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Splicing equipment for optical fibers

23 February 2012

 The article considers the equipment used to connect optical fibers by splicing, describes its operation principles, methods of optical fibers aligning during splicing, as well as characteristics of some models of splicing machines and cleavers.

 

Connections of optical fibers

As is known, popularity of fiber-optic technology for construction of telecommunications networks is associated with their high bandwidth. All the more, the inexorable technological progress in this area results in price reduction for optical data transmission equipment. Therefore more and more telecommunication companies and local operators have the opportunity to use decisions based on fiber optics in their networks.

A major component of a fiber-optic network is an optical cable – a link between the exchange and subscriber equipment. However, reliability of a fiber-optic line largely depends on the cable laying and installation operations, especially that cost of construction works clearly dominates nowadays over the cost of the cable itself.

In this connection, choice of inexpensive and high-quality technologies for splicing the optical fibers and the optical cable itself becomes more and more urgent. Fibers are usually spliced either by mechanical connectors (such as Fibrlok, CoreLink, etc.), or by arc splicing. The first method is usually used for temporary recovery of lines or if just a few connections are required. In this case Insertion Loss and Reflection Loss are evidently greater as compared with splicing, and connection of the fibers of different types can stand a serious problem. In addition it is necessary to install holders for connections of a special design in the cartridges of box or cross connect, or special-purpose cartridges that is not always convenient, and sometimes expensive.

The mechanical connection technology involves the use of the box mechanical connector with V-shaped grooves and the mounting table to install fibers into the connector. That is definitely is not cheap. Of course, if you want to connect 2 or 4 fibers once – there is no reason to buy a splicing machine. But even if create even a small subscriber network, then expenses for installation of fibers during networking and further operation are usually less when using the splicing equipment.

The most popular method for fibers splicing is splicing as the most reliable type of connection that introduces minimal insertion loss and minimal reflection from the weld, and most importantly – stability of mechanical and optical properties of the joint.

 

Influence of fibers spalling on the weld quality

The fibers splicing process is performed by the splicing machine. But not only the splicing machine is important for high-quality connection with low insertion loss. Spalling of the end face of optical fiber (OF) is also very important. It is the quality of spalling that directly affects the quality and time spent on splicing, since most of the splicing machines make previous assessment of the spalling angle and surface of the spalled fiber end, and if they do not meet the necessary requirements, the splicing machine will not perform splicing. In this case it is necessary to perform all the pre-splicing operations anew, which takes extra time (some splicing machines can perform splicing even if the spall is bad, but quality of the weld cannot be the best in this case).

 

 

Fig. 1. Example of influence of poor-quality spalling on splicing (a) prior to splicing, during alignment and (b) after splicing. Spall angle of the right fiber is about 5°. Geometric displacement of cores resulted in high loss (0.25 dB per 1550 nm).

 

Since fiber spall quality affects the quality of the welded joint, it is important to use high-quality precision cleavers. Typically, spall is obtained by scarifying the fiber lateral surface and subsequent application of bending force to that point, which leads to fiber spalling.

Since fiber spall quality affects the quality of the welded joint, it is important to use high-quality precision cleavers. Typically, spall is obtained by scarifying the fiber lateral surface and subsequent application of bending force to that point, which leads to fiber spalling.

Spalls made by mechanical cleavers are characterized by the marks remained after scarifying the OF. This defect has no effect during splicing and it can be neglected. Optical spall without scarifying traces can be obtained only by an ultrasonic cleaver.

 

 

Fig. 2. Butt end of the spalled fiber



Models of cleavers for optical fibers

DEPS Company offers its customers a range of up-to-date high-precision models of cleavers produced by the leading manufacturers of the industry - Fujikura (CT-30A), Ilsintech (MAX CI-01, CI-02, CI-03, CI-03A) and INNO Instruments (VF-77).

 

Fujikura СT-30A

 

 

 

 

INNO Instruments
VF-77

 

 

Ilsintech
MAX CI-01

 

 

Ilsintech
MAX CI-02

 

 

Ilsintech
MAX CI-03

 

 

Ilsintech
MAX CI-03A

 

 

Applied fiber

Standard fiber 125 µm

Diameter of the fiber wrapping

250 – 900 µm

Spall angle

90°±0.5°

90°±0.5°

90°±0.5°

90°±0.4°

90°±0.4°

90°±0.4°

Fiber length cleared of wrapping

6-20 мм

6-20 мм

5-20 мм

5-20 мм

5-20 мм

5-20 мм

Min. blade life, spalls

48 000

48 000

48 000

60 000

60 000

60 000

Dimensions, mm

102 × 82 × 46

81 × 72 × 62

58 × 55 × 48

84 × 65 × 54

88 × 55 × 48

58 × 55 × 48

Weight, g

210

350

360

420

400

360

Other characteristics

    • Gathering device with a container for remains of the spalled fiber;
    Automatic blade movement mechanism.
  • Convenient lever mechanisms that allows opening the top cover with one hand.
    • Oil damping system;
    • Metal protective top cover with clamps;
    • Container for spalled fiber;
    Automatic blade movement mechanism
    • Oil damping system;
    • Gathering device with a container for remains of the spalled fiber;
    Automatic blade movement mechanism.
  • Oil damping system.
   

Main feature of cleavers MAX CI-02, CI-03 and CI-03A is availability of the oil damping system which reduces the shock load on the fiber when touched by the blade - it improves the spall quality, as well as reduces the cleaver blade wear, increasing its life by up to 25 %.

 

(a)

(b)

(c)

   

Fig. 3. Fiber end spall made by a common cleaver (а), cleaver with oil damping (b), ultrasonic cleaver (c).

 

Advantage of cleaver Fujikura CT-30A is a mechanism for automatic blade movement which allows making the spalling process convenient, by one action, and small weight of the cleaver and thoughtful ergonomic design that makes it more convenient in service. It is worth noting that Fujikura company has provided a possibility of work with removable fiber holders (series FH-50 and FH-60), that in combination with Fujikura splicing machine (series FSM-50and FSM-60) greatly facilitates the fibers preparation and splicing.

Peculiarity of INNO Instruments VF-77 is availability of a special lever mechanism on the cleaver top cover that allows opening it with one hand, there is no need to hold the cleaver itself with his other hand. It is very convenient, since a fiber cleared of wrapping and ready for spalling, or some other tool is usually in the other hand.

All the described cleavers are provided with a built-in measuring bar to control the length of the spalled fiber using the short length thermosetting sleeves (40 and 30 mm), as well as blade height and position setup that is necessary when replacing the worn blade with a new one.

Despite its relatively simple appearance and the composite functions performed, remember that the cleaver is a precision instrument, the fiber spall accuracy is ± 0.5° and all the working parts are accurately aligned by the manufacturer to perform the specified function. It is therefore inadmissible to turn the adjusting screw needlessly and, even worse let the tool fall down. At best, it can violate its functioning, and at worst – put it out of action.

 

Technological stages of splicing the optical fibers

Currently, connection of optical fibers by means of splicing is the most common method of arranging the permanent joints. Due to technology practiced for many years, this method allows to arrange the high-quality connections with low values of insertion loss (up to 0.1 dB for different models).

Other benefits of splicing include high rate and feasibility of arranging the connection and its protection, good mechanical features, and reliability.

splicing of optical fibers assumes the melting of ends at fiber guides (by placing them in the field of powerful heat source – e.g., electric discharge field).

When splicing the optical fibers in electric discharge field, the following technological stages are sequentially implemented:

•    putting the protective heat-shrinkable sleeve on one of connected fibers;

•    preparing the butt-end surfaces of connected optical fibers;

•    installing the prepared ends of optical fibers to guide rails of splicing system;

•    two-plane alignment of welded optical fibers;

•    direct splicing of optical fibers;

•    preliminary assessment of weld quality;

•    protection of weld area by heat-shrinkable sleeve.

Modern devices splicing the optical fibers can be classified as follows: by alignment of welded ends at optical fibers (depending on geometrical dimensions of the core/shell or on power loss of light signal spread through the weld area); by number of optical fibers, which can be simultaneously welded (one- and multi-fiber).

There are several ways of aligning the fibers, but three of them are the most common. The most of modern devices are based on aligning the cores or shells of welded optical fibers according to their geometrical dimensions (Profile Alignment System, PAS) – via side illumination of ends at welded fibers. At that, alignment of fibers lit by side illumination is based on analysis of image obtained via microprocessor treatment of signal sent by cameras mounted on the opposite side of weld area. Analysis of transmitted illumination light allows obtaining the information on fiber structure and, consequently, on its core (when illuminating the fiber with parallel light beam, it acts like cylindrical lens). PAS method was suggested and patented by Fujikura Company.
 

 

Рис. 4. Принцип формирования изображения волокна в системе PAS.

 

Fig. 4. Principle of forming the fiber image in PAS system.

 

Second method is based on aligning the cores of optical fibers by emission passing through weld area of optical fibers – on principle of minimizing the loss of test light signal, known as LID (Light Injection and Detection) method. Input and output of optical emission is ensured at fiber-bending points (on special mandrels). Some disadvantage of the method is that it does not consider the physical properties of the fiber after its run-off in weld area. It can result into high loss of fibers with complex profile of refractive index.

The above methods refer to active alignment of fibers – based on analysis of fiber image (or light energy passing through the joint), which is managed by microprocessor of the device.

Method three is passive, when fiber is aligned along the shell during fiber laying into V-grooves. This method assumes strict arrangement of the grooves against each other, and very high requirements are made to geometric parameters of fibers. Typically, this type of alignment is applied if there are no high requirements to insertion loss of welded joints, as insertion loss at this method is a bit higher compared with the active methods.

 

splicing process for optical fibers

During burn-off process, both optical fibers are put simultaneously to prevent greater melting of one of them and hence thinning at weld point. Melting and splicing operations are usually performed automatically. Modern automatic splicing machines are provided with joint heating mode at the end of splicing in order to remove mechanical stress at the optical fibers connection point. This is called a "relaxation mode".

splicing machines have different splicing cycles for optical fibers of different types.

 

 

 

Arc

 

Motor motion

 

 

Fig. 6. Optical fiber splicing cycle performed by automatic splicing machine Fujikura:

A: Preliminary arc power;

B: Primary arc power;

C: Relaxation arc power;

D: Clearing arc;

E: Preliminary arc duration;

F: Reduction;

G: Primary arc duration;

H: Relaxation arc duration;

I: Pause;

J: Duration of relaxation impulse series;

K: Pause;

L: Opening of fibers;

M: Value of fibers opening;

N: Repeated arc.

 

Apart from the above quality control methods for the weld points, some splicing machines use tension test to avoid connection failures during manipulations when the splice is inserted into the cartridge, and later – during operation. Joint optical fiber is strongly fixed in the guide platforms (which are used for adjustment). Upon termination of the splicing phase, those guide platforms controlled by microprocessor diverge in opposite directions, generating a strictly normalized longitudinal tensile force (400 g) applied to the joint point.

With improvement of the splicing equipment quality and splicing technology, possibility to achieve high-quality weld joints of optical fibers becomes greater. Loss on welded joints depends on several factors such as experience of the staff, geometric errors of the welded optical fiber, and materials of which the fibers are made. Often, problems arise when splicing optical fibers of different manufacturers. The matter is that optical fibers of different manufacturers can be made by means of differing engineering processes. As a result, material for optical fiber – quartz glass – is not the same in the fibers of different origin, despite slight difference of optical and mechanical characteristics of optical fibers stated in manufacturers’ specifications.



Features of different models of splicing machines

Modern splicing machines control the splicing process and consider the controlled parameters of the environment such as temperature, humidity, barometric pressure, etc. They are vendor-provided with the splicing control software for the main types of optical fibers of different manufactures and special optical fibers, and make it possible to install additional individual software for splicing the optical fiber. The following table presents characteristics of models of splicing machines, offered by "DEPS".

 

 

Fujikura FSM-60S

 

 

Fujikura
FSM-50S*

 

Fujikura FSM-18S

 

 

Fujikura FSM-11S SpliceMate

 

Coringer AFS-50

 

 

Type of welded fibers

    • Single-mode (SM, ITU-T G.652)
    • Multimode (MM, ITU-T G.651)
    • With offset dispersion area (DS, ITU-T G.653)
    • With offset zero dispersion (NZDS, ITU-TG.655)
    • With offset cutoff wave length (CS, ITU-T G.654)
    • Hyposensitive to bends (ITU-T G.657)
    Erbium-alloyed fiber
    • Single-mode (SM, ITU-T G.652)
    • Multimode (MM, ITU-T G.651)
    • With offset dispersion area (DS, ITU-T G.653)
    • With offset zero dispersion (NZDS, ITU-TG.655)
    With offset cutoff wave length (CS, ITU-T G.654)
    • Single-mode (SM, ITU-T G.652)
    • Multimode (MM, ITU-T G.651)
    • With offset dispersion area (DS, ITU-T G.653)
    With offset zero dispersion (NZDS, ITU-TG.655)
    • Single-mode (SM, ITU-T G.652);
    • Multimode (MM, ITU-T G.651);
    • With offset dispersion area (DS, ITU-T G.653);
    With offset zero dispersion (NZDS, ITU-T G.655).
    • Single-mode (SM, ITU-T G.652)
    • Multimode (MM, ITU-T G.651)
    • With offset dispersion area (DS, ITU-T G.653)
    With offset zero dispersion (NZDS, ITU-TG.655)

Fiber aligning system

PAS

PAS

V-shaped groove

V-shaped groove

PAS

Arc correction for different climatic conditions

available

available

available

available

ARC Test

Diameter of the welded fiber, µm

80-150

80-150

125

125

125

Diameter of the welded fiber wrapping, µm

100-1000

100-1000

250- 1000

250 или 900

200-1500

Standard loss at splicing

0,02 dB (SM)
0,01 dB (ММ)
0,04 dB (DS)
0,04 dB (NZDS)

0,02 dB (SM)
0,01 dB (ММ)
0,04 dB (DS)
0,04 dB (NZDS)

0,05 dB (SM)
0,02 dB (ММ)
0,08 dB (DS)
0,08 dB (NZDS)

0,05 dB (SM)
0,02 dB (ММ)
0,08 dB (DS)
0,08 dB (NZDS)

0,02 dB (SM)
0,01 dB (ММ)

Standard splicing time

9 sec. (for SM fiber)

9 sec. (for SM fiber)

11 sec. (for SM fiber)

15 sec. (for SM fiber)

9 sec. (for SM fiber)

Battery life

160 welds with heat shrinkage (battery BTR-08)

160 welds with heat shrinkage (battery BTR-06(L))

150 welds with heat shrinkage (battery BTR-08)

30 welds with heat shrinkage (battery BTR-07)

40 welds with heat shrinkage

Display

Color LCD, 4,1"

Color LCD, 5.6"

Color LCD, 4,1"

Color LCD, 3,5"

Color LCD, 5.6"

Power supply

100 V−240 V AC through power adapter ADC-13;
10 – 15 V DC from external power source through adapter ADC-13; 
13,2 V DC from battery BTR-08

100 V−240 V AC through power adapter ADC-11;
10 – 15 V DC from external power source through adapter ADC-11; 
13,2 V DC from battery BTR-06 (S/L)

100 V−240 V AC through power adapter ADC-13;
10 – 15 V DC from external power supply through adapter ADC-13; 
13,2 V DC from battery BTR-08

100 V−240 V AC through power adapter ADC-13;
10 V−15 V DC through adapter DCA-02;
11.1 V DC from battery BTR-07

100 V−240 V AC through power adapter;
13.5 V DC from battery.

Front-end interface

USB 1.1 (USB-Mini B) for data and video transmission on PC

USB 1.1 (USB B) for data transmission on PC; video connector RCA/NTSC

USB 1.1 (USB-Mini B) for data and video transmission on PC

USB 1.1

USB data transmission on PC;
VGA interface for video transmission

Dimensions, mm (WхLхH)

136 х 161 х 143

150 х 150 х 150

136 х 161 х 143

110 х 80 х 100

150 х 150 х 150

Weight

2.3 kg (with AC adapter ADC-13)
2.7 kg (with battery BTR-08)

2.7 kg;
2.8 kg with AC adapter ADC-13

2.1 kg (with АС adapter ADC-13)
2.5 kg (with battery BTR-08)

640 g (without battery)
810 g (with battery)

2.5 kg

 

Table continued

Coringer
AFS -48


 

Coringer
AFS -40*

 

INNO Instrument IFS-9

 

 

Ilsintech
Keyman S1

 

Type of welded fibers

    • Single-mode (SM, ITU-T G.652)
    Multimode (MM, ITU-T G.651)
    • Single-mode (SM, ITU-T G.652)
    Multimode (MM, ITU-T G.651)
    • Single-mode SM (ITU-T G.652)
    • Multimode MM (ITU-T G.651)
    • With offset dispersion area DS (ITU-T G.653)
    • With offset zero dispersion NZDS (ITU-T G.655)
    Hyposensitive to bends (ITU-T G.657)
    • Single-mode SM (ITU-T G.652)
    • Multimode MM (ITU-T G.651)
    • With offset dispersion area DS (ITU-T G.653)
    • With offset zero dispersion NZDS (ITU-T G.655)
    Hyposensitive to bends (ITU-T G.657)

Fiber aligning system

PAS

PAS

PAS

PAS

Arc correction for different climatic conditions

ARC Test

ARC Test

available

available

Diameter of the welded fiber, µm

125

125

80-150

80-150

Diameter of the welded fiber wrapping, µm

200-1500

200-1500

100-1000

100-1000

Standard loss at splicing

0,02 dB (SM)
0,01 dB (ММ)

0,02 dB (SM)
0,01 dB (ММ)

0,02 dB (SM)
0,01 dB (ММ)
0,04 dB (DS)
0,04 dB (NZDS)

0,02 dB (SM)
0,01 dB (ММ)
0,04 dB (DS)
0,04 dB (NZDS)

Standard splicing time

9 sec. (for SM fiber)

9 sec. (for SM fiber)

9 sec. (for SM fiber)

9 sec. (for SM fiber)

Battery life

40 welds with heat shrinkage

40 welds with heat shrinkage

About 180 welds with heat shrinkage

About 100 welds with heat shrinkage with battery S-1B and 300 – with battery S-SB

Display

Color LCD, 5"

Color LCD, 5"

Color LCD, 5,6"

Sliding color LCD, 5,6"

Power supply

100 V−240 V AC through power adapter;
11.1 V DC from battery.

100 V−240 V AC through power adapter;
12 V DC from external supply source;
13.5 V DC from battery.

100 V−240 V AC or 12 V DC through power adapter ACM-12;
11.1 V DC from rechargeable battery LBT -10

14.8 V DC from rechargeable battery;
12 V DC from external supply source

Front-end interfaces

Interface RS232

Interface RS232

Interface RS232

USB 2.0, RCA

Dimensions, mm (WxLxH)

150 х 150 х 160

172 х 180 х 200

150 х 150 х 160

150 х 190 х 120

Weight

Weight3.52 kg (with battery)

4.1 kg

2.5 kg

2.6 kg

 

 

It should be noted that all manufacturers of splicing machines almost perfected the technology for splicing the optical fibers in electric arc. They associate all their new models and designs with increased reliability, improved weight and size characteristics, usability of the device, etc. Also, when new fiber types appear, the manufacturers provide for the possibility of those fibers connection in the new software versions for their devices.

 

 

Fig. 7. Mobile workplace

 

Thus, machine Fujikura FSM-11S SpliceMate, due to its dimensions, can easily fit on the palm – it’s ideal for work in tight conditions, and in combination with special optional accessory, it turns into a real mobile workstation for installer (Fig. 7). It will be useful for telecommunication companies when performing small amount of work, such as connection of new subscribers or quick elimination of failures at the optical network.

splicing machines Fujikura FSM-60S и FSM-18S allow operation under severe environment at temperatures -10…+50°, protected from ingress of dust and moisture inside the device. The set also includes a small assembly table which will not be excess especially under field working conditions. The splicing machine is fixed on it to prevent it from falling as a result of manipulation with the table. Strong plastic and rubber inserts on the machine design protect it from mechanical damage in case of falling from a low altitude or not severe impacts. But still do not abuse this protection as everything can be broken.

 

 

    

Fig. 8. Testing of splicing machines of series FSM-60 and FSM-18 by manufacturer, testing for damage resistance, ingress of dust and moisture inside the machine

 

 

    Fig. 9. Working surface of the assembly table and splicing machine Fujikura FSM-60

 

 

All the presented splicing machines Fujikura (except for FSM-50S) can operate with removable fiber clips FH-50 and FH-60, use of which greatly facilitates the installer work in case of large volumes of work on splicing the fibers.

 

Sufficient functional level is also characteristic for splicing machines of two South Korean companies INNO Instrument and Ilsintech  IFS-9 and Keyman S1, respectively, which are novelties at the Ukrainian market of splicing equipment. They were designed on the basis of experience of the world leaders in development of splicing machines – Fujikura and Sumitomo. Manufacturers paid special attention to ergonomics and usability of the device. For example, menu of IFS-9 machine is well structured and different additional useful information is displayed in the form of sensors readings on the environmental parameters (temperature, pressure). Keyman S1 stands out by dual module for heat shrinkage of KDZS (protective sleeves set on the splicing point), sliding monitor that can be hidden into a special compartment during transportation of the splicing machine and a convenient tray-holder for KDZS.

As for other advantages, both machines have modes pre-installed by manufacturer for splicing the fibers of type G.657A (fiber with reduced loss at bends), rechargeable batteries of high capacity (for example, IFS-9 machine is provided with battery of capacity 10800 mA*h, it allows 180-190 splices with heat shrinkage from one charge), and russified menu.

In case of not large amount of work, especially for local telecom operators who do not need the splicing machine every day, but only for expansion of their optical network, or in the case of an accident on the line - the ideal option would be splicing machine Coringer. They proved to be low-cost effective decision with sufficient functional to perform basic fiber splicing operations. Fiber splicing by splicing machine Coringer AFS-40can be found here.

Of course, it is true that all splicing machines for splicing the optical fibers can weld the fiber, similar to the statement that all cars can go. Therefore, there is some competition between manufacturers, and each of them, wishing to stand out, tries to attract the customer’s attention with new features of its new models of splicing machines. This is reflected in increased convenience and simplification of work with splicing machine – design or complete set of the machines provide for various additional devices and capabilities, and increase the machine reliability even under severe operating conditions.

Anyway, remember that regardless of manufacturer, fiber splicing equipment is high-precision equipment that requires careful handling during operation and timely maintenance. Mud, wrapping residues from cable and fibers shall not get into the machine workspace (all operations with cable and fiber shall be performed with the closed protective cover); working surface, fiber clips, optical system of the machine shall be periodically cleaned. It shall considerably prolong the equipment life, save your nerves and money from unexpected repair costs.

 

DEPS Department for Fiber-Optic Technology and Cable Networks

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