Furukawa Electric Broadband Involvement in FTTH Systems

Furukawa Electric

Optical Components for High-Density Optical
Inter-Connect System: OptoUnity
by Masayuki Iwase *, Masato Shiino *, Takeshi Yagi *, Motoharu Tanaka *, Katsutoshi Takakahashi *,Yoshinobu Nekado *, Hideyuki Nasu *, Masahito Morimoto *, Hideo Aoyagi *, Katsuki Suematsu *,Hideki Miyazaki *, Masao Shinoda *, Naoya Nishimura *, Iwao Shimotakahara *, Ryuichi Sugizaki *,Tatsuya Oyama *2, Toshiaki Ozawa *2, Noboru Okada *2 and Kunihiko Yujobo *2

Electric transmission in a system and in such equipment as a high-speed server,
a router, and an LSI tester is reaching its limit, and introduction of optical transmission is considered. We are developing the OptoUnity products as an effort in providing theoptical inter-connection technology that realizes high-speed transmission and a high density
package with a concept of miniaturization. This paper introduces the development of small clad
diameter optical fiber ThreadWave, micro multi-core ferrule μ-Joint, MU type plug, back planeconnector, and right-angled connector μ-Curve, and passive alignment assembly plastic package parallel optical module μ-POEM.

ABSTRACT1.

INTRODUCTION

In recent years, larger amount of information and telecommunications and improvement in the speed are called
for by the rapid spread of the Internet. In order to improve
the speed of the computer which processes the information, the clock speed of CPU unit has been improved. But
also there is a trend to process the information throughparallel operation of two or more CPUs. Therefore, withlarge-scale computers, such as server computers andmainframe computers, a large scale, high speed andhigh-density transmission is required between boards
and between racks, and the optical-inter-connection market which transposes the conventional electric wiring to
optical wiring is expected to expand.
The standardization of optical-inter-connection is considered with IEEE by establishing the 100 GbE (100Gigabit Ethernet) standard in 2009. As far as the market isconcerned, the standardization is expected to be introduced to the high-end field in sometime around 2010,
and is expected to be deployed to personal computers,
digital-appliances products, etc. in 2020. As an opticalinter-connection technology that meets the demand in
highly-dense package for the high-end market, we aredeveloping OptoUnity products; down-sized optical fiber,
optical connector, and high-speed optical module.
This paper introduces the product concept and the status of prototype development.

* Fitel Photonics Lab., R&D Div., Furukawa Electric*2 Telecommunications Co., Furukawa Electric

2.

TARGET SPECIFICATION OF THE
OPTICAL INTER-CONNECTIONSYSTEM

2.1 Benefits of Optical Inter-Connection
The benefits of providing an optical transmission of highspeed electricity signal are; 1) Provides solution foraccess speed and loss limitation (10 Gbps, several
meters), 2) Improvement in packaging density, and
3) Weight saving of wiring material. There are, however,some issues to be solved in applying the present opticalparts as it is. Here, the required specification of high-end
optical inter-connection is considered first.
2.2

Configuration of the Optical Inter-Connection
and Transmission Loss Design
The configuration assumed by optical inter-connection isshown in Figure 1. It assumes transmission between theboards in a rack, or between racks, and the maximum
transmission distance is 20 m. The transmission systemthat is currently adopted is a parallel transmission by
VCSEL (Vertical cavity surface emitting laser) with a wavelength of 850 nm and a multimode fiber with a transmission speed of 2.5 Gbps now in practical use and 10 Gbps
is considered to be used in the future. The loss design ofthe trial transmission path was performed based on suchbackground.
In order to obtain high quality transmission with themulti-mode link using VCSEL, the performance of Tx andreduction of loss (transmission fiber loss, mode dispersion loss and loss in connection with Rx receiving sensi-

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Furukawa Electric Broadband Involvement in FTTH Systems

tivity) are important. The mode dispersion loss of an optical fiber is smaller with Tx that has a smaller gap from
850 nm of the oscillation wavelength of VCSEL, a narrower width of wavelength, and a larger optical extinction
ratio.
Although the increase in Tx optical power extends
transmission distance, there is a limit with the increaseamount considering the eye safety and the reliability of
VCSEL. The increase in a bandwidth of an optical fiberand reduction of bending loss and connection loss isimportant for the reduction of transmission path loss. As
for Rx, the improvement in the absolute characteristic ofreceiving sensitivity (it is dependent on the amplifier IC
characteristic) and reduction of an electric cross-talknoise are needed.
The loss L of the transmission path between Tx module
on one board and Rx module on another board is estimated as 4.2 dB maximum taking into account the following: 0.5 dB each for four optical connections including themodule connectors, the rack or backplane connectors in
addition to four places of small bending diameter; and 0.2
dB for 20-m optical fiber having a propagation loss of 10
dB/km. When the fiber input power of Tx is set at -3 dBm
minimum, the minimum received input power of the target
single channel of Rx will be -10.7 dBm calculating anelectric cross talk penalty of 1.5 dB, the mode dispersion
penalty of 1.0 dB with optical fiber bandwidth 200 MHzkm and L= 4.2 dB of a transmission path, and couplingloss of 1 dB to Photo Detector (PD). The target performance of an optical fiber, an optical connector, and theoptical module were set to make these losses to be themaximum level.
2.3 Target Density of the Optical Connector
The mounting board of high-end transmission equipment
has parts height restrictions (the pitch of a board is determined) for a high dense package, and the standard of theboard pitch is 10 mm or less. Therefore, it is difficult topile up an optical connector perpendicularly. Here, thebandwidth density required for optical inter-connection isexpressed by multiplying the number of fibers per cm inwidth of a mounting board with the access speed perchannel. Figure 2 shows the predicted increase of thetransmission bandwidth per cm in width of an optical connector. Now, the access speed of an optical module is
2.5 Gbps/channel, and since the 12-MPO connector(about 20 mm in width) is used for the optical connector,
bandwidth densities are about 15 Gbps/cm. When the
total signal bandwidth per board necessary for high-end
transmission equipment is assumed to be 3 Tbps andaccess speed is assumed as 10 Gbps/channel, therequired number of fibers is 300. This is equivalent to
25 pieces of the 12-MPO connectors, and a required
board frontage is about 50 cm in width. In this case themounting board will be full with optical connectors since a
mounting board is generally 50 cm. It is necessary tomount not only an optical connector but an electric connector in a mounting board, and also to secure the air
inlet for air cooling.
As shown in Figure 2, by increasing the access speedof one channel to 5 Gbps and 10 Gbps, bandwidth density increases to twice and 4 times, respectively, and therequired number of connectors can be decreased.
However, in order to make increase it by 8 times and 16
times, it is necessary to increase the number of the fiber
ribbon per connector from 12 to 24, 48, etc. There is alimit in the production of connectors with multiple-fibers
since it increases the production cost due to the fall of theyield in the polishing process. Moreover, when multiplying
the fiber in one connector, the branching for the purpose
to increase the thickness of a fiber code and connection
with an optical module etc. becomes a problem and cannot be easily adopted.
Downsizing the connector itself is one of the solutions
in order to raise the packaging density without increasing
the number of fibers per connector. The packaging density required in high-end application is said to be 100
Gbps/cm or more, and the present target is10 Gbps/channel and have 12 fibers to be set within 1 cm
width. By making connector width into 50 % of the present condition, it becomes possible to increase the density
by 8 times with 12 fibers compared with the conventional
product. It is possible to set the access speed to be 20
Gbps/channel or to have 24 fibers while maintaining the
speed by further bandwidth expansion. In the former case
it is also necessary to increase the transmission bandwidth of an optical fiber, which may require an applicationof a single mode fiber. Moreover, the miniaturization of an

Back plane or rack to rack 20 m: Attenuation 0.2 dB

F-F connection loss: 0.5 dB

Total ﬁber-connector
loss budget
L= 4.2 dB max.

Patch code bending loss
: 0.5 dBF-F connection loss: 0.5 dB
PIT = -3 dBm min
0 dBm max
VCSEL- MMF
Coupling loss: 3 dB
10 Gbps 850 nm
VCSEL P0= 0 dBm min,3 dBm max

Bending loss
: 0.5 dBF-F connection loss: 0.5 dB

Patch code bending loss
: 0.5 dBF-F connection loss: 0.5 dB
PIR = -7.2 dBm min-4.2 dBm max
PD- MMF
PD sensitivity
coupling loss: -1 dB
0.5 A/W @850 nm
PPD= -8.2 dBm min,-5.2 dBm max
Mode dispersion
Xtalk penalty
penalty@ 10 Gbps: 1.0 dB@ 10 Gbps: 1.5 dB
X

X・Extinction
ratio
・Wavelength・Spectral
width

Bandwidth/Connector width on
board (Gbps/cm)

Multimode ﬁber
B.W.=200 MHz-km

Bending loss
: 0.5 dBRx minimum received input power
S= 10.7 dBm

Figure 1

Structure and transmission loss budget design of
Optical-Interconnection System.

Present generation
X16
X8
X4
X2

Figure 2

120 Gbps/cm: 12 x 10 Gbps

Half size (1 cm)
12-MTµ-Joint

60 Gbps/cm: 12 x 10 Gbps
30 Gbps/cm: 12 x 5 Gbps

X1 15 Gbps/cm: 12 x 2.5 Gbps

MPO (2 cm)
12-MT

GI-MMF OM3LASERWAVE

2000

Next generation

240 Gbps/cm: 24 x 10 Gbps

2004

2007

New ﬁberHigh Δ n, 80 µm, 125 µm pitch
ThreadWave SM/MM

20102015 Year

Expectation of bandwidth per optical connector widthof one centimeter.

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Furukawa Electric Broadband Involvement in FTTH Systems

optical fiber size and improvement in ease of mounting
may also be needed.

3.

4. PROTOTYPES OF OPTOUNITYPRODUCTS

CONCEPT OF OPTOUNITYThe OptoUnity products, which are the optical components for optical inter-connections are developed basedon the target specification expressed above. OptoUnity isa coined word literally formed with “Opto” and “Unity”,
signifying the unification of the opto-electronic technology of our company and the products were named as
OptoUnity. The OptoUnity product group will open the
optical market of the next generation. The concept of
OptoUnity products are to miniaturizing conventional optical components, raising affinity with electronic productmounting, and realizing high-density mounting. The four
products under development are as follows.
1. Small diameter and small bending radius optical fiber:
ThreadWave, fiber ribbon, and code.
2. Micro multi-port ferrule: μ-Joint, MU type connector
plug, adapter, and back plane connector.
3. Right-angled connector: μ-Curve
4. Passive align type parallel optical module: μ-POEM
Figure 3 shows the pictures of products under development, and conventional components for comparing thesize.
In the following, the trial production result of the proto-

ThreadWave ﬁbers
Optical busµ-POEM

type of each part article is introduced.

4.1 ThreadWave
4.1.1 ThreadWave Fiber
The limitation in bending size of an optical fiber is a big
challenge to meet with high-density mounting requirement. Comparison of minimum bending radius of various
optical fibers is shown in Figure 4. The minimum bending
radius of a conventional optical fiber is 30 mm in relation
to loss and fracture strength. On the other hand, a fiber(FlexiWave), which guarantees 15 mm of bending radius
was recently produced commercially for interior use by
FTTH (Fiber To The Home). However, in optical inter-connection, since it needs to be wired in a narrower board
and rack, there is a demand to have the bending radiussimilar to that of electric wiring. We developed a single
mode (SM) type and a multi- mode (MM) type
ThreadWave fiber, setting a goal to guarantee the bending
radius of 5 mm.
A clad diameter of 80 μm was used for the ThreadWave
fiber to assure mechanical reliability in bending radius of 5mm. Fiber structure is shown in Figure 5. The clad/diameter of covering is 80 / 125 μm, respectively. Although covering is included, the outer diameter is equivalent to theµ-Curve

Right angled connector

Parallel opto-electrical module
10 Gbps VCSEL MM, SM x 12 ch

MT ferruleµ-Jointµ-Joint

Small MT ferrule

Computer, router racksµ-Joint-MU plug

Back plane connector

Figure 3

Conventional SMF : R〜30 mm
FlexiWave : R〜15 mm(developed for FTTH application)
ThreadWave : R〜5 mmµ-Joint-BP

High density back plane connector

Products of OptUnity.

ThreadWave
Multi-mode

Single mode

Conventional
singe mode ﬁber

Coating
diameter
125 µmUV resin coating
Glass ﬁber

Special ﬁber for optical interconnection
Clad diameter
80 µm

Figure 4

Comparison of fiber bending radius.

Clad diameter
80 µm

Core diameter
50 µm

Core diameter
5 µm

Graded Index proﬁleFigure 5

W type proﬁleCross-section of the ThreadWave fibers.

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Furukawa Electric Broadband Involvement in FTTH Systems

conventional glass fiber part of a fiber. SM type has adopted the W-type refractive-index profile to be a broadband
and with low loss. The mode field diameter of the opticalfiber was set at the level similar to that of VCSEL, which isapproximately 5 μm, so that the maximum coupling efficiency with the long wavelength VCSEL of a single mode
would be acquired. Propagation loss is 0.5 dB/km, andtransmission of 10 km or more is possible.
For the MM type, in order to secure the characteristic
equivalent to that of GI-50 conventional fiber and to realize 5 mm in bending radius, it adopted a diameter clad of
80 µm, which is the same as SM. The refractive-index
profile of the core is the GI-type which increased thecore/clad refractive-index ratio by 1 % to 2 % comparedto the conventional one to reduce the bending loss. The
propagation loss in the transmitted wavelength of 850 nm
is 3 dB/km or less, the bending loss is below 0.1 dB/turn(3.18 dB/m) at a bending radius of 5 mm, and for a transmission bandwidth of 200 MHz-km or more is obtained,
which makes the 20m-long transmission to be possible at
10 Gbps.
4.1.2 ThreadWave 12-Fiber Ribbon
A ThreadWave fiber can be formed as a ribbon of 125-μm
pitch, which is half in size when compared with the conventional 250-μm pitch, since the clad and the diameterof coating are 80 and 125 μm, respectively. A comparisonof cross-sections of the conventional 12-fiber ribbon anda ThreadWave 12-fiber ribbon is shown in Figure 6. Moreflexible application is possible by downsizing the width

Conventional optical ﬁbers

Cladding diameter
0.125 mm
Coating diameter
0.250 mm

Dimension of 12-ﬁber
ribbon0.3*3.15 mm

ThreadWave

Cladding diameter
0.080 mm
Coating diameter
0.125 mm

Dimension of 12-ﬁber
ribbon0.16*1.55 mm

Figure 6

and thickness for about 50 %.
4.1.3 ThreadWave Fiber Ribbon Cord
The code that is used to connect a ThreadWave fiber ribbon with apparatus cases is shown in Figure 7. In order tobear the mechanical stress at the time of construction, it
is covered with aramid fiber material, and the outer diameter has been halved from the conventional 12-multimodefiber cord.
4.2 μ-Joint
4.2.1 μ-Joint Ferrule
μ-Joint ferrule was developed as a multi-core light connection ferrule adapted to a ThreadWave fiber ribbon. A
comparison of sectional view with the conventional MT
ferrule is shown in Figure 8. The cross-sectional size of
μ-Joint ferrule is about half (3.4 mm in width, and 1.2 mm
in thickness) of conventional MT ferrule, and is 25 % in
facet area. Length is 4 mm. Moreover, a 0.4 mm diameter
stainless steel pin is used as the guide pin. The fiber holediameter is 80 μm and the pitch is 125 μm.
4.2.2 μ-Joint-MU Connector Plug and Adaptor
Taking advantage of the size of μ-Joint, MU connector isadopted as a connector housing which can be mountedwith high density 1). It is standardized as a JIS C5983:
1997 F14 type single-optical fiber connector, and MU
connector is put in practical use with the FTTH accesssystem termination equipment in a telephone station, etc.
It is possible to install two or more plugs with a spacing of
4.5 mm in between by applying an attachment-anddetachment mechanism with a slider. Figure 9 shows the
picture of plugs, which applied μ-Joint ferrule to MU
housing. Moreover, a μ-Joint-MU plug and 2 plugs adapter are shown in Figure 10.
The connection loss in the multimode fibers without
matching fluid measured by this plug and the adapter
was 0.2 dB or less, as shown in Figure 11. Moreover,more than -25 dB of reflective loss was obtained. Whenthe gross loss (loss budget) of the transmission way (20Comparison of cross-sections: Conventional 12-fiber
ribbon and ThreadWave 12-fiber ribbon.

Standard MT
Fiber pich: 250µm

6.4
φ0.7

2.5

Fiber hole: φ125µmµ-Joint

Fiber hole: φ80µm
3.4

φ0.4

1.2
Fiber pich: 125µm

Figure 7

Pictures of ThreadWave 12-fiber ribbon cord andconventional 12-fiber ribbon.

Figure 8

Cross-section of conventional MT ferrule and μJoint ferrule.

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Furukawa Electric Broadband Involvement in FTTH Systemsm) shown in Figure 2 of Section 2.2 is calculated using
the result obtained above, the calculation will be; 0.2
dB×4 connector connection + 0.1 dB×4 bending loss +propagation loss of 0.06 dB = 1.26 dB, and the marginclose to 3 dB is obtained against the initial target, which is
4.2 dB.
4.2.3 μ-Joint-MU Backplane Connector
The product of single MU connector is available as a backplane connector. It is possible to detach and attach two or
more plugs simultaneously as a whole board by using theprint board housing and back plane housing. Also MU
connector can be combined with electric connectors,
such as HM connector 1). Utilizing this mechanism, superhigh-density back plane connection is realized by adopt-

Figure 9

μ-Joint-MU plugs, upper: without slider, lower: withslider.

ing a multi-fiber connector by μ-Joint ferrule. This is
another reason of adopting the MU connector design.
Figure 12 shows the back plane connector housing of
2 plugs made as an experiment. In a single-MU connector, the back plane connector with a maximum of 8 plugs
is put in practical use, a 12-μ-Joint plug is applied, and,as for the case of 96-fiber and 10 Gbps/channel,
960 Gbps package attachment/detachment are attained.
Since the width of the back plane adapter at this time isabout 45 mm, the bandwidth density is calculated to be
more than 200 Gbps/cm.
4.3 μ-Curve
Although 5 mm in bending radius was realized with theThreadWave fiber, the application of an optical fiber canbe expanded if more smaller bend radius is realized. For
example, in a surface mount type optical module, arranging an optical fiber in parallel direction to a substrate isrequired. Conventionally, the size of the module and thebend radius was restricted when VCSEL or PD --- which
are used for an optical module --- and an optical fiber arecoupled to bend the optic axis by means of the fiber.
Therefore, the method of using reflective mirror combination for miniaturization has been taken. However, since
the spread of the light beam during space propagation
increases coupling loss, expensive parts such as a lens
are required when using the reflective combination method to reduce the loss.
As a solution, we have developed a new technology inwhich an optical fiber is processed at a temperature near
the glass melting point to be bent to almost 90° with abending radius of 1 mm or less 2). Figure 13 shows thephotograph of the fiber ribbon by which the right-angled
bending processing was carried out.

Figure 10 μ-Joint-MU plug and adaptor.

50

Insertion Loss (Dry) (Wavelength : 850 nm)

Figure 12 μ-Joint-MU backplane connector (Left: print board
connector, Right: backplane connector).

Frequency

40

90°Bending 8-ribbon ﬁbers

30
20
10
0

0.1

0.2

0.3

0.4

0.5

Insertion Loss (dB)Figure 11 Connection loss of the μ-Joint-MU multi-mode typeplug in adaptor.

Figure 13 90-degree bending fiber ribbon.

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Furukawa Electric Broadband Involvement in FTTH Systems

μ-Curve is the connector, which has this right-angled
fiber ribbon and is placed in a ferrule of the same size as
the conventional MT. The photograph of a prototype isshown in Figure 14.
The loss of the bent fiber was 0.1 dB or less inThreadWave SM. As for ThreadWave MM shown in Figure
15, by optimization of internal structure of the ferrule, even if
it included connection loss, a loss of 0.5 dB or less was
obtained.

with metal mirror inside the optical module. In the prototype, the optical element (850 nm VCSEL and Pin-PD
array) of 250-μm pitch 4 ch was used.
In contrast, V-pack is the module in which the opticalelement and the short length fiber are simply butt-joined
together inside an optical module, so that direction oflight outputs are perpendicular to printed circuit board
plane. The feature of it is to change, outside the module,
optical direction into the optical interface using 12-fiber
μ-Curve of 250-μm pitch. 12 channels of 250-μm pitch
were used for the optical element.
Both modules have optical elements mounted with anaccuracy of ±1 μm on the silicon substrate, and thegrooves on the silicon substrate are engaged with the
projections on the high-precision body, thereby achieving
passive alignment.
An electric interface is the surface mountable typepackage, which used the plastic printed circuit board. A
signal electrode is LGA (Land Grid Array) of a 0.5-mm
pitch and there are 78 pads. On the electric substrate, a
VCSEL driver IC for multiple channels or a receiving
amplifier IC was installed through the ceramic substrate
for heat dissipation, and connection with an optical ele-

4.4 μ-POEM
4.4.1 Structures
Parallel optical module μ-POEM which performs an electric/optical signal conversion has taken a substantial portion of the costs for optical inter-connection parts, and is
the part that especially needs cost reduction. We havebeen developing the lens-less passive alignment assembly which combined the high precision plastic package
and silicon substrate by MT ferrule molding technique as
the package to reduce the cost 3)-5). This time, two concept-trial-production modules; the reflective coupling
type (R-PACK) and a butt-joint coupling type (V-PACK)
shown in Figure 16, were examined as an optical connection type of an optical fiber and an optical element.
R-pack is the module that was designed to pursue miniaturization, uses 12-fiber μ-Joint for an optical interface
and is performing reflective combination with an opticalelement using the 45-degree polished short length fiber

1.6

Connecting Loss of µ-Curve
ThreadWave MM: Care/ Clad: 50/ 80 µm Δ2％，λ＝850 nm

1.4

Loss（dB）

1.2

7.0 mm
5.0 mm

R= 5 mm 1 turn

1.0
0.8
0.6
0.4
0.2

6.4 mm0.0

2.5 mm

1

ch

2

ch

Optical element/Silicon substrate

Optical coupling Internal light path transfer, using 45°
mirror reﬂection at ﬁber end facemethodSize

850-nm 4 ch multimode
VCSEL/Pin PD

IC

10 Gbps x 4 ch SiGe BiCMOS,
power supply: 3.3 V

Clip

Features0.5-mm pitch LGA

8

ch

9

ch

10 h11 h12ccch

But joint
coupling

Heat sink
IC

External light path transfer,using right-angle bent
optical ﬁber connector μ-Curve

10.0 × 10.0 × 10.0
μ-POEM with μ-Joint

850-nm 12 ch multimode VCSEL/
Pin PDμ-POEM with μ-Curve unit

5 Gbps x 4 ch SiGe BiCMOS,
power supply: 3.3 V
80 μmφ, 250-μm pitch ﬁber ribbon,
right-angle bent optical ﬁber
connector μ-Curve

Optical connector 80 μmφ, 125-μm pitch ﬁber ribbon,
μ-Joint connector
I/F

Electrical I/F

7

ch

Clip

Optical element/Silicon substrate

10.0 × 16.5 × 4.0

Optical element

6chµ-POEM V-packµ-Curve

Heat sink
IC

Structure(W/L/H in mm)

5chFigure 15 Connection loss of the μ-Curve.

µ-POEM R-packµ-Joint

4chChannelFigure 14 μ-Curve connector.

Reﬂection coupling

3chPluggable interposer
implementation

Optical elements and ICs are surface mounted; ultracompact
connectors are used; low-proﬁled

Pluggable interposer
implementation

0.5-mm pitch LGA

Optical elements and ICs are surface mounted; simpliﬁed
module structuring due to the use of right-angle
bent optical ﬁber connector μ-Curve

Figure 16 Structure and feature of μ-POEM parallel optical modules.

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Furukawa Electric Broadband Involvement in FTTH Systems

ment and board trace lines was set with a gold wire. The
footprint of R-pack and V-pack are common. BiCMOS
type IC with the power supply voltage of 3.3 V was used.
The width size of both modules was designed as 10.0 mm
to fulfill the requirements for a high dense package.
R-pack installs, in the metal heat sink, the receptaclemechanism for detaching and attaching a μ-Joint connector and module length is 16.5 mm. 4.0 mm in height was
realized by installing the 45-degree polished fiber, which
serves as a reflective mirror built in a molded package.
On the other hand, by carrying out optical directionchanging outside the module using a μ-Curve connector,
V-pack eliminates reflective mirrors and is attaining simplification of module composition. An optical emitting partis placed at the package upper surface, and the length ofthe package has been downsized to 10.0 mm and theheight to 4.0 mm. When μ-Curve is connected with springclip, the height is 10.0 mm.
A Pb-free solder that can handle a low-temperatureprocess was used for mounting on the board of μ-POEM.
The interposer board with an electric socket (pluggable)
which can be detached and attached as shown in thephotograph of Figure 16 was produced and mounted toincrease efficiency of evaluation of solder mounting andcharacteristic evaluation.
4.4.2 Characteristics
The characteristic of the prototyped module is described.
The eye patterns at the time of whole-channel simultaneous operation of V-pack type 5 Gbps, 12 channels Tx,
and Rx module are shown in Figure 17. Good eye patterns were obtained by a total of 12 channels. The average optical power of Tx is estimated to be -2.0 dBm, andoptical coupling loss is estimated as about 3 dB.
Remarkable cross talk degradation according to simultaneous operation in both modules was not seen.
Figure 18 shows the transmitted waveform at the time ofconnecting Rx module with the V-pack type Tx using a
ThreadWave MM fiber. The optical quenching ratio wasset at 3.0 dB. The light waveforms after transmission when
the length of an optical fiber is 4 m (back to back), 40 m,
and 54 m, and an electric waveform of Rx are shown. As
for the light waveform of Tx, degradation of an eye is seen
according to the increase in transmission distance, andthe increase in jitter was seen in Rx electricity waveform.
The measurement result of a bit error rate is shown in
Figure 19. Minimum received input power at 4 m (back toback), NRZ, PRBS 231-1, and bit error rate 10-12 and at 40-

5 GbpsExtinction ratio
measurement

Rx input
optical waveform
OpticalAttenuatorµ-POEM 12ch Tx
4 m (Back to back)Rxelectric waveform

40 mµ-POEM Rx
54 m

Rx input optical waveform : Extinction ratio = 3.0 dB

Rx Electric waveform

Figure18 Optical waveforms of 5 Gbps x 12 channel transmittermodule over ThreadWave MM.

1e-03

1e-04

1e-05

BER

1e-06
1e-07
1e-08
1e-09
1e-10
1e-11

Extinction ratio 3.0 dB
4 m (Back to Back)
40 m
54 m

1e-12
1e-13
1e-14
-20.0 -19.0 -18.0 -17.0 -16.0 -15.0 -14.0-13.0 -12.0-11.0 -10.0 -9.0 -8.0

Rx Input power (dBm)

Figure 17 Optical and electrical waveform of 5 Gbps, 12channels transmitter and receiver module.

Figure 19 Bit error ratio test of the 5 Gbps μ-POEM V-pack typeover ThreadWave MM fiber.

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m transmission was -13.7 dBm and -12.3 dBm, respectively, and the power penalty was 1.4 dB. It is thought that
40m-long transmission is satisfactory. On the other hand,the error floor was observed in 54 m. The transmission
bandwidth of the ThreadWave MM fiber was 200 MHz-km,
and since it is 5 GHz at 40 m, it is thought that the evaluation result is appropriate and the bandwidth of the opticalfiber has restricted the transmission distance. From thisresult, it has been shown that 5-Gbps transmission using
μ-POEM V-Pack is possible.
The power consumption of 5 Gbps, 12 channels Tx
module and Rx was about 960 mW (80 mW/channel), andabout 1320 mW (110 mW/channel), respectively.
The trial production of 10 Gbps module was performedin R-pack. The optical power waveform of 10 Gbps module with 4 channels and the electric output waveform of
Rx module are shown in Figure 20. Tx optical power is -2
dBm. In the transmission evaluation by Back to Back in
NRZ, PRBS 231-1, and bit error rate 10-12, as for the minimum received input power, -8 dBm and -10 dBm wereobtained with extinction ratio 3.9 dB and 6 dB, respectively.
As described in section 4.2.2, when the loss budget ofa transmission path is 1.26 dB and mode dispersion pen-

alty is set at 1.0 dB in 20-m transmission, the minimum
received input power of Rx is presumed as -4.26 dBm
when Tx output is -2 dBm. This shows a margin of 5.74
dB is obtained to minimum received input power -10 dBm
obtained this time. Even if 1.5 dB of cross talk penalty istaken into consideration, it is thought that sufficient signaltransmission at 10 Gbps is possible.

5.

SUMMARY

OptoUnity products will make a significant contribution in
replacing electric transmission with optical transmission
to enable bandwidth expansion. We have introduced here
the development of components for optical inter-connection which makes high-speed transmission and high-density packaging possible. We intend to promote productdevelopments in response to customers’ requirements,
firmly based on the concept and technologies describedhere aiming at miniaturization and high-density packaging.

REFERENCES
Tx Light wave form

Rx Electric wave form

Figure 20 10-Gbps Waveform of μ-POEM R-pack type (Left: Tx
optical, Right: Rx electrical).

1) Ryo Nagase, Munetake Ohtsuka, Minoru Nakamura: “NTT GIJUTU
Journal”, pp8-11, Oct. 2003. (in Japanese)2) M. Morimoto: “Small-radius 90°-bent single mode fiber for opticalinterconnection”, 2006 Optical Fiber Communications Conference(OFC 2006), OThH5. 2006.
3) M. Iwase et al.: IEEE, Transactions on advanced packaging, 419, 24(2001).
4) M.Iwase: “Passive Alignment Optical Modules using High Precision
Plastic Package and Silicon Optical Bench Technologies”, pp134135, OECC2002 10C1-1, Yokohama, Japan.
5) Masayuki Iwase, Yozo Ishikawa, Takuya Komatsu, Junichi Kasahara,
Nobuhiko Hattori, Masayuki Miura, Naoto Nakamura , Kunio
Odaka: “Optical Transceiver Modules for Gigabit Ethernet PON
FTTH System”, Furukawa Review No.28, pp8-24, 2005.

Furukawa Review, No. 32

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