PAE
including the driver stage’s power consumption, and theGain; and the horizontal axis indicates the output power(Pout). From the diagram we see that for the designed
and prototyped module, at the peak output power of
47.9 dBm and 8 dB power back-off point, the drain
efficiency is 53.8%, the PAE is 45.7%, and the Gain is
31.7 dB. Figure 5 shows the frequency dependence ofthe results of the evaluation using the modulation signalthat has a 20 MHz modulation bandwidth and a 7.5 dB
Peak to Average Power Ratio (PAPR). In the evaluation,
the Digital Pre-Distortion (DPD) is applied and the postDPD characteristics are represented. From the diagram
we see that smooth characteristics are obtained acrossthe 700 MHz from 3.4 - 4.1 GHz. In the 700 MHz band,the characteristics obtained are: average output power(Pave) of 40.3 - 40.8 dBm, PAE of 42.0 - 44.6%, Gainof 28.6 - 31.0 dB, post-DPD ACLR of less than -46 dBc.
Figure 6 shows the results of the DPD evaluation using
the 5G NR (New Radio) 100 MHz modulation signal.
As shown in the diagram, we were able to apply DPDeven for a wideband modulation signal, and we wereable to obtain a characteristic of -51,7 dBc for the postDPD ACLR. Table 1 shows the comparison between
the amplifier with the design described in this article
and other amplifiers for 3 - 4 GHz. We see that thisdesigned and prototyped amplifier module shows thewidest bandwidth characteristics in the 3 - 4 GHz band.
From this conclusion, we were able to demonstrate theeffectiveness of this design method.

－60
4.1

Frequency (GHz)

Fig. 5 Measured frequency characteristic using 20 MHz
modulation signal with 7.5 dB PAPR

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0

Spectrum (w/ DPD)
Spectrum (w/o DPD)

Relative power (dB)

-10
-20
-30
-40
-50
-60
-70
3.4

3.5

3.6
3.7
3.8
Frequency (GHz)

3.9

4.0

Fig. 6 Measured spectrum of the output signal using
5G NR 100MHz modulation signal before and after DPD
Table 1 Comparison of the designed power amplifier modulewith other amplifier operating in 3-4 GHz band
Amplifier
References (2)References (3)References (4)Developed this time

Frequency(GHz)

Drain efficiency(%)

3.3-3.6
3.4-3.8
3.0-3.6
3.4-4.1

50.4-54.8
45.9-50.2
46.6-50.5

5. Conclusion
We have described a new design method which,because it covers almost all the 5G frequencies in the
3 - 4 GHz band, realizes a wider band operation while
making use of the advantages of the conventional
design method. As a result of using this design method
to prototype and evaluate a 10W class GaN amplifier
module, in the 700 MHz band from 3.4 - 4.1 GHz, an
ACLR after digital pre-distortion of -46 dBc was satisfied
with a 20 MHz modulation bandwidth signal, and a
PAE of 42.0 - 44.6% and a gain of 28.6 - 31.0 dB wereachieved. In addition, from the fact that the widest
bandwidth characteristics were obtained comparedto other amplifiers, we were able to demonstrate theeffectiveness of this design method.

PAE
(%)

Modulation bandwidth
(MHz)

40
42.9-47.8

20
20
20
20

42.0-44.6

PAPR
(dB)
7.2
8
7.5
7.5

References(1) Gustafsson, D., et al.: A wideband and compact
GaN MMIC Doherty amplifier for microwave link
applications, IEEE Transactions on Microwave
Theory and Techniques (2013)(2) Maroldt, S., et al.: 3.5-GHz ultra-compact GaN
class-E integrated Doherty MMIC PA for 5G
massive MIMO base station applications, European
Microwave Integrated Circuits Conference (2017)(3) Sakata, S., et al.: A fully integrated GaN Doherty
power amplifier module with a compact frequencydependent compensation circuit for 5G massive
MIMO base stations, IEEE/MTT-S International
Microwave Symposium (2020)(4) Komatsuzaki, Y., et al.: 3.0 - 3.6 GHz wideband,over 46% average efficiency GaN Doherty power
amplifier with frequency dependency compensating
circuits, IEEE Topical Conference on RF/Microwave
Power Amplifiers for Radio and Wireless Applications(2017)

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Wider - temperature - range CWDM
100Gbps EML Chip for Data Centers
Authors: Yusuke Azuma* and Akitsugu Niwa*

1. Introduction
Along with the rapid increase in data communication
capacity, data center network communication speeds
and capacities continue to increase. Meanwhile, because
power consumption is expanding greatly since manytransmission devices are being driven and cooled, thedemand for low power consumption is extremely strong.
Furthermore, reducing the cost of transmission equipment
is also extremely important. To handle these issues, using
an Electro-absorption Modulated Laser (EML) that does
not require temperature adjustment and operates at a wide
range of temperatures is effective. A method to realize
400 Gbps data communication using a four-wavelength
EML chip operating at 100 Gbps is enacted in an Multi
Source Agreement (MSA)(1). The four wavelengths use
a Coarse Wavelength Division Multiplexing (CWDM)
standard in which the wavelength interval is 20 nm and eachwavelength allowable width is 13 nm. Until now, Mitsubishi
Electric has developed a single wavelength 50 Gbps EML
with a chip temperature range of 25 - 75°C which operates
without the need for temperature adjustment, but somedata centers are now deemed to require an EML chip which
operates at a wider temperature range of TLD = 5 - 85°C
with no temperature adjustment. In addition, for 400 Gbps
transmission, operation of 100 Gbps per wavelength isrequired. We developed a semiconductor laser diode chip
which is applied as a light source in optical transceivers
for 400 Gbps optical fiber communication in data centers.
100 Gbps operation is available in temperatures ranging
from 5 to 85°C due to optimized design parameters for thelaser diode and modulator sections.
2. EML Chip Design
Figure 1 shows the EML device structure. For thelaser part, we used a buried heterostructure (Fig. 1(b))
with excellent high temperature characteristics. For theelectro-absorption modulator, we decided on a high mesa
structure (Fig. 1(c)) possessing high extinction ratio andwide bandwidth characteristics, and the entire device
employed our proprietary hybrid waveguide structure
which integrated them monolithically (Fig. 1(a))(2). For the
100 Gbps high speed operation here, it is necessary tosecure both wide bandwidth and extinction ratio throughthe reduced capacity of the Electro-Absorption Modulator(EAM). To reduce the capacity and obtain a wide bandwidth,* High Frequency & Optical Device Works

it is desirable to shorten the length of the electro-absorption
modulator, but there is a trade-off whereby if the electroabsorption modulator is shortened, the extinction ratio is
reduced. The high mesa structure can increase the ratioof optical confinement in the Electro-Absorption (EA) layercompared to other ridge types or buried structures, so it ispossible to obtain a high extinction ratio even with a shortmodulator length. For that reason, here we employed thehigh mesa structure which can ease the trade-off between
the bandwidth and the extinction ratio. The electroabsorption modulator length was made even shorter thanthe conventional devices and the capacity was reduced, but
the design of the extinction ratio that is part of the trade-off
satisfied the FR4 standard(1) of the 100 G Lambda MSA.
In addition, the fiber coupling efficiency of the single mode
fiber was increased by installing a spot size converter
following the EAM.
Spot size
converter(Buried)Electro-absorption
modulator part(High-mesa)

Laser part
(Buried)(a) Top view of entire chip

p−InP

n−InP
Current blocking layer

Active layer(b) Cross-sectional view of buried LD

p−InP

Absorption
layer

n−InP

(c) Cross-sectional view of high-mesa EAM

Fig. 1 Schematic structure of hybrid-waveguide EML
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TECHNICAL REPORTS

Normally, the absorption layer is formed by a multiple
quantum well. Turning the light on and off is controlledusing a phenomenon (quantum confined stark effect) inwhich the light’s absorption spectrum shifts to the longwavelength side due to the application of an electric field
across the quantum well. As in Fig. 2, light from the laserpart which is incident on the Electro-Absorption layer
passes through when there is no electric field, but when
an electric field is applied, the band gap narrows to allow
light to be absorbed. Figure 3 shows an overview of theelectro-absorption modulator’s absorption spectrum. In theabsence of an electric field, the absorption coefficient of thelaser oscillator wavelength is small and so the light passes
Without electric field appliedWith electric field applied

E＞E’Electron
E
Light

E’

Hole
Barrier
layer

Well layer

Fig. 2 Quantum confined Stark effect
Detuning
quantity⊿λAbsorption coefficient (α)

Without electric field applied

3. EML Evaluation Result
Table 1 shows EML’s target specification andevaluation results. Figure 4 shows the frequency response
characteristics (S21) of the product developed here
(1311 nm wavelength band chip). The measurements
were made by contacting an Radio Frequency (RF)probe directly with the submount on which the chip
was implemented. The operating conditions are:chip temperature TLD = 5°C, LD current (Iop) =With electricfield applied

Wavelength

through with almost no absorption; but, when an electricfield is applied, the light’s absorption spectrum shifts to thelong wavelength side due to the quantum confined starkeffect, the absorption coefficient for the laser oscillator
wavelength increases, and so the light is absorbed. The
electro-absorption modulator’s characteristics vary widely
depending on the first peak (the exciton absorption peak) of
the absorption spectrum in the absence of an electric field
and on the laser oscillator wavelength detuning quantity(hereinafter, referred to as “⊿λ”). In the normal range,
the smaller ⊿λ, the greater the extinction ratio and thelower the optical output, and the larger ⊿λ, the smaller theextinction ratio and the higher the optical output. To attainthe desired characteristics across a broad temperature
range, it is necessary to set this ⊿λ appropriately, but
it is difficult to achieve the characteristics across a wide
temperature range because the laser oscillator wavelengthchanges by around 0.1 nm/°C in response to the ElectroAbsorption spectrum changing by around 0.5 nm/°C.
At the low temperature side, ⊿λ becomes large, so it isnecessary to increase the voltage applied to attain thedesired extinction ratio, but if a large voltage is applied,there is the issue that the exciton absorption peak collapses
and the extinction ratio is reduced. Here, these issues
are resolved by devising the absorption layer’s multiple
quantum well design and designing ⊿λ appropriately. At
the high temperature side, there is the issue that the laser’s
optical output is reduced, but even when operating at ahigh temperature of 85°C by devising a current blocking
layer structure, we have ensured that the desired optical
output can be attained.

Laser oscillator
wavelength

Fig. 3 Qualitative diagram of absorption spectra

Table 1 Product target specification and evaluation results
Item

Target specification

Evaluation result
85℃
1274.4nm
1294.6nm
1314.6nm
1334.4nm
48GHz

3dB cutoff frequency≧35GHz5℃
1267.5nm
1287.4nm
1307.5nm
1327.4nm
53GHz

Optical modulation amplitude (chip facet)≧5dBm

8.0~8.6dBm

5.3~7.6dBm

Extinction ratio≧3.5dB

4.7~5.3dB

7.0~7.3dB

TDECQ≦3.4dB

2.4~2.7dB

1.4~2.5dB

Emission wavelength

L0
L1
L2
L3

1264.5~1277.5nm
1284.5~1297.5nm
1304.5~1317.5nm
1324.5~1337.5nm

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TECHNICAL REPORTS
3(Vc) is as shown in the respective diagrams. In the chipend output, we attained an Optical Modulation Amplitude(OMA) of 8.0 - 8.6 dBm @ 5°C, and of 5.3 - 7.6 dBm @85°C, an extinction ratio during modulation (Ex) of 4.7 5.3 dB @ 5°C,7.0 - 7.3 dB @ 85°C, TDECQ 2.4 - 2.7 dB@ 5°C, and 1.4 - 2.5 dB @ 85°C, an so we achieved thetarget specification with a broad temperature range with achip temperature of 5°C and 85°C.

5°C

S21 (dB)

0
85°C

－3
－6
－9
0

10

20
30
Frequency (GHz)40

50

Fig. 4 Experimental result of frequency response

40 mA, EA offset voltage (VEA) = –2.5 V, TLD = 85°C,
Iop = 120 mA, VEA= –1.5 V. To operate the device at
100 Gbps, a passband of 35 GHz or more is requiredin general, and the product developed here attains asufficient bandwidth for 100 Gbps transmission, with53 GHz at 5°C and 48 GHz at 85°C.
Figure 5 shows the optical waveform during Back-ToBack (BTB) 53.125 Gbaud Pulse Amplitude Modulation -4(PAM4) modulation operation for each wavelength band atchip temperatures of 5°C and 85°C. The measurements
were made by contacting an RF probe directly with thesubmount on which the chip was implemented. The
operating conditions are: baud rate of 53.125 Gbaud,
EML modulation voltage amplitude (Vpp) of 1.0 V, Iop =30 mA @ 5°C and 120 mA @ 85°C. The EA center bias

4. Conclusion
We developed a CWDM 4-wavelength 100 Gbps
EML chip operating at chip temperatures from 5 to
85°C, and we attained excellent characteristics thatsatisfied the target specification. Due to this, the opticaltransceiver, which is a system component in data
centers, does not require a Thermo Electric Cooler(TEC) for temperature adjustment of the EML, though it
was required with previous products, and can reduce thepower consumption and cost in data centers.
References(1) 100G Lambda MSA https://100glambda.com/(2) Morita, Y., et al.: 1.3 µm 28 Gb/s EMLs with Hybrid
Waveguide Structure for Low-Power-Consumption
CFP2 Transceivers, Optical Fiber Communication
Conference/National Fiber Optic Engineers
Conference 2013, America, paper OTh4H.5 (2013)

5°C

85°C

Vc＝－2.4V，OMA＝8.6dBm，Ex＝4.8d，TDECQ＝2.7dB

Vc＝－1.1V，OMA＝5.3dBm，Ex＝7.3d，TDECQ＝2.5dB

Vc＝－2.3V，OMA＝8.4dBm，Ex＝5.3d，TDECQ＝2.7dB

Vc＝－1.0V，OMA＝6.4dBm，Ex＝7.3d，TDECQ＝1.9dB

Vc＝－2.3V，OMA＝8.0dBm，Ex＝5.0d，TDECQ＝2.4dB

Vc＝－1.1V，OMA＝6.8dBm，Ex＝7.0d，TDECQ＝1.4dB

Vc＝－2.3V，OMA＝8.2dBm，Ex＝4.7d，TDECQ＝2.4dB

Vc＝－1.1V，OMA＝7.6dBm，Ex＝7.0d，TDECQ＝1.4dB

Lane 0(L0)Lane 1(L1)

Lane 2(L2)Lane 3(L3)

1/53G (seconds)

Fig. 5 53.125 Gbaud PAM4 eye diagrams

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TECHNICAL REPORTS

50Gbps DFB Laser Diode for
5G Base Stations
Authors: Go Sakaino* and Masaaki Shimada** High Frequency & Optical Device Works

Optical output (mW)Time (ps)(a) NRZ
14
Optical output power (mW)

2. Device Design
Until now, we have productized a DFB laser
operating at 25 Gbps in a temperature range from –40°C
to 90°C. With a direct modulation operation DFB laser, it
is important to suppress the optical modulation waveform
degradation due to the oscillation of the light intensity
occurring as a result of the interaction of the electricity
and the light. The frequency of this light intensity
oscillation is referred to as the relaxation oscillation
frequency and it is required to maintain a high value ofthe same order as the modulation frequency in the fulltemperature range of operation. For this reason, there
is a remarkable loss of light and reduction in efficiency
in injecting electric current into the active region athigh temperatures in particular, and it is necessary to
suppress the reduction in the light density in the active
region. In addition, in a package equipped with a DFB
laser chip, it is important to optimize the impedance inthe design of the transmission line of the high frequency
electrical signal to suppress the degradation of the highfrequency characteristics.
In the use of 50GBASE-LR, the four-valued electricalsignal which changes at 26.56 Gbaud is input into the
DFB laser, and the DFB laser chip outputs the fourvalued light signal. The index that determines whether
this optical modulation waveform is good or not is
stipulated in IEEE 802.3cd, and uses the Transmitter andDispersion Eye Closure Quaternary (TDECQ) calculated
from the optical modulation waveform with the waveform
shaped by the Low Pass Filter (LPF) and Feed Forward
Equalizer (FFE).
Because there is a four-valued signal in the PAM4
signal 16waveform, the eye opening is extremely small,so there
14 is a tendency for the waveform quality to be
reduced12 remarkably due to the effect of the DFB laser’s
relaxation
10 oscillation. We conducted a simulation usinga model8 based on the DFB chip model which takes into
consideration
this relaxation oscillation and the 25 Gbps
6DFB laser’s
package developed in 2018, and designed
4
the DFB2 laser chip and package. The results are shownin Fig. 1.0 0 10 20 30 40 50 60 70 80

12
10
8
6
4
2
0

0

10

20

30

50
40
Time (ps)

60

70

80

60

70

80

(a) PAM4 before FFE
14
Optical output power (mW)

1. Introduction
Migration to 5G is accelerating as the volumeof data communication in mobile communications
is increasing. Optical communication devices usedin the fronthaul antenna base stations of 5G mobile
communication networks are required to operate
across a broad temperature range because they are
installed outdoors. In addition, a Disributed Feedback(DFB) laser is used enabling direct modulation sothat low power consumption operation is achieved
without the need for a thermoelectric conversion
element. In the 50GBASE-LR standard supportedby the fronthaul, the Pulse Amplitude Modulation -4(PAM4) modulation method in which the light intensity
is changed from the conventional two-valued to fourvalid is proposed. With this modulation method,even though the DFB laser’s modulation speed isthe same 25 Gbps as for conventional modulation,
50 Gbps transmission is possible. Here, we designed
and developed a 50 Gbps DFB laser chip and industrystandard TO-56CAN package suitable for the PAM4
modulation method.

12
10
8
6
4
2
0

0

10

20

30

50
40
Time (ps)(b) PAM4 after FFE

Fig. 1 Simulated waveforms

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TECHNICAL REPORTS

3. Device Structure and Characteristics
Figure 2 shows an outline photograph of the 50 Gbps
DFB laser with an oscillating wavelength of 1310 nm
developed here. The outline of the CAN package uses
the industry-standard Φ 5.6 mm TO-CAN which makes it
possible to secure compatibility with the previous productand to conform with the compact transceiver standard(SFP56).
The electric current and optical output characteristics
are shown in Fig. 3. In the operating temperature range
from a low temperature of –40°C to a high temperatureof 90°C, the threshold current and the change in theslope efficiency are small, so we were able to achievesufficient characteristics for 50GBASE-LR. At thehigh temperature of 90°C in particular, we achieved athreshold current of 20 mA or less, a slope efficiency of
0.22 mW/mA or more, and a maximum optical output of
12 mW or more.
Figure 4 shows the PAM4 transmission opticalmodulation waveform. The optical waveform is observed
after applying the LPF and the FFE, and the TDECQ
was calculated using a method conforming to IEEE
802.3cd. In addition, in order to correct the DFB laser’s
frequency response, the Pre-Emphasis which highlights
the electrical signal’s rising edge and falling edge inadvance is used and the TDECQ can be improved. In
recent years, driver ICs have been put into use withimproved PE performance, and here, we also conducted
a comparison with and without the PE applied. From thelow temperature to the high temperature, whether the PE
is applied or not, a large eye opening is achieved and,even after 20 km transmission, the optical modulation
waveform is excellent with little disturbance.

–40℃ 25℃

20

70℃

18

Optical output power (mW)

16

80℃

14
90℃

12
10
8
6
4
2
0

0

20

60
40
Current (mA)

80

Fig. 3 I – L characteristics (–40, 25, 70, 80, 90°C)

90℃

–40℃

25℃

90℃

0 km

25℃

20km

20 km

10km

10 km

0 km

–40℃

Fig. 2 50Gbps DFB laser(a) Without Pre-Emphasis(b) With Pre−Emphasis

Fig. 4 Optical waveforms after transmission

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TECHNICAL REPORTS

Figure 5 shows the TDECQ transmission distancedependency. The TDECQ with no PE applied attemperatures of –40°C, 25°C, and 90°C are 2.3 dB,
1.8 dB, and 2.0 dB respectively before transmission(0 km). Furthermore, during the 10 km transmission
required of 50GBASE-LR, the values are 2.1 dB,
1.7 dB, and 2.1 dB, which sufficiently satisfy the standardof 3.2 dB or less. In addition, when the PE is applied,
the TDECQ after the 10 km transmission are 1.1 dB,
0.9 dB, and 1.3 dB, so that the effect of applying the PE
is confirmed.
4↓ IEEE802.3cd criteria of TDECQ ≦ 3.2 dB

TDECQ (dB)

3

4. Conclusion
We developed a 50 Gbps DFB laser suitable for
the PAM4 modulation method targeting the fronthaulof 5G mobile communication networks. Characteristics
satisfying the standard 50GBASE-LR standard wereachieved, the speed was doubled compared to theprevious device to this one, and we were able to realize
5G high speeds and low power consumption.
References(1) IEEE Standards Association : IEEE 802.3cd 50Gb/s,
100Gb/s and 200Gb/s Ethernet Task Forcehttps://www.ieee802.org/3/cd/(2) Sakaino, G., et al.: Direct Modulation DFB Laser for
25 Gbps Optical Transmission, Mitsubishi Electric
ADVANCE Mar.2018 Vol.161, 2~4 (2018)

2

90℃
25℃
–40℃

1

0

0

10
Transmission distance (km)20(a) Without Pre−Emphasis
4↓ IEEE802.3cd criteria of TDECQ ≦ 3.2 dB

TDECQ (dB)

3
90℃
25℃
–40℃

2

1

0

0

10
Transmission distance (km)20(b) With Pre−Emphasis

Fig. 5 Dependence of TDECQ on transmission distance

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1.55µm Tunable DFB-LD for 400G Digital
Coherent Optical Transmission System
Authors: Kazuki Yamaji* and Ryosuke Nagao*

1. Introduction
In metro and long-haul networks, data centerinterconnects, and so on, the demand is rising for highspeed, large capacity digital coherent communication.
In this article, we describe the development of a
wideband, tunable Distributed Feedback Laser Diode(DFB-LD) chip targeting 400 Gbps digital coherent
communication with integrated 16-array DFB-LD and
Semiconductor Optical Amplifier (SOA).
2. Background
Because the speed and capacity of optical communication devices are increasing as communication traffic
increases, multi-value modulation and light polarization
are used, and the demand is rising(1) for digital coherent
communication using digital signal processing inmodulation and demodulation, so wideband variablewavelength lasers are required as local light sources
for that signal beam and the optical receiver. In recent
years in particular, the demand has been rising for a
speed increase from the conventional 100 Gbps to 400
Gbps in metro and long-haul networks and data centerinterconnects.
400G digital coherent communication employs
16QAM (Quadrature Amplitude Modulation) or 64QAM,
which are the combination of intensity modulation of the
optical spectrum and QPSK (Quadrature Phase-Shift
Keying) which modulates optical signals by changing
the light’s phase shift. Such modulation methods requirea light source with low phase noise, narrow spectral
linewidth, and sufficient intensity. The industry standards
group, the Optical Internetworking Forum (OIF),
proposes the specification for the light sources such as
Micro-Integrable Tunable Laser Assembly (ITLA), etc.
applied to those modulation methods. The specification
also includes other requirements such as wavelength
grid, wavelength stability, etc.
The wavelength-tunable laser methods include theexternal resonator type, the Distributed Bragg Reflector(DBR) type, and the Distributed Feedback (DFB) array
type as shown in Table 1. In the development we aredescribing here, we used a DFB array type which
can realize stable optical output with a simple control
to develop the ML9CP61 tunable DFB-LD chip withintegrated SOA to supplement the light intensity.
* High Frequency & Optical Device Works

Table 1 Tunable laser typeType

Outputpower

OpticalTunableControllaspectral
range ofbilitylinewidth wavelength

External
resonator

△

○

△

△

DBR

○

△

○

×

DFB array

△

△

○

○

3. Tunable DFB-LD Chip Design
Figure 1 shows the structure of the tunable
DFB-LD chip we developed. Integrated into the InP
substrate are 16 DFB-LDs with differing oscillating
wavelengths, 16 x 1 Multi Mode Interferer (MMI) optical
couplers combining the DFB-LD’s optical output in the
output port, and SOA to compensate for the losses
occurring in the optical couplers and to amplify the optical
output. For the purpose of a reduction in the reflected
return light, the SOA waveguide is inclined and, at thesame time, the chip end surface has a window structurewith anti-reflective coating. The chip size is 3.8 mm x0.75 mm x 0.1 mm.
Changes in the oscillating wavelengths are carriedout through the selection of the DFB-LD and the chiptemperature adjustment using the Thermoelectric
Cooler (TEC). Because the temperature dependency of
DFB-LD oscillating wavelength is small at approximately
0.1 nm/°C, in the case that DFB-LD array number
is small, it is necessary to significantly change thechip temperature, so the TEC’s power consumption is

16DFB−LD array

16×1 MMI

SOA

Outputlight

Fig. 1 Schematic structure of tunable DFB-LD chip

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4. Element Characteristics
Figure 2 shows the optical output power of thefabricated tunable DFB-LD chip. The Laser Diode (LD)current was set to 220 mA (chip temperature of 25°C) or
250 mA (chip temperature of 55°C), and the SOA current
was set to 400 mA. It was confirmed that an optical output
of 17 dBm or more was obtained with a variation of 1 dBor less across the full range of the 1.55 μm band. Figure 3
shows the output light spectrum when one of the DFBLD arrays is operated. The tunable wavelength widthcorresponding to one DFB-LD at a chip temperature from
25°C to 55°C is 2.9 nm. The Side Mode Suppression
20
19
Optical output (dBm)

18700
Optical spectral Linewidth (kHz)increased. When there are many arrays, although thelosses in the optical coupler parts increase, it is possible
to narrow the temperature adjustment range and thisis advantageous for reducing the power consumption.
Here, the number of arrays is 16 and the temperature
range is 25 - 55°C, and the diffraction grating pitch ofeach DFB-LD is designed to satisfy the wavelength
standard of the 1.55 μm band of OIF-IC-TROSA-01.0(3)and OIF-400ZR-01.0(4). To realize the light spectral
linewidth of 500 kHz or less required for digital coherent
communication, the diffraction grating length waslengthened to 1.4 mm.

600
500
400
300
200
100
0

1

2

3

4

5

6

7 8 9 10 11 12 13 14 15 16
DFB−LD No.

Fig. 4 Optical spectral linewidth of tunable DFB-LD chip

Ratio (SMSR) maintains 45 dB or more in an operating
temperature range of 25°C to 55°C.
Figure 4 shows the light spectral linewidths at 55°C,
an LD current of 250 mA, and an SOA current of 400
mA. The light spectral linewidths are 300 kHz or less, so
realization of the performance target of 500 kHz or lesswas confirmed.
5. LD Modularization
The LD module in Fig. 5 was prototyped using
the fabricated DFB-LD chip. Figure 6 shows the block
diagram. The output light of the DFB-LD chip parallelizedwith a collimating lens is separated by prisms 1 and 2,
then input respectively into a light intensity monitor
PhotoDiode (PD) and a PD for use with a wavelength

17
16
15
14
13
12

Chip temp. 25°C

11

Chip temp. 55°C

10

1

2

3

4

5

6

7 8 9 10 11 12 13 14 15 16
DFB−LD No.

Fig. 2 Output light power of tunable DFB-LD chip
Chip temp. 25°C

–10

Fig. 5 LD module

Chip temp. 55°C

–20
PD

–30

PD

–40

Tunable
DFB laser

Etalon–50–60

Prism2

Prism1

–70
–80
1,545

TEC2

1,555
1,550
Wavelength (nm)1,560

Fig. 3 Optical spectrum of a DFB-LD output light

Collimating
lens…

Normalization output optical power (dB)0

TEC1
PD: PhotoDiodeFig. 6 Schematic block diagram of LD module

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TECHNICAL REPORTS

monitor via an etalon. To control the temperature
independently of the DFB-LD chip, the DFB-LD chip andthe collimating lens are installed above TEC1, and theother parts are installed above TEC2.
Figure 7 shows the LD module’s tunable wavelength
range. The drive current was supplied to the 16 DFB-LDs
in order, the chip temperature was kept between 25°C
and 55°C, and the oscillating wavelength was measured.
It was confirmed that the tunable wavelength range wasfrom 1526.49 nm to 1567.94 nm and that the OIF-ICTROSA-01.0 (1527.99 nm - 1566.72 nm) and the OIF400ZR-01.0 (1528.77 nm - 1567.13 nm) were satisfied.
Figure 8 shows the power consumption simulation
results and the evaluation results. The total values ofthe power consumption of the LD chip and the TEC areshown in the case that the LD module temperature waschanged to between –5°C and 75°C while keeping thetemperature of the LD chip on TEC1 to 25°C or 55°C. In
the simulation, the maximum was 4.0 W with an LD chiptemperature of 25°C and an LD module temperatureof 75°C. The measurement result was 4.3 W under
the same conditions so a value close to the designed
one was obtained, and meeting the power consumption
specifications of the OIF MicroITLA was estimated to bepossible.
20

OIF−400ZR−01.1

18

OIF−IC−TROSA−01.0

16
DFB-LD channel

14

6. Conclusion
We developed a tunable DFB-LD chip for use with
400 Gbps digital coherent communication integrated
with 16 DFB-LDs with differing oscillating wavelengths
and SOA. We realized characteristics suitable for
400 Gbps digital coherent communication with optical
output ≧ 17 dBm, SMSR ≧ 45 dB, linewidth ≦ 300kHz,
and a wavelength range of 1526.49 nm to 1567.94 nm.
We expect that the technology developed here willcontribute to increasing the capacity of digital coherent
communication and contribute to an optimal package
design for the customers’ optical transceiver.
References(1) Suzuki, S., et al.: Research and Development of
Digital Coherent Signal Processing Technology for
Increasing the Capacity of Optical Communication
Networks, Journal of the Institute of Electronic
Information and Communication Engineers, 95, No.
12, 1100 - 1200 (2012)(2) OIF-MicroITLA-01.1
https://www.oiforum.com/wp-content/
uploads/2019/01/OIF-Micro-ITLA-01.1.pdf(3) OIF-IC-TROSA-01.0
https://www.oiforum.com/wp-content/uploads/OIFIC-TROSA-01.0.pdf(4) OIF-400ZR-01.0
https://www.oiforum.com/wp-content/uploads/OIF400ZR-01.0_reduced2.pdf

12
10
8
6
4
2
0
1,520

1,530

1,540
1,550
Wavelength (nm)

1,560

1,570

Fig. 7 Tunable range of oscillation wavelength of
LD module with DFB-LD chip temperature
controlled in the range of 25°C to 55°C

Power consumption (W)543Chip temp. ＝ 25°C (simulation)
Chip temp. ＝ 55°C (simulation)
Chip temp. ＝ 25°C (measurement)
Chip temp. ＝ 55°C (measurement)

2
1
0
–20

0

40
20
LD module temperature (°C)

6080Fig. 8 Power consumption of LD module

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Thermal Diode Infrared Sensor“MelDIR” and User Support Tools
Authors: Yasuki Aihara* and Satoshi Okuda*

1. Introduction
IoT is essential in our lives and accompanying this
we are surrounded by a variety of sensors. Among
those are infrared sensors whose characteristics include
the ability to detect people and objects while securing
privacy. In this paper, we introduce the features of thethermal diode infrared sensor MeIDIR which uses
Mitsubishi Electric unique technology and we introduce
the development of user support tools which support
customers from product planning to commercialization.
2. Thermal Diode Infrared Sensor
The infrared sensor has a function which detects andenables visualization of the heat from objects without
contact by converting the infrared radiation received
into an electric signal. Figure 1 shows those features.
(1) Because the sensor can acquire the heat informationfrom the heat source without contact, it is excellent fromthe view of hygiene and safety. (2) It can determine aperson’s motion or posture from the silhouette of theheat source. This is particularly effective in scenarios
where privacy protection is required, so the sensor canbe used even in toilets or bathrooms where cameras(1) Obtaining
Temperature
Information

cannot be installed. (3) The heat source can be detectedeven in darkness or where there is no visibility due tosmoke, so the sensor can be used with peace of mind
even indoors at night.
Mitsubishi Electric developed new resolution andprice range product MelDIR compared to conventional
thermopiles and bolometers using its unique thermal
diode sensor technology.
The thermal diode Technology features theuse of a PN junction diode formed in the generalsilicon semiconductor manufacturing process for thetemperature detection area. This technology has goodcompatibility with semiconductor processes as well as
for bolometers, so it’s suitable for multi-pixelization. The
thermal diode performs thermoelectric conversion by
detecting the temperature dependence of the forward
voltage drop of the diode.
The forward voltage of the diode changes
approximately linearly with temperature, and its
characteristics are determined by the process conditionsof the semiconductor, so it can be manufactured withhigh uniformity.

(2) Motion/posturedetection from heatsource silhouette(3) Detects heatsources even in darkor smoky spaces

Visibleimage

Thermalimage ofMeIDIR

Fig. 1 Features of infrared sensor* High Frequency & Optical Device Works

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3. MeIDIR Thermal Diode Infrared Sensor
The conventional infrared sensor market haspolarized into low pixel, low cost products for heat
detection uses, and high pixel, high price infrared
cameras for infrared imaging uses. Using unique
technology, Mitsubishi Electric developed infrared
sensor module MeIDIR with a high pixel count at an
unprecedented low cost. Table 1 shows our productlineup. In 2019, we released the MIR8032B1, and it wasused mainly in Japan for monitoring in elderly people’s
facilities and was also installed in air conditioners. In
2023, we released the MIR8060B3, targeting markets
such as factory equipment surveillance and kitchentemperature management which require object detection
at higher temperatures. This product increased the
maximum measurable object temperature from +60°C to+200°C by optimizing the signal processing and the lens.
Because the thermal infrared sensor thermoelectrically converts the temperature rise part, the detection
sensitivity falls if the heat conductance is high between
the temperature detection area and the surrounding
environment. In addition, if the heat conductance is highbetween the surrounding pixels, the resolution decreases
because the heat detected by the pixels is transmitted tothe surrounding pixels. Therefore, the space between
the diode and the silicon substrate is hollowed out toform a structure in which the diode is held by supporting
legs. By placing the electric line in these support legs, thethermal conductance between the diode and the silicon
substrate is lowered while maintaining the structure andelectrical connection. This supporting leg structure isformed by carrying out dry etching of the thin film Silicon
On Insulator (SOI) substrate which enables low cost
manufacture. Figure 2 shows a SEM image of thermal
diode area. It can be confirmed that the hollowed out
structure, in which the 25 um pitch temperature detection
area is maintained by the supporting leg structure, isformed uniformly.
4. User Support Tools
Figure 3 shows the series of user support tools.
We have prepared a proposal paper to support thecustomer’s product concept making stage. It provides a
wealth of thermal image examples to show them ideasof how to use MeIDIR, it indicates the benefits, etc. of
adopting MeIDIR, and provides a stepping stone forstarting their evaluation.
We provide a dedicated demo kit for customers toevaluate MelDIR. In 2022, We released the EVA series ofdemo kits, that integrate MelDIR, shutters, and substrates
and further reduce the substrate area to about 45% of
the conventional size. Figure 4 shows a photograph ofthe demo kit. It’s available and ready to use, it does not
require any additional time for evaluation preparation.
In order to provide design information for therequired hardware and software at the customer’s
product development stage, we developed a reference
design. The reference design summarizes the design
information of the EVA series demo kit, and the design
information for hardware such as BOM and Gerber, andSupporting leg Thermal diode10 µm

Fig. 2 SEM image of thermal diode

Table 1 MelDIR product lineup
Type No.
Launch date
Detectable temperature range
Number of Pixels
Field of View
Frame Rate
NETD
Power consumption
Module Size
Communication interface

MIR8060B3
Mar. 2023-5℃ ~ +200℃
80×60
78°×53°(Typ.)
4 / 8 fps
Selectable
250 mK(Typ.)

MIR8060B1
MIR8032B1
Jul. 2021
Nov. 2019-5℃ ~ +60℃
-5℃ ~ +60℃
80×60
80×32
78°×53°78°×29°(Typ.)(Typ.)
4 / 8 fps
4 fps Fixed
Selectable
100 mK
100 mK(Typ.)(Typ.)
50 mA or less
19.5×13.5×9.5 mm
Serial Peripheral Interface (SPI)

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TECHNICAL REPORTS

Meeting

Concept making

Proposal

Evaluation

Product planning

Demo-kit

Shutter

Use case idea

PP

MP

Reference Design【Demo-kit】【Proposal】

Design/Prototype【Hardware info.】【Application note】【Software info.】

・Operation manual・Specifications

Patient Monitor

Thermal video

Case

Infrared sensor(MEIDIR)

Use of the independent type / already installedsystem is easy (module addition)→ Large scale system improvements are unnecessary①Send results of analysis

Reference Code

Lens

【Viewer】

Gerber data

23:30 Suspicion offall in room 101②Set off an alarm(send the heat image)Place to bemonitored

Controller③Rush out

Nurse center

Detection Algorithm(Human/Posture/Action)
Learning Tool

BOM list

Already installed system

All stage in development would be supported by each toolFig. 3 MelDIR User Support Tools
Table 2 Heat source detection algorithm
and hardware specifications
Item

Fig. 4 Demo kit “EVA-MIR8060B1-MC02V1-01”

the software design such as object detection by deeplearning and reference code, and application notes suchas several kind of manuals. These tools contribute to
reducing product development period.
We provide heat source detection algorithm
using the deep learning in reference designs. The
detection algorithm based on You Only Look Once
(YOLO) is optimized for use with MeIDIR, and it has
the characteristic that it is developed as an edge AI totarget a general-purpose Micro Controller Unit (MCU) forembedded use. Table 2 shows the heat source detection
algorithm and the hardware specifications.
Since November 2022, we have been offering two

Specification

Type No.

MIR8060B1-01

Type No. of Demo kit

EVB-8060B1-MN****

Type No. of reference code

SAPM-MD**V*

Target MCU

STM32H723_G (Cortex-M7
1177 DMIPS@530MHz)

Deep learning algorithm

MobileNetV2-YOLOv3-Nano

Rom size<1MbyteRam size<512Kbyte

Frame rate

7fps(=142ms/frame)algorithms: a human detection algorithm which detects
people in a living room, and a posture detection algorithm
which detects the posture in a toilet stall and judges
whether or not there is any abnormality.
The detection algorithms provided may notachieve sufficient detection accuracy depending on
the customer’s usage conditions. For this reason, wedeveloped and have been offering a model training tool
(MTT-V001) with the purpose of creating an AI model tomatch the respective usage environments. Furthermore,
we have been also offering a manual to summarize theseries of work procedures of extraction of gray scale
images, annotations, AI model creation, and embedding

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TECHNICAL REPORTS

18.0
16.0
14.0
Loss

12.0
10.0
8.0
6.0
4.0
2.0
0

0

2,000

4,000
6,000
8,000
Number of iterations

10,000Fig. 5 Example of a training resultin a MCU, and are arranging an environment in which
the customer themselves can optimize for their own
products.
Figure 5 shows an example of the training result.
It shows that as the number of iterations increases,
the loss is decreased and the calculation is converged.
In this example, for 10,000 iterations, mean Average
Precision (mAP), which is the detection rate index,
achieves 80% or more.
5. Conclusion
We released MIR8060B3 as a new product of MelDIR
in 2023. By expanding the upper limit of the detection
temperature range from the conventional +60°C to+200°C, we have made it possible to meet the growing
needs of monitoring factory equipment and temperature
control in kitchens. Furthermore, we have enhanced
our user support tools to assist in customer evaluationand product development, contributing to a reduction
in time to market. We released the EVA series of demo
kits, that integrate MelDIR, shutters, and substrates andfurther reduce the substrate area to about 45% of theconventional size. Furthermore, in order to provide thehardware and software design information necessary
for the customer’s product development, we prepared areference design.
We aim to expand the application of these productlineup and support tools to a wide variety of fields, andcontribute to the realization of secure, safe, and healthysociety.

Mitsubishi Electric ADVANCE December 2023

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