Development of Series S176
Direct Core Monitoring Fusion Splicers
by Kazunori Yamamoto *, Akio Tanabe *, Sunao Yokomizo *, Jun'ichi Kazama *,Shin'ji Harada *, Hideki Watanabe * and Turemi Hino *The splicers used in the installation of optical fibers for telecommunications systems, have, with the increasing use of WDM technology, been commonly used as
manufacturing equipment in factories producing fiber-optic components. And as component factories shift to China and other Asian countries, prices have collapsed in the face of competition
with new models introduced by other firms. Against this background, we have improved our pricecompetitiveness and at the same time targeted the development of products that cover the fullrange of applications, from outdoor construction jobs to indoor fiber-optic component manufacture. The result has been the series S176 of direct core-monitoring fusion splicers. In terms ofstructure, we have made an appropriate distinction in the use of plastic and metal parts, and havesucceeded in controlling costs while achieving high reliability. In terms of performance, series
S176 has higher fusion splicing speeds, while being able to accommodate special types of fiber.
Particular attention has also been given to the ease of operation of the equipment.

ABSTRACT1.

INTRODUCTION

With the wider penetration of the Internet, the use of
dense wavelength-division multiplexing (DWDM) technology has grown at a dramatic rate. There has been a concomitant growth in the demand for fiber-optic components
and the market for fusion splicers is also growing, nolonger limited to network construction applications, but
expanding to include factories for the manufacture of fiberoptic components.
The series S175 types now in use were developed witha primary focus on construction applications, but large
numbers have also been sold for factory use based on

Photo 1*

S176 type CF (cubic, front monitor) splicer.

Photo 2

their boasting the world's fastest fusion splicing speed,
achieving the best record of sales up until the present.
The shift of the production facilities of fiber-optic manufacturers to Southeast Asia, however, has also meant anincreasingly cut-throat price competition. The new series
S176 of direct core-monitoring fusion splicers has beendeveloped to cover a wide range of applications both inconstruction and factories, while keeping costs low. The
series comprises three of differing configuration: Type CF(cubic, front monitor), type CR (cubic, rear monitor) andtype LP (low profile), allowing customers to select the unit
optimally suited to their needs. Though differing in appearance, all three have in common their major structural com-

S176 type CR (cubic, rear monitor) splicer.

Photo 3

S176 type LP (low profile)
splicer.

Design and Development Gr., Opto-Mechatronics Dept.,
Optical Connecting Products Div.

32a) Types CF and LPb ) Type CR

Fiber
cable

Operator

Fiber-optic
component

Operator

Figure 1

Operating methods for series S176 splicers.

ponents and parts, and plastic has been introduced widely
for those parts for which it can be employed, reducing
costs.
Types CF and CR have been designed primarily for
applications inside factories for the manufacture of fiberoptic components, allowing the splicing of fibers with short
surplus lengths, and free modification of the positional
relationships among fiber-optic components. The units arealso tilted forward, reducing the strain on the cervical andspinal vertebrae of operators, and the units can accommodate batteries, allowing them to be used in overheadstringing of lines during construction.
Type LP has fewer moving parts and is of a more robust
design, enclosed in an aluminum body for construction
applications. It has a lesser overall height, and is also suitable for certain factory applications.
All types provide a fusion splicing time of 11 sec (inhigh-speed mode), the fastest in the world, and make possible low-loss splicing of fibers of a wide variety of specifications.

2.

GENERAL DESCRIPTION

2.1 Equipment Arrangement
For the external appearance of the units see Photos 1
through 3.
In types CF (cubic, front monitor) and LP (low profile),
the operating monitor is located at the front and the windprotective cover for the splicing mechanism open andclose to the front, and the reinforcement sleeve heater at
the rear. This layout is appropriate because, in the layingof optical fiber cables the operator, for reasons of cablearrangement, the fusion splicer is generally operated at
the front while the closure for the cable joint is positioned
to the rear of the splicer. (see Figure 1a).
In type CR (cubic, rear monitor), the operating monitor
is positioned in the rear and the direction of opening andclosing of the wind protective cover and the reinforcement
sleeve heater are on the front. In factories manufacturingfiber-optic components it is usual to position the fiber-optic
components or modules toward the operator to performthe splicing and storing operations, and this layout isappropriate (see Figure 1b).

33

In both of these types, there are cases in which,depending on the cable laying conditions or module configuration, the reverse layout may be more convenient. In
such cases types CF and CR can be made interchangeable by changing the direction of mounting of a sloping
pedestal under the unit (hereinafter referred to as the bottom base) and using a software switch to reverse top tobottom the display on the operating monitor screen. Units
will operate even with the bottom base removed, but by
inclining the unit in the direction of the operator the opticalfiber may be easily put in place without crouching deeply
into the rear of the splicing portion.
Type LP, like that of the previous series S175, is ofrobust construction, with the operating monitor accommodated in an all-aluminum body. The layout of the internal
components has also been changed to make the working
surface lower, reducing the height difference between the
pre-processing steps and the working surface and improving the ease of operation. Batteries cannot be accommodated internally but an optional high-capacity battery optimally suited to factory applications can be installed on therear panel of the unit.
2.2 Specifications
Table 1 shows the main specifications.
2.3 Functions
2.3.1 Fusion of Short Lengths
The key to reducing the size of fiber-optic components
and modules is to reduce the dimensions of the reinforcement sleeve used for the fusion splicing section. To
achieve this the dimensions of the fiber chuck have been
reduced to the maximum extent possible allowing splicing
of fibers with a lead length of 5 mm (left and right total 10mm) for fibers with an outer diameter of 0.25 mm. This
made possible the use extremely small sleeves having an
overall length of 20 mm.
2.3.2 Auto-start
In applications in the inspection process in fiber-optic
component factories, where products are spliced to ameasuring instrument, there are cases in which the number of splices made reaches 300 to 500 per day, andthere is a major need to reduce the fusion splicing time

Furukawa Review, No. 21

2002

Table 1

Specifications of series S176 splicers.

Type designation

S176CF, S176CR

S176LP

169x203x179.5

192x277x154

34%

13%

With respect to splice inspection, it is possible to selecta high-speed mode which simplifies a portion, suitable
when priority is to be given to fusion time.

Dimensions (excluding protrusions (WxDxH) mm)
Reduction from previous model
Weight (kg)
Reduction from previous model

4.2

4.8

33%

24%

85-264 V (50-60 Hz) 85-264 V (50-60 Hz)
Supply voltage

Using S950

Using S950

(parts in common)
Power consumption
Normal/maximum (W)Battery-powered
5-min intervals (splice + sleeve)
Types of fiber spliced

Splicing loss (dB)

Splice loss estimating accuracy

22.66 / 56.23

28.5 / 65.63

30 times (w/ S940)

60 times (w/ S942)

SM, DS, MM, NZDS, CS980, CS980-SM,
FelX1060-SM, EDF-SM, etc.
SM: 0.02

DS: 0.04

MM: 0.01

NZDS: 0.04

±0.05 dB (≤0.4 dB)±15% (>0.4 dB)
Fibers >φ 0.25 mm: 5-16 mm

Length cut

Fibers φ0.4-0.9 mm: 16 mm(optionally supports 10 mm)
High-speed mode 11 sec

Connection timeHigh-precision mode 13 sec
Reduction from previous model: 6 sec

Reinforcement sleeve heating

60-mm sleeve 90 sec

time

20-mm mini sleeve 40 sec

Monitordisplay, automatic switching of magnification

5" color LCD two-screen simultaneous(132x <=> 264x)

2.3.5 Splicing Different Fibers
There are a wide variety of fusion programs provided tohandle the non-zero dispersion fibers used in fiber-optic
communications networks, small mode field diameter single mode fibers used in the manufacture of fiber-optic
components, erbium-doped fibers, and so on. In splicing
between different types of fiber, stable TEC (thermallyexpanded core) fusion, a technique for smoothing out differences in mode field diameter, can be achieved bymeans of the automatic additional arcing function used in
type S175K.
Up to 64 fusion programs can be stored in the internal
memory, and by means of an optional remote control program it is possible to externally store an unlimited number
in a personal computer.
2.3.6 Attenuation Splicing
By means of eccentric fusion it is possible to carry out
attenuation splicing in which the desired amount of opticalattenuation is obtained, eccentric fusion in which thedesired amount of eccentricity is obtained, and high-precision attenuation splicing by connecting up with an opticalpower meter and a personal computer.
2.3.7 Reinforcement Sleeve Heater
In addition to the reinforcement sleeves of series S175,
measuring 40 mm and 60 mm in length, a heater element
adapted to extra-small 20/25/30 mm sleeves has beendeveloped. Cooling fans are also incorporated for
improved cooling and reduced total reinforcement time.

and the burden imposed on the operator. By adding theauto-start function to the automatic selection function of
the conventional fusion program, the work required of theoperator is reduced to merely placing the fiber on thefusion unit and closing the wind cover.

2.3.8 Remote Control Function
Connection with a personal computer supports the editing
and saving of fusion programs, the upgrading of firmware,and trouble-shooting. It also makes possible the high-precision attenuation splicing referred to above.

2.3.3 Arcing Test
In order to optimize the strength of the arc discharge thatmelts the optical fiber, it was necessary in the former
series S175 to perform the arcing test for each type of
fusion program. This poses no particular problem when
there are only a few types of fiber but it imposes a significant operating burden when there are more specialized
fibers, as are used in fiber-optic components. In series
S176, the results of the arcing test are fed back into all of
the fusion programs, so that if the arc test is performed
once at the start of a day's shift, it becomes unnecessary
to repeat it even if the fusion program is changed.

2.3.9 Addition of a Short-Cut Key
The many special functions of the fusion unit and modifications to the program constitute a complex tree structure,
but frequently used functions can be stored and thenrecalled with a single key. Return to the fusion function
can also be accomplished with a single key-push.

2.3.4 Estimated Splice Loss
In addition to the misalignment, bending, tilt and mismatch
losses used conventionally in estimating splice loss, theseries S176 units add cleave angle for improved estimating accuracy.

2.3.10 Fiber Holder System
Conventionally, with a core-aligning fusion unit, a tightholder is used which sets the fiber directly on the fusion
unit by hand. Envisioning a factory situation with inexperienced operators, a new fiber holder system was employed
as an option. Once the fiber has been set into the adapter
and pre-processing steps carried out, it can easily be set
to the fusion unit as is, eliminating the fear of damage tothe fiber.

34

2.3.11 Multiple Power Supplies
Both type CF and type CR have a power supply slot that
accepts any of three power sources--AC, built-in batteries
or external DC.
Type LP can also accept three power supplies, although
the batteries are attached to the rear panel.
2.4 Structure
2.4.1 Optics
The basic structure is the same as that of the previous
series S175, which monitors images of the fiber from X
and Y directions at right-angles to the fiber, using independent optical systems, each provided with an objective
lens and CCD camera for each of the directions.
The dimensions of the optical system determine thedepth dimension of the equipment. Series S175 used an
objective lens of about 10-power and a 1/3-inch CCD, butseries S176 uses a lens of about 7.5-power and a 1/4-inch
CCD, maintaining the same resolution despite the savingin size. The light source is a red LED, but a diffuser isused to reduce directionality and increase uniformity.
2.4.2 Image Processor
The series S176 features dual frame memories. These
allow images from the X and Y directions to be accepted
simultaneously, providing full parallel processing for the

V-block
Ceramic rod
X-Y LinearWay
Swing arm pivot
Ceramic rod

Roller bearing

Roller bearing
X motorY motorMicroscrew

Figure 2

Swing arm

Aligning mechanism of the series S175.

V-block
Ceramic rod
X-Y LinearWay
Swing arm pivot
Ceramic rod

two directions. Data can be read in without wait time fromeither odd- or even field timing, achieving a significant
shortening of the frame data read-in cycle (from 120 msec
in the series S175 to only 45 msec) and resulting in a highdegree of real-time processing.
2.4.3 Aligning Mechanism
In the earlier series S175, the rotary motion of a motor
was converted into straight motion by means of a microscrew (see Figure 2). Series S176, however, uses an
eccentric camshaft to reduce cost and shorten operatingtimes (see Figure 3). The eccentric portion of thecamshaft is engaged by a bearing, and between the aligning arm and eccentric camshaft there is a smooth relative
motion. The relationship between the angle of rotation of
the camshaft and the perpendicular displacement provides a sinusoidal motion, but the range used is 45-135
deg, which produces a substantially linear action. The useof the eccentric camshaft means that the distance traveled
per rotation of the motor is about five times greater than inseries S176, resulting in high-speed alignment action.
This inherently meant an increase in hysteresis due tobacklash, but modifications were made to the control system that solved this problem.
The same mechanism is used for focusing also.
2.4.4 Use of Plastic Parts
Table 2 compares the number of components (including
screws) in the former series S175 and the new series
S176, and it can be seen that the count is reduced bymore than 100. Parts made of plastic are increased toabout 30. Selective use was made of thermoplastics andthermosetting plastics with glass filler, depending on thelevel of performance demanded of the component. A wide
variety of quality tests, shown in Table 3, were carried out
to confirm problem-free performance after 270,000 consecutive operations, and high-temperature, high-humidity
splice loss characteristics. Plastics are even used for thecase cover in both Type CF and Type CR, and electromagnetic discharge noise was successfully suppressed(EN55022, Class 2).
2.5 Splicing Fibers in Different Types
In the manufacture of fiber-optic components and modules, it is common to have to splice together two types offiber having different mode field diameters, and normallythis mismatch in diameters results in splice loss. The difference in mode field diameter is particularly great
between erbium-doped or other high-delta fibers and ordinary single-mode fibers, and the splice loss due to mismatching is extremely large. TEC is the name for the technique whereby this mismatching loss is reduced by heat-

Roller bearing
Roller bearing

Gearing

Table 2

Structural component count.

Swing arm

S176

S175

Total number of components

770

881

Number of molded plastic components

312

Eccentric camshaft
Y motorFigure 335

X motor

Aligning mechanism of the series S176.

Furukawa Review, No. 21

2002

Table 3

Results of reliability tests.

500
450

Main parameters for evaluation

ResultNo change

Splice loss profile, high temperature (50°C)

No change

Splice loss profile, high humidity (40°C, 90%RH)

No change

Splice loss profile, low atmospheric pressure

No change(640 hPa, equiv. to 3600-m elevation)
Splice loss profile after low-temperature (-40°C) andhigh temperature (60°C) storage

φ 125 µm350

φ 150 µm

300
250
200
150
100
50

No change

Pass range

00Splice loss profile after vibration test

50

Figure 5

Splice loss profile after dropping test from height of
1.2 m in original case, packaged

100

150

200

Arc power

No change(1.5 G, 10-500 Hz at 0.1 octave/min sweep)

Relationship between arc power and retort in fibersof different diameter.

No change
140

Splice loss profile after 270,000 operations of

No change

various actuators

120
100

Arc power

1.4
1.2
1

Loss (dB)

φ 80 µm

400

Retort (pixels)

Splice loss profile, low temperature (-10°C)

80
60
40

0.8

20

0.6

0

0.4

70

Bottom point

90

110

130

150

µ

0.2

Figure 6

0
0.000

0.100

0.200

0.300

0.400

0.500

0.600

Correlation between fiber diameter and arc power.

0.700

Contrast ratio

Figure 4

Relationship between splice loss and contrast ratio
for CS980 and single-mode fibers.

ing the splice.
When the splice is heated the core and dopant undergo
thermodiffusion but generally speaking, for fibers with asmall mode field diameter to satisfy single-mode conditions, both the refractive index of the core and the concentration of dopant are high. Thus diffusion proceeds rapidly
and the mode field diameter increases rapidly. In suchcases there is a timing that assures that the two mode
field diameters will match and the splice loss will be minimized. If heating is continued longer, the discrepancy inmode field diameter will be reversed and splice loss again
increases.
Within the equipment the mode field diameter is notdirectly measured; rather the change is quantified indirectly using changes in light-dark contrast in the fiber image.
The relationship between splice loss and contrast ratio
when splicing Corning CS980 fibers to single-mode fibers
is shown in Figure 4, the bottom point in which being
thought to be the point at which the two mode field diameters are substantially the same. Series S176 has an automatic control system that applies added heating incrementally as it monitors the change in contrast until the optimum point is reached.
In some erbium-doped fibers the rate of diffusion of themode field diameter is extremely rapid, and to allow forsuch cases the heating temperature can be lowered toreduce the rate of diffusion, thereby achieving a lower
splice loss.
2.6 Splicing Fibers of Different DiameterIn splicing fibers of different type, the control system caneliminate the differences in core diameter (mode field
diameter) but to make splices between fibers when clad
diameters are different, elaborate care was taken to control the arcing, as well as to adjust the focus during fiber
observation and measure misalignment of the axes.
Figure 5 shows the relationship between arc power andretort in fibers of 80-, 125- and 150-µm diameter, retort
being the amount of retreat due to surface tension whenthe end of the fiber is heated, and value for evaluation
during arcing tests. In other experiments the retort wasconsistently in the range of 90 to 110 pixels showing thatsplice loss was at the minimum. Figure 6 shows a plot offiber diameter against the optimum arc power. From theseresults it may be seen that the series S176 provides automatic compensation for arc power in accordance with thefiber used. And it was not necessary to perform further
arcing tests even when fiber diameter changed.
Focus is adjusted individually for the right and left fibers
for measurement of fiber position.

3.

CHARACTERISTICS

3.1 Splice Loss Profile
Figures 7 and 8 are histograms of splice loss between

36

150

100
0.6
0.5

ave. =0.01 dB

100

60

STD.=0.015 dB

40
50

Splice loss (dB)

Cumulative (%)

Frequency

By conventional equation

80

n=300 splices

20

0.00

0.02

0.04

0.06

0.08

0.10

By standard equation
0.4
0.3
0.2
0.1
0

0

0

Actual value

0

0.12

1

Figure 7

Histogram of splice loss for single-mode fibers.

90

40
30
20

0.11

0.14

0.17

0.20

0.23

0.26

0.29

10
8
6
4
2

0

0
0.08

0

0.32

0

2

Splice loss (dB)Figure 84Comparison of accuracy of equations used to estimate splice loss.

Estimated value (dB)60

STD.=0.033 dB

Cumulative (%)

ave. =0.15 dB

0.05

3

12

80

n=200 splices
Frequency

Figure 9

100

60

2

Relative cleave angle (deg)Splice loss (dB)Histogram of splice loss for Corning CS980 and
Furukawa single-mode fibers.

4

6

8

10

12

Actual value (dB)Figure 10 Accuracy of splice loss estimation for single-mode
fiber.

ordinary single-mode fibers, and between Corning CS980
and Furukawa single-mode fibers.
CS980 and single-mode fibers have mode field diameters with respect to 1550 nm of 6.76 and 10.74 µm
respectively, and the theoretical mismatch loss is 0.90 dB.
The TEC fusion effect results in measured values averaging 0.15 dB, showing that the two mode field diameters
have been adequately matched.

the addition of cleave angle, ca greatly improve the accuracy over conventional estimates.
In the region where relative cleave angle is less than 1deg, estimating accuracy for single-mode fibers is good,as shown in Figure 10.

3.2 Estimating Accuracy
As can be seen from the above, it has become the practice, in calculating estimated splice loss, to take into
account not only misalignment, bending, tilt, and mismatch losses, but also the additional item of cleave angle.
In conventional methodology, when the cleave angle waslarge due to faulty maintenance of the fiber cutter, the estimated loss was sometimes shown as very small in comparison with the value of splice loss actually measured.
The relationship between the relative cleave angles ofthe left and right fibers was found experimentally, andFigure 9 shows the actually measured results, thoseobtained by the conventional estimation equation, and the
newly estimated values using added compensation. With
ordinary fiber cutters the difference in relative cleaveangles is about 1 degree or less, at which estimated loss
values pose no problem. At angles greater than 1 degree,
however, it will be appreciated that the conventional technique of estimation is extremely inaccurate. Though it
must be said that there remains room for improvement,

With a view to a finely-tuned response to varied customer
requirements, a series of fusion splicers comprising three
types has been developed, with cost kept low. In addition
to accommodating different requirements by the presenceor absence of a case or the reinforcement sleeve heater,or modifications to the fiber holder system, a wide varietyof options are also available, including a foot switch for
greater efficiency and easier operation, a tight holder forloose tube-type fiber splicing, a close-in illumination lamp,
and a work table for placement of fiber-optic modules andcase.
Enhancements to basic functions include built-in batteries (Types CF and CR) for splicing short lengths, and asplicing time 35% less than the previous series (11 sec inhigh-speed mode).
This series constitutes a line-up of high-end fusion
splicers that is already commercially available, catering toa wide range of markets, from the laying of fiber-optic
communications networks to the manufacture of fiberoptic components.

37

4.

CONCLUSION

Furukawa Review, No. 21

2002