Development of Direct Core Monitoring Fusion Splicer S175
By Akio Tanabe *, Kazunori Yamamoto *, Jun'ichi Kazama *, Michihiko Kato *,Shinji Harada *, Seiryo Mishima *, Hidekazu Kojima *2, Tsuremi Hino *3,
Nobuharu Suzuki * and Hideyo Kawazoe *2

In order for a fusion splicer to be more compact, lightweight and its operatingtime to be much shorter, a new type of fusion splicer S175 has been developed.
Not only has its basic performance been improved, but also various new functions have been
added to the equipment. Another type of fusion splicer the S175K, which has a special setting
mechanism for splicing special optical fibers, has been added to our products line-up.

ABSTRACT1.

INTRODUCTION

Because of the higher density of its transmission capacity,
the WDM (Wavelength Division Multiplexing) has becomea major transmission system, resulting in the rapid growthof the optical fiber components market. To cope with thismarket change, the demand for the fusion splicer as infactory equipment is rapidly increasing, even though thedemand for installation use, which grew significantly some
10 years ago, is now maturing.
This paper describes the characteristics of direct core
monitoring fusion splicers, S175 and S175K.

2.

STRUCTURE OF THE FUSION SPLICERThis equipment is a fusion splicer for single-core fibers,
which has a core aligning function. The heat source of theequipment is arc discharging, as with conventional ones.
S175 and S175K are not available for the multi-fiber typeribbons; therefore, we offer another type of fusion splicer,
the S148, for multi-fiber ribbons.
As mentioned above, single-core optical fibers are used
for transmission cables and optical fiber devices. The
characteristics of the cable are listed below:(1) Characteristics as transmission cables* Fewer types (mainly for single-mode (SM), multimode (MM), dispersion-shifted (DS) fibers)* Mainly for the splicing of similar cables* Of average quality in many cases (large coreeccentricity)(2) Cable wiring characteristics within optical devices* Many types (erbium-doped fibers (EDF), etc., special types)* Splicing of different types of fibers

S175 was developed to support the application for theformer (transmission cable), and S175K for the latter(cable wiring within optical devices). These two types differ in their arc discharge design and splice loss estimation, which will be described later.

3.

OUTLINE OF EQUIPMENT

3.1 Specifications
Table 1 shows the main specifications of S175. Basically,
almost all the specifications for both S175 and S175K are
the same. However, they differ in splice loss, estimation
accuracy and splice time according to the type of fibers.
3.2 Appearance
Photo 1 shows the appearance of the equipment. BothS175 and S175K appear the same. In order to make themlightweight and robust, the body of the equipment is madeof die-casting aluminum. A translucent polycarbonate
cover on the top (not shown in the photo) is an accessory
part. This cover is so designed to allow the equipment tosplice optical cables with the cover attached. Therefore,
the arc discharge at an installation site exposed to*

Field Equipment Sec., Design & Development Dept., FITEL
Products Div.
*2 Design & Development Dept., FITEL Products Div.
*3 Engineering Dept., FITEL Products Div.

Photo 1

Appearance of S175 splicer

137Table 1
Items

Specifications of S175
Notes

Specifications

Size

111 x 285 x 181 mm

Approx. 20% less than the conventional

Weight6.3 kgApprox. 20% less than the conventional

Power source

Power consumption
Splice loss
Accuracy of splice

AC 85~264 V
DC 10~16 V
20 W (stand-by)
70 W (max)
SM fiber (Furukawa-made)Less than 0.03 dB on average±0.05 dB (<0.4dB)

loss estimation±15% (>0.4dB)

Splicing time

20 secHeat time for

90 secreinforcement(cooling process included)

Approx. 3 times faster than the conventional
Approx. 1.1 times faster than the conventional

5-inch color LCD
Operation monitor

XY 2-image-simultaneous display
Automatic switching of magnifying
ratio (x 132 ↔ x 264)

extremely strong wind, such as on the side of a subway
line, is barely affected by the wind. The body itself isdesigned to prevent the wind from blowing into it, and usually there is no need for setting the cover.
Operation buttons have been made larger, and arelocated near the LCD monitor making it easier to operate.
There are hooks in the front of the body for placing aplate to put tools in, providing space for tools even insmall and uneven places.
3.3 Functions
3.3.1 Automatic Identifying Function for Optical Fiber
Types
The optimum conditions for power and time of arc discharge depend on optical fiber type. Conventionally, program changes have been determined by the operator's
judgement. This equipment identifies optical fibers throughimage processing, and automatically changes programs(SM, MM, DS). Manual selection is also available.

3.3.4 Multi-display
As shown in Photo 2, the following pieces of information
are displayed on a 5-inch color LCD.
* Fiber image (simultaneous display of two images fromtwo directions)* Process name (multi-languages applicable)* Operational auxiliary message (multi-languages
applicable, scroll display applicable)* Fusion splicing program name
* Heating program name
* Heat oven operation monitor* Discharge cycles counter (electrode service hours
warning function)* Timer (built-in calendar free from the year 2000 problem)
3.3.5 Splice Data Memory
It has a memory capacity of up to 400 splicings consistingof splicing dates and splice loss, etc. Creating a histogramon the display or data transmission through a PC is avail-3.3.2 Mismatch Loss Alarm Function
Multi-mode fibers with 50 µm and 62.5 µm core diameters
are mainly used. It is very difficult to distinguish them at
the installation site. Mis-splicing of dissimilar type leads toa substantial splicing loss. The equipment measures thedifference between two fibers through image processing,
and warns not to connect them. This function is also useful with single-mode fibers.
3.3.3 Automatic Additional Arc Function
This method is effective for the attenuation function which
is optional (a function which intentionally shifts the corecenter to obtain desired optical loss), and effective for dissimilar optical fiber jointing by S175K. The additional arc is
automatically continued until splicing conditions are optimized through image processing.
Photo 2138

LCD display in operation

Furukawa Review, No. 19. 2000

able. Discharge inspection data for arc power adjustment
are stored up to 100 cycles.
3.3.6 Remote Control
The following functions are available as options:* Remote control of the equipment* Management of fusion programs and others.
* Management of image data
3.3.7 High Speed Heat Oven
Reduction in operating hours for the reinforcement
process has been attempted by combining a heater element that has an optimized temperature profile for protection sleeves of 40 mm and 60 mm in length and a highpower cooling fan. Using the protection sleeve of 60 mm
length, the reinforcement is completed in 70 seconds forthe heating process, and in 20 seconds for the coolingprocess, totaling 90 seconds. This oven has an automatic
clamp mechanism, which allows the setting of an opticalfiber into the heat oven using both hands, in addition to a
pre-tensioner which automatically removes slack from theoptical cable in the protection sleeve.

Optical fiber(cross section)

Observation mirror
Retracting mechanism
for observation mirror(During arc discharge)

Focus adjustment
mechanism
Magnifying
lens

Switching mechanismof XY observation position

CCD camera

Conventional mechanism

Optical fiber(cross section)
Focus adjustment
mechanism

Focus adjustment
mechanism
Magnifying
lens

Magnifying
lens

CCD camera (X-direction)

Figure 1

EVEN

3.4 Structure of the Equipment
3.4.1 Optics Design
Figure 1 shows a schematic diagram of the optics design.
In order to accurately measure the three dimensional position of an optical fiber, it is necessary to observe it fromthe two directions that are perpendicular to each other.
The equipment has two completely independent optics
systems in each direction. Higher observation accuracy
due to the new improvements greatly contributes to the
reduction in splicing hours.
Conventional two-directional observation method
required the setting of an objective mirror near the opticalfibers. Because of faint scratches or contamination, themirror is a frequent maintenance item and had to be
replaced periodically. The new optics system of the equipment has made the mirror unnecessary and has improved
the MTBF (Mean Time Between Failure) of the splicing
system.
3.4.2 Image Processing Mechanism
A method for inputting camera image signals into theimage processing circuit was designed to simultaneously
process two observation images, and has contributed to
the reduction in processing time.
Figure 2 shows a schematic diagram of the mechanism
for capturing image data. Two interlacing cameras aresynchronized, and the output image signals are alternately
switched field by field in order to digitize them by an A/D
converter. Thus this processing has made it possible tosimultaneously capture two images within a time needed
for capturing one image.

CCD camera (Y-direction)

Adopted new mechanism

3.3.8 Fiber Illuminating Lamp
Using two lamps consisting of high intensity LEDs, theoptical-fiber-positioning V-groove is illuminated in order toeasily set a fiber into it even in a dark place.

Comparison of optics design

ODD ....

CCD camera X

Switch

EVEN

ODD

....

A/D converter

Digital image
processing unit

CCD camera Y
EVEN

ODD

....

Figure 2

Capturing image data

The captured image data are displayed on the LCD
monitor after converting the scanning direction by thescanning converter. The conversion of the display magnifying ratio and the fine adjustment of the display position
are carried out during the image data conversion.
3.4.3 Aligning Mechanism
Figure 3 shows a new aligning mechanism.
Conventionally, in order to make it smaller, the aligningmechanism is divided into two groups, in which one fiber
moves along the X-direction only and then the other along
the Y-direction.
The equipment adopts a new mechanism in which one
fiber is aligned in the XY-directions, the other fiber is fed
only in the Z-direction.
The V-groove block is floating on XY linear bearingsand supported by two swing arms with bearings. Whenone swing arm rotates, the other bearing of the swing arm
works as a guide. Cylindrical ceramic components aremounted at an right angle to the contact points of the139Discharge
electrode

Optical fiber

Arc discharge center
Fixed V-groove

Opticalfiber
2-directional aligning V-groove

Cylindrical ceramic

Narrow arc (S175)

Distributionof heatV-grooveblock
XY linear guide

Swing arm
fulcrum

Ceramic cylinder

Bearing

Bearing

Optical
fiber

Motor

Wide arc (S175K)
Feed screw

Figure 3

Swing arm

Figure 4Distribution of heat during arc discharging

Aligning mechanism

bearings and the V-groove block in order to eliminate fluctuations in the position at which the reaction force of thespring is activated.
3.4.4 Arc Discharge Design
The arc discharge divides into two types by heating areas,a narrow arc and a wide arc. Figure 4 shows a schematic
diagram.
When two fibers with a core displacement shifted fromthe axis of the clad are spliced by aligning their cores, anoffset occurs with respect to both clad axes. However, thesurface tension produced by the melted joint portion will
decrease the offset of the clad axes, resulting in theoccurrence of an offset in the core axes. One method for
decreasing the core offset is the IAS (Intentional Axis
Shift) control method in which the axis adjustment is doneby estimating the direction and length of the shift to becaused by the surface tension beforehand and intentionally shifting the core axes. The effect of the surface tension
can be easily controlled by narrowing the heating area
thereby reducing the deformation range of the joint.
For transmission cable splicing use, therefore, narrowarc discharging is more suitable than wide arc discharging. S175 aligns the axis of the optical fiber with the centerof the arc discharging spot so as to get a narrow arc discharge area, and the strength of the arc discharge is relatively weak.
On the other hand, splicing dissimilar types of opticalfibers (different mode-field diameter) produces a difference in the mode-field diameter at the splicing point andeventually generates an optical loss (mismatch loss). The
mismatch loss can be reduced through a smoothing
process by the arc discharge heat. In order to smoothen
the difference more evenly, it is necessary to heat a widearea, and thus a wide arc is more suitable. S175K offsets
the center of the arc discharge from the axis of the opticalfiber and the arc discharge strength is set high.

140

Photo 3

Identified micro bending deformation of spliced portion

3.4.5 Splice Loss Estimation Program
The estimation of splice loss is made by identifying theshapes of the optical fiber cores through image processing. Evaluation items used are the conventional offset, thecore tilt and new items of the micro-bending in the splicing
point to make a more accurate estimation. Photo 3 shows
the deformation due to micro-bending. For the development of the program, we obtained cooperation from the
Scientific Technology/Analysis Dept. FITEC Corp.
S175K adopts an algorithm in which the change in mismatch loss produced while splicing dissimilar fibers is estimated by using the deformation of the core image (corecontrast) as a reference. Figure 5 shows the relationshipbetween these factors. Lateral coordinates are a parameter called the core-contrast changing ratio, denoting thechange of the core image clarity before and after splicing
represented in the ratio. The clarity of the core image
becomes lower every time the arc discharge occurs. The
splice loss continues to decrease at first, and then begins
to increase. A contrast-changing ratio that minimizes the
splice loss depends on the optical fiber type and thewavelength used, but is barley affected by the arc discharge strength for a selected combination of fibers to be
spliced. After estimating the splice loss from the experimental curve it is possible to get a minimum splice loss by

Furukawa Review, No. 19. 2000

combining the curve with the automatic additional discharge function.

Figure 8 shows the relationship between splice loss andsplice loss estimation of single-mode fiber under the presence of micro-bending.

4.

4.2 Splice Loss and Estimation Accuracy in S175K
Figure 9 shows a histogram of splice loss in the case of
splicing between EDF (Lucent-made HE 980) and SM(Corning-made SMF28). In the ordinary splicing method, amismatch loss of about 0.7 dB is produced. By combining
the wide arc discharge with an automatic additional discharge function, S175K reduced the splice loss to 0.1 dB.
Various combinations of optical fibers from many manufacturers were tested for splice losses in the same way to

CHARACTERISTICS

1.2

6

1

5

Estimation value (dB)

Splice loss (dB)

4.1 Splice Loss and Estimation Accuracy in S175
Figure 6 shows a histogram of splice loss for a singlemode fiber (Furukawa-made). We also carried out the
tests for splice loss of multi-mode fibers and DS fibers andconfirmed a low level of splice losses.
Figure 7 shows a histogram of splice loss for a singlemode fiber of 1 µm core eccentricity.

0.8
0.6
0.4
0.2

4
3
2
1

0
0

0.1

0.2

0.3

0.4

0.5

0.6

0

0.7

0

1

2

Core-contrast change ratio

Figure 5

Splice loss vs. deformation of core image

Figure 8

n=50
Ave. =0.018 dB
σ =0.015 dB
MAX=0.05 dB

5

6

Accuracy of splice loss estimation under the presence of micro-bending

20
15
10

n =20
Ave. =0.097 dB
σ =0.025 dB
MAX=0.14 dB
at 1.55 µm

8Frequency

Frequency

25

6

4

2

5
0
0

0.02 0.04 0.06 0.08

0.1

0.12 0.14 0.16 0.18

0

0.2

0

0.02 0.04 0.06 0.08

Splice loss (dB)Figure 6

0.1

0.12 0.14 0.16 0.18

0.2

Splice loss (dB)Histogram of splice loss for single-mode fiber withordinary eccentricity

Figure 9

Histogram of splice loss between erbium doped fiberand single-mode fiber

0.7

16

12
10
8
6
4

0.6

Estimation value (dB)n=50
Ave. =0.087 dB
σ =0.058 dB
MAX=0.24 dB

14Frequency

4

10

30

0.5
0.4
0.3
0.2
0.1

2

0

0
0

0.04 0.08 0.12 0.16

0.2

0.24 0.28 0.32 0.36

0.4

Splice loss (dB)Figure 7

3

Splice loss (dB)Histogram of splice loss for single-mode fiber withhigh core eccentricity

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Splice loss (dB)Figure 10 Accuracy of splice loss estimation between erbium
doped fiber and single-mode fiber141

Table 2

1.2

Main evaluation items

1

Splice loss (dB)

Results of reliability tests
Results

Splicing characteristics at low temperature (-15°C)

No change

Splicing characteristics at high temperature (+50°C)

No change

Splicing characteristics at high humidity (38°C, 90% RH)

No change

0.8
0.6

at 1.55 µm

Splicing characteristics at low pressure

0.4
0.2
0

(640 Hpa, equivalent to 3660 m height)

at 1.31 µm

Splicing characteristics after storing at low temperature
at 0.98 µm

0

0.1

0.2

0.3

0.4

(-40°C) and high temperature (+60°C)

0.5

Splicing characteristics in vibration tests (1.5 G, sweep-Core contrast changing ratio

ing at 0.1 octave/min. in the range of 10 to 500 Hz)

Figure 11 Wavelength dependency of dissimilar fiber splicing

Splicing characteristics after being dropped from a heightof 1.2 m, packaged in a storage casesee fluctuations in splice loss, but all of them were low.
However, we found that lot-to-lot fluctuations in mode-field
diameters of special fibers were relatively large.
Therefore, fine setting adjustment is needed in thesecases.
Figure 10 shows the relationship between splice loss
and estimation value in the combinations mentioned
above. In order to denote the accuracy in non-optimum
splice conditions, the values of large splice losses generated by excessive or short arc discharge hours are illustrated in the figure. The estimation errors greatly dependon the quality of optical fiber end-faces and the fluctuations in the mode-field diameters.
The mismatch loss is a function of the mode-field diameter (spot-size) 1), and the mode-field diameter is a function of the wavelength; therefore, the mismatch loss iswavelength dependent. This is because the mode-field
diameter change due to wavelength change depends on
the refractive index profile of the optical fiber.
Figure 11 shows the relationship between core imagechange and splice loss in the case of splicing the EDF(FiberCore-made DF1500F-0980) and the FlexCorTM-1060(Corning-made). The core-contrast changing ratio for minimizing splice loss differs for every wavelength; therefore,a different splice setting must be done according to thewavelength used.

5.

No change

No change

No change

No change

CONCLUSION

A direct core monitoring fusion splicer S175 was firstdeveloped. This equipment has the following basic features: small size, lightweight, shortening of splice and heat
reinforcement time, higher accuracy of splice loss estimation, and easy-to-use functions such as: an automatic
identifying function for optical fiber types, and simultaneous displays of two directional observation images on 5inch LCDs. Another type, the S175K, has also been developed with emphasis on splicing of special fibers.
The reliability test of the equipment was carried out inconditions pursuant to Bellcore specifications and all items
were found to have no problems.

REFERENCES

1) D. Marcuse : The Bell System Technical Journal, Vol.56, No.5,
May-June, 1977, pp.703-718.
2) Bellcore Generic Requirement for Single Fiber Single-mode
Optical Splices and Splicing Systems, GR-765-CORE, ISSUE 1,
SEPTEMBER 1995.
Manuscript received on June 22, 1999.

4.3 Reliability Test
Table 2 shows the results of major reliability tests undervarious conditions. Other items were evaluated in the conditions pursuant to Bellcore specifications 2) and no problems were found.

142

Furukawa Review, No. 19. 2000